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Dissertations / Theses on the topic 'Stars: individual (Fomalhaut A)'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

MacGregor, Meredith A., Luca Matra, Paul Kalas, et al. "A Complete ALMA Map of the Fomalhaut Debris Disk." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624433.

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We present ALMA mosaic observations at 1.3. mm (223 GHz) of the Fomalhaut system with a sensitivity of 14 mu Jy/beam. These observations provide the first millimeter map of the continuum dust emission from the complete outer debris disk with uniform sensitivity, enabling the first conclusive detection of apocenter glow. We adopt an MCMC modeling approach that accounts for the eccentric orbital parameters of a collection of particles within the disk. The outer belt is radially confined with an inner edge of 136.3 +/- 0.9. au and width of 13.5 +/- 1.8. au. We determine a best-fit eccentricity of

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2

Matra, L., M. A. MacGregor, P. Kalas, et al. "Detection of Exocometary CO within the 440Myr Old Fomalhaut Belt: A Similar CO+ CO2 Ice Abundance in Exocomets and Solar System Comets." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624435.

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Recent Atacama Large Millimeter/submillimeter Array observations present mounting evidence for the presence of exocometary gas released within Kuiper Belt analogs around nearby main-sequence stars. This represents a unique opportunity to study their ice reservoir at the younger ages when volatile delivery to planets is most likely to occur. We here present the detection of CO J=2-1 emission colocated with dust emission from the cometary belt in the 440 Myr old Fomalhaut system. Through spectrospatial filtering, we achieve a 5.4s detection and determine that the ring's sky-projected rotation ax

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3

Spruyt, Jon. "Gamified Individual Brainstorming : Reaching for the stars." Thesis, Umeå universitet, Institutionen för informatik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-133603.

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Ideation is a critical step in the creation of new solutions to problems. Brainstorming, being the most commonly known ideation method, is mostly done in groups. However, research points out that brainstorming individually is more effective than brainstorming in groups. This paper investigates if negative aspects (reduced enjoyment, motivation and self-rated performance) associated with brainstorming alone can be overcome by using a gamified approach to brainstorming. Gamified and non-gamified prototypes have been made and used in combination with a questionnaire to measure differences in thes

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4

Fossati, L., T. Koskinen, K. France, et al. "Suppressed Far-UV Stellar Activity and Low Planetary Mass Loss in the WASP-18 System." IOP PUBLISHING LTD, 2018. http://hdl.handle.net/10150/627089.

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WASP-18 hosts a massive, very close-in Jupiter-like planet. Despite its young age (< 1 Gyr), the star presents an anomalously low stellar activity level: the measured log R'(HK) activity parameter lies slightly below the basal level; there is no significant time-variability in the log R'(HK) value; there is no detection of the star in the X-rays. We present results of far-UV observations of WASP-18 obtained with COS on board of Hubble Space Telescope aimed at explaining this anomaly. From the star's spectral energy distribution, we infer the extinction (E(B-V) approximate to 0.01 mag) and then

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5

Brunsden, Emily. "The Music of the Stars : Spectroscopy of Pulsations in gamma Doradus Stars." Thesis, University of Canterbury. Astronomy, 2013. http://hdl.handle.net/10092/8373.

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The mysteries of the interior structures of stars are being tackled with asteroseismology. The observable parameters of the surface pulsations of stars inform us of the interior characteristics of numerous classes of stars. The main-sequence gamma Doradus stars, just a little hotter than the Sun, offer the potential of determining stellar structure right down to the core. To determine the structural profile of a star, the observed frequencies and a full geometric description must be determined. This is only possible with long-term spectroscopic monitoring and careful analysis of the pulsation

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6

Boyajian, Tabetha S., Roi Alonso, Alex Ammerman, et al. "The First Post-Kepler Brightness Dips of KIC 8462852." IOP PUBLISHING LTD, 2018. http://hdl.handle.net/10150/626540.

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We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in 2015 October, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1%-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and " Angkor," which persist on timescales from several days to weeks. Our main results so far are as follows: (i) there are no apparent changes of the stellar spectrum

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7

Tutar, Özdarcan D., P. S. Smith, and V. Keskin. "Time-resolved spectropolarimetric observations of polars WX LMi and BY Cam." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/624423.

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Time-series spectropolarimetric observations of polar WX LMi and asynchronous polar BY Cam are presented. Magnetic field properties, radial velocities and optical polarization are investigated via consecutive observations with good phase sampling during a single orbital cycle. Both systems are found to have a decentred dipole magnetic field configuration. One of the poles of WX LMi has a field strength of 49 MG, while the other pole may have possible field strengths of 69, 104 or 207 MG, depending on the harmonic numbers of the cyclotron humps observed in the circularly polarized spectrum. For

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8

Lew, Ben W. P., Daniel Apai, Yifan Zhou, et al. "CLOUD ATLAS: DISCOVERY OF PATCHY CLOUDS AND HIGH-AMPLITUDE ROTATIONAL MODULATIONS IN A YOUNG, EXTREMELY RED L-TYPE BROWN DWARF." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622769.

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Condensate clouds fundamentally impact the atmospheric structure and spectra of exoplanets and brown dwarfs, but the connections between surface gravity, cloud structure, dust in the upper atmosphere, and the red colors of some brown dwarfs remain poorly understood. Rotational modulations enable the study of different clouds in the same atmosphere, thereby providing a method to isolate the effects of clouds. Here, we present the discovery of high peak-to-peak amplitude (8%) rotational modulations in a low-gravity, extremely red (J-K-s = 2.55) L6 dwarf WISEP J004701.06+680352.1 (W0047). Using t

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9

Kiminki, Megan M., Megan Reiter та Nathan Smith. "Ancient eruptions of η Carinae: a tale written in proper motions". OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/622109.

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We analyse eight epochs of Hubble Space Telescope H alpha+[N ii] imaging of eta Carinae's outer ejecta. Proper motions of nearly 800 knots reveal that the detected ejecta are divided into three apparent age groups, dating to around 1250 A.D., to around 1550 A.D., and to during or shortly before the Great Eruption of the 1840s. Ejecta from these groups reside in different locations and provide a firm constraint that eta Car experienced multiple major eruptions prior to the nineteenth century. The 1250 and 1550 events did not share the same axisymmetry as the Homunculus; the 1250 event was parti

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10

Currie, Thayne, Olivier Guyon, Motohide Tamura, et al. "Subaru/SCExAO First-light Direct Imaging of a Young Debris Disk around HD 36546." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624379.

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We present H-band scattered light imaging of a bright debris disk around the A0 star HD 36546 obtained from the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system with data recorded by the HiCIAO camera using the vector vortex coronagraph. SCExAO traces the disk from r similar to 0."3 to r similar to 1" (34-114 au). The disk is oriented in a near east-west direction (PA similar to 75 degrees), is inclined by i similar to 70 degrees-75 degrees, and is strongly forward-scattering (g > 0.5). It is an extended disk rather than a sharp ring; a second, diffuse dust population extends from

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11

Wu, Ya-Lin, Nathan Smith, Laird M. Close, Jared R. Males, and Katie M. Morzinski. "Resolving the H alpha-emitting Region in the Wind of eta Carinae." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624482.

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The massive evolved star. Carinae is the most luminous star in the Milky Way and has the highest steady wind mass-loss rate of any known star. Radiative transfer models of the spectrum by Hillier et al. predict that Ha is mostly emitted in regions of the wind at radii of 6-60 au from the star (2.5-25 mas at 2.35 kpc). We present diffraction-limited images (FWHM similar to 25 mas) with Magellan adaptive optics in two epochs, showing that. Carinae consistently appears similar to 2.5-3 mas wider in Ha emission compared to the adjacent 643 nm continuum. This implies that the H alpha line-forming r

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12

Hełminiak, K. G., M. Kuzuhara, K. Mede, et al. "SEEDS DIRECT IMAGING OF THE RV-DETECTED COMPANION TO V450 ANDROMEDAE, AND CHARACTERIZATION OF THE SYSTEM." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622454.

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We report the direct imaging detection of a low-mass companion to a young, moderately active star V450. And, that was previously identified with the radial velocity (RV) method. The companion was found in high-contrast images obtained with the Subaru Telescope equipped with the HiCIAO camera and AO188 adaptive optics system. From the public ELODIE and SOPHIE archives we extracted available high-resolution spectra and RV measurements, along with RVs from the Lick planet search program. We combined our multi-epoch astrometry with these archival, partially unpublished RVs, and found that the comp

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13

Finzell, Thomas, Laura Chomiuk, Brian D. Metzger, et al. "A Detailed Observational Analysis of V1324 Sco, the Most Gamma-Ray-luminous Classical Nova to Date." IOP PUBLISHING LTD, 2018. http://hdl.handle.net/10150/626558.

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It has recently been discovered that some, if not all, classical novae emit GeV gamma-rays during outburst, but the mechanisms involved in the production ofgamma-rays are still not well understood. We present here a comprehensive multiwavelength data set-from radio to X-rays-for the most gamma-ray-luminous classical nova to date, V1324 Sco. Using this data set, we show that V1324 Sco is a canonical dusty Fe II-type nova, with a maximum ejecta velocity of 2600 km s(-1) and an ejecta mass of a few x 10(-5) M-circle dot. There is also evidence for complex shock interactions, including a double-pe

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14

Kellogg, Kendra, Stanimir Metchev, Paulo A. Miles-Páez, and Megan E. Tannock. "A Statistical Survey of Peculiar L and T Dwarfs in SDSS, 2MASS, and WISE." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625747.

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We present the final results from a targeted search for brown dwarfs with unusual near-infrared colors. From a positional cross-match of the Sloan Digital Sky Survey (SDSS), 2-Micron All-Sky Survey (2MASS), and Wide-Field Infrared Survey Explorer (WISE) catalogs, we have identified 144 candidate peculiar L and T dwarfs. Spectroscopy confirms that 20 of the objects are peculiar or are candidate binaries. Of the 420 objects in our full sample 9 are young (less than or similar to 200 Myr; 2.1%) and another 8 (1.9%) are unusually red, with no signatures of youth. With a spectroscopic J-K-s color o

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15

Min, M., J. Bouwman, C. Dominik, et al. "The abundance and thermal history of water ice in the disk surrounding HD 142527 from the DIGIT Herschel Key Program." EDP SCIENCES S A, 2016. http://hdl.handle.net/10150/622159.

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Context. The presence or absence of ice in protoplanetary disks is of great importance to the formation of planets. By enhancing solid surface density and increasing sticking efficiency, ice catalyzes the rapid formation of planetesimals and decreases the timescale of giant planet core accretion. Aims. In this paper, we analyze the composition of the outer disk around the Herbig star HD 142527. We focus on the composition of water ice, but also analyze the abundances of previously proposed minerals. Methods. We present new Herschel far-infrared spectra and a re-reduction of archival data from

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16

Miles-Páez, Paulo A., Stanimir Metchev, Kevin L. Luhman, Massimo Marengo, and Alan Hulsebus. "The Prototypical Young L/T-Transition Dwarf HD 203030B Likely Has Planetary Mass." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/627091.

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Upon its discovery in 2006, the young L7.5 companion to the solar analog HD 203030 was found to be approximate to 200 K cooler than older late-L dwarfs, which is quite unusual. HD. 203030B offered the first clear indication that the effective temperature at the L-to-T spectral type transition depends on surface gravity: now a well-known characteristic of low-gravity ultra-cool dwarfs. An initial age analysis of the G8V primary star indicated that the system was 130-400 Myr old, and so the companion would be between 12 and 31 M-Jup. Using moderate-resolution near-infrared spectra of HD. 203030B

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17

Lim, Beomdu, Hwankyung Sung, Jinyoung S. Kim, Michael S. Bessell, Narae Hwang, and Byeong-Gon Park. "A CONSTRAINT ON THE FORMATION TIMESCALE OF THE YOUNG OPEN CLUSTER NGC 2264: LITHIUM ABUNDANCE OF PRE-MAIN SEQUENCE STARS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622162.

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The timescale of cluster formation is an essential parameter in order to understand the formation process of star clusters. Pre-main sequence (PMS) stars in nearby young open clusters reveal a large spread in brightness. If the spread were considered to be a result of a real spread in age, the corresponding cluster formation timescale would be about 5-20 Myr. Hence it could be interpreted that star formation in an open cluster is prolonged for up to a few tens of Myr. However, difficulties in reddening correction, observational errors, and systematic uncertainties introduced by imperfect evolu

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18

Johnson-Groh, Mara, Christian Marois, Rosa Robert J. De, et al. "Integral Field Spectroscopy of the Low-mass Companion HD 984 B with the Gemini Planet Imager." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623816.

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We present new observations of the low-mass companion to HD 984 taken with the Gemini Planet Imager (GPI) as a part of the GPI Exoplanet Survey campaign. Images of HD 984 B were obtained in the J (1.12-1.3 mu m) and H (1.50-1.80 mu m) bands. Combined with archival epochs from 2012 and 2014, we fit the first orbit to the companion to find an 18 au (70-year) orbit with a 68% confidence interval between 14 and 28 au, an eccentricity of 0.18 with a 68% confidence interval between 0.05 and 0.47, and an inclination of 119 degrees with a 68% confidence interval between 114 degrees and 125 degrees. To

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19

Sheehan, Patrick D., and Josh A. Eisner. "WL 17: A Young Embedded Transition Disk." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624338.

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We present the highest spatial resolution ALMA observations to date of the Class I protostar WL 17 in the rho Ophiuchus L1688 molecular cloud complex, which show that it has a 12 au hole in the center of its disk. We consider whether WL 17 is actually a Class II disk being extincted by foreground material, but find that such models do not provide a good fit to the broadband spectral energy distribution (SED) and also require such high extinction that it would presumably arise from dense material close to the source, such as a remnant envelope. Self-consistent models of a disk embedded in a rot

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20

Toloza, O., B. T. Gänsicke, J. J. Hermes, et al. "GW Librae: a unique laboratory for pulsations in an accreting white dwarf." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/621433.

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Non-radial pulsations have been identified in a number of accreting white dwarfs in cataclysmic variables. These stars offer insight into the excitation of pulsation modes in atmospheres with mixed compositions of hydrogen, helium, and metals, and the response of these modes to changes in the white dwarf temperature. Among all pulsating cataclysmic variable white dwarfs, GW Librae stands out by having a well-established observational record of three independent pulsation modes that disappeared when the white dwarf temperature rose dramatically following its 2007 accretion outburst. Our analysi

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Bond, Howard E., Gail H. Schaefer, Ronald L. Gilliland, et al. "The Sirius System and Its Astrophysical Puzzles: Hubble Space Telescope and Ground-based Astrometry." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624059.

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Sirius, the seventh-nearest stellar system, is a visual binary containing the metallic-line A1. V star Sirius. A, the brightest star in the sky, orbited in a 50.13. year period by Sirius B, the brightest and nearest white dwarf (WD). Using images obtained over nearly two decades with the Hubble Space Telescope (HST), along with photographic observations covering almost 20 years and nearly 2300 historical measurements dating back to the 19th century, we determine precise orbital elements for the visual binary. Combined with the parallax and the motion of the A component, these elements yield dy

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22

Ricci, L., P. Cazzoletti, I. Czekala, et al. "ALMA Observations of the Young Substellar Binary System 2M1207." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624920.

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We present ALMA observations of the 2M1207 system, a young binary made of a brown dwarf with a planetary-mass companion at a projected separation of about 40 au. We detect emission from dust continuum at 0.89 mm and from the J = 3 - 2 rotational transition of CO from a very compact disk around the young brown dwarf. The small radius found for this brown dwarf disk may be due to truncation from the tidal interaction with the planetary-mass companion. Under the assumption of optically thin dust emission, we estimate. a dust mass of 0.1 M-circle plus. for the 2M1207A disk and a 3 sigma upper limi

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23

Schlawin, E., T. Herter, M. Zhao, J. K. Teske, and H. Chen. "REDUCED ACTIVITY AND LARGE PARTICLES FROM THE DISINTEGRATING PLANET CANDIDATE KIC 12557548b." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621392.

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The intriguing exoplanet candidate KIC 12557548b is believed to have a comet-like tail of dusty debris trailing a small rocky planet. The tail of debris scatters up to 1.3% of the stellar light in the Kepler observatory's bandpass (0.42-0.9 mu m). Observing the tail's transit depth at multiple wavelengths can reveal the composition and particle size of the debris, constraining the makeup and lifetime of the sub-Mercury planet. Early dust particle size predictions from the scattering of the comet-like tail pointed toward a dust size of similar to 0.1 mu m for silicate compositions. These small

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24

Smith, Nathan, Jennifer E. Andrews, and Jon C. Mauerhan. "Massive stars dying alone: the extremely remote environment of SN 2009ip." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/622955.

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We present late-time Hubble Space Telescope (HST) images of the site of supernova (SN) 2009ip taken almost 3 yr after its bright 2012 luminosity peak. SN 2009ip is now slightly fainter in broad filters than the progenitor candidate detected by HST in 1999. The current source continues to be dominated by ongoing late-time circumstellar material interaction that produces strong Ha emission and a weak pseudo-continuum, as found previously for 1-2 yr after explosion. The intent of these observations was to search for evidence of recent star formation in the local (similar to 1 kpc; 10 arcsec) envi

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Chadney, J. M., T. T. Koskinen, M. Galand, Y. C. Unruh, and J. Sanz-Forcada. "Effect of stellar flares on the upper atmospheres of HD 189733b and HD 209458b." EDP SCIENCES S A, 2017. http://hdl.handle.net/10150/626411.

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Stellar flares are a frequent occurrence on young low-mass stars around which many detected exoplanets orbit. Flares are energetic, impulsive events, and their impact on exoplanetary atmospheres needs to be taken into account when interpreting transit observations. We have developed a model to describe the upper atmosphere of extrasolar giant planets (EGPs) orbiting flaring stars. The model simulates thermal escape from the upper atmospheres of close-in EGPs. Ionisation by solar radiation and electron impact is included and photo-chemical and diffusive transport processes are simulated. This m

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Obermeier, Christian, Thomas Henning, Joshua E. Schlieder, et al. "K2 DISCOVERS A BUSY BEE: AN UNUSUAL TRANSITING NEPTUNE FOUND IN THE BEEHIVE CLUSTER." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622698.

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Open clusters have been the focus of several exoplanet surveys, but only a few planets have so far been discovered. The Kepler spacecraft revealed an abundance of small planets around small cool stars, therefore, such cluster members are prime targets for exoplanet transit searches. Kepler's new mission, K2, is targeting several open clusters and star-forming regions around the ecliptic to search for transiting planets around their low-mass constituents. Here, we report the discovery of the first transiting planet in the intermediate-age (800 Myr) Beehive cluster (Praesepe). K2-95 is a faint (

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27

Booth, Mark, William R. F. Dent, Andrés Jordán та ін. "The Northern arc of ε Eridani’s Debris Ring as seen by ALMA". OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/625481.

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We present the first Atacama Large Millimeter/submillimeter Array (ALMA) observations of the closest known extrasolar debris disc. This disc orbits the star is an element of Eri, a K-type star just 3.2 pc away. Due to the proximity of the star, the entire disc cannot fit within the ALMA field of view. Therefore, the observations have been centred 18" North of the star, providing us with a clear detection of the Northern arc of the ring, at a wavelength of 1.3 mm. The observed disc emission is found to be narrow with a width of just 11-13 AU. The fractional disc width we find is comparable to t

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Vivas, A. Katherina, Abhijit Saha, Knut Olsen, et al. "Absolute Magnitudes and Colors of RR Lyrae Stars in DECam Passbands from Photometry of the Globular Cluster M5." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625820.

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We characterize the absolute magnitudes and colors of RR Lyrae stars in the globular cluster M5 in the ugriz filter system of the Dark Energy Camera (DECam). We provide empirical period-luminosity (P-L) relationships in all five bands based on 47 RR Lyrae stars of the type ab and 14 stars of the type c. The P-L relationships were found to be better constrained for the fundamental-mode RR Lyrae stars in the riz passbands, with dispersions of 0.03, 0.02 and 0.02 mag, respectively. The dispersion of the color at minimum light was found to be small, supporting the use of this parameter as a means

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29

Gruyters, Pieter. "Exploring the Chemical Evolution of Globular Clusters and their Stars : Observational Constraints on Atomic Diffusion and Cluster Pollution in NGC 6752 and M4." Doctoral thesis, Uppsala universitet, Observationell astrofysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-230182.

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Through the cosmic matter cycle, the chemical evolution of the Milky Way is imprinted in the elemental abundance patterns of late-type stars (spectral types F to K). Due to their long lifetimes ( 1 Hubble time), these stars are of particular importance when it comes to studying the build-up of elements during the early times of our Galaxy. The chemical composition of the atmospheric layers of such stars is believed to resemble the gas from which they were formed. However, recent observations in globular clusters seem to contradict this assumption. The observations indicate that processes are a

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Shivvers, Isaac, WeiKang Zheng, Dyk Schuyler D. Van, et al. "The nearby Type Ibn supernova 2015G: signatures of asymmetry and progenitor constraints." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/625796.

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We present the results of an extensive observational campaign on the nearby Type Ibn SN 2015G, including data from radio through ultravioletwavelengths. SN2015Gwas asymmetric, showing late-time nebular lines redshifted by similar to 1000 km s(-1). It shared many features with the prototypical SN Ibn 2006jc, including extremely strong He I emission lines and a late-time blue pseudo-continuum. The young SN 2015G showed narrow P-Cygni profiles of He I, but never in its evolution did it showany signature of hydrogen -arguing for a dense, ionized and hydrogenfree circumstellar medium moving outward

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31

Folatelli, Gastón, Dyk Schuyler D. Van, Hanindyo Kuncarayakti, et al. "DISAPPEARANCE OF THE PROGENITOR OF SUPERNOVA iPTF13bvn." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621404.

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Supernova (SN) iPTF13bvn in NGC 5806 was the first Type Ib SN to have been tentatively associated with a progenitor in pre-explosion images. We performed deep ultraviolet (UV) and optical Hubble Space Telescope observations of the SN site similar to 740 days after explosion. We detect an object in the optical bands that is fainter than the pre-explosion object. This dimming is likely not produced by dust absorption in the ejecta; thus, our finding confirms the connection of the progenitor candidate with the SN. The object in our data is likely dominated by the fading SN, implying that the pre-

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Bally, John, Adam Ginsburg, Hector Arce, et al. "The ALMA View of the OMC1 Explosion in Orion." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623202.

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Most massive stars form in dense clusters where gravitational interactions with other. stars may be common. The two nearest forming massive stars, the BN object and Source I, located behind the Orion Nebula, were ejected with velocities of similar to 29 and similar to 13 km s(-1) about 500 years ago by such interactions. This event generated an explosion in the gas. New ALMA observations show in unprecedented detail, a roughly spherically symmetric distribution of over a hundred (CO)-C-12 J = 2-1 streamers with velocities extending from V-LSR = -150 to +145 km s(-1) The streamer radial velocit

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Farihi, J., D. Koester, B. Zuckerman, et al. "Solar abundances of rock-forming elements, extreme oxygen and hydrogen in a young polluted white dwarf." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/622949.

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The T-eff = 20 800 K white dwarf WD 1536+520 is shown to have broadly solar abundances of the major rock-forming elements O, Mg, Al, Si, Ca, and Fe, together with a strong relative depletion in the volatile elements C and S. In addition to the highest metal abundances observed to date, including log (O/He) = -3.4, the helium-dominated atmosphere has an exceptional hydrogen abundance at log (H/He) = -1.7. Within the uncertainties, the metal-to-metal ratios are consistent with the accretion of an H2O-rich and rocky parent body, an interpretation supported by the anomalously high trace hydrogen.

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Smith, Nathan, Charles D. Kilpatrick, Jon C. Mauerhan та ін. "Endurance of SN 2005ip after a decade: X-rays, radio and Hα like SN 1988Z require long-lived pre-supernova mass-loss". OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/623937.

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Supernova (SN) 2005ip was a Type IIn event notable for its sustained strong interaction with circumstellar material (CSM), coronal emission lines and infrared (IR) excess, interpreted as shock interaction with the very dense and clumpy wind of an extreme red supergiant. We present a series of late- time spectra of SN 2005ip and a first radio detection of this SN, plus late-time X-rays, all of which indicate that its CSM interaction is still strong a decade post- explosion. We also present and discuss new spectra of geriatric SNe with continued CSM interaction: SN 1988Z, SN 1993J and SN 1998S.

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Evans, A., D. P. K. Banerjee, R. D. Gehrz, et al. "Rise and fall of the dust shell of the classical nova V339 Delphini." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/624508.

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We present infrared spectroscopy of the classical nova V339 Del, obtained over an similar to 2-yr period. The infrared emission lines were initially symmetrical, with half width half-maximum velocities of 525 km s(-1). In later (t greater than or similar to 77 d, where t is the time from outburst) spectra, however, the lines displayed a distinct asymmetry, with a much stronger blue wing, possibly due to obscuration of the receding component by dust. Dust formation commenced at approximately day 34.75 at a condensation temperature of 1480 +/- 20 K, consistent with graphitic carbon. Thereafter,

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Su, Kate Y. L., Buizer James M. De, George H. Rieke та ін. "The Inner 25 au Debris Distribution in the ϵ Eri System". IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624715.

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Debris disk morphology is wavelength dependent due to the wide range of particle sizes and size-dependent dynamics influenced by various forces. Resolved images of nearby debris disks reveal complex disk structures that are difficult to distinguish from their spectral energy distributions. Therefore, multi-wavelength resolved images of nearby debris systems provide an essential foundation to understand the intricate interplay between collisional, gravitational, and radiative forces that govern debris disk structures. We present the Stratospheric Observatory for Infrared Astronomy (SOFIA) 35 mu

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Dupree, A. K., A. Dotter, C. I. Johnson, et al. "NGC 1866: First Spectroscopic Detection of Fast-rotating Stars in a Young LMC Cluster." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625815.

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High-resolution spectroscopic observations were taken of 29 extended main-sequence turnoff (eMSTO) stars in the young (similar to 200 Myr) Large Magellanic Cloud (LMC) cluster, NGC 1866, using the Michigan/Magellan Fiber System and MSpec spectrograph on the Magellan-Clay 6.5 m telescope. These spectra reveal the first direct detection of rapidly rotating stars whose presence has only been inferred from photometric studies. The eMSTO stars exhibit Ha emission (indicative of Be-star decretion disks), others have shallow broad H alpha absorption (consistent with rotation. greater than or similar

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Spencer, Meghin E., Mario Mateo, Matthew G. Walker, et al. "The Binary Fraction of Stars in Dwarf Galaxies: The Case of Leo II." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624447.

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We combine precision radial velocity data from four different published works of the stars in the Leo II dwarf spheroidal galaxy. This yields a data set that spans 19 years, has 14 different epochs of observation, and contains 372 unique red giant branch stars, 196 of which have repeat observations. Using this multi-epoch data set, we constrain the binary fraction for Leo II. We generate a suite of Monte Carlo simulations that test different binary fractions using Bayesian analysis and determine that the binary fraction for Leo II ranges from 0.30(-0.10)(+0.09) to 0.34(-0.11)(+0.11), depending

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Klement, Robert, Alex C. Carciofi, Thomas Rivinius та ін. "The Outer Disk of the Classical Be Star ψ Per". Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/2701.

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To this date ψ Per is the only classical Be star that was angularly resolved in radio (by the VLA at λ = 2 cm). Gaussian fit to the azimuthally averaged visibility data indicates a disk size (FWHM) of ~500 stellar radii (Dougherty & Taylor 1992). Recently, we obtained new multi-band cm flux density measurements of ψ Per from the enhanced VLA. We modeled the observed spectral energy distribution (SED) covering the interval from ultraviolet to radio using the Monte Carlo radiative transfer code HDUST (Carciofi & Bjorkman 2006). An SED turndown, that occurs between far-IR and radio wavelengths, i

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Huenemoerder, David P., K. G. Gayley, Wolf-Rainer Hamann, et al. "Probing Wolf–Rayet Winds: Chandra/HETG X-Ray Spectra of WR 6." Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etsu-works/2692.

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With a deep Chandra/HETGS exposure of WR 6, we have resolved emission lines whose profiles show that the X-rays originate from a uniformly expanding spherical wind of high X-ray-continuum optical depth. The presence of strong helium-like forbidden lines places the source of X-ray emission at tens to hundreds of stellar radii from the photosphere. Variability was present in X-rays and simultaneous optical photometry, but neither were correlated with the known period of the system or with each other. An enhanced abundance of sodium revealed nuclear-processed material, a quantity related to the e

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Ballering, Nicholas P., Kate Y. L. Su, George H. Rieke, and András Gáspár. "A COMPREHENSIVE DUST MODEL APPLIED TO THE RESOLVED BETA PICTORIS DEBRIS DISK FROM OPTICAL TO RADIO WAVELENGTHS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621242.

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We investigate whether varying the dust composition (described by the optical constants) can solve a persistent problem in debris disk modeling-the inability to fit the thermal emission without overpredicting the scattered light. We model five images of the beta Pictoris disk: two in scattered light from the Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph at 0.58 mu m and HST/Wide Field Camera 3 (WFC 3) at 1.16 mu m, and three in thermal emission from Spitzer/Multiband Imaging Photometer for Spitzer (MIPS) at 24 mu m, Herschel/PACS at 70 mu m, and Atacama Large Millimeter/sub

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Nielsen, Eric L., Robert J. De Rosa, Jason Wang, et al. "DYNAMICAL MASS MEASUREMENT OF THE YOUNG SPECTROSCOPIC BINARY V343 NORMAE AaAb RESOLVED WITH THE GEMINI PLANET IMAGER." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622436.

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We present new spatially resolved astrometry and photometry from the Gemini Planet Imager of the inner binary of the young multiple star system V343 Normae, which is a member of the beta Pictoris (beta Pic) moving group. V343 Normae comprises a K0 and mid-M star in a similar to 4.5 year orbit (AaAb) and a wide 10 '' M5 companion (B). By combining these data with archival astrometry and radial velocities we fit the orbit and measure individual masses for both components of M-Aa = 1.10 +/- 0.10M(circle dot) and M-Ab= 0.290 +/- 0.018 M-circle dot. Comparing to theoretical isochrones, we find good

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Stevenson, Kevin B., Michael R. Line, Jacob L. Bean та ін. "SPITZER PHASE CURVE CONSTRAINTS FOR WASP-43b AT 3.6 AND 4.5μm". IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623051.

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Previous measurements of heat redistribution efficiency (the ability to transport energy from a planet's highly irradiated dayside to its eternally dark nightside) show considerable variation between exoplanets. Theoretical models predict a positive correlation between heat redistribution efficiency and temperature for tidally locked planets; however, recent Hubble Space Telescope (HST) WASP-43b spectroscopic phase curve results are inconsistent with current predictions. Using the Spitzer Space Telescope, we obtained a total of three phase curve observations of WASP-43b (P = 0.813 days) at 3.6

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Sallum, S., J. A. Eisner, P. M. Hinz, et al. "Improved Constraints on the Disk around MWC 349A from the 23 m LBTI." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625165.

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We present new spatially resolved observations of MWC 349A from the Large Binocular Telescope Interferometer (LBTI), a 23 m baseline interferometer made up of two, co-mounted 8 m telescopes. MWC 349A is a B[e] star with an unknown evolutionary state. Proposed scenarios range from a young stellar object, to a B[e] supergiant, to a tight binary system. Radio continuum and recombination line observations of this source revealed a sub-arcsecond bipolar outflow surrounding an similar to 100 mas circumstellar disk. Follow-up infrared studies detected the disk, and suggested that it may have skew and

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Schneider, Glenn, John H. Debes, Carol A. Grady, et al. "The HR 4796A Debris System: Discovery of Extensive Exo-ring Dust Material." IOP PUBLISHING LTD, 2018. http://hdl.handle.net/10150/626527.

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The optically and IR-bright and starlight-scattering HR 4796A ringlike debris disk is one of the most-(and best-) studied exoplanetary debris systems. The presence of a yet-undetected planet has been inferred (or suggested) from the narrow width and inner/outer truncation radii of its r = 1.'' 05 (77 au) debris ring. We present new, highly sensitive Hubble Space Telescope (HST) visible-light images of the HR 4796A circumstellar debris system and its environment over a very wide range of stellocentric angles from 0.'' 32 (23 au) to approximate to 15 '' (1100 au). These very high-contrast images

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Leto, P., Courtney Trigilio, Lidia M. Oskinova, et al. "A Combined Multiwavelength VLA/ALMA/Chandra Study Unveils the Complex Magnetosphere of the B-Type Star HR5907." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etsu-works/2682.

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We present new radio/millimeter measurements of the hot magnetic star HR 5907 obtained with the VLA and ALMA interferometers. We find that HR 5907 is the most radio luminous early type star in the cm–mm band among those presently known. Its multi-wavelength radio light curves are strongly variable with an amplitude that increases with radio frequency. The radio emission can be explained by the populations of the non-thermal electrons accelerated in the current sheets on the outer border of the magnetosphere of this fast-rotating magnetic star. We classify HR 5907 as another member of the growi

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Leto, P., Corrado Trigilio, Lidia M. Oskinova, et al. "The Detection of Variable Radio Emission from the Fast Rotating Magnetic Hot B-Star HR 7355 and Evidence for Its X-Ray Aurorae." Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etsu-works/2695.

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In this paper we investigate the multiwavelengths properties of the magnetic early B-type star HR7355. We present its radio light curves at several frequencies, taken with the Jansky Very Large Array, and X-ray spectra, taken with the XMM X-ray telescope. Modeling of the radio light curves for the Stokes I and V provides a quantitative analysis of the HR7355 magnetosphere. A comparison between HR7355 and a similar analysis for the Ap star CUVir, allows us to study how the different physical parameters of the two stars affect the structure of the respective magnetospheres where the non-thermal

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Sicilia-Aguilar, A., A. Oprandi, D. Froebrich, et al. "The 2014–2017 outburst of the young star ASASSN-13db." EDP SCIENCES S A, 2017. http://hdl.handle.net/10150/626256.

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Context. Accretion outbursts are key elements in star formation. ASASSN-13db is a M5-type star with a protoplanetary disk, the lowest-mass star known to experience accretion outbursts. Since its discovery in 2013, it has experienced two outbursts, the second of which started in November 2014 and lasted until February 2017. Aims. We explore the photometric and spectroscopic behavior of ASASSN-13db during the 2014-2017 outburst. Methods. We use high- and low-resolution spectroscopy and time-resolved photometry from the ASAS-SN survey, the LCOGT and the Beacon Observatory to study the light curve

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Decin, L., A. M. S. Richards, T. J. Millar, et al. "ALMA-resolved salt emission traces the chemical footprint and inner wind morphology of VY Canis Majoris." EDP SCIENCES S A, 2016. http://hdl.handle.net/10150/621992.

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Context. At the end of their lives, most stars lose a significant amount of mass through a stellar wind. The specific physical and chemical circumstances that lead to the onset of the stellar wind for cool luminous stars are not yet understood. Complex geometrical morphologies in the circumstellar envelopes prove that various dynamical and chemical processes are interlocked and that their relative contributions are not easy to disentangle. Aims. We aim to study the inner-wind structure (R < 250 R-star) of the well-known red supergiant VY CMa, the archetype for the class of luminous red supergi

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Balog, Zoltan, Nick Siegler, G. H. Rieke, et al. "PROTOPLANETARY AND TRANSITIONAL DISKS IN THE OPEN STELLAR CLUSTER IC 2395." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622451.

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We present new deep UBVRI images and high-resolution multi-object optical spectroscopy of the young (similar to 6-10 Myr old), relatively nearby (800 pc) open cluster IC 2395. We identify nearly 300 cluster members and use the photometry to estimate their spectral types, which extend from early B to middle M. We also present an infrared imaging survey of the central region using the IRAC and MIPS instruments on board the Spitzer Space Telescope, covering the wavelength range from 3.6 to 24 mu m. Our infrared observations allow us to detect dust in circumstellar disks originating over a typical

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