Four new deeply eclipsing white dwarfs in Zwicky Transient Facility

Kosakowski, Alekzander; Kilic, Mukremin; Brown, Warren R.; Bergeron, P.; Kupfer, Thomas

doi:10.1093/mnras/stac1146

Cited by 8 publications

(5 citation statements)

References 54 publications

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“…The orbital separation estimated from the third Kepler law is a > 3.1 R , which is large enough to accommodate any cool main-sequence star into the system. Comparable white dwarf binaries with a brown dwarf or a low-mass red dwarf companion have already been found (Becklin & Zuckerman 1988;Kawka & Vennes 2003;Farihi et al 2010;Burleigh et al 2011;Kosakowski et al 2022). The initial-final mass relation of Cummings et al (2018) estimates an initial mass of about 1.0 M for a white dwarf mass of M 1 = 0.57 M .…”

Section: Radial Velocity Curve and Evolutionary Statusmentioning

confidence: 81%

EPIC 206197016: A very hot white dwarf orbited by a strongly irradiated red dwarf

Krtička

Kawka

Mikulášek

et al. 2023

A&A

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Context. Very precise satellite photometry has revealed a large number of variable stars whose variability is caused either by surface spots or by binarity. Detailed studies of such variables provide insights into the physics of these objects. Aims. We study the nature of the periodic light variability of the white dwarf EPIC 206197016 that was observed by the K2 mission. Methods. We obtain phase-resolved medium-resolution spectroscopy of EPIC 206197016 using X-shooter spectrograph at VLT to understand the nature of the white dwarf variability. We use non-local thermodynamical equilibrium model atmospheres to determine stellar parameters at individual phases. Results. EPIC 206197016 is a hot DA white dwarf with Teff = 78 kK. The analysis of the spectra reveals periodic radial velocity variations that can result from gravitational interaction with an invisible secondary whose mass corresponds to a red dwarf. The close proximity of the two stars where the semimajor axis is about 3 R⊙ results in the irradiation of the companion with temperatures more than twice as high on the illuminated side compared to the nonilluminated hemisphere. This effect can explain the observed light variations. The spectra of the white dwarf show a particular feature of the Balmer lines called the Balmer line problem, where the observed cores of the lower Balmer lines are deeper than predicted. This can be attributed to either weak pollution of hydrogen in the white dwarf atmosphere by heavy elements or to the presence of a circumstellar cloud or disk.

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Section: Radial Velocity Curve and Evolutionary Statusmentioning

confidence: 81%

EPIC 206197016: A very hot white dwarf orbited by a strongly irradiated red dwarf

Krtička

Kawka

Mikulášek

et al. 2023

A&A

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“…WD J003352.64+385529.70 (G = 18.3 mag) was identified by Kosakowski et al (2022) to have a strong 4.86 hr signal in ZTF, and has all the hallmarks of a WD+dM eclipsing binary, especially featuring ZTF dropouts in both the g and r bands when folded on a period of 4.86465(31) hr. These dropouts align in phase space and show a decrease in amplitude of nearly 100%.…”

Section: Eclipsing White Dwarf Binariesmentioning

confidence: 99%

“…We obtained follow-up time-series photometry and spectroscopy for our most compact new eclipsing system (WD J154008.28-392917.61), located in the southern hemisphere (G = 17.3 mag). Kosakowski et al 2022). Four systems are newly discovered eclipsing binaries containing a white dwarf, including a new 1.3 hr eclipsing CV (WD J154008.28-392917.61, further detailed in Section 4.3.1 and Figure 4).…”

Section: Follow-up Of a New Eclipsing CVmentioning

confidence: 99%

Measuring White Dwarf Variability from Sparsely Sampled Gaia DR3 Multi-epoch Photometry

Steen,

Hermes,

Guidry

et al. 2024

ApJ

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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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“…We used twice the period to fold the light curve, and the primary and secondary eclipses appeared at the same depth. The evolution of the light curve is predicted to be dominated by a white dwarf, while the companion star is a low-luminosity target, such as a brown dwarf or an M dwarf (Kosakowski et al 2022). The classification of the system can be further confirmed by spectrum and high-speed photometric observation.…”

Section: Notes On Individual Objectsmentioning

confidence: 99%

A Systematic Search for Short-period Close White Dwarf Binary Candidates Based on Gaia EDR3 Catalog and Zwicky Transient Facility Data

Ren¹,

Li²,

Ma³

et al. 2023

ApJS

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Galactic short-period close white dwarf binaries (CWDBs) are important objects for space-borne gravitational-wave (GW) detectors in the millihertz frequency bands. Due to the intrinsically low luminosity, only about 25 identified CWDBs are detectable by the Laser Interferometer Space Antenna (LISA), which are also known as verification binaries (VBs). The Gaia Early Data Release 3 (EDR3) provids a catalog containing a large number of CWDB candidates, which also includes parallax and photometry measurements. We crossmatch the Gaia EDR3 and Zwicky Transient Facility public data release 8, and apply period-finding algorithms to obtain a sample of periodic variables. The phase-folded light curves are inspected, and finally we obtain a binary sample containing 429 CWDB candidates. We further classify the samples into eclipsing binaries (including 58 HW Vir-type binaries, 65 EA-type binaries, 56 EB-type binaries, and 41 EW-type binaries) and ellipsoidal variations (209 ELL-type binaries). We discovered four ultrashort period binary candidates with unique light-curve shapes. We estimate the GW amplitude of all of our binary candidates, and calculate the corresponding signal-to-noise ratio (S/N) for TianQin and LISA. We find two (six) potential GW candidates with S/Ns greater than 5 in the nominal mission time of TianQin (LISA), which increases the total number of candidate VBs for TianQin (LISA) to 18 (31).

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Four new deeply eclipsing white dwarfs in Zwicky Transient Facility

Cited by 8 publications

References 54 publications

EPIC 206197016: A very hot white dwarf orbited by a strongly irradiated red dwarf

EPIC 206197016: A very hot white dwarf orbited by a strongly irradiated red dwarf

Measuring White Dwarf Variability from Sparsely Sampled Gaia DR3 Multi-epoch Photometry

A Systematic Search for Short-period Close White Dwarf Binary Candidates Based on Gaia EDR3 Catalog and Zwicky Transient Facility Data

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