Optical Flares and a Long-Lived Dark Spot on a Cool Shallow Contact Binary

SB, Qian; Jj, Wang; LY, Zhu; Snoonthornthum, B.; Lz, Wang; Zhao, Enmin; Xiao, Zhi Yu; WP, Liao; NP, Liu

doi:10.1088/0067-0049/212/1/4

Cited by 85 publications

(57 citation statements)

References 36 publications

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“…The first optical telescope was called CSTAR (the Chinese Small Telescope ARray; Yuan et al 2008) with an effective aperture of 10 cm and field of view (FOV) of 20 deg 2 and was installed at Dome A in January 2008; CSTAR produced a 3-year photometric dataset, and a number of studies of stellar variability have been published (Zhou et al 2010a,b;Wang et al 2011Wang et al , 2012Zhou et al 2013;Wang et al 2013a,b;Meng et al 2013;Huang et al 2013;Fu et al 2014;Qian et al 2014;Wang et al 2014a,b;Zong et al 2015;Huang et al 2015;Wang et al 2015;Yang et al 2015;Oelkers et al 2015Oelkers et al , 2016Liang et al 2016). The second-generation of optical telescope at Dome A is called AST3, which in turn consists of three telescopes, each with an entrance pupil diameter of 0.5 m, and a FOV of 4.3 deg 2 Yuan & Su 2012;Yuan et al 2014Yuan et al , 2015.…”

Section: Introductionmentioning

confidence: 99%

Variable Stars Observed in the Galactic Disk by AST3-1 from Dome A, Antarctica

Wang

et al. 2017

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AST3-1 is the second-generation wide-field optical photometric telescope dedicated to time domain astronomy at Dome A, Antarctica. Here we present the results of i band images survey from AST3-1 towards one Galactic disk field. Based on time-series photometry of 92,583 stars, 560 variable stars were detected with i magnitude ≤ 16.5 mag during eight days of observations; 339 of these are previously unknown variables. We tentatively classify the 560 variables as 285 eclipsing binaries (EW, EB, EA), 27 pulsating variable stars (δ Scuti, γ Doradus, δ Cephei variable and RR Lyrae stars) and 248 other types of variables (unclassified periodic, multi-periodic and aperiodic variable stars). Among the eclipsing binaries, 34 show O'Connell effects. One of the aperiodic variables shows a plateau light curve and another one shows a secondary maximum after peak brightness. We also detected a complex binary system with RS CVn-like light curve morphology; this object is being followed-up spectroscopically using the Gemini South telescope.

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Section: Introductionmentioning

confidence: 99%

Variable Stars Observed in the Galactic Disk by AST3-1 from Dome A, Antarctica

Wang

et al. 2017

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“…Flares were also discovered on binaries, e.g., RS CVn variables (Pandey & Singh 2012) and a W UMa star (CSTAR 038663; Qian et al 2014). RS CVn is a class of detached binaries typically composed of a chromospherically active G or K star (e.g., Berdyugina & Järvinen 2005).…”

Section: Introductionmentioning

confidence: 99%

“…The underlying mechanisms of triggering flares on RS CVn are expected to remain the same because in the single stars the magnetic reconnection in the field connecting the two stars may cause the flare events to be more active (e.g., Gunn et al 1997), and tidal effects play important roles for enhancing the magnetic activity of RS CVn stars (Cuntz et al 2000). Flares on CSTAR 038663 are expected to originate on the surface of the contact binaries based on the observational facts that, (i) the flare amplitude is increasing along the duration, and (ii) the photometric solution reveals a long-lived dark spot on the contact binary, which could be associated with the flares (Qian et al 2014). Using Kepler data, Balona (2015) examined the flare frequency as a function of orbital phase in three eclipsing binaries.…”

Section: Introductionmentioning

confidence: 99%

White-Light Flares on Close Binaries Observed With Kepler

Gao

Xin

Liu

et al. 2016

ApJS

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Based on Kepler data, we present the results of a search for white light flares on 1049 close binaries. We identify 234 flare binaries, of which 6818 flares are detected. We compare the flare-binary fraction in different binary morphologies ("detachedness"). The result shows that the fractions in over-contact and ellipsoidal binaries are approximately 10%-20% lower than those in detached and semi-detached systems. We calculate the binary flare activity level (AL) of all the flare binaries, and discuss its variations along the orbital period (P orb ) and rotation period (P rot , calculated for only detached binaries). We find that the AL increases with decreasing P orb or P rot , up to the critical values at P orb ∼ 3 days or P rot ∼ 1.5 days, and thereafter the AL starts decreasing no matter how fast the stars rotate. We examine the flaring rate as a function of orbital phase in two eclipsing binaries on which a large number of flares are detected. It appears that there is no correlation between flaring rate and orbital phase in these two binaries. In contrast, when we examine the function with 203 flares on 20 non-eclipse ellipsoidal binaries, bimodal distribution of amplitude-weighted flare numbers shows up at orbital phases 0.25 and 0.75. Such variation could be larger than what is expected from the cross section modification.

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“…The most detailed studies of this type refer to the binaries AD Cnc (Qian et al 2007), BI Vul ) and CSTAR 038663 (Qian et al 2014). They revealed that these cool, shortperiod (0.25-0.28 d), shallow-contact binaries exhibit strong magnetic activity (including optical 0.2 mag flares of CSTAR 038663) and multiple period changes.…”

Section: Discussionmentioning

confidence: 99%

Observations and light curve solutions of the W UMa binaries V796 Cep, V797 Cep, CSS J015341.9+381641 and NSVS 3853195

Kjurkchieva

Popov

Ibryamov

et al. 2017

Res. Astron. Astrophys.

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Photometric observations in Sloan g' and i' bands of four W UMa binaries, V796Cep, V797 Cep, CSS J015341.9+381641 and NSVS 3853195, are presented. Our observations showed that CSS J015404.1+382805 and NSVS 3853195 are the same star. We determined the initial epochs T 0 of all targets and improved the period of NSVS 3853195. The light curve solutions of our data revealed that the components of each target are almost the same in mass, temperature, radius and luminosity. The stellar components are of G and K spectral types and undergo partial eclipses. All systems have barely-overcontact configurations and belong to H subtype W UMa binaries. We established that the relation between the luminosity ratio l 2 /l 1 and mass ratio q of our targets is approximately l 2 /l 1 = q 1.5 .

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Optical Flares and a Long-Lived Dark Spot on a Cool Shallow Contact Binary

Cited by 85 publications

References 36 publications

Variable Stars Observed in the Galactic Disk by AST3-1 from Dome A, Antarctica

Variable Stars Observed in the Galactic Disk by AST3-1 from Dome A, Antarctica

White-Light Flares on Close Binaries Observed With Kepler

Observations and light curve solutions of the W UMa binaries V796 Cep, V797 Cep, CSS J015341.9+381641 and NSVS 3853195

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