* Astronomy

Title: Is SS 433 a misaligned ultraluminous X-ray source? Constraints from its reflected signal in the Galactic plane
Author: Ildar Khabibullin, Sergey Sazonov

We evaluate the emission that must arise due to reflection of the putative collimated X-ray radiation of SS 433 by atomic gas and molecular clouds in the Galactic plane and compare the predicted signal with existing RXTE and ASCA data for the region of interest. Assuming that the intrinsic X-ray spectrum of SS 433 is similar to that of ultraluminous X-ray sources (ULXs), we obtain an upper limit of ~4 x 10^39 erg s^-1 on its total (angular-integrated) luminosity in the 2--10 keV energy band, which is only weakly dependent on the half-opening angle, Theta_r, of the emission cone. In contrast, the upper limit on the apparent luminosity of SS 433 (that would be perceived by an observer looking at its supercritical accretion disk face-on) decreases with increasing Theta_r and is ~3 x10^40 erg s^-1 for Theta_r gtrsim Theta_p=21deg, where Theta_p is the precession angle of the baryonic jets (assuming that the emission cones precess in the same manner as the jets). This leaves open the possibility that SS 433 is a misaligned ULX. Further investigation of the reflection signal from the molecular clouds using higher angular resolution observations could improve these constraints with the potential to break the degeneracy between Theta_r and the apparent luminosity.

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ATel 6385: Outburst from SS 433 observed with BOOTES-2/COLORES

Title: Deceleration of SS433 radio jets
Authors: A. A. Panferov

The mildly relativistic jets of SS 433 are believed to inflate the surrounding supernova remnant W50 depositing in its expansion possibly more than 99% of their kinetic energy (Dubner et al. 1998). Where and how this transformation of energy is curried out, it is not yet known. What can we learn from it that the jets decelerate and the deceleration is non-dissipative, i.e. radiatively dark. In this paper we unclose the observed deviations of the precessing radio jets of SS 433, within a few arcseconds from a jets source, from the ballistic track, described by the kinematic model, as a signature of the deceleration which, on other hand, issues from the jets colliding with ambient medium. For that we model kinematics of these colliding jets. The ram pressure on the jets is estimated from the observed profile of brightness of synchrotron radiation along the radio jets. We have found that to fit observed locus the radio jets should be decelerated and twisted, additionally to the precession twist, mostly within the first one-fifth of precession period, and further they extend imitating ballistic jets. The fitted physical parameters of the jet model turned out to be physically reliable and characteristic for SS 433 jets that unlikely to be occasional. This model explains naturally, and meets approval by a) the observed shock-pressed morphology of the radio jets and their brightness, b) the observed ~ 10% deflections from the standard kinematic model --- just a magnitude of the jet speed decrement in the model, c) regularly observed for the radio jets the precession phase deviation from the standard kinematic model prediction, d) dichotomy of distance to the object, 4.8 kpc vs. 5.5 kpc, determined on the basis of the radio jets kinematics on scales of a sub-arcsecond and several arcseconds.

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Title: Peculiarities in the orbital and precessional variability of SS433 from INTEGRAL observations
Authors: A. Cherepashchuk (1), R. Sunyaev (2), S. Molkov (2), E. Antokhina (1), K. Postnov (1), A. Bogomazov (1) (1-Sternberg Astronomical Institute, Moscow, 2-Space Research Institute, Moscow)

Based on multiyear INTEGRAL observations of SS433, a composite IBIS/ISGRI 18-60 keV orbital light curve is constructed around zero precessional phase \psi_{pr}= 0. It shows a peculiar shape characterized by a significant excess near the orbital phase \phi_{orb}= 0.25, which is not seen in the softer 2-10 keV energy band. Such a shape is likely to be due to a complex asymmetric structure of the funnel in a supercritical accretion disk in SS433. The orbital light curve at 40-60 keV demonstrates two almost equal bumps at phases ~ 0.25 and ~ 0.75, most likely due to nutation effects of the accretion disk. The change of the off-eclipse 18-60 keV X-ray flux with the precessional phase shows a double-wave form with strong primary maximum at \psi_{pr}= 0 and weak but significant secondary maximum at \psi_{pr}= 0.6. A weak variability of the 18-60 keV flux in the middle of the orbital eclipse correlated with the disk precessional phase is also observed. The joint analysis of the broadband (18-60 keV) orbital and precessional light curves obtained by INTEGRAL confirms the presence of a hot extended corona in the central parts of the supercritical accretion disk and constrain the binary mass ratio in SS433 in the range 0.5\gtrsim q\gtrsim 0.3, confirming the black hole nature of the compact object. Orbital and precessional light curves in the hardest X-ray band 40-60 keV, which is free from emission from thermal X-ray jets, are also best fitted by the same geometrical model with hot extended corona at q ~ 0.3, stressing the conclusions of the modeling of the broad-band X-ray orbital and precessional light curves.

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