Measuring the masses of magnetic white dwarfs: a <i>NuSTAR</i> legacy survey

Shaw, A. W.; Heinke, C. O.; Mukai, K.; Tomsick, John A.; Doroshenko, V.; Suleimanov, V.; Buisson, D. J. K.; Gandhi, P.; Grefenstette, Brian W.; Hare, Jeremy; Jiang, Jiachen; Ludlam, R. M.; Rana, V.; Sivakoff, Gregory R.

doi:10.1093/mnras/staa2592

Cited by 35 publications

(42 citation statements)

References 76 publications

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“…This is also supported by our white dwarf mass estimates. For the 6 detached magnetic systems with reliable mass estimates we obtain an average white dwarf mass of 𝑀 WD = 0.82 ± 0.07 M , which is higher than the average mass of white dwarfs in pre-CVs (0.67 ± 0.21 M , Zorotovic et al 2011), but is consistent with both non-magnetic CV white dwarf masses (0.83 ± 0.23 M , Zorotovic et al 2011;Schreiber et al 2016) and magnetic CV white dwarf masses (0.77 ± 0.02 M , Shaw et al 2020, 0.84 ± 0.17 M de Martino et al 2020. Although it is worth noting that in general isolated magnetic white dwarfs appear to have higher masses than their non-magnetic counterparts (Ferrario et al 2015;McCleery et al 2020) On the other hand, our measured Roche-lobe filling factors are as low as 0.84, which would place the main-sequence star quite far from Roche-lobe filling.…”

Section: Evolutionary Statussupporting

confidence: 67%

Magnetic white dwarfs in post-common-envelope binaries

Parsons,

Gänsicke,

Schreiber

et al. 2021

Preprint

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Magnitude-limited samples have shown that 20-25 per cent of cataclysmic variables contain white dwarfs with magnetic fields of Mega Gauss strength, in stark contrast to the approximately 5 per cent of single white dwarfs with similar magnetic field strengths. Moreover, the lack of identifiable progenitor systems for magnetic cataclysmic variables leads to considerable challenges when trying to understand how these systems form and evolve. Here we present a sample of six magnetic white dwarfs in detached binaries with low-mass stellar companions where we have constrained the stellar and binary parameters including, for the first time, reliable mass estimates for these magnetic white dwarfs. We find that they are systematically more massive than non-magnetic white dwarfs in detached binaries. These magnetic white dwarfs generally have cooling ages of more than 1 Gyr and reside in systems that are very close to Roche-lobe filling. Our findings are more consistent with these systems being temporarily detached cataclysmic variables, rather than pre-cataclysmic binaries, but we cannot rule out the latter possibility. We find that these systems can display unusual asymmetric light curves that may offer a way to identify them in larger numbers in future. Seven new candidate magnetic white dwarf systems are also presented, three of which have asymmetric light curves. Finally, we note that several newly identified magnetic systems have archival spectra where there is no clear evidence of magnetism, meaning that these binaries have been previously missed. Nevertheless, there remains a clear lack of younger detached magnetic white dwarf systems.

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Section: Evolutionary Statussupporting

confidence: 67%

Magnetic white dwarfs in post-common-envelope binaries

Parsons,

Gänsicke,

Schreiber

et al. 2021

Preprint

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“…This value is lower than the average WD mass for a sample of nearby IPs, where it is about 0.8 M (see e.g. Suleimanov et al 2019;Shaw et al 2020). The discrepancy between these values could be an indication that the contribution of IPs to the Galactic bulge is indeed reduced.…”

Section: Our Results In Broader Astrophysical Contextmentioning

confidence: 78%

Hard X-ray luminosity functions of cataclysmic variables: Joint Swift/BAT and Gaia data

Suleimanov,

Doroshenko,

Werner

2022

Preprint

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Cataclysmic variables (CVs) are the most numerous population among the Galactic objects emitting in hard X-rays. Most probably, they are responsible for the extended hard X-ray emission of the Galactic ridge and the central Galactic regions.Here we consider the sample of CVs detected in the all-sky hard X-ray Swift/BAT survey which were also detected by Gaia and thus have reliable distance estimates. Using these data, we derive accurate estimates for local number density per solar mass (ρ M = 1.37 +0.3 −0.16 . × 10 −5 M −1 ) and luminosity density per solar mass (ρ L = 8.95 +0.15 −0.1 × 10 26 erg s −1 M −1 ) for objects in the sample. These values appear to be in good agreement with the integrated Galactic ridge X-ray emission and Nuclear Stellar Cluster luminosities. Analysis of the differential luminosity functions dρ M /d(log 10 L x ) and dρ L /d(log 10 L x ) confirms that there are two populations of hard X-ray emitting CVs. Intermediate polars dominate at luminosities L > 10 33 erg s −1 , whereas non-magnetic CVs and polars are much more numerous but have lower luminosities on average. As a consequence, the contribution of these populations to the observed hard X-ray luminosity is almost equivalent.

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“…11 Covington et al (2022) examined archival observations of YY Dra from 2018 and identified a 3 mag fade in Swift ultraviolet UVW-and UVM-band observations that coincided with a nondetection of YY Dra in X-ray observations. Likewise, Shaw et al (2020) found no X-ray emission in a 55.4 ks NuSTAR observation of YY Dra in 2018 July. These findings provide independent support for a cessation of accretion onto the WD in 2018.…”

Section: Updated Orbital Periodmentioning

confidence: 97%

Hitting a New Low: The Unique 28 hr Cessation of Accretion in the TESS Light Curve of YY Dra (DO Dra)

Hill

Garnavich

Scaringi

et al. 2022

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We present the Transiting Exoplanet Surveying Satellite light curve of the intermediate polar YY Draconis (YY Dra, also known as DO Dra). The power spectrum indicates that while there is stream-fed accretion for most of the observational period, there is a day-long, flat-bottomed low state at the beginning of 2020 during which the only periodic signal is ellipsoidal variation and there is no appreciable flickering. We interpret this low state to be a complete cessation of accretion, a phenomenon that has been observed only once before in an intermediate polar. Simultaneous ground-based observations of this faint state establish that when accretion is negligible, YY Dra fades to g = 17.37 ± 0.12, which we infer to be the magnitude of the combined photospheric contributions of the white dwarf and its red dwarf companion. Using survey photometry, we identify additional low states in 2018–2019 during which YY Dra repeatedly fades to—but never below—this threshold. This implies relatively frequent cessations in accretion. Spectroscopic observations during future episodes of negligible accretion can be used to directly measure the field strength of the white dwarf by Zeeman splitting. Separately, we search newly available catalogs of variable stars in an attempt to resolve the long-standing dispute over the proper identifier of this system.

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Measuring the masses of magnetic white dwarfs: a NuSTAR legacy survey

Cited by 35 publications

References 76 publications

Magnetic white dwarfs in post-common-envelope binaries

Magnetic white dwarfs in post-common-envelope binaries

Hard X-ray luminosity functions of cataclysmic variables: Joint Swift/BAT and Gaia data

Hitting a New Low: The Unique 28 hr Cessation of Accretion in the TESS Light Curve of YY Dra (DO Dra)

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