Dynamically Forming Extremely Low-Mass White Dwarf Binaries in Wide Orbits

Khurana, Ambreesh; Chawla, Chirag; Chatterjee, Sourav

doi:10.48550/arxiv.2209.06231

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“…In the literature, WOCS 5005 (4913 d) and WOCS 1025 (1154 d) were reported as long-period binaries with an LM WD and a WD as the secondary companions, respectively. As LM WD cannot form through single star evolution within the Hubble time, Pandey et al (2021) speculated that systems like WOCS 5005 could either be formed due to dynamical interactions (Khurana et al 2022) or have the LM WD in the close inner binary of a tertiary system. As we did not detect any eclipses in the light curves of these systems, we can confirm the absence of short-period inner binary with a high inclination that gives rise to eclipses or ellipsoidal variations.…”

Section: Discussionmentioning

confidence: 99%

Photometric variability of blue straggler stars in M67 with TESS and K2

Vernekar

Subramaniam

Jadhav

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Blue straggler stars (BSSs) are formed through mass transfer or mergers in binaries. The recent detections of white dwarf (WD) companions to BSSs in M67 suggested a mass transfer pathway of formation. In search of a close companion to five BSSs in M67 that are known to be spectroscopic binaries, we study the light curves from K2 and TESS data. We use PHOEBE to analyse the light curves and estimate the properties of the companions. We detect variability in WOCS 1007, and the light curve is dominated by ellipsoidal variation. Using the light curve and radial velocity measurements, we estimate its orbital period to be 4.212±0.041 d and e = 0.206±002. The mass of the companion is estimated to be 0.22±0.05 M⊙ with a radius of 0.078±0.027 R⊙, confirming it to be an LM WD with Teff = 14300±1100 K. The estimated mass of the BSS, 1.95±0.26 M⊙, is similar to that estimated from isochrones. The BSS in WOCS 1007 shows δ Scuti pulsations, although it is slightly deformed and likely to be formed through an efficient mass transfer. Though we detect a light curve for WOCS 4003 showing grazing eclipse with ellipsoidal variation, the estimated parameters are inconclusive. Apart from the 0.44 d period, we found smaller eclipses with a period of 1.1 d, suggesting a compact triple system. In the case of WOCS 4003, WOCS 5005, and WOCS 1025, no eclipses or pulsations are detected, confirming the absence of any short-period inner binary with high inclination in these BSSs.

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Section: Discussionmentioning

confidence: 99%