ﻻ يوجد ملخص باللغة العربية
The bright transient AT2018cow has been unlike any other known type of transient. Its high brightness, rapid rise and decay and initially nearly featureless spectrum are unprecedented and difficult to explain using models for similar burst sources. We present evidence for faint gamma-ray emission continuing for at least 8 days, and featureless spectra in the ultraviolet bands -- both unusual for eruptive sources. The X-ray variability of the source has a burst-like character. The UV-optical spectrum does not show any CNO line but is well described by a blackbody. We demonstrate that a model invoking the tidal disruption of a 0.1 - 0.4 Msun Helium White Dwarf (WD) by a 100,000 to one million solar mass Black Hole (BH) located in the outskirts of galaxy Z~137-068 could provide an explanation for most of the characteristics shown in the multi-wavelength observations. A blackbody-like emission is emitted from an opaque photosphere, formed by the debris of the WD disruption. Broad features showing up in the optical/infrared spectra in the early stage are probably velocity broadened lines produced in a transient high-velocity outward moving cocoon. The asymmetric optical/infrared lines that appeared at a later stage are emission from an atmospheric layer when it detached from thermal equilibrium with the photosphere, which undergoes more rapid cooling. The photosphere shrinks when its temperature drops, and the subsequent infall of the atmosphere produced asymmetric line profiles. Additionally, a non-thermal jet might be present, emitting X-rays in the 10-150 keV band.
A small fraction of candidate tidal disruption events (TDEs) show evidence of powerful relativistic jets, which are particularly pronounced at radio wavelengths, and likely contribute non-thermal emission at a wide range of wavelengths. A non-thermal
RBS 1032 is a supersoft ($Gammasim5$), luminous ($sim10^{43}$ erg/s) ROSAT PSPC source which has been associated with an inactive dwarf galaxy at $z=0.026$, SDSS J114726.69+494257.8. We have analyzed an XMM-Newton observation which confirms that RBS
We survey the properties of stars destroyed in TDEs as a function of BH mass, stellar mass and evolutionary state, star formation history and redshift. For Mbh<10^7Msun, the typical TDE is due to a M*~0.3Msun M-dwarf, although the mass function is re
Aims. We investigate the evolution of X-ray selected tidal disruption events. Methods. New events are found in near-real time data from XMM-Newton slews and are monitored by multi-wavelength facilities. Results. In August 2016, X-ray emission was det
Multiwavelength flares from tidal disruption and accretion of stars can be used to find and study otherwise dormant massive black holes in galactic nuclei. Previous well-monitored candidate flares are short-lived, with most emission confined to withi