HD 63021: Chromospheric Activity and Mass Transfer in a Close Binary

Whelan, David G.; Chojnowski, S. Drew; Labadie-Bartz, Jonathan; Daglen, James; Hudson, Ken; Casey, G. M.; Stringfellow, Guy S.; Lester, Kathryn V.; Barry, John P.; Heinerikson, J.; Pankratz, D.; Schreffler, M.; Maderak, Ryan M.; Lotspeich, N.; Vitale-Sullivan, Molly E.; Woodard, M. F.

doi:10.3847/1538-3881/abceb4

Cited by 6 publications

(4 citation statements)

References 56 publications

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“…The light curve morphology -both the periodic and irregular behaviorare similar to that of the mass-transfer binary HD 63021 recently studied byWhelan et al (2021). We suspect that the origin of the photometric variability in that system, which Whelan et al did not explain, is also a combination of reflection and ellipsoidal variability.MNRAS 000,1-27 (2022) …”

supporting

confidence: 69%

Birth of a Be star: an APOGEE search for Be stars forming through binary mass transfer

El-Badry¹,

Conroy²,

Quataert³

et al. 2022

Preprint

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Motivated by recent suggestions that many Be stars form through binary mass transfer, we searched the APOGEE survey for Be stars with bloated, stripped companions. From a well-defined parent sample of 297 Be stars, we identified one mass-transfer binary, HD 15124. The object consists of a main-sequence Be star (𝑀 Be = 5.3 ± 0.6 𝑀 ) with a low-mass (𝑀 donor = 0.92 ± 0.22 𝑀 ), subgiant companion on a 5.47-day orbit. The emission lines originate in an accretion disk caused by ongoing mass transfer, not from a decretion disk as in classical Be stars. Both stars have surface abundances bearing imprint of CNO processing in the donor's core: the surface helium fraction is 𝑌 He ≈ 0.6, and the nitrogen-to-carbon ratio is 1000 times the solar value. The system's properties are well-matched by binary evolution models in which mass transfer begins while a 3 − 5 𝑀 donor leaves the main sequence, with the secondary becoming the Be star. These models predict that the system will soon become a detached Be + stripped star binary like HR 6819 and LB-1, with the stripped donor eventually contracting to become a core helium-burning sdOB star. Discovery of one object in this short-lived (∼1 Myr) evolutionary phase implies the existence of many more that have already passed through it and are now Be + sdOB binaries. We infer that (28 +27 −16 ) % of Be stars have stripped companions, most of which are faint. Together with the dearth of main-sequence companions to Be stars and recent discovery of numerous Be + sdOB binaries in the UV, our results imply that binarity plays an important role in the formation of Be stars.

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supporting

confidence: 69%

Birth of a Be star: an APOGEE search for Be stars forming through binary mass transfer

El-Badry¹,

Conroy²,

Quataert³

et al. 2022

Preprint

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“…There are, however, other cases of mass transfer binaries with highly unequal mass ratios (implying the donor has lost a large fraction of its mass) and slowly-rotating accretors (e.g. Whelan et al 2021).…”

Section: Rotation Rate Of the Subgiantsmentioning

confidence: 99%

Unicorns and Giraffes in the binary zoo: stripped giants with subgiant companions

El-Badry,

Seeburger,

Jayasinghe

et al. 2022

Preprint

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We analyze two binary systems containing giant stars, V723 Mon ("the Unicorn") and 2M04123153+6738486 ("the Giraffe"). Both giants orbit more massive but less luminous companions, previously proposed to be mass-gap black holes. Spectral disentangling reveals luminous companions with star-like spectra in both systems. Joint modeling of the spectra, light curves, and spectral energy distributions robustly constrains the masses, temperatures, and radii of both components: the primaries are luminous, cool giants (𝑇 eff, giant = 3, 800 K and 4, 000 K, 𝑅 giant = 22.5 𝑅 and 25 𝑅 ) with exceptionally low masses (𝑀 giant ≈ 0.4 𝑀 ) that likely fill their Roche lobes. The secondaries are only slightly warmer subgiants (𝑇 eff, 2 = 5, 800 K and 5, 150 K, 𝑅 2 = 8.3 𝑅 and 9 𝑅 ) and thus are consistent with observed UV limits that would rule out main-sequence stars with similar masses (𝑀 2 ≈ 2.8 𝑀 and ≈ 1.8 𝑀 ). In the Unicorn, rapid rotation blurs the spectral lines of the subgiant, making it challenging to detect even at wavelengths where it dominates the total light. Both giants have surface abundances indicative of CNO processing and subsequent envelope stripping. The properties of both systems can be reproduced by binary evolution models in which a 1 − 2 𝑀 primary is stripped by a companion as it ascends the giant branch. The fact that the companions are also evolved implies either that the initial mass ratio was very near unity, or that the companions are temporarily inflated due to rapid accretion. The Unicorn and Giraffe offer a window into into a rarely-observed phase of binary evolution preceding the formation of wide-orbit helium white dwarfs, and eventually, compact binaries containing two helium white dwarfs.

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“…W UMa systems, whose spectral classes range generally from F to K, include two late-type dwarf stars that usually exhibit stellar magnetic activities, such as starspots (Kjurkchieva et al 2019), flares (Huang et al 2020), chromosphere activity (Whelan et al 2021) and magnetic activity cycles (Hu et al 2020). The orbital periods in W UMa systems are usually short, about 0.4 days.…”

Section: Introductionmentioning

confidence: 99%

A Photometric Study of Two Contact Binaries: CRTS J025408.1+265957 and CRTS J012111.1+272933

Ma¹,

Liu²,

Zhang³

et al. 2022

Res. Astron. Astrophys.

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We performed new photometric observations for two contact binaries (i.e., CRTS J025408.1+265957 and CRTS J012111.1+272933), which were observed by the 1.0-m telescope at Xingjiang Astronomical Observatory. From our light curves and several survey data, we derived several sets of photometric solutions. We found that CRTS J025408.1+265957 and CRTS J012111.1+272933 were A- and W-type W UMa, respectively. The results imply that the spot migrates or disappears in two contact binaries, which were identified by chromospheric activity emissions (e.g. Hα emission) from LAMOST spectra. From the O-C curves, the orbital periods of two contact binaries may be increasing, which is interpreted by the mass transfer from the less massive component to the more massive one. With mass transferring, two contact binaries may evolve from the contact configurations to semi-detected ones as predicted by the theory of thermal relaxation oscillation.

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HD 63021: Chromospheric Activity and Mass Transfer in a Close Binary

Cited by 6 publications

References 56 publications

Birth of a Be star: an APOGEE search for Be stars forming through binary mass transfer

Birth of a Be star: an APOGEE search for Be stars forming through binary mass transfer

Unicorns and Giraffes in the binary zoo: stripped giants with subgiant companions

A Photometric Study of Two Contact Binaries: CRTS J025408.1+265957 and CRTS J012111.1+272933

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