A5050750988- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Scientific Research and Discoveries
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Metallurgy and Material Science
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Aluminum Alloys Composites Properties
- Space Exploration and Technology
- Aluminum Alloy Microstructure Properties
University of North Carolina at Chapel Hill
2018-2024
We report the discovery of 74 new pulsating DA white dwarf stars, or ZZ Cetis, from data obtained by Transiting Exoplanet Survey Satellite (TESS) mission, Sectors 1 to 39, corresponding first 3 cycles. This includes objects Southern Hemisphere (Sectors 1-13 and 27-39) Northern 14-26), observed with 120 s- 20 s-cadence. Our sample likely 13 low-mass one extremely candidate, considering mass determinations fitting Gaia magnitudes parallax. In addition, we present follow-up time series...
Tidal disruption and subsequent accretion of planetesimals by white dwarfs can reveal the elemental abundances rocky bodies in exoplanetary systems. Those provide information on composition nebula from which systems formed, is analogous to how meteorite inform our understanding early Solar System. We report detection lithium, sodium, potassium, calcium atmosphere dwarf Gaia DR2 4353607450860305024, we ascribe a planetesimal. Using model atmospheres, determine abundance ratios these elements,...
Abstract Observations of debris disks, the products collisional evolution rocky planetesimals, can be used to trace planetary activity across a wide range stellar types. The most common end points are no exception, as disks have been observed around several dozen white dwarf stars. But instead formation, post-main-sequence signpost destruction, resulting in compact from tidal disruption remnant planetesimals. In this work, we present discovery five new stars with gaseous emission. All...
Abstract White dwarf stars have been used for decades as precise and accurate age indicators. This work presents a test of the reliability white total ages when spectroscopic observations are available. We conduct follow-up spectroscopy 148 individual dwarfs in widely separated double-white-dwarf (WD+WD) binaries. supplement sample with 264 previously published spectra, well 1292 high-confidence spectral types inferred from their Gaia XP spectra. find that fits to optical spectra do not...
We report the discovery of short-period photometric variability and modulated Zeeman-split hydrogen emission in SDSSJ125230.93-023417.72 (EPIC 228939929), a variable white dwarf star observed at long cadence \textit{K2} Campaign 10. The behavior is associated with magnetic ($B=5.0$ MG) spot on stellar surface, making $317.278$-second period direct measurement rotation rate. This object therefore fastest-rotating apparently isolated (without companion) yet discovered, second found to exhibit...
Abstract The bulk abundances of exoplanetesimals can be measured when they are accreted by white dwarfs. Recently, lithium from the accretion was detected in relatively high levels multiple There presently three proposed hypotheses to explain detection excess dwarf photospheres: Big Bang and Galactic nucleosynthesis, continental crust, an exomoon formed spalled ring material. We present new observations previously known lithium-polluted dwarfs (WD J1824+1213, WD J2317+1830, LHS 2534), one...
ABSTRACT We report the discovery of two apparently isolated stellar remnants that exhibit rotationally modulated magnetic Balmer emission, adding to emerging DAHe class white dwarf stars. While previously discovered members this show Zeeman-split triplet emission features corresponding single field strengths, these new objects significant fluctuations in their apparent strengths with variability phase. The hydrogen lines LP 705−64 broaden from 9.4 22.2 MG over an spin period 72.629 min....
Abstract Roughly 2% of white dwarfs harbor planetary debris disks detectable via infrared excesses, but only a few percent these show gaseous component, distinguished by their double-peaked emission at the near-infrared calcium triplet. Previous studies found that most around are variable 3.4 and 4.5 μ m, they analyzed now 21 published showing emission. To test if exhibit large-amplitude stochastic variability in near-infrared, we use light curves generated from unWISE images m corrected for...
We present the discovery of SDSS J135154.46-064309.0, a short-period variable observed using 30-minute cadence photometry in K2 Campaign 6. Follow-up spectroscopy and high-speed support classification as new member rare class ultracompact accreting binaries known AM CVn stars. The spectroscopic orbital period $15.65 \pm 0.12$\,minutes makes this system fourth-shortest known, second type to be discovered by Kepler spacecraft. data show photometric periods at $15.7306 0.0003$\,minutes,...
The presence of planetary material in white dwarf atmospheres, thought to be accreted from a dusty debris disc produced via the tidal disruption planetesimal, is common. Approximately five per cent these discs host co-orbital gaseous component detectable emission atomic transitions - usually 8600 Angstrom CaII triplet. These profiles can highly variable both morphology and strength. Furthermore, morphological variations few systems have been shown periodic, likely by an apsidally precessing...
The bulk abundances of exoplanetesimals can be measured when they are accreted by white dwarfs. Recently, lithium from the accretion was detected in relatively high levels multiple There presently three proposed hypotheses to explain detection excess dwarf photospheres: Big Bang and Galactic nucleosynthesis, continental crust, an exomoon formed spalled ring material. We present new observations previously known lithium-polluted dwarfs (WD J1824+1213, WD J2317+1830, LHS 2534), one with metal...