Discovery of an Ultramassive Pulsating White Dwarf

Hermes, J. J.; Kepler, S. O.; Castanheira, B. G.; Gianninas, A.; Winget, D. E.; Montgomery, M. H.; Brown, Warren R.; Harrold, Samuel T.

doi:10.1088/2041-8205/771/1/l2

Cited by 51 publications

(64 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Even more recently, the McDonald Observatory program has revealed the existence of two additional pulsating extremely low-mass DA white dwarfs (Hermes et al 2013), thus opening up a new and exciting avenue of research in the field of asteroseismology. SDSS J1112+1117 is characterized by T eff 9400 ± 490 K and log g 5.99 ± 0.12 , and shows at least five independent periodicities in its light curve, ranging from 1793 s up to 2856 s. For its part, SDSS J1518+0658 is characterized as having T eff 9810 ± 320 K and log g 6.66 ± 0.06 , and its light curve shows 6 independent periodicities ranging from 1339 s to 3680 s. As pointed out by Hermes et al (2012) and J. J.…”

Section: Introductionmentioning

confidence: 99%

The Newly Discovered Pulsating Low-Mass White Dwarfs: An Extension of the Zz Ceti Instability Strip

Grootel

Fontaine

Brassard

et al. 2012

ApJ

View full text Add to dashboard Cite

In light of the exciting discovery of g-mode pulsations in extremely low-mass, He-core DA white dwarfs, we report on the results of a detailed stability survey aimed at explaining the existence of these new pulsators as well as their location in the spectroscopic Hertzsprung-Russell diagram. To this aim, we calculated some 28 evolutionary sequences of DA models with various masses and chemical layering. These models are characterized by the so-called ML2/α = 1.0 convective efficiency and take into account the important feedback effect of convection on the atmospheric structure. We pulsated the models with the nonadiabatic code MAD, which incorporates a detailed treatment of time-dependent convection. On the other hand, given the failure of all nonadiabatic codes, including MAD, to account properly for the red edge of the strip, we resurrect the idea that the red edge is due to energy leakage through the atmosphere. We thus estimated the location of that edge by requiring that the thermal timescale in the driving region-located at the base of the H convection zone-be equal to the critical period beyond which = 1 g-modes cease to exist. Using this approach, we find that our theoretical ZZ Ceti instability strip accounts remarkably well for the boundaries of the empirical strip, including the low-gravity, low-temperature regime where the three new pulsators are found. We also account for the relatively long periods observed in these stars, and thus conclude that they are true ZZ Ceti stars, but with low masses.

show abstract

Section: Introductionmentioning

confidence: 99%

The Newly Discovered Pulsating Low-Mass White Dwarfs: An Extension of the Zz Ceti Instability Strip

Grootel

Fontaine

Brassard

et al. 2012

ApJ

View full text Add to dashboard Cite

show abstract

“…We detect periods in J0840 ranging from roughly 180 to 800 s meanwhile pulsational periods of BPM 37093 lie in a narrow range of about 510 to 660 s (Kanaan et al 2005) and those of GD 518 range from 425 to 595 s (Hermes et al 2013). Our observed period range is consistent with the calculated period range for a 1.1 M CO-core WD with T eff = 12, 200 K presented in Figure 9 of Montgomery & Winget (1999), which shows the periods of l=2 modes for crystallized mass ratios ranging from 0 to 0.99.…”

Section: Discussionmentioning

confidence: 76%

“…Furthermore, amplitudes reported for GD 518 range from roughly 1 to 4 mma (Hermes et al 2013). The dominant periods of pulsation for J0840 remained consistent within the errors between the four nights of available data over a period of about 3 months.…”

Section: Discussionmentioning

confidence: 99%

“…They also conclude that the mass of the hydrogen envelope in these stars ranges from 10 −4 to 10 −10 M * . The recent discovery of the most massive (M = 1.20 ± 0.03 M ) DAV, GD 518, by Hermes et al (2013) marks the beginning of the population of the extremely high mass end of the ZZ Ceti instability strip. Such objects are likely the remnants of stars with a ZAMS mass of 7 M and could contain ONe or ONeMg cores as a result of carbon burning.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Four new massive pulsating white dwarfs including an ultramassive DAV

Curd

Gianninas

Bell

et al. 2017

Monthly Notices of the Royal Astronomical Society

Self Cite

View full text Add to dashboard Cite

We report the discovery of four massive (M > 0.8 M ) ZZ Ceti white dwarfs, including an ultramassive 1.16 M star. We obtained ground based, time-series photometry for thirteen white dwarfs from the Sloan Digital Sky Survey Data Release 7 and Data Release 10 whose atmospheric parameters place them within the ZZ Ceti instability strip. We detect mono-periodic pulsations in three of our targets (J1053, J1554, and J2038) and identify three periods of pulsation in J0840 (173, 327, and 797 s). Fourier analysis of the remaining nine objects do not indicate variability above the 4 A detection threshold. Our preliminary asteroseismic analysis of J0840 yields a stellar mass M = 1.14 ± 0.01 M , hydrogen and helium envelope masses of M H = 5.8 × 10 −7 M and M He = 4.5 × 10 −4 M , and an expected core crystallized mass ratio of 50-70%. J1053, J1554, and J2038 have masses in the range 0.84 − 0.91M and are expected to have a CO core; however, the core of J0840 could consist of highly crystallized CO or ONeMg given its high mass. These newly discovered massive pulsators represent a significant increase in the number of known ZZ Ceti white dwarfs with mass M > 0.85 M , and detailed asteroseismic modeling of J0840 will allow for significant tests of crystallization theory in CO and ONeMg core white dwarfs.

show abstract

“…Figure 8 shows the T eff -log g diagram of 172 known ZZ Ceti stars with determined atmospheric parameters. These known objects were collected from the literature (14 from Kepler et al (2005), 41 from Mukadam et al (2006), 5 from Voss et al (2006Voss et al ( , 2007, 34 from Castanheira et al (2006from Castanheira et al ( , 2007from Castanheira et al ( , 2010from Castanheira et al ( , 2013, 56 from Gianninas et al (2011), 6 from Green et al (2015, 11 in the Kepler field (Hermes et al 2011;Greiss et al 2014Greiss et al , 2016 and 5 massive or ultramassive ZZ Ceti stars discovered by Hermes et al (2013) and Curd et al (2017)). The positions of our new ZZ Ceti stars are marked in the diagram with the squares with error bars.…”

Section: Significance Criteriamentioning

confidence: 99%

New ZZ Ceti Stars from the LAMOST Survey

Lin

et al. 2017

ApJ

View full text Add to dashboard Cite

The spectroscopic sky survey carried out by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) provides the largest stellar spectra library in the world until now. A large number of new DA white dwarfs had been identified based on the LAMOST spectra. The effective temperature (T eff ) and surface gravity (log g) of most DA white dwarfs were determined and published in the catalogs, e.g. Zhao et al. (2013), Rebassa-Mansergas et al. (2015), Gentile Fusillo et al. (2015 and Guo et al. (2015). We selected ZZ Ceti candidates from the published catalogs by considering whether their T eff are situated in the ZZ Ceti instability strip. The follow-up time-series photometric observations for the candidates were performed in 2015 and 2016. Four stars: LAMOST J004628.31+343319.90, LAMOST J062159.49+252335.9, LAMOST J010302.46+433756.2 and LAMOST J013033.90+273757.9 are finally confirmed to be new ZZ Ceti stars. They show dominant peaks with amplitudes rising above the 99.9% confidence level in the amplitude spectra. As LAMOST J004628.31+343319.90 has an estimated mass of ∼ 0.40 M ⊙ and LAM-OST J013033.90+273757.9 has a mass of ∼ 0.45 M ⊙ derived from their log g values, these two stars are inferred to be potential helium-core white dwarfs.

show abstract

Discovery of an Ultramassive Pulsating White Dwarf

Cited by 51 publications

References 50 publications

The Newly Discovered Pulsating Low-Mass White Dwarfs: An Extension of the Zz Ceti Instability Strip

The Newly Discovered Pulsating Low-Mass White Dwarfs: An Extension of the Zz Ceti Instability Strip

Four new massive pulsating white dwarfs including an ultramassive DAV

New ZZ Ceti Stars from the LAMOST Survey

Contact Info

Product

Resources

About