An Optical and X-Ray Study of the Contact Binary, BH Cassiopeiae

Liu, Junhui; Esamdin, Ali; Hu, Ching Han; Chen, Tingting; Zhang, Junbo; Liu, Jinzhong; Li, Zixi; Ren, Juanjuan; Zheng, Jie; Niu, Hubiao; Bai, C. H.; Ge, Lijuan

doi:10.1088/1538-3873/ab247a

Cited by 15 publications

(7 citation statements)

References 88 publications

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“…Although the X-ray emission mechanism remains puzzling, the stellar dynamo magnetic activity generated by rapid rotation and envelope convection is usually in consideration (Gondoin 2004a). The studies of BH Cas (Liu et al 2019) and 2MASS J11201034−2201340 (Hu et al 2016) indicate that the X-ray light curves do not show any obvious occultation or modulation as optical light curves would. The X-ray spectra of the former can be described by thermal models, while those of the latter can be both fitted by a thermal or a power-law model.…”

Section: Introductionmentioning

confidence: 99%

X-ray emission of contact binary variables within 1 kpc

Liu

Esamdin

et al. 2022

A&A

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Aims. The X-ray emission of contact binaries (EW-type) is an important facet of such systems. Thus, X-ray emitting EW-type binaries (EWXs) are ideal laboratories for studying the X-ray radiation saturation mechanisms as well as binary evolution. By assembling the largest sample to date of EWXs with periods of less than 1 day from the All-Sky Automated Survey for Supernovae Variable Stars Database and X-ray catalogs from the XMM-Newton and ROSAT missions, we aim to conduct a systematic population study of X-ray emission properties of EWXs within 1 kpc. Methods. We carried out correlation analyses for the X-ray luminosity, logL X , and X-ray activity level log(L X /L bol ) versus the orbital period, P, effective temperature, T eff , metallicity [Fe/H], and the surface gravity log g of EWXs. We investigated the relation between X-ray emission and the mass of component stars in the binary systems. We also performed sample simulations to explore the degeneracy between period, mass, and effective temperature for EWXs. Results. We find strong P-logL X and P-log(L X /L bol ) correlations for EWXs with P < ∼ 0.44 days and we provide the linear parametrizations for these relations, on the basis of which the orbital period can be treated as a good predictor for logL X and log(L X /L bol ). The aforementioned binary stellar parameters are all correlated with logL X , while only T eff exhibits a strong correlation with log(L X /L bol ). Then, EWXs with higher temperature show lower X-ray activity level, which could indicate the thinning of the convective area related to the magnetic dynamo mechanism. The total X-ray luminosity of an EWX is essentially consistent with that of an X-ray saturated main sequence star with the same mass as its primary, which may imply that the primary star dominates the X-ray emission. The monotonically decreasing P-log(L X /L bol ) relation and the short orbital periods indicate that EWXs could all be in the X-ray saturated state, and they may inherit the changing trend of the saturated X-ray luminosities along with the mass shown by single stars. For EWXs, the orbital period, mass, and effective temperature increase in concordance. We demonstrate that the period P = 0.44 days corresponds to the primary mass of ∼ 1.1M , beyond which the saturated X-ray luminosity of single stars will not continue to increase with mass. This explains the break in the positive P-logL X relation for EWXs with P > 0.44 days.

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Section: Introductionmentioning

confidence: 99%

X-ray emission of contact binary variables within 1 kpc

Liu

Esamdin

et al. 2022

A&A

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“…Based on present studies, it can be concluded that during the X-ray observations by XMM-Newton, RW Dor and other contact binaries (VW Cep;Gondoin 2004a, 44 Boo;Gondoin 2004b, and BH Cas;Liu et al 2019) were in a quiescent state for some duration. The exact reason for coronal X-ray emission in a quiescent state is debatable in terms of the distribution of magnetic field structures but the presence of loops cannot be ruled out.…”

Section: Loop Size Emitting the Quiescent X-ray Emission In Rw Dormentioning

confidence: 61%

“…Such an orbital period of the third body was observed in VW Cep of about 31 yr (Kaszás et al 1998), which has very similar properties except for the mass ratio. Another source, BH Cas, which exhibits similar properties to RW Dor and VW Cep also has a third body with P 3 = 20.09 yr (Liu et al 2019). For RW Dor, the mass of the third body was noted to be M 3 = 0.175 M e for i = 90°.…”

Section: Non-conservative Mass Loss In Rw Dormentioning

confidence: 95%

“…There could be two possible reasons for such a configuration. The first one is Liu et al (2019) proposed a mechanism where the period of the contact binaries varies and hence the evolution of q, from higher to lower values, is driven by the oscillatory nature of fill-out factor f which depends on the thickness of the CCE. It was shown that the increase or decrease of f can decrease the period of the system and would be able to trigger a merger of the system.…”

Section: Non-conservative Mass Loss In Rw Dormentioning

confidence: 99%

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Optical and X-Ray Studies of Marginal Contact Binary RW Dor Using TESS and XMM-Newton Observatories

Sriram,

Mamatha Rani

2023

Res. Astron. Astrophys.

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Marginal short-period contact binaries are important to understand as they pose a different physical scenario than the predicted theoretical model based on the thermal relaxation oscillation mechanism due to their shallow degree of contact. Here we present the optical and X-ray studies of a contact binary source RW Dor using the Transiting Exoplanet Survey Satellite (TESS) and XMM-Newton telescopes. For the first time we report the varying O’Connell effect and explain the asymmetry with a spot model. Based on the new times of minima, we make a robust estimate of the orbital period of the third body at 47.01 ∼ 0.52 yr with an eccentricity e = 0.21. We show that the period-decreasing trend observed in O − C variation can be explained by both conservative mass transfer from primary to secondary and AML via stellar wind. The X-ray luminosity exhibited by RW Dor did not vary significantly on three different occasions and was found to be about 3.34 × 1029 erg s−1. Assuming that the quiescent X-ray emission is emitted from an undisturbed loop structure, the loop size is estimated to be 0.6–1 × 1010 cm which is ≤Alfvén radius r A ∼ 8 × 1010 cm.

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“…In contrast, the coronae in TX Cnc have uniformly distributed X-ray emitting regions with both components being equally active and having the same brightness per surface area. Two other contact binaries, BH Cas (Liu et al 2019) and 2MASS J11201034-2201340 (Hu et al 2016) were serendipitously detected in unrelated X-ray observations. For both objects no eclipses or significant variability were found, which may, however, be due to the low signal-to-noise ratio of the X-ray light curves.…”

Section: Introductionmentioning

confidence: 97%

X-Ray and UV Observations of the Contact Binary KIC 9832227

Pandel

Molnar

2023

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We investigate the X-ray and UV emission from the contact binary star KIC 9832227, which was observed with XMM-Newton for one orbital cycle. The binary is detected with an average X-ray luminosity of 3.4 × 1030 erg s−1. The X-ray emission is restricted to energies below 3 keV and originates from a multitemperature plasma with temperatures up to 1 keV. The X-ray spectrum has at least two distinct components, a cooler, mostly steady component, and a hotter component exhibiting significant variability. The variable X-ray emission appears to originate from a compact flare near the contact region between the two stars that is being eclipsed by the secondary. We analyze the eclipse profile to constrain the location, size, and density of the flaring region. The remaining X-ray emission is not eclipsed and could originate from the polar region on the primary star or an extended corona. The UV emission exhibits the same nearly sinusoidal modulation at half the orbital period that is observed at longer wavelengths. The primary and secondary eclipses have slightly different depths, which is generally attributed to starspot activity. Using simulations of the UV light curve with stellar atmosphere models, we deduce the presence of a starspot near the polar region of the primary, and we determine the time of primary eclipse.

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An Optical and X-Ray Study of the Contact Binary, BH Cassiopeiae

Cited by 15 publications

References 88 publications

X-ray emission of contact binary variables within 1 kpc

X-ray emission of contact binary variables within 1 kpc

Optical and X-Ray Studies of Marginal Contact Binary RW Dor Using TESS and XMM-Newton Observatories

X-Ray and UV Observations of the Contact Binary KIC 9832227

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