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Optical observations of the black hole candidate XTE J1550-564 during the Sep/Oct 1998 outburst

C. Sanchez-Fernandez·A. J. Castro-Tirado·H. W. Duerbeck·L. Mantegazza·V. Beckmann·V. Burwitz·L. Vanzi·A. Bianchini·M. Della Valle·A. Piemonte·B. Dirsch·I. Hook·L. Yan·A. Gimenez
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Abstract

We report here optical observations during the September/October 1998 outburst of the black hole candidate XTE J1550-564. CCD photometry was obtained for the optical counterpart with the 0.9m Dutch telescope at La Silla since the onset of this event. We analysed 211 U, V and i frames, from Sep 10 to Oct 23. Stochastic flaring activity was observed on Sep 11-16, but no evidence for a superhump period, as seen in other soft X-ray transients, was found. An optical flare nearly simultaneous to an X-ray flare that occurred on Sep 21 was observed in the V-band. A reddened optical spectrum showed the typical emission lines corresponding to X-ray transients in outburst. From the interstellar absorption lines, we derive E(B-V) = 0.70 +/- 0.10 and suggest a distance of about 2.5 kpc. In such case, M_{B} = +7 mag. for the progenitor, which is consistent with the spectral type of a low-mass K0-K5 main-sequence companion.

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C. Sanchez-Fernandez, A. J. Castro-Tirado, H. W. Duerbeck, L. Mantegazza, V. Beckmann, V. Burwitz, L. Vanzi, A. Bianchini, M. Della Valle, A. Piemonte, B. Dirsch, I. Hook, L. Yan, A. Gimenez. 1999-06-27. Optical observations of the black hole candidate XTE J1550-564 during the Sep/Oct 1998 outburst. https://arxiv.org/abs/astro-ph/9906434

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