During a close encounter between a star and a supermassive black hole,the star can get disrupted by the black hole’s tidal forces,resulting in a tidal disruption event(TDE).The accretion of the star’s material onto ...During a close encounter between a star and a supermassive black hole,the star can get disrupted by the black hole’s tidal forces,resulting in a tidal disruption event(TDE).The accretion of the star’s material onto the black hole produces strong emission in different wavelength regimes.Here we report the discovery with the Roentgen Satellite(ROSAT)of an X-ray-selected transient source in an optically non-active galaxy.At the location R.A.:13h31m57s.66 and decl.:-32°43’19".7 a sudden rise in X-ray luminosity by a factor of 8 within 8 days has been observed.Additionally,a very soft X-ray spectrum with a blackbody temperature kT=0.1 keV and a peak luminosity of at least 1×10^(43)erg s^(-1)suggests a TDE interpretation,and the observed properties are very similar to previously identified soft X-ray(ROSAT)TDEs.An optical spectrum taken of the galaxy at the position of RXJ133157.6324319.7 six years after the X-ray outburst does not show any emission lines as would be expected from a persistent active galactic nucleus.The redshift of the galaxy is determined to be 0.051 based on absorption lines.It is therefore likely a member of the galaxy cluster A3560.The rise in X-ray luminosity happens within 8 days and thus appears to be fast for such an event.No X-ray emission was detected 170 days before and 165 days after the event,and none was detected 25 yr later with the Neil Gehrels Swift Observatory.The change in X-ray luminosity is at least a factor of 40.展开更多
The Einstein Probe(EP)is an interdisciplinary mission of time-domain and X-ray astronomy.Equipped with a wide-field lobstereye X-ray focusing imager,EP will discover cosmic X-ray transients and monitor the X-ray varia...The Einstein Probe(EP)is an interdisciplinary mission of time-domain and X-ray astronomy.Equipped with a wide-field lobstereye X-ray focusing imager,EP will discover cosmic X-ray transients and monitor the X-ray variability of known sources in 0.5-4 keV,at a combination of detecting sensitivity and cadence that is not accessible to the previous and current wide-field monitoring missions.EP can perform quick characterisation of transients or outbursts with a Wolter-I X-ray telescope onboard.In this paper,the science objectives of the EP mission are presented.EP is expected to enlarge the sample of previously known or predicted but rare types of transients with a wide range of timescales.Among them,fast extragalactic transients will be surveyed systematically in soft X-rays,which includeγ-ray bursts and their variants,supernova shock breakouts,and the predicted X-ray transients associated with binary neutron star mergers.EP will detect X-ray tidal disruption events and outbursts from active galactic nuclei,possibly at an early phase of the flares for some.EP will monitor the variability and outbursts of X-rays from white dwarfs,neutron stars and black holes in our and neighbouring galaxies at flux levels fainter than those detectable by the current instruments,and is expected to discover new objects.A large sample of stellar X-ray flares will also be detected and characterised.In the era of multi-messenger astronomy,EP has the potential of detecting the possible X-ray counterparts of gravitational wave events,neutrino sources,and ultra-high energyγ-ray and cosmic ray sources.EP is expected to help advance the studies of extreme objects and phenomena revealed in the dynamic X-ray universe,and their underlying physical processes.Besides EP's strength in time-domain science,its follow-up telescope,with excellent performance,will also enable advances in many areas of X-ray astronomy.展开更多
基金supported by the German Bundesministerium fur Bildung,Wissenschaft,Forschung und Technologie(BMBF/DARA)the Max-Planck-Society。
文摘During a close encounter between a star and a supermassive black hole,the star can get disrupted by the black hole’s tidal forces,resulting in a tidal disruption event(TDE).The accretion of the star’s material onto the black hole produces strong emission in different wavelength regimes.Here we report the discovery with the Roentgen Satellite(ROSAT)of an X-ray-selected transient source in an optically non-active galaxy.At the location R.A.:13h31m57s.66 and decl.:-32°43’19".7 a sudden rise in X-ray luminosity by a factor of 8 within 8 days has been observed.Additionally,a very soft X-ray spectrum with a blackbody temperature kT=0.1 keV and a peak luminosity of at least 1×10^(43)erg s^(-1)suggests a TDE interpretation,and the observed properties are very similar to previously identified soft X-ray(ROSAT)TDEs.An optical spectrum taken of the galaxy at the position of RXJ133157.6324319.7 six years after the X-ray outburst does not show any emission lines as would be expected from a persistent active galactic nucleus.The redshift of the galaxy is determined to be 0.051 based on absorption lines.It is therefore likely a member of the galaxy cluster A3560.The rise in X-ray luminosity happens within 8 days and thus appears to be fast for such an event.No X-ray emission was detected 170 days before and 165 days after the event,and none was detected 25 yr later with the Neil Gehrels Swift Observatory.The change in X-ray luminosity is at least a factor of 40.
基金supported by Strategic Priority Program on Space Science of Chinese Academy of Sciences,in collaboration with ESA,MPE and CNES(Grant Nos.XDA15310000,and XDA15052100)supported by the National Natural Science Foundation of China(Grant Nos.61234003,61434004,and 61504141)CAS Interdisciplinary Project(Grant No.KJZD-EW-L11-04)。
文摘The Einstein Probe(EP)is an interdisciplinary mission of time-domain and X-ray astronomy.Equipped with a wide-field lobstereye X-ray focusing imager,EP will discover cosmic X-ray transients and monitor the X-ray variability of known sources in 0.5-4 keV,at a combination of detecting sensitivity and cadence that is not accessible to the previous and current wide-field monitoring missions.EP can perform quick characterisation of transients or outbursts with a Wolter-I X-ray telescope onboard.In this paper,the science objectives of the EP mission are presented.EP is expected to enlarge the sample of previously known or predicted but rare types of transients with a wide range of timescales.Among them,fast extragalactic transients will be surveyed systematically in soft X-rays,which includeγ-ray bursts and their variants,supernova shock breakouts,and the predicted X-ray transients associated with binary neutron star mergers.EP will detect X-ray tidal disruption events and outbursts from active galactic nuclei,possibly at an early phase of the flares for some.EP will monitor the variability and outbursts of X-rays from white dwarfs,neutron stars and black holes in our and neighbouring galaxies at flux levels fainter than those detectable by the current instruments,and is expected to discover new objects.A large sample of stellar X-ray flares will also be detected and characterised.In the era of multi-messenger astronomy,EP has the potential of detecting the possible X-ray counterparts of gravitational wave events,neutrino sources,and ultra-high energyγ-ray and cosmic ray sources.EP is expected to help advance the studies of extreme objects and phenomena revealed in the dynamic X-ray universe,and their underlying physical processes.Besides EP's strength in time-domain science,its follow-up telescope,with excellent performance,will also enable advances in many areas of X-ray astronomy.
