Abstract. Results of simultaneous INTEGRAL and optical observations of the galactic microquasar SS433 in May 2003and INTEGRAL /RXTE observations in March 2004 are presented. Persistent precessional variability with a maximum to minimum uneclipsed hard X-ray flux ratio of ∼4 is discovered. The 18-60 keV X-ray eclipse is found to be in phase with optical and near infrared eclipses. The orbital eclipse observed by INTEGRAL in May 2003 is at least two times deeper and apparently wider than in the soft X-ray band. The broadband 2-100 keV X-ray spectrum simultaneously detected by RXTE/INTEGRAL in March 2004 can be explained by bremsstrahlung emission from optically thin thermal plasma with kT ∼ 30 keV. Optical spectroscopy with the 6-m SAO BTA telescope confirmed the optical companion to be an A5-A7 supergiant. For the first time, spectorscopic indications of a strong heating effect in the optical star atmosphere are found. The measurements of absorption lines which are presumably formed on the non-illuminated side of the supergiant yield its radial velocity semi-amplitude K v = 132 ± 9 km s −1 . The analysis of the observed hard X-ray light curve and the eclipse duration, combined with the spectroscopically determined optical star radial velocity corrected for the strong heating effect, allows us to model SS433 as a massive X-ray binary. Assuming that the hard X-ray source in SS433 is eclipsed by the donor star that exactly fills its Roche lobe, the masses of the optical and compact components in SS433 are suggested to be M v ≈ 30 M and M x ≈ 9 M , respectively. This provides further evidence that SS433 is a massive binary system with supercritical accretion onto a black hole.

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We present broad band power spectra of variations of SS433 in radio, optical and X-ray spectral bands. We show that at frequencies lower than 10 −5 Hz the source demonstrates the same variability pattern in all these bands. The broad band power spectrum can be fitted by one power law down to frequencies ∼10 −7 Hz with flattening afterwards. Such a flattening means that on time scales longer than ∼10 7 s the source variability becomes uncorrelated. This naturally leads to the appearance of quasi-poissonian flares in the source light curve, which have been regularly observed in radio and optical spectral bands. The radio flux power spectrum appears to have a second break at Fourier frequencies ∼10 −5 Hz which can be caused by the smearing of the intrinsic radio variability on timescale of the light-crossing time of the radio emitting region. We find a correlation of the radio and optical fluxes of SS433 and the radio flux is delayed by about ∼2 days with respect to the optical one. Power spectra of optical and X-ray variabilities continue with the same power law from 10 −7 Hz up to ∼0.01−0.05 Hz. The broad band power spectrum of SS433 can be interpreted in terms of self-similar accretion rate modulations in the accretion disk proposed by Lyubarskii (1997, MNRAS, 292, 679) and elaborated by Churazov et al. (2001, MNRAS, 321, 759). We discuss a viscous time-scale in the accretion disk of SS433 with reference to the observed broad band power spectrum.

We report here the multiwavelength observations of the bright supersoft X‐ray source, RBS 1032. Most likely, its optical counterpart is a non‐emission‐line dwarf galaxy with a prominent nucleus. Line and band indices of this nucleus, clearly suggest that its optical spectrum is dominated by the nuclear supermassive globular clusters. No radio and infrared (IRAS) emissions are detected from this dwarf galaxy. Weak near‐infrared (2MASS) emissions have been detected. The optical‐to‐near‐infrared colours are consistent with the globular clusters than those of active galactic nuclei. We have shown here that RBS 1032 is not a foreground object. However, with the available data the possibility of RBS 1032 being a classical nova cannot be completely ruled out. We have demonstrated that RBS 1032 is not a X‐ray‐bright optically normal galaxy. In contrast, we have illustrated that the super‐soft X‐ray emissions of RBS 1032 may be from a binary system, consisting of an intermediate‐mass (∼5 × 104 M⊙) black hole with a white dwarf companion. Most likely this system is hosted by one of the nuclear globular clusters of the dwarf galaxy.