Related papers: The expected evolution of the binary system PTF J2…
Abridged: We report the discovery of two, new, rare, wide, double-degenerate binaries that each contain a magnetic and a non-magnetic star. The components of SDSSJ092646.88+132134.5 + J092647.00+132138.4 and SDSSJ150746.48+521002.1 +…
We propose a formation channel for the previously unexplained helium-rich subdwarf O (He-rich sdO) stars in which post-subdwarf B (sdB) stars (i.e. hybrid COHe white dwarfs) reignite helium burning in a shell after gaining matter from their…
The Hubble Space Telescope observation of the double white dwarf (WD) binary SDSS J125733.63$+$542850.5 reveal that the massive WD has a surface gravity log$g_1\sim8.7$ (which implies a mass of $M_1\sim1.06~{\rm M_\odot}$) and an effective…
We study the evolution of close binary systems in order to account for the existence of the recently observed binary system containing the most massive millisecond pulsar ever detected, PSR J0740+6620, and its ultra-cool helium white dwarf…
We describe the evolution of double degenerate binary systems, consisting of components obeying the zero temperature mass radius relationship for white dwarf stars, from the onset of mass transfer to one of several possible outcomes…
Splaver and coworkers have measured the masses of the white dwarf and the neutron star components of the PSR J1713+0747 binary system pair by Shapiro Delay. We attempt to find the original configuration of this system performing a set of…
We report the results of XMM-Newton observations of HD49798/RXJ0648.0-4418, the only known X-ray binary consisting of a hot sub-dwarf and a white dwarf. The white dwarf rotates very rapidly (P=13.2 s) and has a dynamically measured mass of…
Approximately 150 low-mass white dwarfs, with masses below 0.4Msun, have been discovered. The majority of these low-mass WDs are observed in binary systems as they cannot be formed through single-star evolution within the Hubble time. In…
The evolution of binaries consisting of evolved main sequence stars (1 < M_d/Msun < 3.5) with white dwarf companions (0.7 < M_wd/Msun < 1.2) is investigated through the thermal mass transfer phase. Taking into account the stabilizing effect…
PSR J1713+0747 is a binary system comprising millisecond radio pulsar with a spin period of 4.57 ms, and a low-mass white dwarf (WD) companion orbiting the pulsar with a period of 67.8 days. Using the general relativistic Shapiro delay, the…
The white dwarf (WD) + helium (He) star binary channel plays an important role in the single degenerate scenario for the progenitors of type Ia supernovae (SNe Ia). Previous studies on the WD + main sequence star evolution have shown that…
The bright subdwarf-O star (sdO), HD 49798, is in a 1.55 day orbit with a compact companion that is spinning at 13.2 seconds. Using the measurements of the effective temperature ($T_{\rm eff}$), surface gravity ($\log g$), and surface…
We present results of a systematic investigation of the evolution of low-mass (0.35, 0.40, and 0.65 solar mass) helium donors in semidetached binaries with accretors - white dwarfs. In the initial models of evolutionary sequences abundance…
Massive short-period binaries involving hot subdwarf stars (sdO/Bs) are rare but important to constraining pathways for binary star evolution. Moreover, some of the most promising candidate progenitor systems leading to Type Ia supernovae…
The detonation of an overlying helium layer on a $0.8-1.1\,\mathrm{M}_{\odot}$ carbon-oxygen (CO) white dwarf (WD) can detonate the CO WD and create a thermonuclear supernova (SN). Many authors have recently shown that when the mass of the…
Helium star - carbon-oxygen white dwarf (CO WD) binaries are potential single-degenerate progenitor systems of thermonuclear supernovae. Revisiting a set of binary evolution calculations using the stellar evolution code $\texttt{MESA}$, we…
Motivated by the discovery of a handful of pulsating, extremely low mass white dwarfs (ELM WDs, mass $M \lesssim 0.17\, M_\odot$) which likely have WD companions, this paper discusses binary formation models for these systems. Formation of…
We discuss the mass-radius (M-R) relations for low-mass (M<0.1 Msun) white dwarfs (WDs) of arbitrary degeneracy and evolved (He, C, O) composition. We do so with both a simple analytical model and models calculated by integration of…
Some binary systems composed of a white dwarf (WD) and a hot subdwarf (sdB) helium star will make contact within the helium burning lifetime of the sdB star. The accreted helium on the WD inevitably undergoes a thermonuclear instability,…
We present optical and X-ray observations of two tidally distorted, extremely low-mass white dwarfs (WDs) with massive companions. There is no evidence of neutron stars in our Chandra and XMM observations of these objects. SDSS…