| 1. |
- Bacchus, E., et al.
(författare)
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Project 1640 observations of the white dwarf HD 114174 B
- 2017
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 469:4, s. 4796-4805
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Tidskriftsartikel (refereegranskat)abstract
- We present the first near infrared spectrum of the faint white dwarf companion HD 114174 B, obtained with Project 1640. Our spectrum, covering the Y, J and H bands, combined with previous TaRgetting bENchmark-objects with Doppler Spectroscopy (TRENDS) photometry measurements, allows us to place further constraints on this companion. We suggest two possible scenarios; either this object is an old, low-mass, cool H atmosphere white dwarf with T-eff similar to 3800 K or a high-mass white dwarf with T-eff > 6000 K, potentially with an associated cool (T-eff similar to 700 K) brown dwarf or debris disc resulting in an infrared excess in the L' band. We also provide an additional astrometry point for 2014 June 12 and use the modelled companion mass combined with the radial velocity and direct imaging data to place constraints on the orbital parameters for this companion.
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| 2. |
- Tremblay, P. -E, et al.
(författare)
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3D Model Atmospheres for Extremely Low-Mass White Dwarfs
- 2015
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 809:2
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Tidskriftsartikel (refereegranskat)abstract
- We present an extended grid of mean three-dimensional (3D) spectra for low-mass, pure-hydrogen atmosphere DA white dwarfs (WDs). We use CO5BOLD radiation-hydrodynamics 3D simulations covering T-eff = 6000-11,500 K and log g = 5-6.5 (g in cm s(-2)) to derive analytical functions to convert spectroscopically determined 1D temperatures and surface gravities to 3D atmospheric parameters. Along with the previously published 3D models, the 1D to 3D corrections are now available for essentially all known convective DA WDs (i.e., log g - 5-9). For low-mass WDs, the correction in temperature is relatively small (a few percent at the most), but the surface gravities measured from the 3D models are lower by as much as 0.35 dex. We revisit the spectroscopic analysis of the extremely low-mass (ELM) WDs, and demonstrate that the 3D models largely resolve the discrepancies seen in the radius and mass measurements for relatively cool ELM WDs in eclipsing double WD and WD + millisecond pulsar binary systems. We also use the 3D corrections to revise the boundaries of the ZZ Ceti instability strip, including the recently found ELM pulsators.
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