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Journal articles on the topic 'Parallaxe'
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1
Upgren, A. R. "Variations in External Parallax Errors." Symposium - International Astronomical Union 109 (1986): 247–51. http://dx.doi.org/10.1017/s0074180900076658.
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The present astrometric program of the Van Vleck Observatory began in 1967. Since then it has emphasized parallaxes and proper motions of stars of the lower main sequence which are not identified on the basis of proper motion and are therefore not biased towards high space velocity. Later an analysis was made from parallax and proper motion data from 70 stars in the spectral range dK3-M2 (Upgren 1973) which found the average external mean error in parallax to be 8.0 ± 1.7 mas (milliarcseconds). This external error was found to vary little from one parallax to another and to have no correlation with the formal internal errors for the individual parallax determinations. Hanson and Lutz (1983) confirm this result using the parallaxes of 14 members of the Hyades cluster also determined at Van Vleck. They find a mean external parallax error of 9.4 ± 1.8 mas and suggest that the proximity of the two determinations may be evidence that Van Vleck parallaxes may be characterized by a single external error. Their slightly larger figure may or may not reflect the relatively fewer plates and epochs of observation from which the Hyades parallaxes were determined.
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Breuval, Louise, Pierre Kervella, Richard I. Anderson, Adam G. Riess, Frédéric Arenou, Boris Trahin, Antoine Mérand, et al. "The Milky Way Cepheid Leavitt law based on Gaia DR2 parallaxes of companion stars and host open cluster populations." Astronomy & Astrophysics 643 (November 2020): A115. http://dx.doi.org/10.1051/0004-6361/202038633.
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Aims. Classical Cepheids provide the foundation for the empirical extragalactic distance ladder. Milky Way Cepheids are the only stars in this class accessible to trigonometric parallax measurements. However, the parallaxes of Cepheids from the second Gaia data release (GDR2) are affected by systematics because of the absence of chromaticity correction, and occasionally by saturation. Methods. As a proxy for the parallaxes of 36 Galactic Cepheids, we adopt either the GDR2 parallaxes of their spatially resolved companions or the GDR2 parallax of their host open cluster. This novel approach allows us to bypass the systematics on the GDR2 Cepheids parallaxes that is induced by saturation and variability. We adopt a GDR2 parallax zero-point (ZP) of −0.046 mas with an uncertainty of 0.015 mas that covers most of the recent estimates. Results. We present new Galactic calibrations of the Leavitt law in the V, J, H, KS, and Wesenheit WH bands. We compare our results with previous calibrations based on non-Gaia measurements and compute a revised value for the Hubble constant anchored to Milky Way Cepheids. Conclusions. From an initial Hubble constant of 76.18 ± 2.37 km s−1 Mpc−1 based on parallax measurements without Gaia, we derive a revised value by adopting companion and average cluster parallaxes in place of direct Cepheid parallaxes, and we find H0 = 72.8 ± 1.9 (statistical + systematics) ±1.9 (ZP) km s−1 Mpc−1 when all Cepheids are considered and H0 = 73.0 ± 1.9 (statistical + systematics) ±1.9 (ZP) km s−1 Mpc−1 for fundamental mode pulsators only.
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Gliese, Wilhelm. "Astrometric Desiderata for Nearby Stars." Symposium - International Astronomical Union 109 (1986): 653–67. http://dx.doi.org/10.1017/s0074180900077160.
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Astrometric desiderata for nearby stars concern, in first line, the parallax measurements, avoidance and elimination of effects of bias in trigonometric parallax programs: Bias towards large proper motions, preference of parallaxes with positive accidental errors, the Malmquist bias. For some of the nearby stars we do not yet know accurate positions, for some other objects no reliable proper motions were measured. Finally, for calibrating color-luminosity relations the necessity to observe further precise trigonometric parallaxes is demonstrated and emphasized.
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Van Altena, William F., Terrence M. Girard, and John T. Lee. "Calibration of the Mass-Luminosity Relation Using Trigonometric Parallaxes. I." International Astronomical Union Colloquium 135 (1992): 276–83. http://dx.doi.org/10.1017/s0252921100006564.
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AbstractThe calibration of luminosities using trigonometric parallaxes introduces well-known errors that are a function of the ratio of the parallax error to the parallax, when the sample is chosen from stars with measured parallaxes larger than some minimum parallax. In this paper it is shown that similar errors are also introduced into the mass axis of the mass-luminosity relation (MLR) and can result in a biased MLR. The bias is shown to be related to the Lutz-Kelker correction to the absolute magnitude, as extended by Hanson for the case of selection effects in the data sample. The size of the correction in the mass axis is substantial and for the case of a uniform distribution in space, it can amount to a multiplicative factor of 1.17 in the mass for a ten sigma (σ/π = 0.10) parallax and a factor of 1.62 for a five sigma (σ/π = 0.20) parallax.
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Xu, Y., S. B. Bian, M. J. Reid, J. J. Li, B. Zhang, Q. Z. Yan, T. M. Dame, et al. "A comparison of the local spiral structure from Gaia DR2 and VLBI maser parallaxes." Astronomy & Astrophysics 616 (August 2018): L15. http://dx.doi.org/10.1051/0004-6361/201833407.
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Context. The Gaia mission has released the second data set (Gaia DR2), which contains parallaxes and proper motions for a large number of massive, young stars. Aims. We investigate the spiral structure in the solar neighborhood revealed by Gaia DR2 and compare it with that depicted by VLBI maser parallaxes. Methods. We examined three samples with different constraints on parallax uncertainty and distance errors and stellar spectral types: (1) all OB stars with parallax errors of less than 10%; (2) only O-type stars with 0.1 mas errors imposed and with parallax distance errors of less than 0.2 kpc; and (3) only O-type stars with 0.05 mas errors imposed and with parallax distance errors of less than 0.3 kpc. Results. In spite of the significant distance uncertainties for stars in DR2 beyond 1.4 kpc, the spiral structure in the solar neighborhood demonstrated by Gaia agrees well with that illustrated by VLBI maser results. The O-type stars available from DR2 extend the spiral arm models determined from VLBI maser parallaxes into the fourth Galactic quadrant, and suggest the existence of a new spur between the Local and Sagittarius arms.
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Shao, Zhengyi, and Lu Li. "Gaia parallax of Milky Way globular clusters – A solution of mixture model." Monthly Notices of the Royal Astronomical Society 489, no. 3 (August 21, 2019): 3093–101. http://dx.doi.org/10.1093/mnras/stz2317.
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Abstract We have established a mixture model approach to derive the parallax of the Milky Way globular clusters. It avoids the problem of cluster membership determination and provides a completely independent astrometrical solution by purely using the parallax data. This method is validated with simulated clusters of Pancino et al.. We have resolved 120 real globular clusters by the mixture model using parallaxes of the second data release of Gaia . They construct the largest direct parallax sample up to now. In comparison with other direct parallax results based on cluster members, including 75 clusters of Gaia Collaboration, our method presents its accuracy, especially for some particular clusters. A systematic offset of −27.6 ± 1.7 μas, together with a scatter of 22.8 ± 1.3 μas is found in comparison with other indirect parallax measurements. They are consistent with the global value and the variation of the zero-point of current Gaia parallaxes. Distances of several specific nearby globular clusters are discussed while the closest ones can reach high precisions, even taking the systematic error into account.
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Sato, Yoshiyuki. "Kojin Karatani et la théorie marxiste de la « parallaxe » : au-delà du structuralisme." Actuel Marx 67, no. 1 (2020): 101. http://dx.doi.org/10.3917/amx.067.0101.
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Jullien, Vincent. "Relativité, determinatio et parallaxe, remarques sur le traitement cartésien de trois controverses scientifiques." Articles 38, no. 2 (January 11, 2012): 493–521. http://dx.doi.org/10.7202/1007461ar.
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Trois sujets de philosophie naturelle, fort controversés à l’époque où Descartes élabore sa physique (incluant son système du Monde) sont particulièrement présents dans les Principes de la philosophie de Descartes, le principe de relativité des mouvements des corps matériels, la nature que l’on nommera plus tard vectorielle de la grandeur, qui caractérise l’état de mouvement d’un corps et que Descartes contribue à constituer par la notion de determinatio et l’objection parallactique contre l’héliocentrisme. On examine ici comment l’actualité du débat scientifique permet de comprendre l’argumentation cartésienne et on insiste sur le caractère polémique de ce traité. On peut notamment relever que les théories galiléennes pèsent d’un grand poids dans la modification des conceptions cartésiennes du mouvement et que les arguments, alors les plus récents, avancés en astronomie soutiennent la mise au point du système du monde cartésien. Il s’agit de mettre l’histoire des sciences au service d’une meilleure intelligence de la somme philosophique cartésienne.
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van Altena, William F., and John T. Lee. "The Yale Parallax Catalogue." Symposium - International Astronomical Union 133 (1988): 269–74. http://dx.doi.org/10.1017/s0074180900139695.
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A new edition of the General Catalogue of Trigonometric Stellar Parallaxes is being prepared at the Yale University Observatory. The Catalogue will include all published photographic parallaxes, a reference to the source of the published parallax, UBV photoelectric photometry, MK spectral types, cross identifications with other catalogues, data on the binary nature of the stars and auxiliary information to aid in determining the reliability of the data. An analysis of the parallaxes corrected to absolute has been made to study the accidental and systematic errors of the parallaxes. The new edition will be available in both printed and magnetic tape versions.
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Mehl, Édouard. "De Copernic à Descartes : l’Empyrée, la parallaxe stellaire et le mouvement de la Terre." Revue des sciences philosophiques et théologiques 99, no. 2 (2015): 239. http://dx.doi.org/10.3917/rspt.992.0239.
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Murray, C. A., P. M. Corben, and R. W. Argyle. "Trigonometric Parallaxes Obtained with the UK Schmidt Telescope." Symposium - International Astronomical Union 109 (1986): 213–21. http://dx.doi.org/10.1017/s0074180900076592.
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In continuation of a long term programme of measurement of parallaxes and proper motions in the South Galactic Cap from plates taken with the UK Schmidt Telescope and measured in GALAXY at RGO, data for some 800 red stars brighter than B = 17.5 have been derived from two independent plate series. The parallaxes obtained from unfiltered IIaO plates show a large systematic error depending on magnitude compared with those obtained from IIaD plates with GG 495 filter. After correction, the combined trigonometric parallaxes show very satisfactory agreement with photometric parallaxes, and the average r.m.s. error of a combined parallax is found to be about ±0″.012 both from internal and external evidence.
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Schönrich, Ralph, Paul McMillan, and Laurent Eyer. "Distances and parallax bias in Gaia DR2." Monthly Notices of the Royal Astronomical Society 487, no. 3 (May 29, 2019): 3568–80. http://dx.doi.org/10.1093/mnras/stz1451.
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ABSTRACT We derive Bayesian distances for all stars in the radial velocity sample of Gaia DR2, and use the statistical method of Schönrich, Binney & Asplund to validate the distances and test the Gaia parallaxes. In contrast to other methods, which rely on special sources, our method directly tests the distances to all stars in our sample. We find clear evidence for a near-linear trend of distance bias f with distance s, proving a parallax offset δp. On average, we find ${\delta _{\rm p}}= -0.054 \, {\rm mas}$ (parallaxes in Gaia DR2 need to be increased) when accounting for the parallax uncertainty underestimate in the Gaia set (compared to ${\delta _{\rm p}}= -0.048 \, {\rm mas}$ on the raw parallax errors), with negligible formal error and a systematic uncertainty of about $0.006 \, {\rm mas}$. The value is in concordance with results from asteroseismic measurements, but differs from the much lower bias found on quasar samples. We further use our method to compile a comprehensive set of quality cuts in colour, apparent magnitude, and astrometric parameters. Lastly, we find that for this sample δp appears to strongly depend on σp (when including the additional $0.043 \, {\rm mas}$) with a statistical confidence far in excess of 10σ and a proportionality factor close to 1, though the dependence varies somewhat with σp. Correcting for the σp dependence also resolves otherwise unexplained correlations of the offset with the number of observation periods ${n_{\rm vis}}$ and ecliptic latitude. Every study using Gaia DR2 parallaxes/distances should investigate the sensitivity of its results on the parallax biases described here and – for fainter samples – in the DR2 astrometry paper.
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Mints, Alexey, and Saskia Hekker. "Isochrone fitting in the Gaia era." Astronomy & Astrophysics 618 (October 2018): A54. http://dx.doi.org/10.1051/0004-6361/201832739.
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Context. Currently, galactic exploration is being revolutionized by a flow of new data: Gaia provides measurements of stellar distances and kinematics; growing numbers of spectroscopic surveys provide values of stellar atmospheric parameters and abundances of elements; and Kepler and K2 missions provide asteroseismic information for an increasing number of stars. Aims. In this work, we aim to determine stellar distances and ages using Gaia and spectrophotometric data in a consistent way. We estimate precisions of age and distance determinations with Gaia end-of-mission (EoM) and Tycho-Gaia astrometric solution (TGAS) parallax precisions. Methods. To this end, we incorporated parallax and extinction data into the isochrone fitting method used in the Unified tool to estimate Distances, Ages, and Masses (UniDAM). We prepared datasets that allowed us to study the improvement of distance and age estimates with the inclusion of TGAS and Gaia EoM parallax precisions in isochrone fitting. Results. Using TGAS parallaxes in isochrone fitting, we are able to reduce distance and age estimate uncertainties for TGAS stars for distances up to 1 kpc by more than one third compared to results based only on spectrophotometric data. With Gaia EoM parallaxes in isochrone fitting, we will be able to further decrease our distance uncertainties by about a factor of 20 and age uncertainties by a factor of 2 for stars up to 10 kpc away from the Sun. Conclusions. We demonstrate that we will be able to improve our distance estimates for about one third of stars in spectroscopic surveys and to decrease log(age) uncertainties by about a factor of two for over 80% of stars as compared to the uncertainties obtained without parallax priors using Gaia EoM parallaxes consistently with spectrophotometry in isochrone fitting.
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Moffett, T. J., Thomas G. Barnes, and David S. Evans. "White Dwarf Candidates for Trigonometrical Parallax Determinations." Symposium - International Astronomical Union 111 (1985): 365–68. http://dx.doi.org/10.1017/s0074180900078979.
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The visual surface brightness relation is applied to the determination of parallaxes of white dwarfs on the assumption, borne out by previous studies of white dwarfs of known parallax, that these show only a small range of linear diameters.
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Piecka, M., and E. Paunzen. "Aggregates of clusters in the Gaia data." Astronomy & Astrophysics 649 (May 2021): A54. http://dx.doi.org/10.1051/0004-6361/202040139.
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Context. The precision of the parallax measurements by Gaia is unprecedented. As of Gaia Data Release 2, the number of known nearby open clusters has increased. Some of the clusters appear to be relatively close to each other and form aggregates, which makes them interesting objects to study. Aims. We study the aggregates of clusters which share several of the assigned member stars in relatively narrow volumes of the phase space. Methods. Using the most recent list of open clusters, we compare the cited central parallaxes with the histograms of parallax distributions of cluster aggregates. The aggregates were chosen based on the member stars which are shared by multiple clusters. Results. Many of the clusters in the aggregates have been assigned parallaxes which coincide with the histograms. However, clusters that share a large number of members in a small volume of the phase space display parallax distributions which do not coincide with the values from the literature. This is the result of ignoring a possibility of assigning multiple probabilities to a single star. We propose that this small number of clusters should be analysed anew.
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Pont, F., M. Mayor, C. Turon, and D. A. Vandenberg. "Distance and Age of M92 From Hipparcos Subdwarfs." Highlights of Astronomy 11, no. 1 (1998): 563. http://dx.doi.org/10.1017/s1539299600022176.
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The parallax data gathered by Hipparcos for field subdwarfs allow a muchmore precise determination of globular cluster distances by direct sequencefitting than was previously possible. We determined the distance and age ofthe old, representative globular cluster M92 from a set of more than 500 subdwarf candidates with Hipparcos parallaxes. Precise [Fe/H] values were derived using the equivalent width of the CORAVEL cross-correlation function.Our best estimate of the distance of M92 is (m — M)v = 14.67 ± 0.08 (including binaries with a statistical correction) or (m — M)v = 14.74 ± 0.08 (classic treatment, i.e. excluding binaries). The agreement of the cluster sequence with the position of extreme metal-poor field subdwarfs is remarkable [figure, left]. The distance found is slightly higher than previously thought. The corresponding ages, derived by comparing the luminosity of the turnoff and subgiant-branchstars with up-to-date evolution models [figure, right], are 14±1.2 Gyr or 13±1.2 Gyr respectively, implying a minimum age of 13 Gyr for the Universe.Other authors have claimed that larger distances, and smaller ages, resulted from Hipparcos subdwarf parallaxes. Although there are some differences in the data sets used by each author, the main difference resides in the treatment of systematic and selection biases. We have examined at some length the biases affecting the determination of the mean luminosity of a set of subdwarfs selected in the usual way. By means of Monte Carlo simulations, we show that selection biases act in a direction opposite to the classic Lutz-Kelker bias affecting parallax data, and that they can be dominant. The biases introduced are of the order of 0.1 mag.It is pointed out that, now that the whole Hipparcos catalogue is available, we shall be able to greatly reduce the systematic biases by refining the fitting procedure. Firstly, by imposing no [Fe/H] limits and fitting the subdwarf locus for all [Fe/H] values at the same time. Secondly, by imposing no parallax error limit and fitting the data in parallax space instead of magnitude space (comparing observed parallaxes directly with parallaxes predicted from the models).
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Kurayama, T. "VERA observation of the massive star forming region G34.4+0.23." Proceedings of the International Astronomical Union 3, S248 (October 2007): 202–3. http://dx.doi.org/10.1017/s1743921308019066.
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AbstractWe observed with VERA the massive star forming region G34.4+0.23, to obtain parallaxes and proper motions. Four infrared dark clouds were observed and water maser were found in two dark clouds, MM1 and MM4. In MM1, the distribution of maser spots shows a “V-shaped” structure and most features co-moving with this structure. Phase-referenced images have peaks and their motion is much larger than the expected parallax. Further analysis is needed to correctly interpret our measurement of parallax.
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Anguita, C. A., and M. T. Ruiz. "CCD Parallaxes for Faint Southern High Proper Motion Stars." Symposium - International Astronomical Union 141 (1990): 455. http://dx.doi.org/10.1017/s0074180900087283.
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In April 1985, we started a program to measure trigonometric parallaxes for faint southern high proper motion stars, using a CCD at the Cassegrain focus of the Cerro Tololo Interamerican Observatory (CTIO) 1.5-m telescope. The program stars (mR > 16; μ ≥ 1 arcsec/year) were selected from the LHS Catalogue and the University of Chile proper motion program.The X and Y positions of the stellar image centroids were obtained using the algorithms of DAOPHOT program packages. The precision of the measurement of one stellar image is about 6 milliarcseconds (0.02 pix). For stars with 16 < mR < 19.5 a precision of 2 milliarcseconds in the parallax determination can be obtained in a one year period. Trigonometric parallaxes for some stars common to other parallax programs are given, showing an agreement with those results within the quoted mean errors.Several technical aspects of the present program are also discussed.
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Mishenina, Tamara V., Caroline Soubiran, Valery V. Kovtyukh, and Stanislav I. Belik. "Li abundances and chromospheric activity of BY Dra type stars." Proceedings of the International Astronomical Union 5, S268 (November 2009): 343–44. http://dx.doi.org/10.1017/s1743921310004394.
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AbstractAtmospheric parameters and Li abundances have been determined for 162 stars observed at high resolution, high signal to noise ratio with the ELODIE echelle spectrograph (OHP, France). Among them, about 70 stars are active stars with a large fraction of BY Dra type stars. For all stars, rotational velocities were obtained with a calibration of the cross-correlation function, effective temperatures by the line depth ratio method, surface gravities by the parallaxe method and by the ionization balance of iron. The frequency of stars with observed lithium is significantly higher in active stars than in non active stars. Among active stars, no clear correlation has been found between different indicators of activity for our sample stars, but some correlation of an index R′H K and vsini is observed.
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Khan, S., A. Miglio, B. Mosser, F. Arenou, K. Belkacem, A. G. A. Brown, D. Katz, et al. "New light on the Gaia DR2 parallax zero-point: influence of the asteroseismic approach, in and beyond the Kepler field." Astronomy & Astrophysics 628 (August 2019): A35. http://dx.doi.org/10.1051/0004-6361/201935304.
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The importance of studying the Gaia DR2 parallax zero-point by external means was underlined by the articles that accompanied the release, and initiated by several works making use of Cepheids, eclipsing binaries, and asteroseismology. Despite a very efficient elimination of basic-angle variations, a small fluctuation remains and shows up as a small offset in the Gaia DR2 parallaxes. By combining astrometric, asteroseismic, spectroscopic, and photometric constraints, we undertake a new analysis of the Gaia parallax offset for nearly 3000 red-giant branch (RGB) and 2200 red clump (RC) stars observed by Kepler, as well as about 500 and 700 red giants (all either in the RGB or RC phase) selected by the K2 Galactic Archaeology Program in campaigns 3 and 6. Engaging in a thorough comparison of the astrometric and asteroseismic parallaxes, we are able to highlight the influence of the asteroseismic method, and measure parallax offsets in the Kepler field that are compatible with independent estimates from literature and open clusters. Moreover, adding the K2 fields to our investigation allows us to retrieve a clear illustration of the positional dependence of the zero-point, in general agreement with the information provided by quasars. Lastly, we initiate a two-step methodology to make progress in the simultaneous calibration of the asteroseismic scaling relations and of the Gaia DR2 parallax offset, which will greatly benefit from the gain in precision with the third data release of Gaia.
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Oh, ungyo. "Die Parallaxe der Übersetzung feministischer Literatur am Beispiel der deutschen Übersetzung von Han Kangs Die Vegetarierin." Journal for german Culture and Literature 28 (December 31, 2019): 685–707. http://dx.doi.org/10.32681/jgcl.28.25.
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Cahais, J., L. Schwarz, V. Bridoux, E. Huet, and J. J. Tuech. "L’image est-elle droite pour tout le monde ? Introduction de l’effet de parallaxe en chirurgie laparoscopique." Journal de Chirurgie Viscérale 154, no. 1 (February 2017): 10–14. http://dx.doi.org/10.1016/j.jchirv.2016.04.017.
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Harris, H. C., C. C. Dahn, D. G. Monet, and J. R. Pier. "Trigonometric parallaxes of Planetary Nebulae." Symposium - International Astronomical Union 180 (1997): 40–45. http://dx.doi.org/10.1017/s0074180900129766.
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The accuracy of parallaxes obtained with ground-based CCD cameras now often reaches or exceeds 0.5 milliarcseconds. This improved accuracy permits us to measure significant parallaxes and determine distances for the nearest planetary nebulae. At present, the central stars of 11 planetary nebulae have been observed as part of the USNO parallax program. We now have determined distances with accuracies better than 20 percent for four central stars and better than 50 percent for five more. This paper gives the present status of the program, a brief interpretation of the results, and future prospects.
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Chan, Victor C., and Jo Bovy. "The Gaia DR2 parallax zero-point: hierarchical modelling of red clump stars." Monthly Notices of the Royal Astronomical Society 493, no. 3 (February 27, 2020): 4367–81. http://dx.doi.org/10.1093/mnras/staa571.
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ABSTRACT The systematic offset of Gaia parallaxes has been widely reported with Gaia’s second data release, and it is expected to persist in future Gaia data. In order to use Gaia parallaxes to infer distances to high precision, we develop a hierarchical probabilistic model to determine the Gaia parallax zero-point offset along with the calibration of an empirical model for luminosity of red clump stars by combining astrometric and photometric measurements. Using a cross-matched sample of red clump stars from the Apache Point Observatory Galactic Evolution Experiment and Gaia Data Release 2 (DR2), we report the parallax zero-point offset in DR2 to be $\varpi _0 = -48 \pm 1\,\mu \text{as}$. We infer the red clump absolute magnitude to be −1.622 ± 0.004 in Ks, 0.435 ± 0.004 in G, −1.019 ± 0.004 in J, and −1.516 ± 0.004 in H. The intrinsic scatter of the red clump is ∼0.09 mag in J, H, and Ks, or ∼ 0.12 mag in G. We tailor our models to accommodate more complex analyses such as investigating the variations of the parallax zero-point with each source’s observed magnitude, observed colour, and sky position. In particular, we find fluctuations of the zero-point across the sky to be of order or less than a few 10s of $\mu \text{as}$.
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Lai, Wan. "High-Precision Parallaxes and Their Astrophysical Applications." Symposium - International Astronomical Union 156 (1993): 213–18. http://dx.doi.org/10.1017/s0074180900173243.
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As demonstrated by USNO CCD parallax program, a CCD attached to a modest aperature telescope is capable of measuring stellar trigonometric parallax to a precision better than 1.0 mas. consequently, many objects previously regarded as being too distant for ground-based trigonometric distance determinations can now be considered.In this paper we show the High-precision parallaxes will provide a very good opportunity for the refinement of H-R digrammes and the calibration of luminosity criteria, we also refer to the open cluster and to determination of accurate stellar masses from close binanies.
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Perren, G. I., E. E. Giorgi, A. Moitinho, G. Carraro, M. S. Pera, and R. A. Vázquez. "Sixteen overlooked open clusters in the fourth Galactic quadrant." Astronomy & Astrophysics 637 (May 2020): A95. http://dx.doi.org/10.1051/0004-6361/201937141.
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Aims. This paper has two main objectives: (1) To determine the intrinsic properties of 16 faint and mostly unstudied open clusters in the poorly known sector of the Galaxy at 270° −300° to probe the Milky Way structure in future investigations. (2) To address previously reported systematics in Gaia DR2 parallaxes by comparing the cluster distances derived from photometry with those derived from parallaxes. Methods. Deep UBVI photometry of 16 open clusters was carried out. Observations were reduced and analyzed in an automatic way using the ASteCA package to obtain individual distances, reddening, masses, ages, and metallicities. Photometric distances were compared to those obtained from a Bayesian analysis of Gaia DR2 parallaxes. Results. Ten out of the sixteen clusters are true or highly probable open clusters. Two of them are quite young and follow the trace of the Carina Arm and the already detected warp. The remaining clusters are placed in the interarm zone between the Perseus and Carina Arms, as expected for older objects. We found that the cluster van den Berg-Hagen 85 is 7.5 × 109 yr old, which means that it is one of the oldest open clusters detected in our Galaxy so far. The relationship of these ten clusters with the Galaxy structure in the solar neighborhood is discussed. The comparison of distances from photometry and parallaxes data in turn reveals a variable level of disagreement. Conclusions. Various zero-point corrections for Gaia DR2 parallax data recently reported were considered for a comparison between photometry- and parallax-based distances. The results tend to improve with some of these corrections. Photometric distance analysis suggests an average correction of ∼+0.026 mas (to be added to the parallaxes). The correction may have a more intricate dependence on distance, but addressing this level of detail will require a larger cluster sample.
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Andrade, Manuel. "Colour-dependent accurate modelling of dynamical parallaxes and masses of visual binaries." Astronomy & Astrophysics 630 (September 26, 2019): A96. http://dx.doi.org/10.1051/0004-6361/201936199.
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Context. Two fundamental characteristics of binary systems are the masses of their components and their distance to the Earth. In this way, the dynamical parallax is an accurate and very helpful tool. Nevertheless, there has been some concern with regard to the use of a unique linear mass–luminosity relation (MLR) for the entire main sequence (MS). Aims. This article describes the accurate computation of both dynamical parallaxes and individual masses of visual binaries. The main aim is to formulate a model which would be suitable for binary systems attending to the exact locations of the components on the MS in the HR diagram. Methods. An analytical model was developed which allows calculation of dynamical parallaxes and individual masses using a non-linear MLR valid for the entire MS. This up-to-date MLR is given by a polynomial of degree 20. In contrast to previous approaches, this model can be applied even in the case of components with unequal masses, that is, with an arbitrarily large difference of magnitudes between them. On the other hand, considering the fundamental equation of the theory that forms the basis of the model, we propose to estimate uncertainties in parallax and masses using Monte Carlo simulations. Results. The model was validated by means of numerical tests using a synthetic sample comprising 103 systems. The results are much more accurate than those for previous models reported in the literature for deriving dynamical parallaxes and masses. Furthermore, we present dynamical parallaxes and individual masses for the 19 double-lined spectro-interferometric systems with definitive visual orbits and compare the former with the orbital parallaxes as well as with those measured by HIPPARCOS and Gaia. It is worth mentioning that the latter can only be a reliable source when the orbital motion is taken into account. Thus, at present, many Gaia DR2 parallaxes of binaries are biased. Conclusions. Our model, composed of an exact analytical theory, along with a non-linear MLR, guarantees high accuracy even in cases where the components are of unequal mass.
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Chaboyer, Brian, G. Feiden, G. F. Benedict, B. E. McArthur, T. E. Harrison, A. McWilliam, E. P. Nelan, R. J. Patterson, and A. Sarajedini. "Parallaxes of metal-poor main-sequence stars." Proceedings of the International Astronomical Union 8, S289 (August 2012): 87–90. http://dx.doi.org/10.1017/s1743921312021175.
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AbstractOur team was awarded 108 orbits of Hubble Space Telescope time to obtain parallaxes and photometry of nine metal-poor stars with [Fe/H] < −1.5 dex. The parallaxes are obtained from observations with the Fine Guidance Sensor (FGS 1r; 11 orbits per star) and photometry was obtained with the Advanced Camera for Surveys (one orbit per star). The first data were obtained in October 2008, and the data collection is ongoing. It is anticipated that the observations will be complete in June 2013. Preliminary data reduction has been completed for five of our target stars. The parallax errors vary from 0.12 to 0.16 milli-arcseconds, and the parallaxes are at least an order of magnitude more accurate than existing Hipparcos parallaxes for these stars. The errors in the true distance modulus range from 0.02 to 0.03 mag. Ground-based high-resolution spectra have been analyzed to obtain accurate abundances for three stars. The properties of the two stars with accurate abundances and parallaxes are in excellent agreement with those predicted by stellar evolution models.
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Smart, R. L., R. Pannunzio, M. G. Lattanzi, and B. Mclean. "Completing the Local Sample with Tycho." Highlights of Astronomy 11, no. 1 (1998): 443. http://dx.doi.org/10.1017/s1539299600021742.
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The Tycho Catalogue contains proper motions and low precision parallaxes with a median precisions of 25 mas, while having high precision B and V magnitudes (median precision of 0.07 and 0.06 respectivly). The number of highparallax stars is quite unexpected, with over 30 previously unreferenced, non-Hipparcos, stars with a parallax >500 mas and over 2000 with a parallax >250 mas. While many of these are probably mistakes, the completeness limit of Tycho and the precise magnitudes provide us with a way to intelligently build a complete picture of the nearby star field. Catalogues of nearby stars provide us with many fundamental parameters in the field of stellar astronomy, but the completness of known stars within say even 8pcs is still underestimated by about 30%, i.e., 50-60 systems (T.J. Henry, CSSS8, ASP Conf Series 64, 1994).In a new program at Torino we are using the Tycho Catalogue to intelligently build a list of possible candidates for a 1Opc volume. Figure 1 shows that Tycho will contain basically all ZAMS to spectral type M3 within 10 pes, M5 to 4pcs and M6 to 2pcs. A comparison of the photometric and Tycho distances provides a list free of giants and systems where binarity has affected the color. This list is then added to the Torino Parallax program where we expect to provide more precise parallaxes.
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Maíz Apellániz, J., M. Pantaleoni González, and R. H. Barbá. "Validation of the accuracy and precision ofGaiaEDR3 parallaxes with globular clusters." Astronomy & Astrophysics 649 (April 28, 2021): A13. http://dx.doi.org/10.1051/0004-6361/202140418.
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Context.The recent early third data release (EDR3) from theGaiamission has produced parallaxes for 1.468 × 109sources with better quality than those reported in the previous data release. Nevertheless, there are calibration issues with the data that require corrections to the published values and uncertainties.Aims.We want to properly characterize the behavior of the random and systematic uncertainties of theGaiaEDR3 parallaxes in order to maximize the precision of the derived distances without compromising their accuracy. We also aim to provide a step-by-step procedure for the calculation of distances to stars and stellar clusters when using these parallaxes.Methods.We reanalyzed some of the data presented in the calibration papers for quasar and Large Magellanic Cloud (LMC) parallaxes and combine these results with measurements for six bright globular clusters. We calculated the angular covariance of EDR3 parallaxes at small separations (up to a few degrees) based on the LMC results and combined it with the results for larger angles using quasars to obtain an approximate analytical formula for the angular covariance over the whole sky. The results for the six globular clusters were used to validate the parallax bias correction as a function of magnitude, color, and ecliptic latitude and to determine the multiplicative constantkused to convert internal uncertainties to external ones.Results.The angular covariance at zero separation is estimated to be 106 μas2, yielding a minimum (systematic) uncertainty for EDR3 parallaxes of 10.3 μas for individual stars or compact stellar clusters. This value can be slightly reduced for globular clusters that span ≳30′ after considering the behavior of the angular covariance of the parallaxes for small separations. A recent parallax bias correction is found to work quite well, except perhaps for the brighter magnitudes, where improvements may be possible. The value ofkis found to be 1.1–1.7 and to depend onG. We find that stars with moderately large values of the renormalized unit weight error can still provide useful parallaxes, albeit with larger values ofk. We give accurate and preciseGaiaEDR3 distances to the six globular clusters, and for the specific case of 47 Tuc we are able to beat the angular covariance limit through the use of the background Small Magellanic Cloud as a reference and derive a high-precision distance of 4.53 ± 0.06 kpc. Finally, a recipe for the derivation of distances to stars and stellar clusters usingGaiaEDR3 parallaxes is given.
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Szabados, L. "Suggestion to Revise the Hipparcos-Parallax of Cepheids Belonging to Binary Systems." Highlights of Astronomy 11, no. 1 (1998): 580. http://dx.doi.org/10.1017/s1539299600022395.
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It has been suspected (Szabados 1997) that the apparent orbit of previously unresolved binaries involving a Cepheid component falsifies the Hipparcos-parallaxes deduced for these Cepheids. Since the incidence of binaries among Cepheids exceeds 50 per cent, this adverse effect on the parallax determination is a major error source.An obvious remedy is to repeat the determination of the five astrometric parameters for the Cepheids, members in binary systems, taking into accountthe orbital elements known from spectroscopic studies. This will result in more precise parallaxes and cosmic distance scale. Moreover, these Cepheidsare ideal targets for the future microarcsec astrometric missions.This study was partly supported by OTKA-grants T 014852 and T 022946.
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Zhao, Liang, Shoudong Huang, Yanbiao Sun, Lei Yan, and Gamini Dissanayake. "ParallaxBA: bundle adjustment using parallax angle feature parametrization." International Journal of Robotics Research 34, no. 4-5 (January 26, 2015): 493–516. http://dx.doi.org/10.1177/0278364914551583.
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Sun, Jun, Bing Lu, Xiao Hong Wu, and Jun Ming Li. "Study of the Parallax Correction Algorithm Based on the Multiple Regulatory Factors." Advanced Materials Research 466-467 (February 2012): 876–80. http://dx.doi.org/10.4028/www.scientific.net/amr.466-467.876.
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Binocular recognition extracts bitmap information based on different viewpoints of two horizontal lines. If it is not appropriate enough to deal with the left and right images, the computation of two images' horizontal parallaxes and vertical parallax will bring on the error. This article proposes one kind of effective algorithm that adjusts the image to be right based on traditional displacement correction algorithm, and completes the image remodeling through the two pairs of matching feature points and detection of the correlation distances. Experimental results show that the method can adjust the horizontal and vertical parallax effectively, so that the displaying effect of the stereoscopic image achieves best.
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Pan, X. P. "Systematic biases and uncertainties of Hipparcos parallax." Proceedings of the International Astronomical Union 3, S248 (October 2007): 78–81. http://dx.doi.org/10.1017/s1743921308018668.
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AbstractGround-based optical/IR interferometers have provided strong support to the space-based astrometric mission Hipparcos ever since the Hipparcos instrument was in operation in 1989. Interferometric observations also produced critical corrections of orbital motion to many targets, including radio stars, which link the Hipparcos system to the International Celestial Reference Frame (ICRF). In particular, orbital parallax from interferometers confirmed the 10% bias of the Pleiades distance from Hipparcos, and thus avoids revision of classical astronomy. Significant offsets and errors of Hipparcos parallax introduced by binary jitters are demonstrated in this work. By comparing the Hipparcos results with long baseline interferometry and other techniques including spectroscopy, multi-color photometry, Main-Sequence fitting, light curve measurements, Lunar occultation, Fine Guidance Sensor, etc., systematic biases and uncertainties of Hipparcos parallaxes are investigated and analyzed. We have established good models for major error sources of Hipparcos parallax, such as zonal bias, binary jitters, and luminosity-dependent errors. The lessons learned from the systematic biases of Hipparcos parallax are valuable to future space missions like SIM and Gaia.
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Grenon, M. "The Age of Old Galactic Populations." Highlights of Astronomy 11, no. 1 (1998): 560–61. http://dx.doi.org/10.1017/s1539299600022152.
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As a preparation to the HIPPARCOS mission, a large observing programme on NLTT stars (propermotion > 0.18 ″/yr) was started in Genevaphotometry. The original programme consists of 10047 stars brighter than mR = 11.5, or mR = 12.5 if of colour class m. Among them, 7813 targets could be included in the HIPPARCOS programme, selected according to their observability and internal priorities in favour of large parallaxe stars (photometric distances < 100 pc) and high-velocity stars. The bulk of new nearby, halo, mild-metal poor and SMR stars in the HIP Catalogue originates from this proposal (N° 139). No less than 208 new nearby stars with π ≥ 40 mas were discovered south of δ +10°, the closest has π(HIP)= 182 mas. Radial velocities were obtained with CORAVEL at OHP and ESO. Most aspects of the early evolution of the Galaxy may be addressed with this sample. Here we discuss, as examples, the ages of the thick disk and of the galactic bulge.
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Kervella, Pierre, Antoine Mérand, Alexandre Gallenne, Boris Trahin, Simon Borgniet, Grzegorz Pietrzynski, Nicolas Nardetto, and Wolfgang Gieren. "Optical interferometry and Gaia parallaxes for a robust calibration of the Cepheid distance scale." Proceedings of the International Astronomical Union 12, S330 (April 2017): 305–8. http://dx.doi.org/10.1017/s1743921317006792.
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AbstractWe present the modeling tool we developed to incorporate multi-technique observations of Cepheids in a single pulsation model: the Spectro-Photo-Interferometry of Pulsating Stars (SPIPS). The combination of angular diameters from optical interferometry, radial velocities and photometry with the coming Gaia DR2 parallaxes of nearby Galactic Cepheids will soon enable us to calibrate the projection factor of the classical Parallax-of-Pulsation method. This will extend its applicability to Cepheids too distant for accurate Gaia parallax measurements, and allow us to precisely calibrate the Leavitt law's zero point. As an example application, we present the SPIPS model of the long-period Cepheid RS Pup that provides a measurement of its projection factor, using the independent distance estimated from its light echoes.
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Kobayashi, H. "VERA status and results." Proceedings of the International Astronomical Union 8, S289 (August 2012): 194. http://dx.doi.org/10.1017/s1743921312021370.
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AbstractVERA is a Very Long Baseline Interferometry (VLBI) array for astrometry, composed of four 20 m radio telescopes. They are located over a range of around 2300 km in Japan. VERA consists of a two-beam system equipped with 2, 6.7, 8, 22, and 43 GHz receivers. The two-beam system is used for phase referencing of the VLBI observations, to compensate for atmospheric-turbulence effects between two nearby objects. It has achieved measurements of annual parallaxes within 5 kpc with 10% accuracy. Observed sources are water, SiO, and methanol masers, which are found in molecular gas around star-forming regions and evolved stars. We have carried out a large program of astrometry to reveal the Galaxy's structure and velocity field. VERA has already measured trigonometric parallaxes of more than 30 sources and observed around a hundred sources using the two-beam astrometry technique. Maser sources are associated with high-mass star-forming regions, which are thought to trace the arm structure of the Galaxy. Using annual parallax and proper-motion measurements, their structure will be shown without kinematic distance assumptions. Some sources exhibit large differences between trigonometric-parallax measurements and kinematic distances. We present the status of the VERA project as well as recent results.
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Tsujimoto, T., M. Miyamoto, and Y. Yoshii. "The Absolute Magnitude Of RR Lyrae Stars." Highlights of Astronomy 11, no. 1 (1998): 580. http://dx.doi.org/10.1017/s1539299600022383.
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The present determination of the absolute magnitude .Mv(RR) of RR Lyrae stars is twofold, relying upon Hipparcos proper motions and trigonometric parallaxes separately. First, applying the statistical parallax method to the proper motions, we find < Mv(RR)>= 0.69 ± 0.10 for 99 halo RR Lyraes with <[Fe/H]> = -1.58. Second, applying the Lutz-Kelker correction to the RR Lyrae HIP95497 with the most accurately measured parallax, we obtain Mv(RR) = 0.57-0.74 at [Fe/H]=-1.6. Furthermore, allowing full use of low accuracy and negative parallaxes as well for 125 RR Lyraes with - 2.49≤[Fe/H]≤0.07, the maximum likelihood estimation yields the relation, Mv(RR)= (0.59±0.37)+(0.20±0.63)([Fe/H]+1.60), which formally agrees with the recent preferred relation. The same estimation yields again My (RR) = 0.65 ± 0.33 for the 99 halo RR Lyraes. Although the formal errors in the latter two estimates are rather large, all of the four results suggest the fainter absolute magnitude, My(RR)=0.6-0.7 at [Fe/H]=-1.6. The present results still provide the lower limit on the age of the universe which is inconsistent with a fiat, matter-dominated universe and current estimates of the Hubble constant.
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Dahn, C. C. "Review of CCD parallax measurements." Symposium - International Astronomical Union 189 (1997): 19–24. http://dx.doi.org/10.1017/s0074180900116444.
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Several groups, using 1-m to 2-m telescopes on ‘visitor’ arrangements, have employed CCDs to measure stellar trigonometric parallaxes with precisions in the range ± 2–5 mas. More intensive observing efforts now routinely achieve sub-mas results with the best obtained to date in the ± 0.3–0.5 mas range. Selective dimming of bright target stars using neutral density spots now permit CCD parallax measures of stars as bright as R ~ 4.
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Choi, Yoon Kyung, Andreas Brunthaler, Karl M. Menten, and Mark J. Reid. "Trigonometric parallax of the protoplanetary nebula OH 231.8+4.2." Proceedings of the International Astronomical Union 7, S283 (July 2011): 330–31. http://dx.doi.org/10.1017/s1743921312011271.
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AbstractWe report trigonometric parallx measurements for H2O masers around the protoplanetary nebula OH 231.8+4.2 carried out with the Very Long Baseline Array. Based on astrometric monitoring for 1 year, we measured a trigonometric parallax of 0.89 ± 0.04 mas, corresponding to a distance of 1.12+0.05−0.05 kpc. This is the most accurate distance to OH 231.8+4.2, and the first one based on an annual parallax measurement. The distribution and internal motions of the H2O masers are consistent with the bipolar outflow suggested in literatures.
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Clementini, G., L. Eyer, V. Ripepi, M. Marconi, T. Muraveva, A. Garofalo, L. M. Sarro, et al. "Gaia Data Release 1." Astronomy & Astrophysics 605 (September 2017): A79. http://dx.doi.org/10.1051/0004-6361/201629925.
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Context. Parallaxes for 331 classical Cepheids, 31 Type II Cepheids, and 364 RR Lyrae stars in common between Gaia and the Hipparcos and Tycho-2 catalogues are published in Gaia Data Release 1 (DR1) as part of the Tycho-Gaia Astrometric Solution (TGAS). Aims. In order to test these first parallax measurements of the primary standard candles of the cosmological distance ladder, which involve astrometry collected by Gaia during the initial 14 months of science operation, we compared them with literature estimates and derived new period-luminosity (PL), period-Wesenheit (PW) relations for classical and Type II Cepheids and infrared PL, PL-metallicity (PLZ), and optical luminosity-metallicity (MV-[Fe/H]) relations for the RR Lyrae stars, with zero points based on TGAS. Methods. Classical Cepheids were carefully selected in order to discard known or suspected binary systems. The final sample comprises 102 fundamental mode pulsators with periods ranging from 1.68 to 51.66 days (of which 33 with σϖ/ϖ< 0.5). The Type II Cepheids include a total of 26 W Virginis and BL Herculis stars spanning the period range from 1.16 to 30.00 days (of which only 7 with σϖ/ϖ< 0.5). The RR Lyrae stars include 200 sources with pulsation period ranging from 0.27 to 0.80 days (of which 112 with σϖ/ϖ< 0.5). The new relations were computed using multi-band (V,I,J,Ks) photometry and spectroscopic metal abundances available in the literature, and by applying three alternative approaches: (i) linear least-squares fitting of the absolute magnitudes inferred from direct transformation of the TGAS parallaxes; (ii) adopting astrometry-based luminosities; and (iii) using a Bayesian fitting approach. The last two methods work in parallax space where parallaxes are used directly, thus maintaining symmetrical errors and allowing negative parallaxes to be used. The TGAS-based PL,PW,PLZ, and MV− [Fe/H] relations are discussed by comparing the distance to the Large Magellanic Cloud provided by different types of pulsating stars and alternative fitting methods. Results. Good agreement is found from direct comparison of the parallaxes of RR Lyrae stars for which both TGAS and HST measurements are available. Similarly, very good agreement is found between the TGAS values and the parallaxes inferred from the absolute magnitudes of Cepheids and RR Lyrae stars analysed with the Baade-Wesselink method. TGAS values also compare favourably with the parallaxes inferred by theoretical model fitting of the multi-band light curves for two of the three classical Cepheids and one RR Lyrae star, which were analysed with this technique in our samples. The K-band PL relations show the significant improvement of the TGAS parallaxes for Cepheids and RR Lyrae stars with respect to the Hipparcos measurements. This is particularly true for the RR Lyrae stars for which improvement in quality and statistics is impressive. Conclusions. TGAS parallaxes bring a significant added value to the previous Hipparcos estimates. The relations presented in this paper represent the first Gaia-calibrated relations and form a work-in-progress milestone report in the wait for Gaia-only parallaxes of which a first solution will become available with Gaia Data Release 2 (DR2) in 2018.
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Lindegren, L., J. Hernández, A. Bombrun, S. Klioner, U. Bastian, M. Ramos-Lerate, A. de Torres, et al. "Gaia Data Release 2." Astronomy & Astrophysics 616 (August 2018): A2. http://dx.doi.org/10.1051/0004-6361/201832727.
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Context. Gaia Data Release 2 (Gaia DR2) contains results for 1693 million sources in the magnitude range 3 to 21 based on observations collected by the European Space Agency Gaia satellite during the first 22 months of its operational phase. Aims. We describe the input data, models, and processing used for the astrometric content of Gaia DR2, and the validation of these resultsperformed within the astrometry task. Methods. Some 320 billion centroid positions from the pre-processed astrometric CCD observations were used to estimate the five astrometric parameters (positions, parallaxes, and proper motions) for 1332 million sources, and approximate positions at the reference epoch J2015.5 for an additional 361 million mostly faint sources. These data were calculated in two steps. First, the satellite attitude and the astrometric calibration parameters of the CCDs were obtained in an astrometric global iterative solution for 16 million selected sources, using about 1% of the input data. This primary solution was tied to the extragalactic International Celestial Reference System (ICRS) by means of quasars. The resulting attitude and calibration were then used to calculate the astrometric parameters of all the sources. Special validation solutions were used to characterise the random and systematic errors in parallax and proper motion. Results. For the sources with five-parameter astrometric solutions, the median uncertainty in parallax and position at the reference epoch J2015.5 is about 0.04 mas for bright (G < 14 mag) sources, 0.1 mas at G = 17 mag, and 0.7 masat G = 20 mag. In the proper motion components the corresponding uncertainties are 0.05, 0.2, and 1.2 mas yr−1, respectively.The optical reference frame defined by Gaia DR2 is aligned with ICRS and is non-rotating with respect to the quasars to within 0.15 mas yr−1. From the quasars and validation solutions we estimate that systematics in the parallaxes depending on position, magnitude, and colour are generally below 0.1 mas, but the parallaxes are on the whole too small by about 0.03 mas. Significant spatial correlations of up to 0.04 mas in parallax and 0.07 mas yr−1 in proper motion are seen on small (< 1 deg) and intermediate (20 deg) angular scales. Important statistics and information for the users of the Gaia DR2 astrometry are given in the appendices.
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Andrei, Alexandre H., Richard L. Smart, Beatrice Bucciarelli, Jucira L. Penna, Federico Marocco, Mario G. Lattanzi, Mariateresa Crosta, and Ramakrishna Teixeira. "The parsec program: a large sample of brown dwarf trigonometric parallaxes." Proceedings of the International Astronomical Union 8, S289 (August 2012): 48–51. http://dx.doi.org/10.1017/s1743921312021096.
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AbstractWe report on the parsec program, which observed 140 L and T dwarfs on a regular basis from 2007 to 2011, using the WIFI camera on the ESO/2.2 m telescope. Trigonometric parallaxes at 5 mas precision are derived for 49 objects, and mas yr−1-level proper motions are derived for approximately 200,000 objects in the same fields. We discuss image cleaning, object centroiding, and astrometric methods, in particular three different approaches for trigonometric parallax determination.
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Gontcharov, George A., and Aleksandr V. Mosenkov. "On the discrepancy between asteroseismic and Gaia DR1 TGAS parallaxes." Monthly Notices of the Royal Astronomical Society: Letters 470, no. 1 (May 29, 2017): L97—L101. http://dx.doi.org/10.1093/mnrasl/slx083.
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Abstract Recently, a deviation of the Gaia Tycho–Gaia Astrometric Solution (TGAS) parallaxes from the asteroseismic ones for giants was found. We show that for parallaxes ϖ < 1.5 mas it can be explained by a selection effect in favour of bright and luminous giants in the Tycho-2 and TGAS catalogues. Another explanation of this deviation seems to be valid for ϖ > 1.5 mas based on the best extinction estimates: The deviation may be caused not by a bias of parallax, but by an underestimation of the extinction (and, consequently, an overestimation of the calculated absolute magnitude) in the asteroseismic results. We demonstrate that the reliable estimates of the reddening and extinction (about 0.22 mag of the visual extinction for the Kepler field) better fit both the giants and main-sequence stars to the PARSEC, MIST and YaPSI isochrones.
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Kovalevsky, J. "Hipparcos Astrometric Results." Highlights of Astronomy 11, no. 1 (1998): 536–38. http://dx.doi.org/10.1017/s1539299600021973.
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AbstractThe astrometric results of Hipparcos include the positions at epoch (1991.25), the proper motion in the new IAU extragalactic reference system (ICRS), and parallaxes for about 118 000 stars. One dimensional positions are also given for 48 asteroids and 3 satellites. Due to the non-isotropy of the scanning law, the uncertainties are position dependent. Some indications of the remaining correlations are given. Various tests and comparisons show that systematic errors in parallax, if any, are not larger than 0.1 millisecond of arc.
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Ngeow, Chow-Choong, Anupam Bhardwaj, and Shashi M. Kanbur. "G-Band Period-Luminosity Relation For Galactic Cepheids Based on Gaia DR1 Measurements." Proceedings of the International Astronomical Union 12, S330 (April 2017): 337–38. http://dx.doi.org/10.1017/s1743921317006305.
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AbstractClassical Cepheids (hereafter Cepheids) are important standard candle as they obey the famous period-luminosity (PL) relation. Parallax measurements from Gaia offer a unique opportunity to derive or calibrate the PL relations for Galactic Cepheids, as traditionally their distances were measured via different methods. In this work, we attempted to derive the Gaia G-band PL relation based on the Gaia Data Release 1 (DR1) measurements. We adopted the inferred distances provided by Astraatmadja & Bailer-Jones (2016), calculated using two priors in a Bayesian analysis, and cross-matched to known Galactic Cepheids. The resulting G-band PL relation, however, exhibits a much larger scatter than expected. Hence the inferred distances based on the Gaia DR1 parallaxes are not suitable for calibrating the Galactic PL relation, and future Data Releases with improved parallax measurements are desirable.
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Lindegren, L., F. van Leeuwen, C. Petersen, and S. Söderhjelm. "First Results of the Sphere Solution Based on HIPPARCOS Data." Highlights of Astronomy 9 (1992): 413. http://dx.doi.org/10.1017/s1539299600009333.
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AbstractResults from a test solution of the positions and parallaxes for about 10,000 stars are presented in statistical form. The solution is based on about 1300 hours of Hipparcos observations made from November 1989 to February 1991, representing about 1/5 of the scientifically useful data collected in that period. Due to the short time span of the data no attempt was made to determine proper motions. The positions, many of which are already in the 2-5 milli-arcsec accuracy range, clearly reveal systematic errors of up to 0.2 arcsec in the ground-based positions of the Input Catalogue. Perhaps the most convincing evidence of the quality of the satellite data is provided by the distribution of trigonometric parallaxes determined in this solution. By comparison with the expected distribution of true parallaxes, based on a standard model of the Galaxy, we conclude that the external errors of the best parallaxes have a standard deviation around 5 milli-arcsec. Any global offset of the parallax zero point appears to be less than 1 milli-arcsec. The accuracy obtained is consistent with pre-launch predictions, if allowance is made for the reduced data collection efficiency due to the faulty orbit, and supports the assertion that the 2 milli-arcsec goal can still be reached in the present orbit. Details of the solution are being published in Astronomy & Astrophysics.
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Vasiliev, Eugene, and Holger Baumgardt. "Gaia EDR3 view on galactic globular clusters." Monthly Notices of the Royal Astronomical Society 505, no. 4 (May 24, 2021): 5978–6002. http://dx.doi.org/10.1093/mnras/stab1475.
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ABSTRACT We use the data from Gaia Early Data Release 3 (EDR3) to study the kinematic properties of Milky Way globular clusters. We measure the mean parallaxes and proper motions (PM) for 170 clusters, determine the PM dispersion profiles for more than 100 clusters, uncover rotation signatures in more than 20 objects, and find evidence for radial or tangential PM anisotropy in a dozen richest clusters. At the same time, we use the selection of cluster members to explore the reliability and limitations of the Gaia catalogue itself. We find that the formal uncertainties on parallax and PM are underestimated by $10{-}20{{\ \rm per\ cent}}$ in dense central regions even for stars that pass numerous quality filters. We explore the spatial covariance function of systematic errors, and determine a lower limit on the uncertainty of average parallaxes and PM at the level 0.01 mas and 0.025 mas yr$^{-1}$ , respectively. Finally, a comparison of mean parallaxes of clusters with distances from various literature sources suggests that the parallaxes for stars with $G>13$ (after applying the zero-point correction suggested by Lindegren et al.) are overestimated by $\sim 0.01\pm 0.003$ mas. Despite these caveats, the quality of Gaia astrometry has been significantly improved in EDR3 and provides valuable insights into the properties of star clusters.
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Benedict, G., W. Jefferys, B. McArthur, E. Nelan, A. Whipple, Q. Wang, D. Story, et al. "Hubble Space Telescope: A Generator of Sub-Milliarcsecond Precision Parallaxes." Symposium - International Astronomical Union 166 (1995): 89–94. http://dx.doi.org/10.1017/s0074180900227903.
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Hubble Space Telescope Fine Guidance Sensor 3 can generate sub-milliarcsecond precision parallaxes in eighteen months. We discuss the internal precision and external accuracy of our observations of Proxima Centauri and Barnard's Star. For some classes of targets Hubble Space Telescope will remain the parallax tool of choice for years to come. It can offer 0.5 mas precision. It will remain useful by satisfying urgent needs for quick results, by offering a 13 magnitude dynamic range, and by providing an unparalleled binary dissection capability.
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Aghakhanloo, Mojgan, Jeremiah W. Murphy, Nathan Smith, John Parejko, Mariangelly Díaz-Rodríguez, Maria R. Drout, Jose H. Groh, Joseph Guzman, and Keivan G. Stassun. "Inferring the parallax of Westerlund 1 from Gaia DR2." Monthly Notices of the Royal Astronomical Society 492, no. 2 (December 31, 2019): 2497–509. http://dx.doi.org/10.1093/mnras/stz3628.
Full textAbstract:
ABSTRACT Westerlund 1 (Wd1) is potentially the largest star cluster in the Galaxy. That designation critically depends upon the distance to the cluster, yet the cluster is highly obscured, making luminosity-based distance estimates difficult. Using Gaia Data Release 2 (DR2) parallaxes and Bayesian inference, we infer a parallax of $0.35^{+0.07}_{-0.06}$ mas corresponding to a distance of $2.6^{+0.6}_{-0.4}$ kpc. To leverage the combined statistics of all stars in the direction of Wd1, we derive the Bayesian model for a cluster of stars hidden among Galactic field stars; this model includes the parallax zero-point. Previous estimates for the distance to Wd1 ranged from 1.0 to 5.5 kpc, although values around 5 kpc have usually been adopted. The Gaia DR2 parallaxes reduce the uncertainty from a factor of 3 to 18 per cent and rules out the most often quoted value of 5 kpc with 99 per cent confidence. This new distance allows for more accurate mass and age determinations for the stars in Wd1. For example, the previously inferred initial mass at the main-sequence turn-off was around 40 M⊙; the new Gaia DR2 distance shifts this down to about 22 M⊙. This has important implications for our understanding of the late stages of stellar evolution, including the initial mass of the magnetar and the LBV in Wd1. Similarly, the new distance suggests that the total cluster mass is about four times lower than previously calculated.