scholarly journals A white dwarf catalogue from Gaia-DR2 and the Virtual Observatory

2018 ◽  
Vol 480 (4) ◽  
pp. 4505-4518 ◽  
Author(s):  
F M Jiménez-Esteban ◽  
S Torres ◽  
A Rebassa-Mansergas ◽  
G Skorobogatov ◽  
E Solano ◽  
...  
Keyword(s):  
White Dwarf ◽  
Virtual Observatory ◽  
Gaia Dr2

The completeness of Gaia-selected samples of white dwarfs

2019 ◽  
Vol 15 (S357) ◽  
pp. 170-174
Author(s):  
Terry D. Oswalt ◽  
Jay B. Holberg ◽  
Edward M. Sion
Keyword(s):  
White Dwarf ◽  
Proper Motion ◽  
White Dwarfs ◽  
Color Index ◽  
Apparent Magnitude ◽  
Order Of Magnitude ◽  
Gaia Dr2 ◽  
Photometric Color

AbstractThe Gaia DR2 has dramatically increased the ability to detect faint nearby white dwarfs. The census of the local white dwarf population has recently been extended from 25 pc to 50 pc, effectively increasing the sample by roughly an order of magnitude. Here we examine the completeness of this new sample as a function of variables such as apparent magnitude, distance, proper motion, photometric color index, unresolved components, etc.

scholarly journals Gaia white dwarfs within 40 pc II: the volume-limited Northern hemisphere sample

2020 ◽  
Vol 499 (2) ◽  
pp. 1890-1908 ◽  
Author(s):  
Jack McCleery ◽  
Pier-Emmanuel Tremblay ◽  
Nicola Pietro Gentile Fusillo ◽  
Mark A Hollands ◽  
Boris T Gänsicke ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
White Dwarf ◽  
White Dwarfs ◽  
Binary Systems ◽  
Mass Range ◽  
Wide Binary ◽  
William Herschel ◽  
Initial Selection ◽  
Gaia Dr2 ◽  
Kinematic Properties

ABSTRACT We present an overview of the sample of Northern hemisphere white dwarfs within 40 pc of the Sun detected from Gaia Data Release 2 (DR2). We find that 521 sources are spectroscopically confirmed degenerate stars, 111 of which were first identified as white dwarf candidates from Gaia DR2 and followed up recently with the William Herschel Telescope and Gran Telescopio Canarias. Three additional white dwarf candidates remain spectroscopically unobserved and six unresolved binaries are known to include a white dwarf but were not in our initial selection in the Gaia DR2 Hertzsprung–Russell diagram. Atmospheric parameters are calculated from Gaia and Pan-STARRS photometry for all objects in the sample, confirming most of the trends previously observed in the much smaller 20 pc sample. Local white dwarfs are overwhelmingly consistent with Galactic disc kinematics, with only four halo candidates. We find that DAZ white dwarfs are significantly less massive than the overall DA population ($\overline{M}_\mathrm{DAZ}$ = 0.59 M⊙, $\overline{M}_\mathrm{DA}$ = 0.66 M⊙). It may suggest that planet formation is less efficient at higher mass stars, producing more massive white dwarfs. We detect a sequence of crystallized white dwarfs in the mass range from 0.6 $\lesssim M/\mbox{$\mathrm{M}_\odot $}\ \lesssim$ 1.0 and find that the vast majority of objects on the sequence have standard kinematic properties that correspond to the average of the sample, suggesting that their nature can be explained by crystallization alone. We also detect 26 double degenerates and white dwarf components in 56 wide binary systems.

scholarly journals Random Forest identification of the thin disc, thick disc, and halo Gaia-DR2 white dwarf population

2019 ◽  
Vol 485 (4) ◽  
pp. 5573-5589 ◽  
Author(s):  
S Torres ◽  
C Cantero ◽  
A Rebassa-Mansergas ◽  
G Skorobogatov ◽  
F M Jiménez-Esteban ◽  
...  
Keyword(s):  
Random Forest ◽  
White Dwarf ◽  
Thick Disc ◽  
Thin Disc ◽  
Gaia Dr2

scholarly journals A new white dwarf companion around the Δμ star GJ 3346

2020 ◽  
Vol 494 (3) ◽  
pp. 3481-3490
Author(s):  
M Bonavita ◽  
C Fontanive ◽  
S Desidera ◽  
V D’Orazi ◽  
A Zurlo ◽  
...  
Keyword(s):  
Effective Temperature ◽  
White Dwarf ◽  
Proper Motion ◽  
Main Sequence ◽  
Archival Data ◽  
Data Sets ◽  
Selection Methods ◽  
Open Time ◽  
Substellar Companions ◽  
Gaia Dr2

ABSTRACT We present the discovery of a white dwarf companion at ∼3.6 arcsec from GJ 3346, a nearby (π ∼ 42 mas) K star observed with SPHERE@VLT as part of an open time survey for faint companions to objects with significant proper motion discrepancies (Δμ) between Gaia DR1 and Tycho-2. Syrius-like systems like GJ 3346 AB, which include a main-sequence star and a white dwarf, can be difficult to detect because of the intrinsic faintness of the latter. They have, however, been found to be common contaminants for direct imaging (DI) searches. White dwarfs have in fact similar brightness to substellar companions in the infrared, while being much brighter in the visible bands like those used by Gaia. Combining our observations with Gaia DR2 and with several additional archival data sets, we were able to fully constrain the physical properties of GJ 3346 B, such as its effective temperature (11 × 103 ± 500 K) as well as the cooling age of the system (648 ± 58 Myr). This allowed us to better understand the system history and to partially explain the discrepancies previously noted in the age indicators for this object. Although further investigation is still needed, it seems that GJ 3346, which was previously classified as young, is in fact most likely to be older than 4 Gyr. Finally, given that the mass (0.58 ± 0.01 M⊙) and separation (85 au) of GJ 3346 B are compatible with the observed Δμ, this discovery represents a further confirmation of the potential of this kind of dynamical signatures as selection methods for DI surveys targeting faint, substellar companions.

scholarly journals Gaia DR2 white dwarfs in the Hercules stream

2019 ◽  
Vol 629 ◽  
pp. L6 ◽  
Author(s):  
Santiago Torres ◽  
Carles Cantero ◽  
María E. Camisassa ◽  
Teresa Antoja ◽  
Alberto Rebassa-Mansergas ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Age Distribution ◽  
Thick Disk ◽  
Velocity Space ◽  
Dwarf Stars ◽  
The Past ◽  
White Dwarf Stars ◽  
Dynamic Variables ◽  
Gaia Dr2

Aims. We analyzed the velocity space of the thin- and thick-disk Gaia white dwarf population within 100 pc by searching for signatures of the Hercules stellar stream. We aimed to identify objects belonging to the Hercules stream, and by taking advantage of white dwarf stars as reliable cosmochronometers, to derive a first age distribution. Methods. We applied a kernel density estimation to the UV velocity space of white dwarfs. For the region where a clear overdensity of stars was found, we created a 5D space of dynamic variables. We applied a hierarchichal clustering method, HDBSCAN, to this 5D space, and identified those white dwarfs that share similar kinematic characteristics. Finally, under general assumptions and from their photometric properties, we derived an age estimate for each object. Results. The Hercules stream was first revealed as an overdensity in the UV velocity space of the thick-disk white dwarf population. Three substreams were then found: Hercules a and Hercules b, formed by thick-disk stars with an age distribution that peaked 4 Gyr in the past and extends to very old ages; and Hercules c, with a ratio of 65:35 of thin to thick stars and a more uniform age distribution that is younger than 10 Gyr.

scholarly journals Lithium pollution of a white dwarf records the accretion of an extrasolar planetesimal

Science ◽  
2020 ◽  
Vol 371 (6525) ◽  
pp. 168-172
Author(s):  
B. C. Kaiser ◽  
J. C. Clemens ◽  
S. Blouin ◽  
P. Dufour ◽  
R. J. Hegedus ◽  
...  
Keyword(s):  
Solar System ◽  
White Dwarf ◽  
Big Bang ◽  
Early Solar System ◽  
Big Bang Nucleosynthesis ◽  
Lithium Abundance ◽  
Sodium Potassium ◽  
Elemental Abundances ◽  
Exoplanetary Systems ◽  
Gaia Dr2

Tidal disruption and subsequent accretion of planetesimals by white dwarfs can reveal the elemental abundances of rocky bodies in exoplanetary systems. Those abundances provide information on the composition of the nebula from which the systems formed, which is analogous to how meteorite abundances inform our understanding of the early Solar System. We report the detection of lithium, sodium, potassium, and calcium in the atmosphere of the white dwarf Gaia DR2 4353607450860305024, which we ascribe to the accretion of a planetesimal. Using model atmospheres, we determine abundance ratios of these elements, and, with the exception of lithium, they are consistent with meteoritic values in the Solar System. We compare the measured lithium abundance with measurements in old stars and with expectations from Big Bang nucleosynthesis.

Testing white dwarf cosmochronology using wide double white dwarfs

2019 ◽  
Vol 15 (S357) ◽  
pp. 197-201
Author(s):  
Tyler Heintz ◽  
JJ Hermes
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Mass Relation ◽  
Final Mass ◽  
Gaia Dr2

AbstractWe present a sample of nearly 650 widely separated double white dwarf binaries found using Gaia DR2 astrometry. We derive preliminary total ages for each white dwarf in our sample using Gaia photometry and compare the total ages of both components of each binary in our sample. We find agreement within 3 sigma between the two ages ∼85% of the time with median age uncertainties of ∼3.5 Gyr depending on which initial-final mass relation is used. When a subsample with the most precise ages is used, the agreement within 3 sigma drops to ∼70% with median age uncertainties of 300-600 Myr.

scholarly journals White Dwarf Model Atmospheres: Synthetic Spectra for Supersoft Sources

2011 ◽  
Vol 7 (S281) ◽  
pp. 60-63
Author(s):  
Thomas Rauch
Keyword(s):  
Stellar Evolution ◽  
White Dwarf ◽  
Model Atmosphere ◽  
Parameter Range ◽  
Spectral Energy ◽  
Virtual Observatory ◽  
Metal Line ◽  
Energy Distributions ◽  
Synthetic Spectra ◽  
High Level

AbstractThe Tübingen NLTE Model-Atmosphere Package (TMAP) calculates fully metal-line blanketed white dwarf model atmospheres and spectral energy distributions (SEDs) at a high level of sophistication. Such SEDs are easily accessible via the German Astrophysical Virtual Observatory (GAVO) service TheoSSA. We discuss applications of TMAP models to (pre) white dwarfs during the hottest stages of their stellar evolution, e.g. in the parameter range of novae and supersoft sources.

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