Ultraviolet and optical observations of HDE 245770/ A 0535+26 system during an X-ray flare

Giovannelli, F.; Ferrari-Toniolo, M.; Giangrande, A.; Persi, P.; Bartolini, C.; Гуарниери, А.; Piccioni, A.

doi:10.1007/bf01246056

Cited by 6 publications

(3 citation statements)

References 12 publications

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“…(1982) derived the mass loss rate using the theoretical line profiles of Castor and Lamers (1979) applied to the CIv line (1548-51 _A). The outflow velocity was estimated 660 km s-l, in agreement with the values found from previous observations by Giovannelli et al (1981) and later by de Loore et al (1984). Analysing also the Silv line (1394-403 4), they quoted the most probable value of the mass loss rate of HDE245770 as …”

Section: Uv Observationsmentioning

confidence: 62%

“…The results did not show substantial variations with respect to those obtained, with the same satellite, during an X-ray quiescent phase . The observed IR excess and the asymmetry of the UV resonance lines of HDE 245770 supported the presence of an expanding envelope surrounding the star (Persi et al, 1979;Giovannelli et al, 1980Giovannelli et al, , 1981. The colour excess E(B -V) = 0.75 + 0.05 mag was derived by Giovannelli et al (1980) filling the observed 2200 A extinction feature and using the interstellar extinction law of Seaton (1979).…”

Section: General Considerations On Transient X-ray Sourcesmentioning

confidence: 98%

“…No optical variations were observed during the decays of two different X-ray flares: March 1979 X-ray flare-up (Sims and Fraser, 1979;Bartolini et al, 1979) and October 1980 X-ray flare-up (Oda et al, 1980a, b;Bartolini et al, 1980). During the decay of the October 1980 X-ray outburst, Giovannelli et al (1981) performed UV observations of HDE 245770 with IUE satellite at VILSPA base. The results did not show substantial variations with respect to those obtained, with the same satellite, during an X-ray quiescent phase .…”

Section: General Considerations On Transient X-ray Sourcesmentioning

confidence: 99%

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A 0535 + 26/HDE 245770: A typical X-ray/Be system

Giovannelli

Graziati

1992

Space Sci Rev

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Abstract. Among the X-ray/Be systems, A 0535 + 26/HDE 245770 has been noted, since its discovery, for its peculiar features in several respects, in a wide energy range. For this reason and for a series of concomitant favorable causes, this system has been one of the most studied among the massive X-ray binary systems. The most remarkable incident was that its optical identification with an early-type-emission-line star (O9.7IIie) has led to a deep studies on Be stars and their interactions with neutron stars, which have allowed to discover, without unbiguity, the presence of optical indicators of consequent X-ray flares, as well as that Be stars in X-ray/Be systems behave just as 'normal' Be stars. Overmore, thanks to the multifrequency coordinated observations of this system, the X-ray emissions from binary companion of the Be stars are best explained by assuming the presence of a thick equatorial disk with low expansion velocity and a thin polar region with high expansion velocity. This picture reconciled the strong discrepancy in mass loss rate evaluations coming from IR and from UV measurements, assuming that the observed regions are enterely distinct from each other, one being a high-density, low-velocity region, and the other being a low-density, very hot, rapidly-expanding disk-like zone.Since, this picture seems to be the best up-to-date frame to cuckold all the experimental panorama available on X-ray/Be systems, we would like to paint in this paper the multifrequency behaviour of A 0535 + 26/HDE 245770, which is the best studied among such systems, in order to stimulate future coordinated experimental-theoretical works on this very interesting class of objects.

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Section: Uv Observationsmentioning

confidence: 62%