arXiv subjects

S. Zharikov

Publications and source records attributed to S. Zharikov.

42 records · Page 3Linked to original sources

arXiv2003

Evolution of the polarization of the optical afterglow of the gamma-ray burst GRB 030329

We report 31 polarimetric observations of the afterglow of GRB 030329 with high signal-to-noise and high sampling frequency. We establish the polarization light curve, detect sustained polarization at the percent level, and find significant variability of polarization degree and angle. The data imply that the afterglow magnetic field has small coherence length and is mostly random, probably generated by turbulence.

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arXiv2003

FS Aur - a new class of Cataclysmic Variables or the missing link between Intermediate Polars and SW Sex objects?

FS Aur is a known dwarf nova with an orbital period of about 85.7 minutes. It has been assumed to be a member of the SU UMa subclass of cataclysmic variables (CVs), but previous searches for superhumps and superoutburst have been unsuccessful. We conducted a series of photometric and spectroscopic observations of FS Aur during quiescence. We confirmed its short orbital period from radial velocity measurements. However, the long-term photometry revealed an unexpected result: the system also shows a distinct 0.24 mag modulation in the BVR photometric bands with a period of 205.5 min, which is 2.4 times longer than the orbital period. We discuss various possible causes for such a peculiar behavior.

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arXiv2003

The Characteristics of Magnetic CVs in the Period Gap

We have observed several magnetic cataclysmic variables located in the range between 2 and 3 hours, known as the period gap. This work was prompted by the recent discovery of RX J1554.2+2721. It has 2.54 hours orbital period and shows almost pure cyclotron continuum in a low luminosity state, similar to HS1023+3900, HS0922+1333 and RBS206. These are low accretion rate polars (LARPs) known to have mass transfer rates of order of a few 10^-13Msun/year. The aim of the study was to find out, if magnetic systems filling the period gap are in any way different from their counterparts outside that range of periods. The only significant difference we encounter, is much higher number of asynchronous magnetic systems to-wards longer periods than below the gap.

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arXiv2001

SBS 1150+599A: an extremely oxygen-poor planetary nebula in the Galactic halo?

We report results of a spectrophotometric study of SBS 1150+599A and discuss the nature of this object based upon our data. Our study shows that SBS 1150+599A is most probably a planetary nebula located in the Galactic halo and not a cataclysmic variable as originally proposed by the authors of the Second Byurakan Survey from low resolution spectroscopy. We have further elaborated on the properties of SBS 1150+599A (now becoming PN G135.9+55.9) with tools used for planetary nebula analysis. Our photoionization models show that, in order to match the observational constraints, the oxygen abundance in the nebula is probably extremely low, around 1/500 solar, which is one order of magnitude lower than the most oxygen-poor planetary nebulae known so far. This finding has strong implications on our understanding of the formation of planetary nebulae and of the evolution of the Galactic halo.

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arXiv2000

RX J1420.4+5334 - another tidal disruption event?

We have discovered a transient X-ray source, RX J1420.4+5334, which displays a ROSAT flux variation of >150 between the ROSAT All-Sky-Survey in 1990 and a preceding pointed ROSAT observations in July 1990. Optical observations suggest a non-active galaxy as the only visible counterpart. We therefore tentatively identify RX J1420.4+5334 as a tidal disruption event in a non-active galaxy.

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arXiv1999

Search for GRB X-ray afterglows in the ROSAT all-sky survey

We describe a search for X-ray afterglows from gamma-ray bursts using the ROSAT all-sky survey (RASS) data. If the emission in the soft X-ray band is significantly less beamed than in the gamma-ray band, we expect to detect many afterglows in the RASS. We found 23 afterglow candidates, where about 4 detections are predicted. However, follow-up spectroscopy of several counterpart candidates strongly suggests a flare star origin of the RASS events in many cases. We conclude that the RASS data are consistent with comparable beaming angles in the X-ray (within a few hours of the burst) and gamma-ray bands. However, models predicting a large amount of energy emerging as a nearly isotropic X-ray component of the early afterglow are severely constrained by the ROSAT data. In particular, a so far undetected class of ``dirty fireballs'' and delayed ``rebursts'' are constrained.

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