W Ursae Majoris Contact Binary Variables as X-Ray Sources

Chen, W. P.; Sanchawala, K.; Chiu, Mu-Chen

doi:10.1086/499206

Cited by 22 publications

(34 citation statements)

References 14 publications

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“…As Fig. 12, but for the contact-binary, W-UMa-type star UY Scl (period ≈ 31 ks, Chen et al (2006)), PN only; two observations, each of duration ∼ 30 ks, with a gap of ∼ 6 ks from the end of the first to the start of the second observation. Figs.…”

Section: Hardness-ratio Light-curvesmentioning

confidence: 88%

A survey of stellar X-ray flares from theXMM-Newtonserendipitous source catalogue: HIPPARCOS-Tycho cool stars

Pye

Rosen

Fyfe

et al. 2015

A&A

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Context. The X-ray emission from flares on cool (i.e. spectral-type F-M) stars is indicative of very energetic, transient phenomena, associated with energy release via magnetic reconnection. Aims. We present a uniform, large-scale survey of X-ray flare emission. The XMM-Newton Serendipitous Source Catalogue and its associated data products provide an excellent basis for a comprehensive and sensitive survey of stellar flares -both from targeted active stars and from those observed serendipitously in the half-degree diameter field-of-view of each observation. Methods. The 2XMM Catalogue and the associated time-series ("light-curve") data products have been used as the basis for a survey of X-ray flares from cool stars in the Hipparcos-Tycho-2 catalogue. In addition, we have generated and analysed spectrally-resolved (i.e. hardness-ratio), X-ray light-curves. Where available, we have compared XMM OM UV/optical data with the X-ray light-curves. Results. Our sample contains ∼130 flares with well-observed profiles; they originate from ∼70 stars. The flares range in duration from ∼10 3 to ∼10 4 s, have peak X-ray fluxes from ∼10 −13 to ∼10 −11 erg cm −2 s −1 , peak X-ray luminosities from ∼10 29 to ∼10 32 erg s −1 , and X-ray energy output from ∼10 32 to ∼10 35 erg. Most of the ∼30 serendipitously-observed stars have little previously reported information. The hardness-ratio plots clearly illustrate the spectral (and hence inferred temperature) variations characteristic of many flares, and provide an easily accessible overview of the data. We present flare frequency distributions from both target and serendipitous observations. The latter provide an unbiased (with respect to stellar activity) study of flare energetics; in addition, they allow us to predict numbers of stellar flares that may be detected in future X-ray wide-field surveys. The serendipitous sample demonstrates the need for care when calculating flaring rates, especially when normalising the number of flares to a total exposure time, where it is important to consider both the stars seen to flare and those from which variability was not detected (i.e. measured as non-variable), since in our survey, the latter outnumber the former by more than a factor ten. The serendipitous variable and "non-variable" stars appear very similar in terms of the distributions of general properties such as quiescent X-ray luminosity; from the available data, it is unclear whether the distinction by flaring is due to an additional, intrinsic property such as intra-system interactions in a close binary system, or is simply the result of limited observations and detection thresholds on a random flaring process, with no real difference between the two samples, or may be a combination of these effects. However, the number of detected flares compared with the number of stars not seen to vary is broadly consistent with estimates based on Poisson statistics.

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Section: Hardness-ratio Light-curvesmentioning

confidence: 88%

A survey of stellar X-ray flares from theXMM-Newtonserendipitous source catalogue: HIPPARCOS-Tycho cool stars

Pye

Rosen

Fyfe

et al. 2015

A&A

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“…J01564714-0021127 This is an eclipsing binary with a 0.5 day period (Chen et al 2006), but it is single in the AstraLux images.…”

Section: A Notes On Individual Binaries and Multiple Systemsmentioning

confidence: 99%

The Astralux Large M-Dwarf Multiplicity Survey

Janson

Hormuth

Bergfors

et al. 2012

ApJ

245

359

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We present the results of an extensive high-resolution imaging survey of M-dwarf multiplicity using the Lucky Imaging technique. The survey made use of the AstraLux Norte camera at the Calar Alto 2.2m telescope and the AstraLux Sur camera at the ESO New Technology Telescope in order to cover nearly the full sky. In total, 761 stars were observed (701 M-type and 60 late K-type), among which 182 new and 37 previously known companions were detected in 205 systems. Most of the targets have been observed during two or more epochs, and could be confirmed as physical companions through common proper motion, often with orbital motion being confirmed in addition. After accounting for various bias effects, we find a total M-dwarf multiplicity fraction of 27 ± 3% within the AstraLux detection range of 0.08-6 ′′ (semi-major axes of ∼3-227 AU at a median distance of 30 pc). We examine various statistical multiplicity properties within the sample, such as the trend of multiplicity fraction with stellar mass and the semi-major axis distribution. The results indicate that M-dwarfs are largely consistent with constituting an intermediate step in a continuous distribution from higher-mass stars down to brown dwarfs. Along with other observational results in the literature, this provides further indications that stars and brown dwarfs may share a common formation mechanism, rather than being distinct populations.

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“…Factoring in the relationship between the X-ray intensity and the orbital period (Chen et al 2006), 2MASS J11201034 −2201340 is within a reasonable range on the X-ray intensity versusorbital period plot (see Figure 7). Stȩpień et al (2001) categorized W UMa-type stars into hot…”

Section: Indications From X-ray Emissionmentioning

confidence: 75%

“…The strength of the X-ray emission is related to the binary orbital period and the spectral type (Stȩpień et al 2001;Chen et al 2006). Chromospheric activity is related to the presence of cool spots, which cause asymmetry, known as the O'Connell effect (O'Connell 1951;Wilsey & Beaky 2009), in the orbital profile.…”

Section: Introductionmentioning

confidence: 99%

Discovery of an X-Ray-Emitting Contact Binary System 2mass J11201034−2201340

Yang

Chou

et al. 2016

Self Cite

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We report the detection of orbital modulation, a model solution, and the X-ray properties of a newly discovered contact binary, Two Micron All Sky Survey (2MASS) J11201034−2201340. We serendipitously found this X-ray point source outside the error ellipse when searching for possible X-ray counterparts of γ-ray millisecond pulsars among the unidentified objects detected by the Fermi Gamma-ray Space Telescope. The optical counterpart of the X-ray source (unrelated to the γ-ray source) was then identified using archival databases. The long-term Catalina Real-Time Transient Survey detected a precise signal with a period of ( ) = P 0.28876208 56 days. A follow-up observation made by the Super Light Telescope of Lulin Observatory revealed the binary nature of the object. Utilizing archived photometric data of multi-band surveys, we construct the spectral energy distribution (SED), which is well fit by a K2V spectral template. The fitting result of the orbital profile using the Wilson-Devinney code suggests that 2MASS J11201034-2201340 is a short-period A-type contact binary and the more massive component has a cool spot. The X-ray emission was first noted in observations made by Swift, and then further confirmed and characterized by an XMM-Newton observation. The X-ray spectrum can be described by a power law or thermal Bremsstrahlung. Unfortunately, we could not observe significant X-ray orbital modulation. Finally, according to the SED, this system is estimated to be 690 pc from Earth with a calculated X-ray intensity of ( ) -0.7 1.5 10 30 erg s, which is in the expected range of an X-ray emitting contact binary.

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W Ursae Majoris Contact Binary Variables as X-Ray Sources

Cited by 22 publications

References 14 publications

A survey of stellar X-ray flares from theXMM-Newtonserendipitous source catalogue: HIPPARCOS-Tycho cool stars

A survey of stellar X-ray flares from theXMM-Newtonserendipitous source catalogue: HIPPARCOS-Tycho cool stars

The Astralux Large M-Dwarf Multiplicity Survey

Discovery of an X-Ray-Emitting Contact Binary System 2mass J11201034−2201340

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