Journal articles: 'Binary stars Survey SARG'

1

Ratajczak, Milena, Maciej Konacki, Shrinivas R. Kulkarni, and Matthew W. Muterspaugh. "The Keck I/HIRES and TNG/SARG Radial Velocity Survey of Speckle Binaries." Proceedings of the International Astronomical Union 7, S282 (July 2011): 472–73. http://dx.doi.org/10.1017/s1743921311028146.

Full text

Abstract:

AbstractA sample of about 160 speckle binary stars was observed with the Keck I telescope and its Échelle HIRES spectrograph over the years 2003-2007 in an effort to detect substellar and planetary companions to components of binary and multiple star systems. This data set was supplemented with the data obtained at the TNG telescope equipped with the SARG Échelle spectrograph over the years 2006-2007. The high-resolution (R = 65000 for HIRES and R = 86000 for SARG) and high signal-to-noise (typically 75-150) spectra were used to derive radial velocities of the components of the observed speckle binaries. Here, we present a summary of this effort, which includes the discovery of new triple star systems and improved orbital solutions of a few known binaries.

APA, Harvard, Vancouver, ISO, and other styles

2

Carolo, Elena, Silvano Desidera, Raffaele Gratton, Aldo Martinez Fiorenzano, Michael Endl, Rosario Cosentino, Mauro Barbieri, et al. "Planet candidates from the SARG visual binary survey." Proceedings of the International Astronomical Union 6, S276 (October 2010): 403–4. http://dx.doi.org/10.1017/s1743921311020539.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Sissa, E., R. Gratton, S. Desidera, A. F. Martinez Fiorenzano, A. Bonfanti, E. Carolo, D. Vassallo, R. U. Claudi, M. Endl, and R. Cosentino. "Hα-activity and ages for stars in the SARG survey." Astronomy & Astrophysics 596 (December 2016): A76. http://dx.doi.org/10.1051/0004-6361/201628531.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Matijevič, G., T. Zwitter, and U. Munari. "Binary stars in the RAVE survey." EPJ Web of Conferences 19 (2012): 09006. http://dx.doi.org/10.1051/epjconf/20121909006.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Traven, G., S. Feltzing, T. Merle, M. Van der Swaelmen, K. Čotar, R. Church, T. Zwitter, et al. "The GALAH survey: multiple stars and our Galaxy." Astronomy & Astrophysics 638 (June 2020): A145. http://dx.doi.org/10.1051/0004-6361/202037484.

Full text

Abstract:

Context. Binary stellar systems form a large fraction of the Galaxy’s stars. They are useful as laboratories for studying the physical processes taking place within stars, and must be correctly taken into account when observations of stars are used to study the structure and evolution of the Galaxy. The advent of large-scale spectroscopic and photometric surveys allows us to obtain large samples of binaries that permit characterising their populations. Aims. We aim to obtain a large sample of double-lined spectroscopic binaries (SB2s) by analysis of spectra from the GALAH survey in combination with photometric and astrometric data. A combined analysis will provide stellar parameters of thousands of binary stars that can be combined to form statistical observables of a given population. We aim to produce a catalogue of well-characterised systems, which can in turn be compared to models of populations of binary stars, or to follow-up individual systems of interest. Methods. We obtained a list of candidate SB2 systems from a t-distributed stochastic neighbour embedding (t-SNE) classification and a cross-correlation analysis of GALAH spectra. To compute parameters of the primary and secondary star, we used a Bayesian approach that includes a parallax prior from Gaia DR2, spectra from GALAH, and apparent magnitudes from APASS, Gaia DR2, 2MASS, and WISE. We used a Markov chain Monte Carlo approach to sample the posterior distributions of the following model parameters for the two stars: Teff[1,2], logg[1,2], [Fe/H], Vr[1,2], vmic[1,2], vbroad[1,2], R[1,2], and E(B−V). Results. We present results for 12 760 binary stars detected as SB2s. We construct the statistical observables T1∕T2, ΔVr, and R1∕R2, which demonstrate that our sample mostly consists of dwarfs, with a significant fraction of evolved stars and several dozen members of the giant branch. The majority of these binary stars is concentrated at the lower boundary of the ΔVr distribution, and the R1∕R2 ratio is mostly close to unity. The derived metallicity of our binary stars is statistically lower than that of single dwarf stars from the same magnitude-limited sample. Conclusions. Our sample of binary stars represents a large population of well-characterised double-lined spectroscopic binaries that are appropriate for statistical studies of the binary populations. The derived stellar properties and their distributions show trends that are expected for a population of close binary stars (a < 10 AU) detected through double lines in their spectra. Our detection technique allows us to probe binary systems with mass ratios 0.5 ≤q ≤ 1.

APA, Harvard, Vancouver, ISO, and other styles

6

Martínez Fiorenzano, A. F., R. G. Gratton, S. Desidera, R. Cosentino, M. Cecconi, and M. Endl. "Line bisector analysis of stars with companions in the SARG survey at the TNG." EAS Publications Series 42 (2010): 137–41. http://dx.doi.org/10.1051/eas/1042013.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Baade, Dietrich. "Binary Be Stars and Be Binaries." Symposium - International Astronomical Union 151 (1992): 147–56. http://dx.doi.org/10.1017/s0074180900122144.

Full text

Abstract:

Two hypotheses have been put forward for the rôle of binarity in Be stars: (1) All Be stars are interacting binaries. (2) Roughly one-half of the observed Be stars are post-mass exchange binaries with compact companions. Contrary to (1), (2) does not attempt to explain also the existence of disks in Be stars. After the spin-up by mass and angular momentum transfer, the B star somehow has to succeed to form and maintain the disk. Since rapid rotation is only necessary but not sufficient for this transformation, the effect of duplicity would merely be to give more stars the opportunity to become a Be star. Model (1) is not nearly realistic as is also underlined by a new spectroscopic survey for cool companions. The verification of (2) on the basis of the ROSAT All-Sky Survey has just begun; but a serious deficiency of white dwarf companions is already apparent. Binarity currently provides no extra clue on the origin of the Be phenomenon.

APA, Harvard, Vancouver, ISO, and other styles

8

Bergfors, Carolina, Wolfgang Brandner, Stefan Hippler, Thomas Henning, Markus Janson, and Felix Hormuth. "The AstraLux Binary M Dwarfs Survey." Proceedings of the International Astronomical Union 7, S282 (July 2011): 460–61. http://dx.doi.org/10.1017/s1743921311028080.

Full text

Abstract:

AbstractBinary/multiple properties provide clues to the formation of stars. In the AstraLux binary survey, we use the Lucky Imaging technique to search for companions to a large sample of young, nearby M dwarfs. We present results from observations of the first sub-sample, consisting of 124 M dwarfs in the southern sky.

APA, Harvard, Vancouver, ISO, and other styles

9

Ritchie, B. W., J. S. Clark, I. Negueruela, and F. Najarro. "A VLT/FLAMES survey for massive binaries in Westerlund 1." Astronomy & Astrophysics 660 (April 2022): A89. http://dx.doi.org/10.1051/0004-6361/202142405.

Full text

Abstract:

Context. The galactic cluster Westerlund 1 contains a rich population of evolved, massive stars. A high binary fraction has been inferred from previous multi-wavelength observations. Aims. We use multi-epoch spectroscopy of a large sample of early-type stars in Westerlund 1 to identify new binaries and binary candidates in the cluster. Methods. VLT/FLAMES was used with the GIRAFFE spectrograph in HR21 mode to obtain spectra of ∼100 OB stars over a 14-month baseline in 2008 and 2009, supplemented with follow-up observations in 2011 and 2013. Radial velocities were obtained from strong Paschen series absorption lines in the I-band. Results. We identify 20 new OB I–III binaries, a WN9h binary, and a WC9d binary, greatly increasing the number of directly confirmed binary systems in Westerlund 1, while 12 O9−9.5 Iab−III stars are identified as candidate binaries based on radial velocity changes that are inconsistent with photospheric variability. The 173.9 day SB1 W1030 represents the first longer-period system identified in the cluster, while the determination of a 53.95 day period for W44 (WR L) makes it the first Wolf-Rayet binary in Westerlund 1 with a confirmed orbital period greater than ten days. Our results suggest the binary fraction in the OB population is at least ∼40%, and may be significantly higher. Conclusions. These results demonstrate that binary systems can be effectively identified in the population of OB I−III stars evolving off the main sequence in Westerlund 1. Future multi-epoch surveys will be able to fully characterise this population.

APA, Harvard, Vancouver, ISO, and other styles

10

Budding, E., O. B. Slee, and K. Jones. "Further Discussion of Binary Star Radio Survey Data." Publications of the Astronomical Society of Australia 15, no. 2 (1998): 183–88. http://dx.doi.org/10.1071/as98183.

Full text

Abstract:

AbstractStatistical information on 8280 individual radio observations of binary stars, predominantly at 8·4 GHz using the Parkes 64 m antenna, is presented. Three main groups are distinguished: (i) RS CVn stars, (ii) classical Algol binaries (EA2s), and (iii) detached pairs of generally early type (ETBs).The RS CVn stars more frequently gave rise to detectable fluxes, while the ETBs, in these data, are a small and rather heterogeneous class. The Algols' emission appears to increase near conjunction phases, though we cannot clearly distinguish any special property of the Algols' phase-dependent behaviour that is not also shared by the RS CVn binaries. Both these categories' data show a bimodal, phase-dependent pattern to the distribution of detections, suggesting that these binary types share similar underlying physical properties, though there could also be other factors at play. The sample sizes of the Algols and particularly the ETB detections are too small for effective, discriminatory statistics, however.

APA, Harvard, Vancouver, ISO, and other styles

11

Guerrero Roncel, Martín A., and You-Hua Chu. "An X-ray survey of Wolf-Rayet stars in the Magellanic Clouds." Symposium - International Astronomical Union 212 (2003): 718–19. http://dx.doi.org/10.1017/s0074180900213193.

Full text

Abstract:

We have used archival Chandra-acis observations to search for X-ray emission from WR stars in the Magellanic Clouds (MCs), where the low interstellar absorption and known distances make it easy to compare X-ray luminosities with spectral types and binary status of WR stars. We have detected X-ray emission from ~20 WR stars in the MCs with X-ray luminosities of 6.6×1032-1.4×1035 ergs s–1. The analysis of the X-ray spectra of the brightest sources indicates that the X-ray emitting gas has temperatures ≥ 1.0×107 K, as expected in colliding winds. We will compare these results with the binary status of the WR stars to determine the amounts of the X-ray emission produced in the colliding winds for WR stars in binary systems and to assess the X-ray emission from single WR stars.

APA, Harvard, Vancouver, ISO, and other styles

12

Patrick, L. R., D. J. Lennon, N. Britavskiy, C. J. Evans, H. Sana, W. D. Taylor, A. Herrero, et al. "The VLT-FLAMES Tarantula Survey." Astronomy & Astrophysics 624 (April 2019): A129. http://dx.doi.org/10.1051/0004-6361/201834951.

Full text

Abstract:

Aims. The incidence of multiplicity in cool, luminous massive stars is relatively unknown compared to their hotter counterparts. In this work we present radial velocity (RV) measurements and investigate the multiplicity properties of red supergiants (RSGs) in the 30 Doradus region of the Large Magellanic Cloud using multi-epoch visible spectroscopy from the VLT-FLAMES Tarantula Survey. Methods. Exploiting the high density of absorption features in visible spectra of cool stars, we used a novel slicing technique to estimate RVs of 17 candidate RSGs in 30 Doradus from cross-correlation of the observations with model spectra. Results. We provide absolute RV measurements (precise to better than ±1 km s−1) for our sample and estimate line-of-sight velocities for the Hodge 301 and SL 639 clusters, which agree well with those of hot stars in the same clusters. By combining results for the RSGs with those for nearby B-type stars, we estimate systemic velocities and line-of-sight velocity dispersions for the two clusters, obtaining estimates for their dynamical masses of log(Mdyn/M⊙) = 3.8 ± 0.3 for Hodge 301, and an upper limit of log(Mdyn/M⊙) < 3.1 ± 0.8 for SL 639, assuming virial equilibrium. Analysis of the multi-epoch data reveals one RV variable, potential binary candidate (VFTS 744), which is likely a semi-regular variable asymptotic giant branch star. Calculations of semi-amplitude velocities for a range of RSGs in model binary systems and literature examples of binary RSGs were used to guide our RV variability criteria. We estimate an upper limit on the observed binary fraction for our sample of 0.3; for this sample we are sensitive to maximum periods for individual objects in the range 1–10 000 days and mass ratios above 0.3 depending on the data quality. From simulations of RV measurements from binary systems given the current data, we conclude that systems within the parameter range q > 0.3, log P [days] < 3.5 would be detected by our variability criteria at the 90% confidence level. The intrinsic binary fraction, accounting for observational biases, is estimated using simulations of binary systems with an empirically defined distribution of parameters in which orbital periods are uniformly distributed in the 3.3 < log P [days] < 4.3 range. A range of intrinsic binary fractions are considered; a binary fraction of 0.3 is found to best reproduce the observed data. Conclusions. We demonstrate that RSGs are effective extragalactic kinematic tracers by estimating the kinematic properties, including the dynamical masses of two LMC young massive clusters. In the context of binary evolution models, we conclude that the large majority of our sample consists of effectively single stars that are either currently single or in long-period systems. Further observations at greater spectral resolution or over a longer baseline, or both, are required to search for such systems.

APA, Harvard, Vancouver, ISO, and other styles

13

Siegler, Nick, Laird M. Close, Eric E. Mamajek, and Melanie Freed. "Discovery of Three Very Low Mass Binary Systems: An Adaptive Optics Survey of M6.0–M7.5 Stars." Symposium - International Astronomical Union 211 (2003): 257–60. http://dx.doi.org/10.1017/s0074180900210681.

Full text

Abstract:

We have used the adaptive optics system Hōkūpa'a at Gemini North to search for companions from a flux-limited (Ks > 12) survey of 30 nearby M6.0–M7.5 dwarfs. Our observations, which are sensitive to companions with separations > 0.1″ (~ 2.8 AU), detect 3 new binary systems. This implies an overall binary fraction of 9±4% for M6.0–M7.5 binaries. This binary frequency is somewhat less than the 19±7% measured for late M stars and ~ 20% for L stars, but is still statistically consistent. However, the result is significantly lower than the binary fractions observed amongst solar mass main sequence stars (~60%) and early M stars (~35%).

APA, Harvard, Vancouver, ISO, and other styles

14

Matijevič, G., T. Zwitter, U. Munari, O. Bienaymé, J. Binney, J. Bland-Hawthorn, C. Boeche, et al. "DOUBLE-LINED SPECTROSCOPIC BINARY STARS IN THE RAVE SURVEY." Astronomical Journal 140, no. 1 (June 8, 2010): 184–95. http://dx.doi.org/10.1088/0004-6256/140/1/184.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Albrecht, Simon, J. N. Winn, D. C. Fabrycky, G. Torres, and J. Setiawan. "The BANANA Survey: Spin-Orbit Alignment in Binary Stars." Proceedings of the International Astronomical Union 7, S282 (July 2011): 397–98. http://dx.doi.org/10.1017/s1743921311027906.

Full text

Abstract:

AbstractBinaries are not always neatly aligned. Previous observations of the DI Herculis system showed that the spin axes of both stars are highly inclined with respect to one another and the orbital axis. Here, we report on our ongoing survey to measure relative orientations of spin-axes in a number of eclipsing binary systems.These observations will hopefully lead to new insights into star and planet formation, as different formation scenarios predict different degrees of alignment and different dependencies on the system parameters. Measurements of spin-orbit angles in close binary systems will also create a basis for comparison for similar measurements involving close-in planets.

APA, Harvard, Vancouver, ISO, and other styles

16

Clark, J. S., F. Najarro, I. Negueruela, B. W. Ritchie, C. González-Fernández, and M. E. Lohr. "A VLT/FLAMES survey for massive binaries in Westerlund 1." Astronomy & Astrophysics 623 (March 2019): A83. http://dx.doi.org/10.1051/0004-6361/201834245.

Full text

Abstract:

Context. Recent observational studies indicate that a large number of OB stars are found within binary systems which may be expected to interact during their lifetimes. Significant mass transfer or indeed merger of both components is expected to modify evolutionary pathways, facilitating the production of exceptionally massive stars which will present as blue stragglers. Identification and characterisation of such objects is crucial if the efficiency of mass transfer is to be established; a critical parameter in determining the outcomes of binary evolutionary channels. Aims. The young and coeval massive cluster Westerlund 1 hosts a rich population of X-ray bright OB and Wolf–Rayet stars where the emission is attributed to shocks in the wind collision zones of massive binaries. Motivated by this, we instigated a study of the extremely X-ray luminous O supergiants Wd1-27 and -30a. Methods. We subjected a multi-wavelength and -epoch photometric and spectroscopic dataset to quantitative non-LTE model atmosphere and time-series analysis in order to determine fundamental stellar parameters and search for evidence of binarity. A detailed examination of the second Gaia data release was undertaken to establish cluster membership. Results. Both stars were found to be early/mid-O hypergiants with luminosities, temperatures and masses significantly in excess of other early stars within Wd1, hence qualifying as massive blue stragglers. The binary nature of Wd1-27 remains uncertain but the detection of radial velocity changes and the X-ray properties of Wd1-30a suggest that it is a binary with an orbital period ≤10 days. Analysis of Gaia proper motion and parallactic data indicates that both stars are cluster members; we also provide a membership list for Wd1 based on this analysis. Conclusions. The presence of hypergiants of spectral types O to M within Wd1 cannot be understood solely via single-star evolution. We suppose that the early-B and mid-O hypergiants formed via binary-induced mass-stripping of the primary and mass-transfer to the secondary, respectively. This implies that for a subset of objects massive star-formation may be regarded as a two-stage process, with binary-driven mass-transfer or merger yielding stars with masses significantly in excess of their initial “birth” mass.

APA, Harvard, Vancouver, ISO, and other styles

17

Bergfors, Carolina, Wolfgang Brandner, Sebastian Daemgen, and Thomas Henning. "Lucky Imaging Survey for Binary Exoplanet Hosts." Proceedings of the International Astronomical Union 7, S282 (July 2011): 193–94. http://dx.doi.org/10.1017/s1743921311027311.

Full text

Abstract:

AbstractBinary or multiple stars are common in our neighbourhood, and many of the exoplanets we know of belong to a star in such a system. The influence of a second star on planet formation can be probed by comparing properties of planets in binary/multiple-star systems with those of single-star planets. We present some of the results from our Lucky Imaging survey for binary companions to hosts of transiting exoplanets.

APA, Harvard, Vancouver, ISO, and other styles

18

Quist, Carl F., and Lennart Lindegren. "Binarity of Hipparcos Main Sequence Survey Stars." Symposium - International Astronomical Union 200 (2001): 64–68. http://dx.doi.org/10.1017/s0074180900225060.

Full text

Abstract:

Hipparcos observations of double stars, mainly A and F primaries, are modelled in order to check the statistics of double-star solutions in the Hipparcos Catalogue and to set quantitative limits on binary distributions. The number of companions per primary is estimated to 0.25 ± 0.05 for semi-major axes from 1 to 10 AU, and to 0.43 ± 0.20 for the range 10–100 AU. The total multiplicity found is between 0.9 and 1.2.

APA, Harvard, Vancouver, ISO, and other styles

19

Gray, Сandace, and Paul A. Mason. "A VLA Survey of Magnetic Cataclysmic Variable Stars." International Astronomical Union Colloquium 194 (July 2004): 267. http://dx.doi.org/10.1017/s0252921100153114.

Full text

Abstract:

Cataclysmic Variables (CVs) are close binaries containing a white dwarf primary and a Rochelobe filling red dwarf secondary. In magnetic CVs (MCVs) the white dwarfs have magnetic fields that are sufficiently strong (106 – 108 Gauss) to direct the accretion flow onto the surface of the primary. MCVs are divided into the lower field intermediate polars (IPs) and the higher field polars. Typically, IPs have accretion disks that are disrupted in the center and magnetically channelled flow onto the poles. Polars are diskless, an accretion stream flowing from the inner Lagrangian point impacts directly onto one or both magnetic poles. In addition, polars tend to have white dwarfs which rotate in synchronism with the binary orbit, while IPs have white dwarfs which rotate faster than the binary period. There are a few rare exceptions to this characterization, such as the slightly asynchronous polars and the stream-fed IPs.

APA, Harvard, Vancouver, ISO, and other styles

20

Halbwachs, J. L., M. Mayor, and S. Udry. "Multiplicity among solar-type stars." Astronomy & Astrophysics 619 (November 2018): A81. http://dx.doi.org/10.1051/0004-6361/201833377.

Full text

Abstract:

Context. The statistical properties of binary stars are clues for understanding their formation process. A radial velocity survey was carried on amongst nearby G-type stars and the results were published in 1991. Aims. The survey of radial velocity measurements was extended towards K-type stars. Methods. A sample of 261 K-type stars was observed with the spectrovelocimeter CORAVEL (COrrelation RAdial VELocities). Those stars with a variable radial velocity were detected on the basis of the P(Χ2) test. The orbital elements of the spectroscopic binaries were then derived. Results. The statistical properties of binary stars were derived from these observations and published in 2003. We present the catalogue of the radial velocity measurements obtained with CORAVEL for all the K stars of the survey and the orbital elements derived for 34 spectroscopic systems. In addition, the catalogue contains eight G-type spectroscopic binaries that have received additional measurements since 1991 and for which the orbital elements are revised or derived for the first time.

APA, Harvard, Vancouver, ISO, and other styles

21

De Rosa, R. J., B. Smith, J. Bulger, J. Patience, C. Marois, I. Song, B. Macintosh, J. Graham, R. Doyon, and M. Bessell. "Debris Disks and Multiplicity within the 75pc Volume-limited A-Star (VAST) Survey." Proceedings of the International Astronomical Union 8, S299 (June 2013): 334–35. http://dx.doi.org/10.1017/s174392131300882x.

Full text

Abstract:

AbstractWe present the preliminary findings of an investigation of the multiplicity of debris disk stars identified within our Volume-limited A-star (VAST) multiplicity survey. Previous studies have produced conflicting results regarding the multiplicity fraction of debris disk-hosting stars compared with non-excess stars. By combining our large-scale volume-limited AO survey of A-type stars with the all-sky WISE catalogue, we have investigated the frequency of binary companions to a large sample of A-type stars with and without measured 22μm excess. The results of this study will allow for a greater understanding of the interaction between a companion star and a circumstellar debris disk, informing future study into the formation and stability of planetary-mass companions within binary systems.

APA, Harvard, Vancouver, ISO, and other styles

22

Mason, B. D., H. A. McAlister, and W. I. Hartkopf. "A Speckle Duplicity Survey of the Hyades Cluster." International Astronomical Union Colloquium 135 (1992): 561–63. http://dx.doi.org/10.1017/s0252921100007156.

Full text

Abstract:

Due to its proximity to the Sun, the Hyades serves the critical role of luminosity calibration of all cluster main sequences, and hence is one of the lower rungs in the cosmic distance ladder. We attempt here to use the enhanced capabilities of speckle interferometry, in comparison with classical techniques, to add to the list of binary and multiple stars in the Hyades. New systems will not only eventually help to improve our knowledge of the cluster distance, but they will also help further our understanding of the formation and evolution of binary and multiple stars in the cluster environment.

APA, Harvard, Vancouver, ISO, and other styles

23

Mason, Brian D., Douglas R. Gies, William I. Hartkopf, William G. Bagnuolo, Jr., Theo ten Brummelaar, and Harold A. McAlister. "ICCD Speckle Observations of Binary Stars. XIX. An Astrometric/Spectroscopic Survey of O Stars." Astronomical Journal 115, no. 2 (February 1998): 821–47. http://dx.doi.org/10.1086/300234.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Ghez, A., G. Neugebauer, and K. Matthews. "A Two-Dimensional Near—Infrared Speckle Imaging Survey of T Tauri Stars in Taurus and Ophiuchus." International Astronomical Union Colloquium 135 (1992): 1–9. http://dx.doi.org/10.1017/s0252921100006059.

Full text

Abstract:

AbstractWe present the results of a magnitude limited (K≤8.5 mag) multiplicity survey of T Tauri stars in the two nearest star forming regions, Taurus-Auriga and Ophiuchus-Scorpius (D = 150 pc), observable from the northern hemisphere. Each of the 70 stars in the sample was imaged at 2.2 μm using two-dimensional speckle interferometry resulting in a survey sensitive to binary stars with separations ranging from 0.″09 to about 2″.5.The frequency of double stars with separation in this range is 46±8%. A division between the classical T Tauri stars and the weak-lined T Tauri stars shows no distinction. Furthermore, no difference is observed between the binary frequencies in the two star forming regions although the clouds have very different properties.Given the limited angular separation range that this survey is sensitive to, both the spectroscopic and wide binaries will be missed. The rate at which binaries are detected suggests that most, if not all, T Tauri stars have companions.

APA, Harvard, Vancouver, ISO, and other styles

25

Ruiz–Lapuente, Pilar, Jonay González Hernández, Hugo Tabernero, David Montes, Ramon Canal, Javier Mendez, and Luigi Bedin. "Survey for the Binary Progenitor in SN1006 and Update on SN1572." Proceedings of the International Astronomical Union 7, S281 (July 2011): 322–25. http://dx.doi.org/10.1017/s1743921312015293.

Full text

Abstract:

AbstractWe have completed a survey down to R = 15 mag of the stars within a circle of 4 arcmin radius around the nominal center of the remnant of SN 1006, one of the three historical Type Ia supernovae (the other two being SN 1572 and SN 1604), in search of a possible surviving binary companion of the white dwarf whose explosion gave rise to the supernova. The stellar parameters (effective temperature, surface gravity, and metallicity), as well as the radial velocities of all the stars, have been measured from spectra obtained with the UVES spectrograph at the VLT, and from the former and the available photometry, distances have been determined. Chemical abundances of the Fe-peak elements Cr, Mn, Co, and Ni have also been measured to check for possible contamination of the stellar surface by the supernova ejecta. The limiting magnitude of the survey would allow us to find stellar companions of the red-giant type, subgiant stars, and main–sequence stars down to F5–6. Unlike in SN 1572, where a subgiant of type G0–1 has been proposed as the companion of SN 1572, for SN 1006 we can discard the possibility that SN 1006 had a red giant or subgiant companion.

APA, Harvard, Vancouver, ISO, and other styles

26

Kuruwita, Rajika L., Michael Ireland, Aaron Rizzuto, Joao Bento, and Christoph Federrath. "Multiplicity of disc-bearing stars in Upper Scorpius and Upper Centaurus-Lupus." Monthly Notices of the Royal Astronomical Society 480, no. 4 (August 3, 2018): 5099–112. http://dx.doi.org/10.1093/mnras/sty2108.

Full text

Abstract:

ABSTRACT We present observations of disc-bearing stars in Upper Scorpius (US) and Upper Centaurus-Lupus (UCL) with moderate resolution spectroscopy in order to determine the influence of multiplicity on disc persistence after ${\sim }5\hbox{--}20\, \mathrm{Myr}$. Discs were identified using infrared (IR) excess from the Wide-field Infrared Survey Explorer (WISE) survey. Our survey consists of 55 US members and 28 UCL members, using spatial and kinematic information to assign a probability of membership. Spectra are gathered from the ANU 2.3 m telescope using the Wide Field Spectrograph (WiFeS) to detect radial velocity variations that indicate the presence of a companion. We identify two double-lined spectroscopic binaries, both of which have strong IR excess. We find the binary fraction of disc-bearing stars in US and UCL for periods up to 20 yr to be $0.06^{+0.07}_{-0.02}$ and $0.13^{+0.06}_{-0.03}$, respectively. Based on the multiplicity of field stars, we obtain an expected binary fraction of ${\sim }0.12^{+0.02}_{-0.01}$. The determined binary fractions for disc-bearing stars do not vary significantly from the field, suggesting that overall lifetime of discs may not differ between single and binary star systems.

APA, Harvard, Vancouver, ISO, and other styles

27

Zinnecker, H., R. Köhler, and H. Jahreiß. "Binary Statistics Among Population II Stars." International Astronomical Union Colloquium 191 (August 2004): 33–36. http://dx.doi.org/10.1017/s0252921100008393.

Full text

Abstract:

AbstractPopulation II stars are old, metal-poor, Galactic halo stars with high proper motion. We have carried out a visual binary survey of 164 halo stars in the solar neighborhood (median distance 100 pc), using infrared speckle interferometry, adaptive optics, and wide field direct imaging. The sample is based on the lists of Population II stars of Carney et al. (1994) and Norris (1986), with reliable distances from HIPPARCOS measurements.At face value, we found 33 binaries, 6 triples, and 1 quadruple system. When we limit ourselves to K-band flux ratios larger than 0.1 (to avoid background contamination), the numbers drop to 9 binaries and 1 triple, corresponding to a binary frequency of 6–7% above our angular resolution limit of about 0.1 arcsec. If we count all systems with K-band flux ratios greater than 0.01, we obtain 15 more binaries and 3 more triples, corresponding to a binary frequency for projected separations in excess of 10 AU of around 20 %. This is to be compared with the frequency of spectroscopic binaries (up to a period of 3000 days) of Population II stars of about 15 % (Latham et al. 2002). We also determined a semi-major axis distribution for our visual Population II binary and triple systems, which appears to be remarkably different from that of Population I stars. Second epoch-observations must help confirm the reality of our results.

APA, Harvard, Vancouver, ISO, and other styles

28

White, Russel J., and Andrea M. Ghez. "Young Binary Stars in Taurus-Auriga." Symposium - International Astronomical Union 200 (2001): 332–41. http://dx.doi.org/10.1017/s0074180900225382.

Full text

Abstract:

We present the results of a high spatial resolution ultraviolet, optical and near-infrared survey of 44 young binary stars in Taurus-Auriga with separations of 10–1000 AU. The observations were carried out using the Hubble Space Telescope and NASA's IRTF. The binary star properties corroborate our previous work that suggests fragmentation is the dominant binary star formation mechanism. Of particular interest, we find that the components of binary systems are more coeval than randomly paired single T Tauri stars. Several important conclusions are drawn regarding the evolution of circumstellar material in binary systems. The mass accretion rates for primary stars are similar to single stars, which suggests that a companion as close as 10 AU has little effect on the mass accretion rate. These accretion rates, if constant, require replenishment of the inner circumstellar disks for at least the closest (≲ 100 AU) binary systems. On average, circumprimary disks appear to survive longer and accrete at a higher rate than circumsecondary disks do. This suggests that circumprimary disks are being preferentially replenished, possibly from a circumbinary reservoir with low angular momentum relative to the binary. The relative T Tauri types and the binary mass ratios tentatively suggest that systems with separations ≲ 200 AU share a common circumbinary reservoir. The higher mass accretion rates of primary stars relative to secondary stars is most likely due to their larger relative mass.

APA, Harvard, Vancouver, ISO, and other styles

29

Williams, Thomas R. "Roberts of Lovedale and Eclipsing Binary Stars." International Astronomical Union Colloquium 98 (1988): 48–49. http://dx.doi.org/10.1017/s0252921100092162.

Full text

Abstract:

Alexander William Roberts, a great humanitarian and teacher in South Africa, was also a luminary in the astronomical world. This paper discusses his work on variable stars and touches briefly on his career in other areas. Born and educated in Scotland, Roberts migrated to South Africa in 1883, at age 25, to teach at the Native College at Lovedale. He studied mathematical astronomy as a recreational pursuit, but became an active observer in 1889. After two years of general observing, be began a systematic survey using binoculars and an old one-inch theodolite. He carefully plotted all visible stars in selected areas and ranked them in order of their apparent brightness, doing so repeatedly on six evenings for each of the selected areas. His composite sketch became a reference chart as he searched for changes in these fields. With this technique, Roberts discovered more than 20 variable stars.

APA, Harvard, Vancouver, ISO, and other styles

30

Zhao, J. K., G. Zhao, and T. D. Oswalt. "Three Wide Binaries in LAMOST Pilot Survey." Proceedings of the International Astronomical Union 9, S298 (May 2013): 456. http://dx.doi.org/10.1017/s1743921313007217.

Full text

Abstract:

AbstractThree wide binary candidates that have been identified in the Large sky Area Multi-Object Spectroscopic Telescope (LAMOST) pilot survey data are presented. All three consist of main sequence stars of relatively late spectral type.

APA, Harvard, Vancouver, ISO, and other styles

31

Gallardo Cava, I., V. Bujarrabal, J. Alcolea, M. Gómez-Garrido, and M. Santander-García. "Chemistry of nebulae around binary post-AGB stars: A molecular survey of mm-wave lines,." Astronomy & Astrophysics 659 (March 2022): A134. http://dx.doi.org/10.1051/0004-6361/202142339.

Full text

Abstract:

Context. There is a class of binary post-asymptotic giant branch (post-AGB) stars that exhibit remarkable near-infrared excess. Such stars are surrounded by Keplerian or quasi-Keplerian disks, as well as extended outflows composed of gas escaping from the disk. This class can be subdivided into disk- and outflow-dominated sources, depending on whether it is the disk or the outflow that represents most of the nebular mass, respectively. The chemistry of this type of source has been practically unknown thus far. Aims. Our objective is to study the molecular content of nebulae around binary post-AGB stars that show disks with Keplerian dynamics, including molecular line intensities, chemistry, and abundances. Methods. We focused our observations on the 1.3, 2, 3 mm bands of the 30mIRAM telescope and on the 7 and 13 mm bands of the 40 m Yebes telescope. Our observations add up ~600 h of telescope time. We investigated the integrated intensities of pairs of molecular transitions for CO, other molecular species, and IRAS fluxes at 12, 25, and 60 μm. Additionally, we studied isotopic ratios, in particular 17O/18O, to analyze the initial stellar mass, as well as 12CO/13CO, to study the line and abundance ratios. Results. We present the first single-dish molecular survey of mm-wave lines in nebulae around binary post-AGB stars. We conclude that the molecular content is relatively low in nebulae around binary post-AGB stars, as their molecular lines and abundances are especially weaker compared with AGB stars. This fact is very significant in those sources where the Keplerian disk is the dominant component of the nebula. The study of their chemistry allows us to classify nebulae around AC Her, the Red Rectangle, AI CMi, R Sct, and IRAS 20056+1834 as O-rich, while that of 89 Her is probably C-rich. The calculated abundances of the detected species other than CO are particularly low compared with AGB stars. The initial stellar mass derived from the 17O/18O ratio for the Red Rectangle and 89 Her is compatible with the central total stellar mass derived from previous mm-wave interferometric maps. The very low 12CO/13CO ratios found in binary post-AGB stars reveal a high 13CO abundance compared to AGB and other post-AGB stars.

APA, Harvard, Vancouver, ISO, and other styles

32

Walton, N. A., J. R. Walsh, and G. Dudziak. "An imaging and spectroscopic survey of the Abell Planetary Nebulae." Symposium - International Astronomical Union 180 (1997): 287. http://dx.doi.org/10.1017/s0074180900131043.

Full text

Abstract:

The Abell catalogue of planetary nebulae (PN) are distinguished by their large size, low surface brightness and generally faint central stars. They are thought to be old PN approaching the White Dwarf cooling track. A number have evidence for late thermal pulses (H-poor ejecta near the central star, e.g. A78) and binary central stars.

APA, Harvard, Vancouver, ISO, and other styles

33

McAlister, Harold A., William I. Hartkopf, Donald J. Hutter, Michael M. Shara, and Otto G. Franz. "ICCD speckle observations of binary stars. I - A survey for duplicity among the bright stars." Astronomical Journal 93 (January 1987): 183. http://dx.doi.org/10.1086/114297.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Lu, Phillip K., Pierre Demarque, William van Altena, Harold McAlister, and William Hartkopf. "ICCD speckle observations of binary stars. III - A survey for duplicity among high-velocity stars." Astronomical Journal 94 (November 1987): 1318. http://dx.doi.org/10.1086/114569.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Roberts, Jr., Lewis C., Nils H. Turner, and Theo A. ten Brummelaar. "Adaptive Optics Photometry and Astrometry of Binary Stars. II. A Multiplicity Survey of B Stars." Astronomical Journal 133, no. 2 (January 9, 2007): 545–52. http://dx.doi.org/10.1086/510335.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Lagadec, Eric, Tijl Verhoelst, Djamel Mékarnia, Olga Suárez, Albert A. Zijlstra, Philippe Bendjoya, Ryszard Szczerba, et al. "A mid-infrared imaging survey of post-AGB stars." Proceedings of the International Astronomical Union 7, S283 (July 2011): 59–62. http://dx.doi.org/10.1017/s1743921312010691.

Full text

Abstract:

AbstractPost-AGB stars are key objects for the study of the dramatic morphological changes of low- to intermediate-mass stars on their evolution from the Asymptotic Giant Branch (AGB) towards the planetary nebula stage. There is growing evidences that binary interaction processes may very well have a determining role in the shaping process of many objects, but so far direct evidence is still weak. We aim at a systematic study of the dust distribution around a large sample of post-AGB stars as a probe of the symmetry breaking in the nebulae around these systems. We used imaging in the mid-infrared to study the inner part of these evolved stars to probe direct emission from dusty structures in the core of post-AGB stars in order to better understand their shaping mechanisms. We imaged a sample of 93 evolved stars and nebulae in the mid-infrared using VISIR/VLT, T-Recs/Gemini South and Michelle/Gemini North. We found that all the the proto-planetary nebulae we resolved show a clear departure from spherical symmetry. 59 out of the 93 observed targets appear to be non resolved. The resolved targets can be divided in two categories. The nebulae with a dense central core, that are either bipolar and multipolar. The nebulae with no central core have an elliptical morphology. The dense central torus observed likely host binary systems which triggered fast outflows that shaped the nebulae.

APA, Harvard, Vancouver, ISO, and other styles

37

Hutter, D. J., C. Tycner, R. T. Zavala, J. A. Benson, C. A. Hummel, and H. Zirm. "Surveying the Bright Stars by Optical Interferometry. III. A Magnitude-limited Multiplicity Survey of Classical Be Stars." Astrophysical Journal Supplement Series 257, no. 2 (December 1, 2021): 69. http://dx.doi.org/10.3847/1538-4365/ac23cb.

Full text

Abstract:

Abstract We present the results of a multiplicity survey for a magnitude-limited sample of 31 classical Be stars conducted with the Navy Precision Optical Interferometer and the Mark III Stellar Interferometer. The interferometric observations were used to detect companions in 10 previously known binary systems. For two of these sources (66 Oph and β Cep) new orbital solutions were obtained, while for a third source (υ Sgr) our observations provide the first direct, visual detection of the hot companion to the primary star. Combining our interferometric observations with an extensive literature search, we conclude that an additional four sources (o Cas, 15 Mon, β Lyr, and β Cep) also contain wider binary components that are physical companions to the narrow binaries, thus forming hierarchical multiple systems. Among the sources not previously confirmed as spectroscopic or visual binaries, BK Cam was resolved on a number of nights within a close physical proximity of another star with relative motion possibly suggesting a physical binary. Combining our interferometric observations with an extensive literature search, we provide a detailed listing of companions known around each star in the sample, and discuss the multiplicity frequency in the sample. We also discuss the prospects for future multiplicity studies of classical Be stars by long-baseline optical interferometry.

APA, Harvard, Vancouver, ISO, and other styles

38

Leinert, Ch, N. Weitzel, M. Haas, R. Lenzen, H. Zinnecker, J. Christou, S. T. Ridgway, R. Jameson, and A. Richichi. "A Survey of Young Stars in Taurus for Multiplicity." International Astronomical Union Colloquium 135 (1992): 21–29. http://dx.doi.org/10.1017/s0252921100006072.

Full text

Abstract:

AbstractWe surveyed all stars in Taurus (3h 45m < α < 4h 15m, 15° < δ < 35°) for multiplicity which are contained in the Herbig-Bell catalogue of young stars and have a 2 micron brightness of K ≤ 9.5 mag. This sample consists of 106 stellar systems (single or multiple), of which 43 are double or multiple according to the criteria of our survey, i.e. with separations of ≈0″.2 ≤ d ≤ 10″. Of these, 23 binaries are new detections found in this survey. The resulting degree of multiplicity, 43/106 = 41±6%, is higher than found for main-sequence stars. Provided that the period distribution is the same for young stars as on the main sequence, our result implies that the vast majority of stars are born in binary or multiple systems.

APA, Harvard, Vancouver, ISO, and other styles

39

Drake, S. A., T. Simon, and J. L. Linsky. "A 6 centimeter radio survey of short-period active binary stars." Astronomical Journal 91 (May 1986): 1229. http://dx.doi.org/10.1086/114095.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Prato, L. "A Survey for Young Spectroscopic Binary K7–M4 Stars in Ophiuchus." Astrophysical Journal 657, no. 1 (March 2007): 338–46. http://dx.doi.org/10.1086/510882.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Prša, Andrej, Joshua Pepper, and Keivan G. Stassun. "EXPECTED LARGE SYNOPTIC SURVEY TELESCOPE (LSST) YIELD OF ECLIPSING BINARY STARS." Astronomical Journal 142, no. 2 (July 12, 2011): 52. http://dx.doi.org/10.1088/0004-6256/142/2/52.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Hernandez, M. S., M. R. Schreiber, S. G. Parsons, B. T. Gänsicke, F. Lagos, R. Raddi, O. Toloza, et al. "The White Dwarf Binary Pathways Survey – IV. Three close white dwarf binaries with G-type secondary stars." Monthly Notices of the Royal Astronomical Society 501, no. 2 (December 14, 2020): 1677–89. http://dx.doi.org/10.1093/mnras/staa3815.

Full text

Abstract:

ABSTRACT Constraints from surveys of post-common envelope binaries (PCEBs) consisting of a white dwarf plus an M-dwarf companion have led to significant progress in our understanding of the formation of close white dwarf binary stars with low-mass companions. The white dwarf binary pathways project aims at extending these previous surveys to larger secondary masses, i.e. secondary stars of spectral-type AFGK. Here, we present the discovery and observational characterization of three PCEBs with G-type secondary stars and orbital periods between 1.2 and 2.5 d. Using our own tools as well as MESA, we estimate the evolutionary history of the binary stars and predict their future. We find a large range of possible evolutionary histories for all three systems and identify no indications for differences in common envelope evolution compared to PCEBs with lower mass secondary stars. Despite their similarities in orbital period and secondary spectral type, we estimate that the future of the three systems is very different: TYC 4962-1205-1 is a progenitor of a cataclysmic variable system with an evolved donor star, TYC 4700-815-1 will run into dynamically unstable mass transfer that will cause the two stars to merge, and TYC 1380-957-1 may appear as supersoft source before becoming a rather typical cataclysmic variable star.

APA, Harvard, Vancouver, ISO, and other styles

43

Bell, S. A., and D. L. Pollacco. "A new deep imaging survey of Planetary Nebulae with known binary central stars." Symposium - International Astronomical Union 180 (1997): 210. http://dx.doi.org/10.1017/s0074180900130335.

Full text

Abstract:

Binarity in central stars is often thought to be the most likely explanation for the bipolar and axisymmetric shapes seen in planetary nebulae. Theoretical computations show that low mass stellar companions — possibly even planets, merged nuclei and long period systems will also produce bipolar-shaped nebulae. As such all known short period binary central stars are expected to have an axisymmetric nebula surrounding them.

APA, Harvard, Vancouver, ISO, and other styles

44

Köhler, Rainer, Monika G. Petr-Gotzens, Mark J. McCaughrean, Jerome Bouvier, Gaspard Duchêne, Andreas Quirrenbach, and Hans Zinnecker. "Binary Stars in the Orion Nebula Cluster." Proceedings of the International Astronomical Union 2, S240 (August 2006): 114–16. http://dx.doi.org/10.1017/s1743921307003912.

Full text

Abstract:

AbstractWe report on a high-spatial-resolution survey for binary stars in the periphery of the Orion Nebula Cluster, at 5–15 arcmin (0.65 – 2 pc) from the cluster center. We observed 228 stars with adaptive optics systems, in order to find companions at separations of 0.13 – 1.12 arcsec (60 – 500 AU), and detected 13 new binaries. Combined with the results of Petr (1998), we have a sample of 275 objects, about half of which have masses from the literature and high probabilities to be cluster members. We used an improved method to derive the completeness limits of the observations, which takes into account the elongated point spread function of stars at relatively large distances from the adaptive optics guide star. The multiplicity of stars with masses >2 M⊙ is found to be significantly larger than that of low-mass stars. The companion star frequency of low-mass stars is comparable to that of main-sequence M-dwarfs, less than half that of solar-type main-sequence stars, and 3.5 to 5 times lower than in the Taurus-Auriga and Scorpius-Centaurus star-forming regions. We find the binary frequency of low-mass stars in the periphery of the cluster to be the same or only slightly higher than for stars in the cluster core (< 3′ from θ1C Ori). This is in contrast to the prediction of the theory that the low binary frequency in the cluster is caused by the disruption of binaries due to dynamical interactions. There are two ways out of this dilemma: Either the initial binary frequency in the Orion Nebula Cluster was lower than in Taurus-Auriga, or the Orion Nebula Cluster was originally much denser and dynamically more active. A detailed report of this work has been published in Astronomy & Astrophysics (Köhler et al. 2006).

APA, Harvard, Vancouver, ISO, and other styles

45

Kouwenhoven, M. B. N., A. G. A. Brown, A. Gualandris, L. Kaper, S. F. Portegies Zwart, and H. Zinnecker. "The Primordial Binary Population in OB Associations." International Astronomical Union Colloquium 191 (August 2004): 139–40. http://dx.doi.org/10.1017/s0252921100008642.

Full text

Abstract:

AbstractWe present the first results of our adaptive optics survey of 200 (mainly) A-type stars in the nearby OB association Sco OB2, which we will use, together with literature data and detailed simulations of young star clusters, to determine the primordial binary population.

APA, Harvard, Vancouver, ISO, and other styles

46

McAlister, Harold A., Brian D. Mason, William I. Hartkopf, Lewis C. ,. Jr Roberts, and Michael M. Shara. "ICCD Speckle Observations of Binary Stars. XIV. A brief Survey for Duplicity Among White Dwarf Stars." Astronomical Journal 112 (September 1996): 1169. http://dx.doi.org/10.1086/118086.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

McAlister, Harold A., Brian D. Mason, William I. Hartkopf, and Michael M. Shara. "ICCD speckle observations of binary stars. X - A further survey for duplicity among the bright stars." Astronomical Journal 106 (October 1993): 1639. http://dx.doi.org/10.1086/116753.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Chojnowski, S. Drew, Swetlana Hubrig, Sten Hasselquist, Rachael L. Beaton, Steven R. Majewski, D. A. García-Hernández, and David DeColibus. "The SDSS/APOGEE catalogue of HgMn stars." Monthly Notices of the Royal Astronomical Society 496, no. 1 (June 3, 2020): 832–50. http://dx.doi.org/10.1093/mnras/staa1527.

Full text

Abstract:

ABSTRACT We report on H-band spectra of chemically peculiar Mercury–Manganese (HgMn) stars obtained via the SDSS/APOGEE survey. As opposed to other varieties of chemically peculiar stars such as classical Ap/Bp stars, HgMn stars lack strong magnetic fields and are defined by extreme overabundances of Mn, Hg, and other heavy elements. A satisfactory explanation for the abundance patterns remains to be determined, but low rotational velocity is a requirement and involvement in binary/multiple systems may be as well. The APOGEE HgMn sample currently consists of 269 stars that were identified among the telluric standard stars as those whose metallic absorption content is limited to or dominated by the H-band Mn ii lines. Due to the fainter magnitudes probed by the APOGEE survey as compared to past studies, only 9/269 stars in the sample were previously known as HgMn types. The 260 newly identified HgMn stars represents a more than doubling of the known sample. At least 32 per cent of the APOGEE sample are found to be binary or multiple systems, and from multi-epoch spectroscopy, we were able to determine orbital solutions for at least one component in 32 binaries. Many of the multilined systems include chemically peculiar companions, with noteworthy examples being the HgMn+Ap/Bp binary HD 5429, the HgMn+HgMn binary HD 298641, and the HgMn+Bp Mn + Am triple system HD 231263. As a further peculiarity, roughly half of the sample produces narrow emission in the C i 16895 Å line, with widths and radial velocities that match those of the Mn ii lines.

APA, Harvard, Vancouver, ISO, and other styles

49

Clark, J. S., B. W. Ritchie, and I. Negueruela. "A VLT/FLAMES survey for massive binaries in Westerlund 1." Astronomy & Astrophysics 635 (March 2020): A187. http://dx.doi.org/10.1051/0004-6361/201935903.

Full text

Abstract:

Context. The formation, properties, and evolution of massive stars remain subject to considerable theoretical and observational uncertainty. This impacts on fields as diverse as galactic feedback, the production of cosmic rays, and the nature of the progenitors of both electromagnetic and gravitational wave transients. Aims. The young massive clusters many such stars reside within provide a unique laboratory for addressing these issues. In this work we provide a comprehensive stellar census of Westerlund 1 in order to to underpin such efforts. Methods. We employed optical spectroscopy of a large sample of early-type stars to determine cluster membership for photometrically-identified candidates, characterise their spectral type, and identify new candidate spectroscopic binaries. Results. Sixty nine new members of Westerlund 1 are identified via I-band spectroscopy. Together with previous observations, they illustrate a smooth and continuous morphological sequence from late-O giant through to OB supergiant. Subsequently, the progression bifurcates, with one branch yielding mid-B to late-F hypergiants, and cool supergiants, and the other massive blue stragglers prior to a diverse population of H-depleted WRs. We identify a substantial population of O-type stars with very broad Paschen series lines, a morphology that is directly comparable to known binaries in the cluster. In a few cases additional low-resolution R-band spectroscopy is available, revealing double-lined He I profiles and confirming binarity for these objects; suggesting a correspondingly high binary fraction amongst relatively unevolved cluster members. Conclusions. Our current census remains incomplete, but indicates that Westerlund 1 contains at least 166 stars with initial masses estimated to lie between ∼25 M⊙ and ∼50 M⊙, with more massive stars already lost to supernova. Our data is consistent with the cluster being co-eval, although binary interaction is clearly required to yield the observed stellar population, which is characterised by a uniquely rich cohort of hypergiants ranging from spectral type O to F, with both mass-stripped primaries and rejuvenated secondaries or merger products present. Future observations of Wd1 and similar stellar aggregates hold out the prospect of characterising both single- and binary- evolutionary channels for massive stars and determining their relative contributions. This in turn will permit the physical properties of such objects at the point of core-collapse to be predicted, which is of direct relevance for understanding the formation of relativistic remnants such as the magnetars associated with Wd1 and other young massive clusters.

APA, Harvard, Vancouver, ISO, and other styles

50

Zinnecker, H., W. Brandner, and B. Reipurth. "Pre-Main Sequence Binaries: The ESO Imaging Survey." International Astronomical Union Colloquium 135 (1992): 50–59. http://dx.doi.org/10.1017/s0252921100006102.

Full text

Abstract:

AbstractWe have observed a complete sample of southern Hα emission line pre-main sequence (PMS) stars associated with the nearby dark clouds Chamaeleon and Ophiuchus in an effort to detect binary companions. We have used the high resolution CCD camera SUSI (0.13″ /pixel) at the ESO 3.5m New Technology Telescope (NTT). The observations were carried out in the Gunn z filter (0.95μ). As a result, we have discovered 28 companions out of 160 objects surveyed in the range of angular separation 0″.5 – 10″. We present histograms of semi-major axes and of brightness ratios of these PMS binaries. Taking small incompleteness corrections into account, the frequency of PMS binaries with semi-major axes in the range 100-1500 AU is 20%, while it is only 15% in same range for solar-type Main Sequence (MS) stars. Extrapolation yields a total PMS binary frequency of 70%. Evolutionary and environmental implications are briefly discussed.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Binary stars Survey SARG'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles