210 results on '"J J Hermes"'
Search Results
2. JWST Directly Images Giant Planet Candidates Around Two Metal-polluted White Dwarf Stars
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Susan E. Mullally, John Debes, Misty Cracraft, Fergal Mullally, Sabrina Poulsen, Loic Albert, Katherine Thibault, William T. Reach, J. J. Hermes, Thomas Barclay, Mukremin Kilic, and Elisa V. Quintana
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DA stars ,Exoplanet astronomy ,Exoplanet detection methods ,James Webb Space Telescope ,Astrophysics ,QB460-466 - Abstract
We report the discovery of two directly imaged, giant planet candidates orbiting the metal-rich, hydrogen atmosphere white dwarfs WD 1202−232 and WD 2105−82. JWST’s Mid-Infrared Instrument (MIRI) data on these two stars show a nearby resolved source at a projected separation of 11.47 and 34.62 au, respectively. Assuming the planets formed at the same time as their host stars, with total ages of 5.3 and 1.6 Gyr, the MIRI photometry is consistent with giant planets with masses ≈1–7 M _Jup . The probability of both candidates being false positives due to red background sources is approximately 1 in 3000. If confirmed, these would be the first directly imaged planets that are similar in both age and separation to the giant planets in our own solar system, and they would demonstrate that widely separated giant planets like Jupiter survive stellar evolution. Giant planet perturbers are widely used to explain the tidal disruption of asteroids around metal-polluted white dwarfs. Confirmation of these two planet candidates with future MIRI imaging would provide evidence that directly links giant planets to metal pollution in white dwarf stars.
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- 2024
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3. Two new white dwarfs with variable magnetic Balmer emission lines
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Joshua S Reding, J J Hermes, J C Clemens, R J Hegedus, and B C Kaiser
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- 2023
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4. Using 3.4 μm Variability toward White Dwarfs as a Signpost of Remnant Planetary Systems
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Joseph A. Guidry, J. J. Hermes, Kishalay De, Lou Baya Ould Rouis, Brison B. Ewing, and B. C. Kaiser
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White dwarf stars ,Debris disks ,Variable stars ,Exoplanet systems ,Infrared excess ,Transient detection ,Astrophysics ,QB460-466 - Abstract
Roughly 2% of white dwarfs harbor planetary debris disks detectable via infrared excesses, but only a few percent of these disks show a gaseous component, distinguished by their double-peaked emission at the near-infrared calcium triplet. Previous studies found that most debris disks around white dwarfs are variable at 3.4 and 4.5 μ m, but they analyzed only a few of the now 21 published disks showing calcium emission. To test if most published calcium emission disks exhibit large-amplitude stochastic variability in the near-infrared, we use light curves generated from the unWISE images at 3.4 μ m that are corrected for proper motion to characterize the near-infrared variability of these disks against samples of disks without calcium emission, highly variable cataclysmic variables, and 3215 isolated white dwarfs. We find that most calcium emission disks are extremely variable: 6/11 with sufficient signal-to-noise show high-amplitude variability in their 3.4 μ m light curves. These results lend further credence to the notion that disks showing gaseous debris in emission are the most collisionally active. Under the assumption that 3.4 μ m variability is characteristic of white dwarfs with dusty debris disks, we generate a catalog of 104 high-confidence near-infrared variable white dwarfs, 84 of which are published as variable for the first time. We do near-infrared spectroscopic follow-up of seven new candidate 3.4 μ m variables, confirming at least one new remnant planetary system, and posit that empirical near-infrared variability can be a discovery engine for debris disks showing gaseous emission.
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- 2024
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5. A Test of Spectroscopic Age Estimates of White Dwarfs Using Wide WD+WD Binaries
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Tyler M. Heintz, J. J. Hermes, P.-E. Tremblay, Lou Baya Ould Rouis, Joshua S. Reding, B. C. Kaiser, and Jennifer L. van Saders
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Binary stars ,White dwarf stars ,Stellar ages ,Astrophysics ,QB460-466 - Abstract
White dwarf stars have been used for decades as precise and accurate age indicators. This work presents a test of the reliability of white dwarf total ages when spectroscopic observations are available. We conduct follow-up spectroscopy of 148 individual white dwarfs in widely separated double-white-dwarf (WD+WD) binaries. We supplement the sample with 264 previously published white dwarf spectra, as well as 1292 high-confidence white dwarf spectral types inferred from their Gaia XP spectra. We find that spectroscopic fits to optical spectra do not provide noticeable improvement to the age agreement among white dwarfs in wide WD+WD binaries. The median age agreement is ≈1.5 σ for both photometrically and spectroscopically determined total ages, for pairs of white dwarfs with each having a total age uncertainty < 20%. For DA white dwarfs, we further find that photometrically determined atmospheric parameters from spectral energy distribution fitting give better total age agreement (1.0 σ , 0.2 Gyr, or 14% of the binary’s average total age) compared to spectroscopically determined parameters from Balmer-line fits (agreement of 1.5 σ , 0.3 Gyr, or 28% of binary’s average total age). We find further evidence of a significant merger fraction among wide WD+WD binaries: across multiple spectroscopically identified samples, roughly 20% are inconsistent with a monotonically increasing initial–final mass relation. We recommend the acquisition of an identification spectrum to ensure the correct atmospheric models are used in photometric fits in order to determine the most accurate total age of a white dwarf star.
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- 2024
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6. Discovery of a Proto–White Dwarf with a Massive Unseen Companion
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Gautham Adamane Pallathadka, Vedant Chandra, Nadia L. Zakamska, Hsiang-Chih Hwang, Yossef Zenati, J. J. Hermes, Kareem El-Badry, Boris T. Gänsicke, Sean Morrison, Nicole R. Crumpler, and Stefan Arseneau
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Binary stars ,White dwarf stars ,Neutron stars ,Low mass stars ,Astrophysics ,QB460-466 - Abstract
We report the discovery of SDSS J022932.28+713002.7, a nascent extremely low-mass (ELM) white dwarf (WD) orbiting a massive (>1 M _⊙ at 2 σ confidence) companion with a period of 36 hr. We use a combination of spectroscopy, including data from the ongoing fifth-generation Sloan Digital Sky Survey (SDSS-V), and photometry to measure the stellar parameters of the primary pre-ELM WD. The lightcurve of the primary WD exhibits ellipsoidal variation, which we combine with radial velocity data and PHOEBE binary simulations to estimate the mass of the invisible companion. We find that the primary WD has mass M _1 = ${0.18}_{-0.02}^{+0.02}$ M _⊙ and the unseen secondary has mass M _2 = ${1.19}_{-0.14}^{+0.21}$ M _⊙ . The mass of the companion suggests that it is most likely a near-Chandrasekhar-mass WD or a neutron star. It is likely that the system recently went through a Roche lobe overflow from the visible primary onto the invisible secondary. The dynamical configuration of the binary is consistent with the theoretical evolutionary tracks for such objects, and the primary is currently in its contraction phase. The measured orbital period puts this system on a stable evolutionary path which, within a few gigayears, will lead to a contracted ELM WD orbiting a massive compact companion.
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- 2024
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7. Measuring White Dwarf Variability from Sparsely Sampled Gaia DR3 Multi-epoch Photometry
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Maya Steen, J. J. Hermes, Joseph A. Guidry, Annabelle Paiva, Jay Farihi, Tyler M. Heintz, Brison B. Ewing, and Nathaniel Berry
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White dwarf stars ,Periodic variable stars ,Light curves ,Astrophysics ,QB460-466 - Abstract
White dwarf stars are ubiquitous in the Galaxy, and are essential to understanding stellar evolution. While most white dwarfs are photometrically stable and reliable flux standards, some can be highly variable, which can reveal unique details about the endpoints of low-mass stellar evolution. In this study, we characterize a sample of high-confidence white dwarfs with multi-epoch photometry from Gaia Data Release 3. We compare these Gaia light curves with light curves from the Zwicky Transiting Facility and the Transiting Exoplanet Survey Satellite to see when Gaia data independently can accurately measure periods of variability. From this sample, 105 objects have variability periods measured from the Gaia light curves independently, with periods as long as roughly 9.5 days and as short as 256.2 s (roughly 4 minutes), including seven systems with periods shorter than 1000 s. We discover 86 new objects from the 105 target samples, including pulsating, spotted, and binary white dwarfs, and even a new 68.4 minute eclipsing cataclysmic variable. The median amplitude of the absolute photometric variability we confirm from Gaia independently is 1.4%, demonstrating that Gaia epoch photometry is capable of measuring short-term periods even when observations are sparse.
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- 2024
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8. A MIRI Search for Planets and Dust around WD 2149+021
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Sabrina Poulsen, John Debes, Misty Cracraft, Susan E. Mullally, William T. Reach, Mukremin Kilic, Fergal Mullally, Loic Albert, Katherine Thibault, J. J. Hermes, Thomas Barclay, and Elisa V. Quintana
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Exoplanet astronomy ,Circumstellar dust ,White dwarf stars ,High contrast techniques ,Direct imaging ,Photometry ,Astronomy ,QB1-991 - Abstract
The launch of JWST has ushered in a new era of high-precision infrared astronomy, allowing us to probe nearby white dwarfs for cold dust, exoplanets, and tidally heated exomoons. While previous searches for these exoplanets have successfully ruled out companions as small as 7–10 Jupiter masses ( M _Jup) , no instrument prior to JWST has been sensitive to the likely more common sub-Jovian-mass planets around white dwarfs. In this paper, we present the first multiband photometry (F560W, F770W, F1500W, F2100W) taken of WD 2149+021 with the Mid-Infrared Instrument on JWST. After a careful search for both resolved and unresolved planets, we do not identify any compelling candidates around WD 2149+021. Our analysis indicates that we are sensitive to companions as small as ∼0.5 M _Jup outwards of 1.″263 (28.3 au) and ∼1.0 M _Jup at the innermost working angle (0.″654, 14.7 au) at 3 Gyr with 5 σ confidence, placing significant constraints on any undetected companions around this white dwarf. The results of these observations emphasize the exciting future of sub-Jovian planet detection limits by JWST, which can begin to constrain how often these planets survive their host stars' evolution.
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- 2024
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9. Flare Hunting in Hot Subdwarf and White Dwarf Stars from Cycles 1–5 of TESS Photometry
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Keyu Xing, Weikai Zong, Roberto Silvotti, Jian-Ning Fu, Stéphane Charpinet, Tianqi Cang, J. J. Hermes, Xiao-Yu Ma, Haotian Wang, Xuan Wang, Tao Wu, and Jiaxin Wang
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White dwarf stars ,B subdwarf stars ,Stellar flares ,Photometry ,Random Forests ,Astrophysics ,QB460-466 - Abstract
Stellar flares are critical phenomena on stellar surfaces, which are closely tied to stellar magnetism. While extensively studied in main-sequence (MS) stars, their occurrence in evolved compact stars, specifically hot subdwarfs and white dwarfs (WDs), remains scarcely explored. Based on Cycles 1–5 of TESS photometry, we conducted a pioneering survey of flare events in ∼12,000 compact stars, corresponding to ∼38,000 light curves with a 2 minute cadence. Through dedicated techniques for detrending light curves, identifying preliminary flare candidates, and validating them via machine learning, we established a catalog of 1016 flares from 193 compact stars, including 182 from 58 sdB/sdO stars and 834 from 135 WDs, respectively. However, all flaring compact stars showed signs of contamination from nearby objects or companion stars, preventing sole attribution of the detected flares. For WDs, it is highly probable that the flares originated from their cool MS companions. In contrast, the higher luminosities of sdB/sdO stars diminish companion contributions, suggesting that detected flares originated from sdB/sdO stars themselves or through close magnetic interactions with companions. Focusing on a refined sample of 23 flares from 13 sdB/sdO stars, we found their flare frequency distributions were slightly divergent from those of cool MS stars; instead, they resemble those of hot B/A-type MS stars having radiative envelopes. This similarity implies that the flares on sdB/sdO stars, if these flares did originate from them, may share underlying mechanisms with hot MS stars, which warrants further investigation.
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- 2024
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10. The Morphology of the Asteroidal Dust around White Dwarf Stars: Optical and Near-infrared Pulsations in G29-38
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Ted von Hippel, J. Farihi, J. L. Provencal, S. J. Kleinman, J. E. Pringle, A. Swan, G. Fontaine, J. J. Hermes, J. Sargent, Z. Savery, W. Cooper, V. Kim, V. Kozyreva, M. Krugov, A. Kusakin, A. Moss, W. Ogloza, Erika Pakštienė, A. Serebryanskiy, Eda Sonbas, B. Walter, M. Zejmo, and S. Zola
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Circumstellar dust ,Asteroseismology ,White dwarf stars ,ZZ Ceti stars ,Astrophysics ,QB460-466 - Abstract
More than 36 yr have passed since the discovery of the infrared excess from circumstellar dust orbiting the white dwarf G29-38, which at 17.5 pc it is the nearest and brightest of its class. The precise morphology of the orbiting dust remains only marginally constrained by existing data, subject to model-dependent inferences, and thus fundamental questions of its dynamical origin and evolution persist. This study presents a means to constrain the geometric distribution of the emitting dust using stellar pulsations measured at optical wavelengths as a variable illumination source of the dust, which reradiates primarily in the infrared. By combining optical photometry from the Whole Earth Telescope with 0.7–2.5 μ m spectroscopy obtained with SpeX at NASA’s Infrared Telescope Facility, we detect luminosity variations at all observed wavelengths, with variations at most wavelengths corresponding to the behavior of the pulsating stellar photosphere, but toward the longest wavelengths the light curves probe the corresponding time variability of the circumstellar dust. In addition to developing methodology, we find the pulsation amplitudes decrease with increasing wavelength for principal pulsation modes, yet increase beyond ≈2 μ m for nonlinear combination frequencies. We interpret these results as combination modes derived from the principal modes of identical ℓ values and discuss the implications for the morphology of the warm dust. We also draw attention to some discrepancies between our findings and theoretical expectations for the results of the nonlinearity imposed by the surface convection zone on mode–mode interactions and on the behavior of the first harmonic of the highest-amplitude pulsation mode.
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- 2024
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11. Measuring the Mass–Radius Relation of White Dwarfs Using Wide Binaries
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Stefan Arseneau, Vedant Chandra, Hsiang-Chih Hwang, Nadia L. Zakamska, Gautham Adamane Pallathadka, Nicole R. Crumpler, J. J. Hermes, Kareem El-Badry, Hans-Walter Rix, Keivan G. Stassun, Boris T. Gänsicke, Joel R. Brownstein, and Sean Morrison
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White dwarf stars ,DA stars ,Gaia ,Astrophysics ,QB460-466 - Abstract
Measuring the mass–radius relation of individual white dwarfs is an empirically challenging task that has been performed for only a few dozen stars. We measure the white dwarf mass–radius relation using the gravitational redshifts and radii of 135 white dwarfs in wide binaries with main-sequence companions. We obtain the radial velocities of these systems using the main-sequence companion, and subtract these Doppler redshifts from the white dwarfs’ apparent motions, isolating their gravitational redshifts. We use Gaia data to calculate the surface temperatures and radii of these white dwarfs, thereby deriving an empirical gravitational redshift–radius relation. This work demonstrates the utility of low-resolution Galactic surveys to measure the white dwarf equation of state. Our results are consistent with theoretical models, and represent the largest sample of individual white dwarf gravitational redshift measurements to date.
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- 2024
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12. Discovery of a young pre-intermediate polar
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David J Wilson, Odette Toloza, John D Landstreet, Boris T Gänsicke, Jeremy J Drake, J J Hermes, and Detlev Koester
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- 2021
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13. Collisions in a gas-rich white dwarf planetary debris disc
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Andrew Swan, Scott J Kenyon, Jay Farihi, Erik Dennihy, Boris T Gänsicke, J J Hermes, Carl Melis, and Ted von Hippel
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- 2021
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14. The Eighteenth Data Release of the Sloan Digital Sky Surveys: Targeting and First Spectra from SDSS-V
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Andrés Almeida, Scott F. Anderson, Maria Argudo-Fernández, Carles Badenes, Kat Barger, Jorge K. Barrera-Ballesteros, Chad F. Bender, Erika Benitez, Felipe Besser, Jonathan C. Bird, Dmitry Bizyaev, Michael R. Blanton, John Bochanski, Jo Bovy, William Nielsen Brandt, Joel R. Brownstein, Johannes Buchner, Esra Bulbul, Joseph N. Burchett, Mariana Cano Díaz, Joleen K. Carlberg, Andrew R. Casey, Vedant Chandra, Brian Cherinka, Cristina Chiappini, Abigail A. Coker, Johan Comparat, Charlie Conroy, Gabriella Contardo, Arlin Cortes, Kevin Covey, Jeffrey D. Crane, Katia Cunha, Collin Dabbieri, James W. Davidson Jr, Megan C. Davis, Anna Barbara de Andrade Queiroz, Nathan De Lee, José Eduardo Méndez Delgado, Sebastian Demasi, Francesco Di Mille, John Donor, Peter Dow, Tom Dwelly, Mike Eracleous, Jamey Eriksen, Xiaohui Fan, Emily Farr, Sara Frederick, Logan Fries, Peter Frinchaboy, Boris T. Gänsicke, Junqiang Ge, Consuelo González Ávila, Katie Grabowski, Catherine Grier, Guillaume Guiglion, Pramod Gupta, Patrick Hall, Keith Hawkins, Christian R. Hayes, J. J. Hermes, Lorena Hernández-García, David W. Hogg, Jon A. Holtzman, Hector Javier Ibarra-Medel, Alexander Ji, Paula Jofre, Jennifer A. Johnson, Amy M. Jones, Karen Kinemuchi, Matthias Kluge, Anton Koekemoer, Juna A. Kollmeier, Marina Kounkel, Dhanesh Krishnarao, Mirko Krumpe, Ivan Lacerna, Paulo Jakson Assuncao Lago, Chervin Laporte, Chao Liu, Ang Liu, Xin Liu, Alexandre Roman Lopes, Matin Macktoobian, Steven R. Majewski, Viktor Malanushenko, Dan Maoz, Thomas Masseron, Karen L. Masters, Gal Matijevic, Aidan McBride, Ilija Medan, Andrea Merloni, Sean Morrison, Natalie Myers, Szabolcs Mészáros, C. Alenka Negrete, David L. Nidever, Christian Nitschelm, Daniel Oravetz, Audrey Oravetz, Kaike Pan, Yingjie Peng, Marc H. Pinsonneault, Rick Pogge, Dan Qiu, Solange V. Ramirez, Hans-Walter Rix, Daniela Fernández Rosso, Jessie Runnoe, Mara Salvato, Sebastian F. Sanchez, Felipe A. Santana, Andrew Saydjari, Conor Sayres, Kevin C. Schlaufman, Donald P. Schneider, Axel Schwope, Javier Serna, Yue Shen, Jennifer Sobeck, Ying-Yi Song, Diogo Souto, Taylor Spoo, Keivan G. Stassun, Matthias Steinmetz, Ilya Straumit, Guy Stringfellow, José Sánchez-Gallego, Manuchehr Taghizadeh-Popp, Jamie Tayar, Ani Thakar, Patricia B. Tissera, Andrew Tkachenko, Hector Hernandez Toledo, Benny Trakhtenbrot, José G. Fernández-Trincado, Nicholas Troup, Jonathan R. Trump, Sarah Tuttle, Natalie Ulloa, Jose Antonio Vazquez-Mata, Pablo Vera Alfaro, Sandro Villanova, Stefanie Wachter, Anne-Marie Weijmans, Adam Wheeler, John Wilson, Leigh Wojno, Julien Wolf, Xiang-Xiang Xue, Jason E. Ybarra, Eleonora Zari, and Gail Zasowski
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Surveys ,Astronomy databases ,Astronomy data acquisition ,Astronomy software ,Astrophysics ,QB460-466 - Abstract
The eighteenth data release (DR18) of the Sloan Digital Sky Survey (SDSS) is the first one for SDSS-V, the fifth generation of the survey. SDSS-V comprises three primary scientific programs or “Mappers”: the Milky Way Mapper (MWM), the Black Hole Mapper (BHM), and the Local Volume Mapper. This data release contains extensive targeting information for the two multiobject spectroscopy programs (MWM and BHM), including input catalogs and selection functions for their numerous scientific objectives. We describe the production of the targeting databases and their calibration and scientifically focused components. DR18 also includes ∼25,000 new SDSS spectra and supplemental information for X-ray sources identified by eROSITA in its eFEDS field. We present updates to some of the SDSS software pipelines and preview changes anticipated for DR19. We also describe three value-added catalogs (VACs) based on SDSS-IV data that have been published since DR17, and one VAC based on the SDSS-V data in the eFEDS field.
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- 2023
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15. Erratum: 'Testing White Dwarf Age Estimates Using Wide Double White Dwarf Binaries from Gaia EDR3' (2022, ApJ, 934, 148)
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Tyler M. Heintz, J. J. Hermes, Kareem El-Badry, Charlie Walsh, Jennifer L. van Saders, C. E. Fields, and Detlev Koester
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Astrophysics ,QB460-466 - Published
- 2023
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16. A test of the planet–star unipolar inductor for magnetic white dwarfs
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N Walters, J Farihi, T R Marsh, S Bagnulo, J D Landstreet, J J Hermes, N Achilleos, A Wallach, M Hart, and C J Manser
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- 2021
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17. Constraining planet formation around 6–8 M⊙ stars
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Dimitri Veras, Pier-Emmanuel Tremblay, J J Hermes, Catriona H McDonald, Grant M Kennedy, Farzana Meru, and Boris T Gänsicke
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- 2020
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18. Pulse Timing Discovery of a Three-day Companion to the Hot Subdwarf BPM 36430
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Bryce A. Smith, Brad N. Barlow, Benjamin Rosenthal, J. J. Hermes, and Veronika Schaffenroth
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- 2022
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19. A DZ white dwarf with a 30 MG magnetic field
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M A Hollands, S Stopkowicz, M-P Kitsaras, F Hampe, S Blaschke, and J J Hermes
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Earth and Planetary Astrophysics (astro-ph.EP) ,Chemical Physics (physics.chem-ph) ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Physics - Chemical Physics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics - Earth and Planetary Astrophysics - Abstract
Magnetic white dwarfs with field strengths below 10 MG are easy to recognise since the Zeeman splitting of spectral lines appears proportional to the magnetic field strength. For fields $\geq 100$ MG, however, transition wavelengths become chaotic, requiring quantum-chemical predictions of wavelengths and oscillator strengths with a non-perturbative treatment of the magnetic field. While highly accurate calculations have previously been performed for hydrogen and helium, the variational techniques employed become computationally intractable for systems with more than three to four electrons. Modern computational techniques, such as finite-field coupled-cluster theory, allow the calculation of many-electron systems in arbitrarily strong magnetic fields. Because around 25 percent of white dwarfs have metal lines in their spectra, and some of those are also magnetic, the possibility arises for some metals to be observed in very strong magnetic fields, resulting in unrecognisable spectra. We have identified SDSSJ114333.48+661531.83 as a magnetic DZ white dwarf, with a spectrum exhibiting many unusually shaped lines at unknown wavelengths. Using atomic data calculated from computational finite-field coupled-cluster methods, we have identified some of these lines arising from Na, Mg, and Ca. Surprisingly, we find a relatively low field strength of 30 MG, where the large number of overlapping lines from different elements make the spectrum challenging to interpret at a much lower field strength than for DAs and DBs. Finally we model the field structure of SDSSJ1143+6615 finding the data are consistent with an offset dipole., Comment: 17 pages, 8 figures, Accepted for publication in MNRAS
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- 2023
20. Partly burnt runaway stellar remnants from peculiar thermonuclear supernovae
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R Raddi, M A Hollands, D Koester, J J Hermes, B T Gänsicke, U Heber, K J Shen, D M Townsley, A F Pala, J S Reding, O F Toloza, I Pelisoli, S Geier, N P Gentile Fusillo, U Munari, and J Strader
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- 2019
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21. Detections and constraints on white dwarf variability from time-series GALEX observations
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D M Rowan, M A Tucker, B J Shappee, and J J Hermes
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- 2019
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22. Two substellar survivor candidates: one found and one missing
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N Walters, J Farihi, T R Marsh, E Breedt, P W Cauley, T von Hippel, and J J Hermes
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Earth and Planetary Astrophysics (astro-ph.EP) ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,FOS: Physical sciences ,Astronomy and Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics - Earth and Planetary Astrophysics - Abstract
This study presents observations of two possible substellar survivors of post-main sequence engulfment, currently orbiting white dwarf stars. Infrared and optical spectroscopy of GD 1400 reveal a 9.98 h orbital period, where the benchmark brown dwarf has $M_2=68\pm8$ M$_{\rm Jup}$, $T_{\rm eff}\approx2100$ K, and a cooling age under 1 Gyr. A substellar mass in the lower range of allowed values is favoured by the gravitational redshift of the primary. Synthetic brown dwarf spectra are able to reproduce the observed CO bands, but lines below the bandhead are notably overpredicted. The known infrared excess towards PG 0010+281 is consistent with a substellar companion, yet no radial velocity or photometric variability is found despite extensive searches. Three independent stellar mass determinations all suggest enhanced mass loss associated with binary evolution, where the youngest total age for an isolated star is $7.5\pm2.5$ Gyr. A possible solution to this conundrum is the cannibalization of one or more giant planets, which enhanced mass loss post-main sequence, but were ultimately destroyed. PG 0010+281 is likely orbited by a debris disk that is comfortably exterior to the Roche limit, adding to the growing number of non-canonical disks orbiting white dwarfs. At present, only L-type (brown) dwarfs are known to survive direct engulfment during the post-main sequence, whereas T- and Y-type substellar companions persist at wide separations. These demographics indicate that roughly 50 M$_{\rm Jup}$ is required to robustly avoid post-main sequence annihilation, suggesting all closely-orbiting giant planets are consumed, which may contribute to mass loss and magnetic field generation in white dwarfs and their immediate progenitors., Comment: 15 pages, 8 figures, 3 tables. Accepted to MNRAS, dedicated to the memory of Tom Marsh
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- 2022
23. Evidence for mass accretion driven by spiral shocks onto the white dwarf in SDSS J123813.73–033933.0
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A F Pala, B T Gänsicke, T R Marsh, E Breedt, J J Hermes, J D Landstreet, M R Schreiber, D M Townsley, L Wang, A Aungwerojwit, F–J Hambsch, B Monard, G Myers, P Nelson, R Pickard, G Poyner, D E Reichart, R Stubbings, P Godon, P Szkody, D De Martino, V S Dhillon, C Knigge, and S G Parsons
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- 2018
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24. Discovery of the first resolved triple white dwarf
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M Perpinyà-Vallès, A Rebassa-Mansergas, B T Gänsicke, S Toonen, J J Hermes, N P Gentile Fusillo, and P-E Tremblay
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- 2018
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25. Testing White Dwarf Age Estimates Using Wide Double White Dwarf Binaries from Gaia EDR3
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Tyler M. Heintz, J. J. Hermes, Kareem El-Badry, Charlie Walsh, Jennifer L. van Saders, C. E. Fields, and Detlev Koester
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White dwarf stars ,Wide binary stars ,Stellar ages ,Astrophysics ,QB460-466 - Abstract
White dwarf (WD) stars evolve simply and predictably, making them reliable age indicators. However, self-consistent validation of the methods for determining WD total ages has yet to be widely performed. This work uses 1565 wide (>100 au) WD+WD binaries and 24 new triples containing at least two WDs to test the accuracy and validity of WD total age determinations. For these 1589 wide double WD binaries and triples, we derive the total age of each WD using photometric data from all-sky surveys, in conjunction with Gaia parallaxes and current hydrogen atmosphere WD models. Ignoring the initial-to-final mass relation and considering only WD cooling ages, we find that roughly 21%–36% of the more massive WDs in a system have a shorter cooling age. Since more massive WDs should be born as more massive main-sequence stars, we interpret this unphysical disagreement as evidence of prior mergers or the presence of an unresolved companion, suggesting that roughly 21%–36% of wide WD+WD binaries were once triples. Among the 423 wide WD+WD pairs that pass high-fidelity cuts, we find that 25% total age uncertainties are generally appropriate for WDs with masses >0.63 M _⊙ and temperatures
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- 2022
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26. New Variable Hot Subdwarf Stars Identified from Anomalous Gaia Flux Errors, Observed by TESS, and Classified via Fourier Diagnostics
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Brad N. Barlow, Kyle A. Corcoran, Isabelle M. Parker, Thomas Kupfer, Péter Németh, J. J. Hermes, Isaac D. Lopez, Will J. Frondorf, David Vestal, and Jazzmyn Holden
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- 2022
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27. The Pulsating Helium-atmosphere White Dwarfs. I. New DBVs from the Sloan Digital Sky Survey
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Zachary P. Vanderbosch, J. J. Hermes, Don E. Winget, Michael H. Montgomery, Keaton J. Bell, Atsuko Nitta, and S. O. Kepler
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- 2022
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28. Asteroseismology of PG 1541 + 651 and BPM 31594 with TESS
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Alejandra D Romero, Gabriela Oliveira da Rosa, S O Kepler, Paul A Bradley, Murat Uzundag, Keaton J Bell, J J Hermes, and G R Lauffer
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Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,FOS: Physical sciences ,Astronomy and Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
We present the photometric data from TESS for two known ZZ Ceti stars, PG 1541+651 and BPM 31594. Before TESS, both objects only had observations from short runs from ground-based facilities, with three and one period detected, respectively. The TESS data allowed the detection of multiple periodicities, 12 for PG 1541$+$651, and six for BPM 31594, which enables us to perform a detailed asteroseismological study. For both objects we found a representative asteroseismic model with canonical stellar mass ~ 0.61 Msun and thick hydrogen envelopes, thicker than 10^(-5.3) M_*. The detection of triplets in the Fourier transform also allowed us to estimate mean rotation periods, being ~22 h for PG 1541+651 and 11.6 h for BPM 31594, which is consistent with range of values reported for other ZZ Ceti stars., Comment: 12 pages, 11 figures. Accepted for publication in MNRAS
- Published
- 2022
29. Anatomy of the hyper-runaway star LP 40–365 with Gaia
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R Raddi, M A Hollands, B T Gänsicke, D M Townsley, J J Hermes, N P Gentile Fusillo, and D Koester
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- 2018
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30. Masses of White Dwarf Binary Companions to Type Ia Supernovae Measured from Runaway Velocities
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Evan B. Bauer, Vedant Chandra, Ken J. Shen, and J. J. Hermes
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- 2021
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31. The SN Ia runaway LP 398-9: detection of circumstellar material and surface rotation
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Vedant Chandra, Hsiang-Chih Hwang, Nadia L Zakamska, Simon Blouin, Andrew Swan, Thomas R Marsh, Ken J Shen, Boris T Gänsicke, J J Hermes, Odelia Putterman, Evan B Bauer, Evan Petrosky, Vikram S Dhillon, Stuart P Littlefair, and Richard P Ashley
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,FOS: Physical sciences ,Astronomy and Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
A promising progenitor scenario for Type Ia supernovae (SNeIa) is the thermonuclear detonation of a white dwarf in a close binary system with another white dwarf. After the primary star explodes, the surviving donor can be spontaneously released as a hypervelocity runaway. One such runaway donor candidate is LP 398-9, whose orbital trajectory traces back $\approx 10^5$ years to a known supernova remnant. Here we report the discovery of carbon-rich circumstellar material around LP 398-9, revealed by a strong infrared excess and analyzed with follow-up spectroscopy. The circumstellar material is most plausibly composed of inflated layers from the star itself, mechanically and radioactively heated by the past companion's supernova. We also detect a 15.4 hr periodic signal in the UV and optical light curves of LP 398-9, which we interpret as surface rotation. The rotation rate is consistent with theoretical predictions from this supernova mechanism, and the brightness variations could originate from surface inhomogeneity deposited by the supernova itself. Our observations strengthen the case for this double-degenerate SNIa progenitor channel, and motivate the search for more runaway SNIa donors., Accepted to MNRAS
- Published
- 2022
32. 8.9 hr Rotation in the Partly Burnt Runaway Stellar Remnant LP 40-365 (GD 492)
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J. J. Hermes, Odelia Putterman, Mark A. Hollands, David J. Wilson, Andrew Swan, Roberto Raddi, Ken J. Shen, and Boris T. Gänsicke
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- 2021
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33. I Spy Transits and Pulsations: Empirical Variability in White Dwarfs Using Gaia and the Zwicky Transient Facility
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Joseph A. Guidry, Zachary P. Vanderbosch, J. J. Hermes, Brad N. Barlow, Isaac D. Lopez, Thomas M. Boudreaux, Kyle A. Corcoran, Keaton J. Bell, M. H. Montgomery, Tyler M. Heintz, Barbara G. Castanheira, Joshua S. Reding, Bart H. Dunlap, D. E. Winget, Karen I. Winget, and J. W. Kuehne
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- 2021
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34. Seeing Double: ASASSN-18bt Exhibits a Two-component Rise in the Early-time K2 Light Curve
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B. J. Shappee, T. W.-S. Holoien, M. R. Drout, K. Auchettl, M. D. Stritzinger, C. S. Kochanek, K. Z. Stanek, E. Shaya, G. Narayan, J. S. Brown, S. Bose, D. Bersier, J. Brimacombe, Ping Chen, Subo Dong, S. Holmbo, B. Katz, J. A. Munoz, R. L. Mutel, R. S. Post, J. L. Prieto, J. Shields, D. Tallon, T. A. Thompson, P. J. Vallely, S. Villanueva Jr, L. Denneau, H. Flewelling, A. N. Heinze, K. W. Smith, B. Stalder, J. L. Tonry, H. Weiland, T. Barclay, G. Barentsen, A. M. Cody, J. Dotson, F. Foerster, P. Garnavich, M. Gully-Santiago, C. Hedges, S. Howell, D. Kasen, S. Margheim, R. Mushotzky, A. Rest, B. E. Tucker, A. Villar, A. Zenteno, G. Beerman, R. Bjella, G. Castillo, J. Coughlin, B. Elsaesser, S. Flynn, R. Gangopadhyay, K. Griest, M. Hanley, J. Kampmeier, R. Kloetzel, L. Kohnert, C. Labonde, R. Larsen, K. A. Larson, K. M. McCalmont-Everton, C. McGinn, L. Migliorini, J. Moffatt, M. Muszynski, V. Nystrom, D. Osborne, M. Packard, C. A. Peterson, M. Redick, L. H. Reedy, S. E. Ross, B. Spencer, K. Steward, J. E. Van Cleve, J. Vinícius de Miranda-Cardoso, T. Weschler, A. Wheaton, J. Bulger, K. C. Chambers, H. A. Flewelling, M. E. Huber, T. B. Lowe, E. A. Magnier, A. S. B. Schultz, C. Z. Waters, M. Willman, E. Baron, Zhihao Chen, James M. Derkacy, Fang Huang, Linyi Li, Wenxiong Li, Xue Li, Jun Mo, Liming Rui, Hanna Sai, Lifan Wang, Lingzhi Wang, Xiaofeng Wang, Danfeng Xiang, Jicheng Zhang, Jujia Zhang, Kaicheng Zhang, Tianmeng Zhang, Xinghan Zhang, Xulin Zhao, P. J. Brown, J. J. Hermes, J. Nordin, S. Points, A. Sodor, and G. M. Strampelli
- Subjects
Astrophysics - Abstract
On 2018 February 4.41, the All-Sky Automated Survey for SuperNovae (ASAS-SN) discovered ASASSN-18bt in the K2 Campaign 16 field. With a redshift of z=0.01098 and a peak apparent magnitude of B(max)=14.31, ASASSN-18bt is the nearest and brightest SNe Ia yet observed by the Kepler spacecraft. Here we present the discovery of ASASSN-18bt, the K2 light curve, and prediscovery data from ASAS-SN and the Asteroid Terrestrial-impact Last Alert System. The K2 early-time light curve has an unprecedented 30-minute cadence and photometric precision for an SN Ia light curve, and it unambiguously shows a ∼4 day nearly linear phase followed by a steeper rise. Thus, ASASSN-18bt joins a growing list of SNe Ia whose early light curves are not well described by a single power law. We show that a double-power-law model fits the data reasonably well, hinting that two physical processes must be responsible for the observed rise. However, we find that current models of the interaction with a nondegenerate companion predict an abrupt rise and cannot adequately explain the initial, slower linear phase. Instead, we find that existing published models with shallow 56Ni are able to span the observed behavior and, with tuning, may be able to reproduce the ASASSN-18bt light curve. Regardless, more theoretical work is needed to satisfactorily model this and other early-time SNe Ia light curves. Finally, we use Swift X-ray nondetections to constrain the presence of circumstellar material (CSM) at much larger distances and lower densities than possible with the optical light curve. For a constant-density CSM, these nondetections constrain ρ<4.5×10(exp 5)per cu.cm at a radius of 4×10(exp 15) cm from the progenitor star. Assuming a wind-like environment, we place mass loss limits of M˙ < 8 x 10(exp -6) M(ʘ)per yr for v(w)=100 km/s, ruling out some symbiotic progenitor systems. This work highlights the power of well-sampled early-time data and the need for immediate multiband, high-cadence follow-up for progress in understanding SNe Ia.
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- 2018
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35. Photometric and Spectroscopic Properties of Type Ia Supernova 2018oh with Early Excess Emission from the Kepler 2 Observations
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Thomas Barclay, W. Li, X. Wang, J. Vinko, J. Mo, G. Hosseinzadeh, D. J. Sand, J. Zhang, H. Lin, T. Zhang, L. Wang, Z. Chen, D. Xiang, L. Rui, F. Huang, X. Li, X. Zhang, L. Li, E. Baron, J. M. Derkacy, X. Zhao, H. Sai, K. Zhang, D. A. Howell, C. McCully, I. Arcavi, S. Valenti, D. Hiramatsu, J. Burke, A. Rest, P. Garnavich, B. E. Tucker, G. Narayan, E. Shaya, S. Margheim, A. Zenteno, A. Villar, G. Dimitriadis, R. J. Foley, Y.-C. Pan, D. A. Coulter, O. D. Fox, S. W. Jha, D. O. Jones, D. N. Kasen, C. D. Kilpatrick, A. L. Piro, A. G. Riess, C. Rojas-Bravo, B. J. Shappee, T. W.-S. Holoien, K. Z. Stanek, M. R. Drout, K. Auchettl, C. S. Kochanek, J. S. Brown, S. Bose, D. Bersier, J. Brimacombe, P. Chen, S. Dong, S. Holmbo, J. A. Munoz, R. L. Mutel, R. S. Post, J. L. Prieto, J. Shields, D. Tallon, T. A. Thompson, P. J. Vallely, S. Villanueva Jr, S. J. Smartt, K. W. Smith, K. C. Chambers, H. A. Flewelling, M. E. Huber, E. A. Magnier, C. Z. Waters, A. S. B. Schultz, J. Bulger, T. B. Lowe, M. Willman, K. Sarneczky, A. Pal, J. C. Wheeler, A. Bodi, Zs. Bognar, B. Csak, B. Cseh, G. Csornyei, O. Hanyecz, B. Ignacz, Cs. Kalup, R. Konyves-Toth, L. Kriskovics, A. Ordasi, I. Rajmon5, A. Sodor, R. Szabo, R. Szakats, G. Zsidi, P. Milne, J. E. Andrews, N. Smith, C. Bilinski, P. J. Brown, J. Nordin, S. C. Williams, L. Galbany, J. Palmerio, I. M. Hook, C. Inserra, K. Maguire, Regis Cartier, A. Razza, C. P. Gutierrez, J. J. Hermes, J. S. Reding, B. C. Kaiser, J. L. Tonry, A. N. Heinze, L. Denneau, H. Weiland, B. Stalder, G. Barentsen, J Dotson, T Barclay, M Gully-Santiago, C. Hedges, A. M. Cody, S Howell, J. Coughlin, J. E. Van Cleve, J. Vinicius de Miranda Cardoso, K. A. Larson, K. M. McCalmont-Everton, C. A. Peterson, S. E. Ross, L. H. Reedy, D. Osborne, C. McGinn, L. Kohnert, L. Migliorini, A. Wheaton, B. Spencer, C. Labonde, G. Castillo, G. Beerman, K. Steward, M. Hanley, R. Larsen, R. Gangopadhyay, R. Kloetzel, T. Weschler, V. Nystrom, J. Moffatt, M. Redick, K. Griest, M. Packard, M. Muszynski, J. Kampmeier, R. Bjella, S. Flynn, and B. Elsaesser
- Subjects
Astrophysics ,Astronomy - Abstract
Supernova (SN) 2018oh (ASASSN-18bt) is the first spectroscopically confirmed Type Ia supernova (SN Ia) observed in the Kepler field. The Kepler data revealed an excess emission in its early light curve, allowing us to place interesting constraints on its progenitor system. Here we present extensive optical, ultraviolet, and nearinfrared photometry, as well as dense sampling of optical spectra, for this object. SN 2018oh is relatively normal in its photometric evolution, with a rise time of 18.3±0.3 days and Δ(m15)(B)=0.96±0.03 mag, but it seems to have bluer B−V colors. We construct the “UVOIR” bolometric light curve having a peak luminosity of 1.49×10(Exp 43) erg/s, from which we derive a nickel mass as 0.55±0.04M(ʘ) by fitting radiation diffusion models powered by centrally located 56Ni. Note that the moment when nickel-powered luminosity starts to emerge is +3.85 days after the first light in the Kepler data, suggesting other origins of the early-time emission, e.g., mixing of 56Ni to outer layers of the ejecta or interaction between the ejecta and nearby circumstellar material or a nondegenerate companion star. The spectral evolution of SN 2018oh is similar to that of a normal SN Ia but is characterized by prominent and persistent carbon absorption features. The CII features can be detected from the early phases to about 3 weeks after the maximum light, representing the latest detection of carbon ever recorded in an SN Ia. This indicates that a considerable amount of unburned carbon exists in the ejecta of SN 2018oh and may mix into deeper layers.
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- 2018
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36. Discovery of a young pre-intermediate polar
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John D. Landstreet, David J. Wilson, Jeremy J. Drake, J. J. Hermes, Detlev Koester, Boris T. Gänsicke, and Odette Toloza
- Subjects
Physics ,Rotation period ,010308 nuclear & particles physics ,FOS: Physical sciences ,White dwarf ,Cataclysmic variable star ,Astronomy and Astrophysics ,Field strength ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Orbital period ,01 natural sciences ,Common envelope ,Intermediate polar ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,010303 astronomy & astrophysics ,Stellar evolution ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics - Abstract
We present the discovery of a magnetic field on the white dwarf component in the detached post common envelope binary (PCEB) CC Cet. Magnetic white dwarfs in detached PCEBs are extremely rare, in contrast to the high incidence of magnetism in single white dwarfs and cataclysmic variables. We find Zeeman-split absorption lines in both ultraviolet Hubble Space Telescope (HST) spectra and archival optical spectra of CC Cet. Model fits to the lines return a mean magnetic field strength of approximately 600-700 kG. Differences in the best-fit magnetic field strength between two separate HST observations and the high v sin i of the lines indicate that the white dwarf is rotating with a period ~0.5 hours, and that the magnetic field is not axisymmetric about the spin axis. The magnetic field strength and rotation period are consistent with those observed among the intermediate polar class of cataclysmic variable, and we compute stellar evolution models that predict CC Cet will evolve into an intermediate polar in 7-17 Gyr. Among the small number of known PCEBs containing a confirmed magnetic white dwarf, CC Cet is the hottest (and thus youngest), with the weakest field strength, and cannot have formed via the recently proposed crystallisation/spin-up scenario. In addition to the magnetic field measurements, we update the atmospheric parameters of the CC Cet white dwarf via model spectra fits to the HST data and provide a refined orbital period and ephemeris from TESS photometry., Accepted for publication in MNRAS
- Published
- 2021
37. $\textit{Gaia}$ white dwarfs within 40 pc III: spectroscopic observations of new candidates in the southern hemisphere
- Author
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Mairi W O’Brien, P-E Tremblay, N P Gentile Fusillo, M A Hollands, B T Gänsicke, D Koester, I Pelisoli, E Cukanovaite, T Cunningham, A E Doyle, A Elms, J Farihi, J J Hermes, J Holberg, S Jordan, B L Klein, S J Kleinman, C J Manser, D De Martino, T R Marsh, J McCleery, C Melis, A Nitta, S G Parsons, R Raddi, A Rebassa-Mansergas, M R Schreiber, R Silvotti, D Steeghs, O Toloza, S Toonen, S Torres, A J Weinberger, B Zuckerman, and GBR
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,FOS: Physical sciences ,Astronomy and Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
We present a spectroscopic survey of 248 white dwarf candidates within 40 pc of the Sun; of these 244 are in the southern hemisphere. Observations were performed mostly with the Very Large Telescope (X-Shooter) and Southern Astrophysical Research Telescope. Almost all candidates were selected from $\textit{Gaia}$ Data Release 3 (DR3). We find a total of 246 confirmed white dwarfs, 209 of which had no previously published spectra, and two main-sequence star contaminants. Of these, 100 white dwarfs display hydrogen Balmer lines, 69 have featureless spectra, and two show only neutral helium lines. Additionally, 14 white dwarfs display traces of carbon, while 37 have traces of other elements that are heavier than helium. We observe 36 magnetic white dwarfs through the detection of Zeeman splitting of their hydrogen Balmer or metal spectral lines. High spectroscopic completeness (> 97 per cent) has now been reached, such that we have 1058 confirmed $\textit{Gaia}$ DR3 white dwarfs out of 1083 candidates within 40 pc of the Sun at all declinations., 49 pages, 19 figures. Accepted by MNRAS on 8 November, 2022
- Published
- 2022
38. The ELM Survey. VIII. Ninety-eight Double White Dwarf Binaries
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Warren R. Brown, Mukremin Kilic, Alekzander Kosakowski, Jeff J. Andrews, Craig O. Heinke, Marcel A. Agüeros, Fernando Camilo, A. Gianninas, J. J. Hermes, and Scott J. Kenyon
- Published
- 2020
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39. Circular polarimetry of suspect wind-accreting magnetic pre-polars
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Pasi Hakala, Steven G Parsons, Thomas R Marsh, Boris T Gänsicke, Gavin Ramsay, Axel Schwope, and J J Hermes
- Subjects
High Energy Astrophysical Phenomena (astro-ph.HE) ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,QC ,QB - Abstract
We present results from a circular polarimetric survey of candidate detached magnetic white dwarf - M dwarf binaries obtained using the Nordic Optical Telescope, La Palma. We obtained phase resolved spectropolarimetry and imaging polarimetry of seven systems, five of which show clearly variable circular polarisation. The data indicate that these targets have white dwarfs with magnetic field strengths > 80 MG. Our study reveals that cyclotron emission can dominate the optical luminosity at wavelengths corresponding to the cyclotron emission harmonics, even in systems where the white dwarfs are only wind-accreting. This implies that a very significant fraction of the the stellar wind of the companion star is captured by the magnetic white dwarf reducing the magnetic braking in pre-CVs. Furthermore, the polarimetric confirmation of several detached, wind-accreting magnetic systems provides observational constraints on the models of magnetic CV evolution and white dwarf magnetic field generation. We also find that the white dwarf magnetic field configuration in at least two of these systems appears to be very complex., 13 pages, 10 figures, accepted for publication in MNRAS, Figure 10 was replaced by a corrected one
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- 2022
40. Relentless and complex transits from a planetesimal debris disc
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J Farihi, J J Hermes, T R Marsh, A J Mustill, M C Wyatt, J A Guidry, T G Wilson, S Redfield, P Izquierdo, O Toloza, B T Gänsicke, A Aungwerojwit, C Kaewmanee, V S Dhillon, A Swan, Science & Technology Facilities Council, and University of St Andrews. School of Physics and Astronomy
- Subjects
Earth and Planetary Astrophysics (astro-ph.EP) ,010308 nuclear & particles physics ,White dwarfs ,FOS: Physical sciences ,Astronomy and Astrophysics ,Circumstellar matter ,3rd-DAS ,01 natural sciences ,individual (WD 1054–226), [Stars] ,Planetary systems ,QC Physics ,Astrophysics - Solar and Stellar Astrophysics ,13. Climate action ,Space and Planetary Science ,0103 physical sciences ,QB Astronomy ,010303 astronomy & astrophysics ,QC ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics - Earth and Planetary Astrophysics ,QB - Abstract
This article reports quasi-continuous transiting events towards WD 1054-226 at d=36.2 pc and V=16.0 mag, based on simultaneous, high-cadence, multi-wavelength imaging photometry using ULTRACAM over 18 nights from 2019 to 2020 March. The predominant period is 25.02 h, and corresponds to a circular orbit with blackbody Teq = 323 K, where a planetary surface can nominally support liquid water. The light curves reveal remarkable night-to-night similarity, with changes on longer timescales, and lack any transit-free segments of unocculted starlight. The most pronounced dimming components occur every 23.1 min -- exactly the 65th harmonic of the fundamental period -- with depths of up to several per cent, and no evident color dependence. Myriad additional harmonics are present, as well as at least two transiting features with independent periods. High-resolution optical spectra are consistent with stable, photospheric absorption by multiple, refractory metal species, with no indication of circumstellar gas. Spitzer observations demonstrate a lack of detectable dust emission, suggesting that the otherwise hidden circumstellar disk orbiting WD 1054-226 may be typical of polluted white dwarfs, and only detected via favorable geometry. Future observations are required to constrain the orbital eccentricity, but even if periastron is near the Roche limit, sublimation cannot drive mass loss in refractory parent bodies, and collisional disintegration is necessary for dust production., 22 pages, 2 tables, and 15 figures including the appendix, accepted to MNRAS
- Published
- 2022
41. WD1032 + 011, an inflated brown dwarf in an old eclipsing binary with a white dwarf
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T. R. Marsh, Don Winget, Boris T. Gänsicke, V. S. Dhillon, S. P. Littlefair, Zachary P. Vanderbosch, Claudia Belardi, John H. Debes, Sarah L. Casewell, J. J. Hermes, I. P. Braker, Steven G. Parsons, K. I. Winget, and Matthew R. Burleigh
- Subjects
Earth and Planetary Astrophysics (astro-ph.EP) ,Physics ,010308 nuclear & particles physics ,Brown dwarf ,FOS: Physical sciences ,Binary number ,White dwarf ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,Photometry (optics) ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,0103 physical sciences ,Thick disk ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,10. No inequality ,Low Mass ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Astrophysics - Earth and Planetary Astrophysics - Abstract
We present the discovery of only the third brown dwarf known to eclipse a non-accreting white dwarf. Gaia parallax information and multi-colour photometry confirm that the white dwarf is cool (9950$\pm$150K) and has a low mass (0.45$\pm$0.05~MSun), and spectra and lightcurves suggest the brown dwarf has a mass of 0.067 $\pm$0.006 MSun (70 MJup) and a spectral type of L5 $\pm$1. The kinematics of the system show that the binary is likely to be a member of the thick disk and therefore at least 5 Gyr old. The high cadence lightcurves show that the brown dwarf is inflated, making it the first brown dwarf in an eclipsing white dwarf-brown dwarf binary to be so., Accepted for publication in MNRAS, 11 pages, 7 Figures
- Published
- 2020
42. A 20 Second Cadence View of Solar-type Stars and Their Planets with TESS: Asteroseismology of Solar Analogs and a Recharacterization of pi Men c
- Author
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Daniel Huber, Timothy R. White, Travis S. Metcalfe, Ashley Chontos, Michael M. Fausnaugh, Cynthia S. K. Ho, Vincent Van Eylen, Warrick H. Ball, Sarbani Basu, Timothy R. Bedding, Othman Benomar, Diego Bossini, Sylvain Breton, Derek L. Buzasi, Tiago L. Campante, William J. Chaplin, Jørgen Christensen-Dalsgaard, Margarida S. Cunha, Morgan Deal, Rafael A. García, Antonio García Muñoz, Charlotte Gehan, Lucía González-Cuesta, Chen Jiang, Cenk Kayhan, Hans Kjeldsen, Mia S. Lundkvist, Stéphane Mathis, Savita Mathur, Mário J. P. F. G. Monteiro, Benard Nsamba, Jia Mian Joel Ong, Erika Pakštienė, Aldo M. Serenelli, Victor Silva Aguirre, Keivan G. Stassun, Dennis Stello, Sissel Norgaard Stilling, Mark Lykke Winther, Tao Wu, Thomas Barclay, Tansu Daylan, Maximilian N. Günther, J. J. Hermes, Jon M. Jenkins, David W. Latham, Alan M. Levine, George R. Ricker, Sara Seager, Avi Shporer, Joseph D. Twicken, Roland K. Vanderspek, Joshua N. Winn, National Aeronautics and Space Administration (US), National Science Foundation (US), Australian Research Council, Danish National Research Foundation, Fundação para a Ciência e a Tecnologia (Portugal), European Commission, Research Council of Lithuania, Alexander von Humboldt Foundation, Ministerio de Ciencia e Innovación (España), Chinese Academy of Sciences, and Kavli Foundation
- Subjects
Earth and Planetary Astrophysics (astro-ph.EP) ,Radial velocity ,010308 nuclear & particles physics ,Exoplanets ,Asteroseismology ,FOS: Physical sciences ,Astronomy and Astrophysics ,Light curves ,01 natural sciences ,G stars ,Transits ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics - Earth and Planetary Astrophysics - Abstract
We present an analysis of the first 20 second cadence light curves obtained by the TESS space telescope during its extended mission. We find improved precision of 20 second data compared to 2 minute data for bright stars when binned to the same cadence (˜10%-25% better for T ? 8 mag, reaching equal precision at T ˜ 13 mag), consistent with pre-flight expectations based on differences in cosmic-ray mitigation algorithms. We present two results enabled by this improvement. First, we use 20 second data to detect oscillations in three solar analogs (? Pav, ? Tuc, and p Men) and use asteroseismology to measure their radii, masses, densities, and ages to ˜1%, ˜3%, ˜1%, and ˜20% respectively, including systematic errors. Combining our asteroseismic ages with chromospheric activity measurements, we find evidence that the spread in the activity-age relation is linked to stellar mass and thus the depth of the convection zone. Second, we combine 20 second data and published radial velocities to recharacterize p Men c, which is now the closest transiting exoplanet for which detailed asteroseismology of the host star is possible. We show that p Men c is located at the upper edge of the planet radius valley for its orbital period, confirming that it has likely retained a volatile atmosphere and that the "asteroseismic radius valley"remains devoid of planets. Our analysis favors a low eccentricity for p Men c (, D.H. acknowledges support from the Alfred P. Sloan Foundation, the National Aeronautics and Space Administration (80NSSC19K0379, 80NSSC21K0652), and the National Science Foundation (AST-1717000). T.S.M. acknowledges support from NASA grant 80NSSC20K0458. Computational time at the Texas Advanced Computing Center was provided through XSEDE allocation TG-AST090107. A.C. acknowledges support from the National Science Foundation through the Graduate Research Fellowship Program (DGE 1842402). W.H.B. performed computations using the University of Birmingham's BlueBEAR High Performance Computing service. T.R.B. acknowledges support from the Australian Research Council through Discovery Project DP210103119. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (Grant DNRF106). M.S.C. and M.D. acknowledge the support by FCT/MCTES through the research grants UIDB/04434/2020, UIDP/04434/2020 and PTDC/FIS-AST/30389/2017, and by FEDER—Fundo Europeu de Desenvolvimento Regional through COMPETE2020—Programa Operacional Competitividade e Internacionalização (grant: POCI-01-0145-FEDER-030389). T.L.C. is supported by Fundação para a Ciência e a Tecnologia (FCT) in the form of a work contract (CEECIND/00476/2018). M.S.C. is supported by national funds through FCT in the form of a work contract. H.K. and E.P. acknowledge the grant from the European Social Fund via the Lithuanian Science Council (LMTLT) grant No. 09.3.3-LMT-K-712-01-0103. R.A.G. and S.N.B. acknowledge the support received from the CNES with the PLATO and GOLF grants. B.N. acknowledges postdoctoral funding from the Alexander von Humboldt Foundation and "Branco Weiss fellowship Science in Society" through the SEISMIC stellar interior physics group. S.M. acknowledges support by the Spanish Ministry of Science and Innovation with the Ramon y Cajal fellowship number RYC-2015-17697 and the grant number PID2019-107187GB-I00. T.W. acknowledges support from the B-type Strategic Priority Program of the Chinese Academy of Sciences (grant No. XDB41000000) from the NSFC of China (grant Nos. 11773064, 11873084, and 11521303), from the Youth Innovation Promotion Association of Chinese Academy of Sciences, and from the Ten Thousand Talents Program of Yunnan for Top-notch Young Talents. T.W. also gratefully acknowledges the computing time granted by the Yunnan Observatories and provided by the facilities at the Yunnan Observatories Supercomputing Platform. T.D. acknowledges support from MIT's Kavli Institute as a Kavli postdoctoral fellow.
- Published
- 2022
43. Discovery of 74 new bright ZZ Ceti stars in the first three years of TESS
- Author
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Alejandra D Romero, S O Kepler, J J Hermes, Larissa Antunes Amaral, Murat Uzundag, Zsófia Bognár, Keaton J Bell, Madison VanWyngarden, Andy Baran, Ingrid Pelisoli, Gabriela da Rosa Oliveira, Detlev Koester, T S Klippel, Luciano Fraga, Paul A Bradley, Maja Vučković, Tyler M Heintz, Joshua S Reding, B C Kaiser, Stéphane Charpinet, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)
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oscillations [Stars] ,stars: white dwarfs ,FOS: Physical sciences ,Astronomy and Astrophysics ,Surveys ,surveys ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Anãs brancas ,Pulsacoes estelares ,[SDU]Sciences of the Universe [physics] ,Asterosismologia ,White dwarfs [Stars] ,stars: oscillations ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
We report the discovery of 74 new pulsating DA white dwarf stars, or ZZ Cetis, from the data obtained by the Transiting Exoplanet Survey Satellite (TESS) mission, from Sectors 1 to 39, corresponding to the first 3 cycles. This includes objects from the Southern Hemisphere (Sectors 1-13 and 27-39) and the Northern Hemisphere (Sectors 14-26), observed with 120 s- and 20 s-cadence. Our sample likely includes 13 low-mass and one extremely low-mass white dwarf candidate, considering the mass determinations from fitting Gaia magnitudes and parallax. In addition, we present follow-up time series photometry from ground-based telescopes for 11 objects, which allowed us to detect a larger number of periods. For each object, we analysed the period spectra and performed an asteroseismological analysis, and we estimate the structure parameters of the sample, i.e., stellar mass, effective temperature and hydrogen envelope mass. We estimate a mean asteroseismological mass of _~ 0.635 +/-0.015 Msun, excluding the candidate low or extremely-low mass objects. This value is in agreement with the mean mass using estimates from Gaia data, which is ~ 0.631 +/- 0.040 Msun, and with the mean mass of previously known ZZ Cetis of = 0.644 +/-0.034 Msun. Our sample of 74 new bright ZZ~Cetis increases the number of known ZZ~Cetis by $\sim$20 per cent., Comment: Accepted for publication in MNRAS
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- 2022
44. Searching for TESS Photometric Variability of Possible JWST Spectrophotometric Standard Stars
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Susan E. Mullally, G. C. Sloan, J. J. Hermes, Michael Kunz, Kelly Hambleton, Ralph Bohlin, Scott W. Fleming, Karl D. Gordon, Catherine Kaleida, and Khalid Mohamed
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Earth and Planetary Astrophysics (astro-ph.EP) ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics - Instrumentation and Methods for Astrophysics ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,Astrophysics::Galaxy Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics - Earth and Planetary Astrophysics - Abstract
We use data from the Transiting Exoplanet Survey Satellite (TESS) to search for, and set limits on, optical to near-infrared photometric variability of the well-vetted, candidate James Webb Space Telescope (JWST) spectrophotometric standards. Our search of 37 of these candidate standards has revealed measurable periodic variability in 15 stars. The majority of those show variability that is less than half a percent; however, four stars are observed to vary photometrically, from minimum to maximum flux, by more than 1% (the G dwarf HD 38949 and three fainter A dwarfs). Variability of this size would likely impact the error budget in the spectrophotometric calibration of the science instruments aboard JWST. For the 22 candidate standards with no detected variability, we report upper limits on the observed changes in flux. Despite some systematic noise, all stars brighter than 12 magnitude in the TESS band show a 3 sigma upper limit on the total change in brightness of less than half a percent on time scales between an hour and multiple weeks, empirically establishing their suitability as spectrophotometric standards. We further discuss the value and limits of high-cadence, high-precision photometric monitoring with TESS as a tool to vet the suitability of stars to act as spectrophotometric standards., Comment: 17 pages, 5 figures, 3 tables, accepted for publication by AAS Journals
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- 2022
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45. Velocity-imaging the rapidly precessing planetary disc around the white dwarf HE 1349–2305 using Doppler tomography
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Dimitri Veras, Boris T. Gänsicke, Pablo Rodríguez-Gil, Joshua S. Reding, David J. Wilson, B. C. Kaiser, Mark Hollands, C. J. Manser, Erik Dennihy, J. J. Hermes, T. R. Marsh, Paula Izquierdo, Nicola P Gentile Fusillo, and John H. Debes
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Planetesimal ,DEBRIS DISC ,stars: individual: HE 1349-2305 ,TIDAL DISRUPTION ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astronomy & Astrophysics ,IA PROGENITOR SURVEY ,circumstellar matter ,0201 Astronomical and Space Sciences ,SPECTROGRAPH ,COLLISIONAL CASCADES ,Astrophysics::Solar and Stellar Astrophysics ,Emission spectrum ,ACCRETION ,Spectroscopy ,ESO ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,white dwarfs ,QB ,Physics ,Earth and Planetary Astrophysics (astro-ph.EP) ,Science & Technology ,SPECTROSCOPY ,NUMERICAL SIMULATIONS ,White dwarf ,ROCHE LIMITS ,Astronomy and Astrophysics ,Doppler tomography ,line: profiles ,Orbital period ,Debris ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Physical Sciences ,accretion, accretion discs ,Astrophysics::Earth and Planetary Astrophysics ,stars: planetary systems ,Excitation ,Astrophysics - Earth and Planetary Astrophysics - Abstract
The presence of planetary material in white dwarf atmospheres, thought to be accreted from a dusty debris disc produced via the tidal disruption of a planetesimal, is common. Approximately five per cent of these discs host a co-orbital gaseous component detectable via emission from atomic transitions - usually the 8600 Angstrom CaII triplet. These emission profiles can be highly variable in both morphology and strength. Furthermore, the morphological variations in a few systems have been shown to be periodic, likely produced by an apsidally precessing asymmetric disc. Of the known gaseous debris discs, that around HE1349-2305 has the most rapidly evolving emission line morphology, and we present updated spectroscopy of the CaII triplet of this system. The additional observations show that the emission line morphologies vary periodically and consistently, and we constrain the period to two aliases of 459$\pm$3d and 502$\pm$3d. We produce images of the CaII triplet emission from the disc in velocity space using Doppler tomography - only the second such imaging of a white dwarf debris disc. We suggest that the asymmetric nature of these velocity images is generated by gas moving on eccentric orbits with radially-dependent excitation conditions via photo-ionisation from the white dwarf. We also obtained short-cadence (~ 4 min) spectroscopy to search for variability on the time-scale of the disc's orbital period (~ hours) due to the presence of a planetesimal, and rule out variability at a level of ~ 1.4 per cent., Comment: 14 Pages, 10 Figures, accepted for publication in MNRAS
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- 2021
46. Unexpected Short-period Variability in Dwarf Carbon Stars from the Zwicky Transient Facility
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J. J. Hermes, Silvia Toonen, Benjamin R. Roulston, Paul J. Green, and Low Energy Astrophysics (API, FNWI)
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Physics ,010308 nuclear & particles physics ,White dwarf ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Light curve ,Orbital period ,01 natural sciences ,Carbon star ,Tidal locking ,Radial velocity ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,010303 astronomy & astrophysics ,Main sequence ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics - Abstract
Dwarf carbon (dC) stars, main sequence stars showing carbon molecular bands, are enriched by mass transfer from a previous asymptotic-giant-branch (AGB) companion, which has since evolved to a white dwarf. While previous studies have found radial-velocity variations for large samples of dCs, there are still relatively few dC orbital periods in the literature and no dC eclipsing binaries have yet been found. Here, we analyze photometric light curves from DR5 of the Zwicky Transient Facility for a sample of 944 dC stars. From these light curves, we identify 34 periodically variable dC stars. Remarkably, of the periodic dCs, 82\% have periods less than two days. We also provide spectroscopic follow-up for four of these periodic systems, measuring radial velocity variations in three of them. Short-period dCs are almost certainly post-common-envelope binary systems, since the periodicity is most likely related to the orbital period, with tidally locked rotation and photometric modulation on the dC either from spots or from ellipsoidal variations. We discuss evolutionary scenarios that these binaries may have taken to accrete sufficient C-rich material while avoiding truncation of the thermally pulsing AGB phase needed to provide such material in the first place. We compare these dCs to common-envelope models to show that dC stars probably cannot accrete enough C-rich material during the common-envelope phase, suggesting another mechanism like wind-Roche lobe overflow is necessary. The periodic dCs in this paper represent a prime sample for spectroscopic follow-up and for comparison to future models of wind-Roche lobe overflow mass transfer., Comment: 23 pages, 5 figures, 5 tables, accepted to ApJ
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- 2021
47. Pulsating hydrogen-deficient white dwarfs and pre-white dwarfs observed with TESS
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A. H. Córsico, M. Uzundag, S. O. Kepler, L. G. Althaus, R. Silvotti, P. A. Bradley, A. S. Baran, D. Koester, K. J. Bell, A. D. Romero, J. J. Hermes, and N. P. Gentile Fusillo
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Space and Planetary Science ,Astronomy and Astrophysics - Abstract
Context. The TESS space mission has recently demonstrated its great potential to discover new pulsating white dwarf and pre-white dwarf stars, and to detect periodicities with high precision in already known white-dwarf pulsators. Aims. We report the discovery of two new pulsating He-rich atmosphere white dwarfs (DBVs) and present a detailed asteroseismological analysis of three already known DBV stars employing observations collected by the TESS mission along with ground-based data. Methods. We processed and analyzed TESS observations of the three already known DBV stars PG 1351+489 (TIC 471015205), EC 20058−5234 (TIC 101622737), and EC 04207−4748 (TIC 153708460), and the two new DBV pulsators WDJ152738.4−50207.4 (TIC 150808542) and WD 1708−871 (TIC 451533898), whose variability is reported for the first time in this paper. We also carried out a detailed asteroseismological analysis using fully evolutionary DB white-dwarf models built considering the complete evolution of the progenitor stars. We constrained the stellar mass of three of these target stars by means of the observed period spacing, and derived a representative asteroseismological model using the individual periods, when possible. Results. We extracted frequencies from the TESS light curves of these DBV stars using a standard pre-whitening procedure to derive the potential pulsation frequencies. All the oscillation frequencies that we found are associated with g-mode pulsations with periods spanning from ∼190 s to ∼936 s. We find hints of rotation from frequency triplets in some of the targets, including the two new DBVs. For three targets, we find constant period spacings, which allowed us to infer their stellar masses and constrain the harmonic degree ℓ of the modes. We also performed period-to-period fit analyses and found an asteroseismological model for three targets, with stellar masses generally compatible with the spectroscopic masses. Obtaining seismological models allowed us to estimate the seismological distances and compare them with the precise astrometric distances measured with Gaia. We find a good agreement between the seismic and the astrometric distances for three stars (PG 1351+489, EC 20058-5234, and WD 1708-871); although, for the other two stars (EC 04207-4748 and WD J152738.4-50207), the discrepancies are substantial. Conclusions. The high-quality data from the TESS mission continue to provide important clues which can be used to help determine the internal structure of pulsating pre-white dwarf and white dwarf stars through the tools of asteroseismology.
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- 2022
48. A 99-minute Double-lined White Dwarf Binary from SDSS-V
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Hans-Walter Rix, Boris T. Gänsicke, Vedant Chandra, Axel Schwope, Dan Maoz, Gagik Tovmassian, Matthias R. Schreiber, Nadia L. Zakamska, Warren R. Brown, J. J. Hermes, Hsiang-Chih Hwang, Odette Toloza, Evan B. Bauer, Keith Inight, and Carles Badenes
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Physics ,Astrophysics::High Energy Astrophysical Phenomena ,White dwarf ,Binary number ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,QB - Abstract
We report the discovery of SDSS J133725.26+395237.7 (hereafter SDSS J1337+3952), a double-lined white dwarf (WD+WD) binary identified in early data from the fifth generation Sloan Digital Sky Survey (SDSS-V). The double-lined nature of the system enables us to fully determine its orbital and stellar parameters with follow-up Gemini spectroscopy and Swift UVOT ultraviolet fluxes. The system is nearby ($d = 113$ pc), and consists of a $0.51\, M_\odot$ primary and a $0.32\, M_\odot$ secondary. SDSS J1337+3952 is a powerful source of gravitational waves in the millihertz regime, and will be detectable by future space-based interferometers. Due to this gravitational wave emission, the binary orbit will shrink down to the point of interaction in $\approx 220$ Myr. The inferred stellar masses indicate that SDSS J1337+3952 will likely not explode as a Type Ia supernova (SN Ia). Instead, the system will probably merge and evolve into a rapidly rotating helium star, and could produce an under-luminous thermonuclear supernova along the way. The continuing search for similar systems in SDSS-V will grow the statistical sample of double-degenerate binaries across parameter space, constraining models of binary evolution and SNe Ia., Accepted to ApJ
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- 2021
49. EPIC 228782059: Asteroseismology of what could be the coolest pulsating helium-atmosphere white dwarf (DBV) known?
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R. M. Duan, J. J. Hermes, Zachary P. Vanderbosch, X. Y. Ma, S. Charpinet, J.-N. Fu, Y. H. Chen, Weikai Zong, Beijing Normal University (BNU), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and ANR-17-CE31-0018,INSIDE,Inversion astérosismique de la stratification en carbone / oxygène des noyaux d'étoiles de faible masse évoluées(2017)
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Rotation period ,Physics ,010504 meteorology & atmospheric sciences ,Star (game theory) ,White dwarf ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Light curve ,01 natural sciences ,Asteroseismology ,Photometry (optics) ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,0103 physical sciences ,Instability strip ,Spectroscopy ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,0105 earth and related environmental sciences - Abstract
We present analysis of a new pulsating helium-atmosphere (DB) white dwarf, EPIC~228782059, discovered from 55.1~days of {\em K2} photometry. The long duration, high quality light curves reveal 11 independent dipole and quadruple modes, from which we derive a rotational period of $34.1 \pm 0.4$~hr for the star. An optimal model is obtained from a series of grids constructed using the White Dwarf Evolution Code, which returns $M_{*} = 0.685 \pm 0.003 M_{\odot}$, $T_{\rm{eff}}= 21{,}910 \pm 23$\,K and $\log g = 8.14 \pm0.01$\,dex. These values are comparable to those derived from spectroscopy by Koester \& Kepler ($20{,}860 \pm 160$\,K and $7.94 \pm0.03$\,dex). If these values are confirmed or better constrained by other independent works, it would make EPIC~228782059 one of the coolest pulsating DB white dwarf star known, and would be helpful to test different physical treatments of convection, and to further investigate the theoretical instability strip of DB white dwarf stars., 9 pages, 5 figures, 2 tables, accepted by ApJ
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- 2021
50. The Rapid Rotation of the Strongly Magnetic Ultramassive White Dwarf EGGR 156
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Kurtis A. Williams, J. J. Hermes, and Zachary P. Vanderbosch
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Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,FOS: Physical sciences ,Astronomy and Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
The distribution of white dwarf rotation periods provides a means for constraining angular momentum evolution during the late stages of stellar evolution, as well as insight into the physics and remnants of double degenerate mergers. Although the rotational distribution of low mass white dwarfs is relatively well constrained via asteroseismology, that of high mass white dwarfs, which can arise from either intermediate mass stellar evolution or white dwarf mergers, is not. Photometric variability in white dwarfs due to rotation of a spotted star is rapidly increasing the sample size of high mass white dwarfs with measured rotation periods. We present the discovery of 22.4 minute photometric variability in the lightcurve of EGGR 156, a strongly magnetic, ultramassive white dwarf. We interpret this variability as rapid rotation, and our data suggest that EGGR 156 is the remnant of a double degenerate merger. Finally, we calculate the rate of period change in rapidly rotating, massive, magnetic WDs due to magnetic dipole radiation. In many cases, including EGGR 156, the period change is not currently detectable over reasonable timescales, indicating that these WDs could be very precise clocks. For the most highly magnetic, rapidly rotating massive WDs, such as ZTF J1901+1450 and RE J0317$-$853, the period change should be detectable and may help constrain the structure and evolution of these exotic white dwarfs., Replaced to correct two typos in equations on page 12. No calculations or conclusions affected. 15 pages, 5 figures, accepted for publication in the Astronomical Journal
- Published
- 2022
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