scholarly journals A hyper-runaway white dwarf in Gaia DR2 as a Type Iax supernova primary remnant candidate

2019 ◽  
Vol 489 (1) ◽  
pp. 420-426 ◽  
Author(s):  
Nicholas J Ruffini ◽  
Andrew R Casey
Keyword(s):  
White Dwarf ◽  
High Velocity ◽  
White Dwarfs ◽  
Milky Way ◽  
Elemental Abundances ◽  
Type Ia ◽  
Gaia Dr2 ◽  
Rule Out

ABSTRACT Observations of stellar remnants linked to Type Ia and Type Iax supernovae are necessary to fully understand their progenitors. Multiple progenitor scenarios predict a population of kicked donor remnants and partially burnt primary remnants, both moving with relatively high velocity. But only a handful of examples consistent with these two predicted populations have been observed. Here we report the likely first known example of an unbound white dwarf that is consistent with being the fully cooled primary remnant to a Type Iax supernova. The candidate, LP 93-21, is travelling with a galactocentric velocity of $v_{\textrm {gal}} \simeq 605\, {\rm km}\, {\rm s}^{-1}$, and is gravitationally unbound to the Milky Way. We rule out an extragalactic origin. The Type Iax supernova ejection scenario is consistent with its peculiar unbound trajectory, given anomalous elemental abundances are detected in its photosphere via spectroscopic follow-up. This discovery reflects recent models that suggest stellar ejections likely occur often. Unfortunately the intrinsic faintness of white dwarfs, and the uncertainty associated with their direct progenitor systems, makes it difficult to detect and confirm such donors.

scholarly journals A white dwarf bound to the transiting planetary system WASP-98

2020 ◽  
Vol 497 (4) ◽  
pp. 4416-4422
Author(s):  
John Southworth ◽  
Pier-Emmanuel Tremblay ◽  
Boris T Gänsicke ◽  
Daniel Evans ◽  
Teo Močnik
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Planetary System ◽  
Planetary Systems ◽  
Precise Determination ◽  
Spectral Lines ◽  
Low Metallicity ◽  
Gaia Dr2 ◽  
Rule Out

ABSTRACT WASP-98 is a planetary system containing a hot Jupiter transiting a late-G dwarf. A fainter star, 12 arcsec away, has previously been identified as a white dwarf, with a distance and proper motion consistent with a physical association with the planetary system. We present spectroscopy of the white dwarf, with the aim of determining its mass, radius, and temperature and hence the age of the system. However, the spectra show the featureless continuum and lack of spectral lines characteristic of the DC class of white dwarfs. We therefore fitted theoretical white dwarf spectra to the ugriz apparent magnitudes and Gaia DR2 parallax of this object in order to determine its physical properties and the age of the system. We find that the system is old, with a lower limit of 3.6 Gyr, but theoretical uncertainties preclude a precise determination of its age. Its kinematics are consistent with membership of the thick disc, but do not allow us to rule out the thin-disc alternative. The old age and low metallicity of the system suggest that it is subject to an age–metallicity relation, but analysis of the most metal-rich and metal-poor transiting planetary systems yields only insubstantial evidence of this. We conclude that the study of bound white dwarfs can yield independent ages to planetary systems, but such analysis may be better suited to DA and DB rather than DC white dwarfs.

scholarly journals The effects of different Type Ia SN yields on Milky Way chemical evolution

2021 ◽  
Vol 503 (3) ◽  
pp. 3216-3231
Author(s):  
Marco Palla
Keyword(s):  
Chemical Evolution ◽  
White Dwarf ◽  
Time Distribution ◽  
Milky Way ◽  
Massive Stars ◽  
Abundance Patterns ◽  
Type Ia ◽  
Low Metallicity ◽  
Explosion Mechanism ◽  
Chemical Evolution Model

ABSTRACT We study the effect of different Type Ia SN nucleosynthesis prescriptions on the Milky Way chemical evolution. To this aim, we run detailed one-infall and two-infall chemical evolution models, adopting a large compilation of yield sets corresponding to different white dwarf progenitors (near-Chandrasekar and sub-Chandrasekar) taken from the literature. We adopt a fixed delay time distribution function for Type Ia SNe, in order to avoid degeneracies in the analysis of the different nucleosynthesis channels. We also combine yields for different Type Ia SN progenitors in order to test the contribution to chemical evolution of different Type Ia SN channels. The results of the models are compared with recent LTE and NLTE observational data. We find that ‘classical’ W7 and WDD2 models produce Fe masses and [α/Fe] abundance patterns similar to more recent and physical near-Chandrasekar and sub-Chandrasekar models. For Fe-peak elements, we find that the results strongly depend either on the white dwarf explosion mechanism (deflagration-to-detonation, pure deflagration, double detonation) or on the initial white dwarf conditions (central density, explosion pattern). The comparison of chemical evolution model results with observations suggests that a combination of near-Chandrasekar and sub-Chandrasekar yields is necessary to reproduce the data of V, Cr, Mn and Ni, with different fractions depending on the adopted massive stars stellar yields. This comparison also suggests that NLTE and singly ionized abundances should be definitely preferred when dealing with most of Fe-peak elements at low metallicity.

scholarly journals The most massive white dwarfs in the solar neighbourhood

2021 ◽  
Vol 503 (4) ◽  
pp. 5397-5408
Author(s):  
Mukremin Kilic ◽  
P Bergeron ◽  
Simon Blouin ◽  
A Bédard
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Transverse Velocity ◽  
Maximum Mass ◽  
Model Calculations ◽  
Rapid Rotation ◽  
Rotation Rates ◽  
Binary Mergers ◽  
Chandrasekhar Limit

ABSTRACT We present an analysis of the most massive white dwarf candidates in the Montreal White Dwarf Database 100 pc sample. We identify 25 objects that would be more massive than $1.3\, {\rm M}_{\odot }$ if they had pure H atmospheres and CO cores, including two outliers with unusually high photometric mass estimates near the Chandrasekhar limit. We provide follow-up spectroscopy of these two white dwarfs and show that they are indeed significantly below this limit. We expand our model calculations for CO core white dwarfs up to M = 1.334 M⊙, which corresponds to the high-density limit of our equation-of-state tables, ρ = 109 g cm−3. We find many objects close to this maximum mass of our CO core models. A significant fraction of ultramassive white dwarfs are predicted to form through binary mergers. Merger populations can reveal themselves through their kinematics, magnetism, or rapid rotation rates. We identify four outliers in transverse velocity, four likely magnetic white dwarfs (one of which is also an outlier in transverse velocity), and one with rapid rotation, indicating that at least 8 of the 25 ultramassive white dwarfs in our sample are likely merger products.

scholarly journals Three Hypervelocity White Dwarfs in Gaia DR2: Evidence for Dynamically Driven Double-degenerate Double-detonation Type Ia Supernovae

2018 ◽  
Vol 865 (1) ◽  
pp. 15 ◽  
Author(s):  
Ken J. Shen ◽  
Douglas Boubert ◽  
Boris T. Gänsicke ◽  
Saurabh W. Jha ◽  
Jennifer E. Andrews ◽  
...  
Keyword(s):  
White Dwarfs ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Ia Supernovae ◽  
Gaia Dr2

scholarly journals Are the Precursors of Type Ia Supernovae Double Degenerate Mergers?

2004 ◽  
Vol 194 ◽  
pp. 111-112
Author(s):  
Lilia Ferrario
Keyword(s):  
Neutron Stars ◽  
White Dwarf ◽  
White Dwarfs ◽  
Observational Evidence ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Ia Supernovae

AbstractI argue that the observational evidence for white dwarf-white dwarf mergers supports the view that they give rise to ultra-massive white dwarfs or neutron stars through accretion induced collapse. The implications for the progenitors of Type Ia SNe are discussed.

scholarly journals The DECam minute cadence survey – II. 49 variables but no planetary transits of a white dwarf

2019 ◽  
Vol 490 (1) ◽  
pp. 1066-1075 ◽  
Author(s):  
Kyra Dame ◽  
Claudia Belardi ◽  
Mukremin Kilic ◽  
Armin Rest ◽  
A Gianninas ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Point Sources ◽  
Habitable Zone ◽  
Significant Evidence ◽  
Rr Lyrae ◽  
M Dwarf ◽  
Rule Out ◽  
Planetary Transits

Abstract We present minute cadence photometry of 31 732 point sources observed in one 3 $\rm deg^{2}$ DECam pointing centred at RA = 09:03:02 and Dec. = −04:35:00 over eight consecutive half-nights. We use these data to search for eclipse-like events consistent with a planetary transit of a white dwarf and other sources of stellar variability within the field. We do not find any significant evidence for minute-long transits around our targets, hence we rule out planetary transits around ∼370 white dwarfs that should be present in this field. Additionally, we identify 49 variables, including 40 new systems. These include 23 detached or contact stellar binaries, one eclipsing white dwarf + M dwarf binary, 16 δ Scuti, three RR Lyrae, and two ZZ Ceti pulsators. Results from the remaining two fields in our survey will allow us to place more stringent constraints on the frequency of planets orbiting white dwarfs in the habitable zone.

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 The evolution of ultra-massive white dwarfs

2019 ◽  
Vol 625 ◽  
pp. A87 ◽  
Author(s):  
María E. Camisassa ◽  
Leandro G. Althaus ◽  
Alejandro H. Córsico ◽  
Francisco C. De Gerónimo ◽  
Marcelo M. Miller Bertolami ◽  
...  
Keyword(s):  
Phase Separation ◽  
White Dwarf ◽  
White Dwarfs ◽  
Outer Boundary ◽  
Asymptotic Giant Branch ◽  
Type Ia ◽  
Chemical Profiles ◽  
Supernova Explosions ◽  
Carbon Burning ◽  
The Impact

Ultra-massive white dwarfs are powerful tools used to study various physical processes in the asymptotic giant branch (AGB), type Ia supernova explosions, and the theory of crystallization through white dwarf asteroseismology. Despite the interest in these white dwarfs, there are few evolutionary studies in the literature devoted to them. Here we present new ultra-massive white dwarf evolutionary sequences that constitute an improvement over previous ones. In these new sequences we take into account for the first time the process of phase separation expected during the crystallization stage of these white dwarfs by relying on the most up-to-date phase diagram of dense oxygen/neon mixtures. Realistic chemical profiles resulting from the full computation of progenitor evolution during the semidegenerate carbon burning along the super-AGB phase are also considered in our sequences. Outer boundary conditions for our evolving models are provided by detailed non-gray white dwarf model atmospheres for hydrogen and helium composition. We assessed the impact of all these improvements on the evolutionary properties of ultra-massive white dwarfs, providing updated evolutionary sequences for these stars. We conclude that crystallization is expected to affect the majority of the massive white dwarfs observed with effective temperatures below 40 000 K. Moreover, the calculation of the phase separation process induced by crystallization is necessary to accurately determine the cooling age and the mass-radius relation of massive white dwarfs. We also provide colors in the Gaia photometric bands for our H-rich white dwarf evolutionary sequences on the basis of new model atmospheres. Finally, these new white dwarf sequences provide a new theoretical frame to perform asteroseismological studies on the recently detected ultra-massive pulsating white dwarfs.

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 Optical detection of the rapidly spinning white dwarf in V1460 Her

2021 ◽  
Author(s):  
Ingrid Pelisoli ◽  
R T Marsh ◽  
R P Ashley ◽  
Pasi Hakala ◽  
A Aungwerojwit ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Binary Systems ◽  
Hubble Space Telescope ◽  
Cataclysmic Variable ◽  
Optical Photometry ◽  
Arrival Times ◽  
Precise Ephemeris ◽  
History Of

Abstract Accreting magnetic white dwarfs offer an opportunity to understand the interplay between spin-up and spin-down torques in binary systems. Monitoring of the white dwarf spin may reveal whether the white dwarf spin is currently in a state of near-equilibrium, or of uni-directional evolution towards longer or shorter periods, reflecting the recent history of the system and providing constraints for evolutionary models. This makes the monitoring of the spin history of magnetic white dwarfs of high interest. In this paper we report the results of a campaign of follow-up optical photometry to detect and track the 39 sec white dwarf spin pulses recently discovered in Hubble Space Telescope data of the cataclysmic variable V1460 Her. We find the spin pulsations to be present in g-band photometry at a typical amplitude of 0.4 per cent. Under favourable observing conditions, the spin signal is detectable using 2-meter class telescopes. We measured pulse-arrival times for all our observations, which allowed us to derive a precise ephemeris for the white dwarf spin. We have also derived an orbital modulation correction that can be applied to the measurements. With our limited baseline of just over four years, we detect no evidence yet for spin-up or spin-down of the white dwarf, obtaining a lower limit of $|P/\dot{P}| > 4\times 10^{7}$ years, which is already 4 to 8 times longer than the timescales measured in two other cataclysmic variable systems containing rapidly rotating white dwarfs, AE Aqr and AR Sco.

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