X-ray spectroscopy of the W UMa-type binary VW Cephei

Gondoin, P.

doi:10.1051/0004-6361:20034416

Cited by 23 publications

(22 citation statements)

References 44 publications

(40 reference statements)

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“…It is worth noting that the X-ray liminosities of S20 and S27 are peculiarly high. They are one order of magnitude brighter in X-rays than 44 Boo (Gondoin 2004b) and VW Cep (Gondoin 2004c), two nearby representatives of the W UMa-type binary class recently observed with XMM-Newton. Hence, the nature of S27 and S20 previously identified as WV 28 (Kafka & Honeycutt 2003), remains uncertain.…”

Section: X-ray Sources In Ngc 188mentioning

confidence: 74%

X-ray observations of the old open stellar cluster NGC 188

Gondoin

2005

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Abstract. I present the analysis results from XMM-Newton observations of the old open stellar cluster NGC 188, which has an age of about 7 Gyr and a near solar metallicity. 58 X-ray sources were detected in the field of view of the EPIC MOS and pn cameras, and 46 sources are new X-ray detections. Visible counterparts were found for 20 sources including the variable star WV 28, the W UMa-type binaries V371 Cep and V372 Cep, and the red giant V11. 9 X-ray sources are identified with probable cluster non-members, while 43 X-ray sources are of unknown membership. X-ray emission was detected from 6 stars with high membership probability above a luminosity threshold of 10 30 erg s −1 . This indicates the presence of very active latetype stars in NGC 188 in spite of its old age. The HR diagram positions of two of these stars just above the main sequence are reminiscent of those for W Ursae Majoris-type contact binaries. Two other sources could be either members of close binary systems or the product of the coalescence of W UMa type binaries into single stars. One X-ray source in NGC 188 is located at the bottom of the red giant branch in an evolutionary status similar to that of an FK Comae-type star. Another X-ray source detected in NGC 188 has the HR diagram position of an M type star. Its X-ray to bolometric luminosity ratio, greater than the canonical 10 −3 saturation level, suggests that the star was flaring during XMM-Newton observations. M stars are most likely the most numerous X-ray sources in NGC 188 at lower X-ray luminosity thresholds.

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Section: X-ray Sources In Ngc 188mentioning

confidence: 74%

X-ray observations of the old open stellar cluster NGC 188

Gondoin

2005

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“…The VW Cephei field VW Cephei, a W UMa-type binary system, has been observed by BeppoSAX twice (May 1998 andOctober 1998). Following the investigations performed by Gondoin (2004), we fit separately the LECS and MECS data of both data sets with the  optically thin plasma model. In each observation, a three-component model, having different temperatures but the same metal abundance, gives the best representation of the data.…”

Section: The H1846-786 Fieldmentioning

confidence: 99%

BeppoSAX/PDS serendipitous detections at high galactic latitudes

Landi

Malizia

Bassani

2005

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Abstract. At a flux limit of ∼10−11 erg cm −2 s −1 in the 20-100 keV band, the PDS instrument on-board BeppoSAX offers the opportunity to study the extragalactic sky with an unprecedented sensitivity. In this work we report on the results of a search in the BeppoSAX archive for serendipitous high energy sources at high galactic latitudes (|b| ≥ 13• ). We have defined a set of twelve regions in which the PDS/MECS cross-calibration constant is higher than the nominal value. We attribute this mismatch to the presence of a serendipitous source in the PDS field of view. In four cases the likely high energy emitter is also present in the MECS field of view. In these cases, we have performed a broad band spectral analysis (1.5-100 keV) to understand the source spectral behaviour and compare it with previous BeppoSAX observations when available. In eight cases the identification of the source likely to provide the PDS spectrum is based on indirect evidence (extrapolation to lower energies and/or comparison with previous observations). This approach led to the discovery of six new hard X-ray emitting objects (PKS 2356-611, 2MASX J14585116-1652223, NGC 1566, NGC 7319, PKS 0101-649 and ESO 025-G002) and to the presentation the PDS spectrum of NGC 3227 for the first time. In the remaining five cases we provide extra BeppoSAX observations that can be compared with measurements already published and/or in the archive.

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“…WUMa type stars are strong X-ray emitters but with luminosities lower, in general, than those of the detached, subgiant RS CVn type binaries, possibly due to saturation effects (Vilhu & Heise 1986;Stepien et al 2001;Gondoin 2004). Since the components in W UMa systems have the shortest periods possible for two non-degenerate main-sequence stars, these objects are of great interest in the study of the relation between stellar rotation rate and X-ray activity.…”

Section: Introductionmentioning

confidence: 99%

X-ray spectroscopy of the W UMa-type binary 44 Bootis

Gondoin¹

2004

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Abstract. 44 Boo B, a W UMa-type binary system, was observed in June 2001 during one entire revolution period with the XMM−Newton observatory. The count rate in the 0.3 to 2 keV band is constant in average with 5 to 20% count rate increases reminiscent of flares. Spectral fitting of the EPIC spectra indicates a corona configuration with little contribution from quiet regions, similar to the Sun. On the contrary, the (2-9) × 10 6 K temperature range of the "cool" plasma suggests that the active corona around the two companions is densely filled with low-lying loops similar to those found in solar-type active regions. The 44 Boo O VII He-like triplet constrains the electron density to an upper limit n e < 8.6 × 10 10 cm −3 . We argue that this low-lying loop system may be overlaid by larger loops. Magnetic reconnection phenomena in this large loops system may explain the characteristic flare decay time in the light curve that implies loop lengths of about 16 × 10 9 cm. An extended corona around 44 Boo would explain the absence of eclipses in its X-ray light curve. The average element abundance in 44 Boo corona is found to be lower than the solar photospheric value. The spectral analysis indicates enhanced abundances of oxygen and neon relative to iron which suggest an inverse FIP effect. Compared with other active binary systems such as RSCVn or BY Dra, 44 Boo has relatively less material at temperatures higher than 10 7 K and the temperature of its hottest plasma component appears to be lower.

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X-ray spectroscopy of the W UMa-type binary VW Cephei

Cited by 23 publications

References 44 publications

X-ray observations of the old open stellar cluster NGC 188

X-ray observations of the old open stellar cluster NGC 188

BeppoSAX/PDS serendipitous detections at high galactic latitudes

X-ray spectroscopy of the W UMa-type binary 44 Bootis

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