Transient supersoft X-ray emission from V751 Cyg during the optical low-state

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dc.creatorGreiner, J.
dc.creatorTovmassian, G. H.
dc.creatorDiStefano, R.
dc.creatorPrestwich, A.
dc.creatorGonzález-Riestra, R.
dc.creatorSzentasko, L.
dc.creatorChavarria, C.
dc.date1998-12-02
dc.date.accessioned2026-07-07T02:29:27Z
dc.date.available2026-07-07T02:29:27Z
dc.descriptionWe have observed V751 Cyg with the ROSAT HRI during its recent optical low state and clearly detect it at a count rate of 0.015 cts/s. The X-ray intensity is a factor of ~20 higher than the upper limit obtained with the ROSAT PSPC during the optical high state. Spectral investigations suggest a very soft X-ray spectrum. We investigate archival IUE data of V751 Cyg and derive a distance of V751 Cyg of d~500 pc based on the extinction estimate of E(B-V)=0.25+-0.05. This implies that the X-ray emission is very luminous, on the order of 10^34-10^36 erg/s. The spectrum during the optical low-state is characterized by a very blue continuum and the presence of strong emission lines of the Balmer series and HeI. Also, HeII 4686 A is clearly detected. We establish that V751 Cyg is a transient supersoft X-ray source and speculate that other VY Scl stars may also be of similar type.
dc.description15 pages, 9 figs., accepted for Astronomy & Astrophysics; also available from http://www.obs.aip.de/~jcg/publis.html
dc.identifierhttps://arxiv.org/abs/astro-ph/9812054
dc.identifierhttp://arxiv.org/abs/astro-ph/9812054
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/13479
dc.subjectAstrophysics
dc.titleTransient supersoft X-ray emission from V751 Cyg during the optical low-state
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