相关论文: X-ray response to disk evolution in two gamma-Cas …
We report optical and infrared observations of the massive X-ray binary system 4U1145-619 (V801 Cen) which show that the circumstellar disc of the Be star component is in decline. Infrared J,H,K,L magnitudes of V801Cen have been monitored…
Contemporaneous multiwavelength observations with H.E.S.S., SALT, Fermi-LAT, Swift, and ATOM show that the blazar PKS 1510-089 suffered a significant decrease in its optical flux, degree of optical polarization and high-energy gamma-ray (E…
We report the discovery of a flaring X-ray source with an optical counterpart with Halpha emission and red-excess, in the direction of the SMC. A 100 ksec X-ray observation with Chandra detected a flare lasting 6 ksec in the source CXO…
The Be star zeta Tau was recently reported to be a gamma Cas analog; that is, it displays an atypical (bright and hard) X-ray emission. The origin of these X-rays remains debated.The first X-ray observations indicated a very large…
Integral field unit (IFU) spectra of face-on star-forming galaxies from the MaNGA survey are stacked in radial bins so as to reach a S/N high enough to measure emission lines and Lick indices out to 2.5-3 R_e. Two thirds of galaxies have…
We report new Chandra observations of seven optically faint, z \sim 4 radio-quiet quasars. We have combined these new observations with previous Chandra observations of radio-quiet quasars to create a sample of 174 sources. These sources…
Since the Halpha and UV fluxes from galaxies are sensitive to stellar populations of ages < 10^7 and ~ 10^8 yr respectively, their ratio f(Halpha)/f(UV) provides us with a tool to study the recent t < 10^8 yr star formation history of…
We present results from an H-alpha monitoring campaign of the Be X-ray binary systems HDE 245770 = A 0535+26 and X Per. We use the H-alpha equivalent widths together with adopted values of the Be star effective temperature, disk…
Although about 40% of the soft X-ray background emission in 0.4 to 1 keV range has extragalactic origins and thus is totally blocked by the Galactic absorption in midplane directions, it decreases at most by about 20 % in midplane. Suzaku…
A growing number of early Be stars discovered in X-ray surveys exhibit X-ray luminosities intermediate between those of normal stars and those of most Be/X-ray binaries in quiescence. Their X-ray spectra are also much harder than those of…
Using new and archival spectra from the Goddard High Resolution Spectrograph, we have searched for evidence of chromospheric and transition region emission in six stars of mid- to late-A spectral type. Two of the stars, alpha Aql (A7 IV-V)…
The origin of the extended soft X-ray emission around nearby highly inclined disk galaxies (often called as X-ray corona) remains uncertain. The emission could arise from volume-filling hot gas and/or its interaction with cool gas.…
We employ panoramic, multicolour (BRz') and narrow-band Halpha imaging of the cluster Cl0024.0+1652 (z=0.39) from Subaru covering a ~30 arcmin field, to determine cluster membership and star formation rates for a large sample of galaxies…
The Halpha and mid-infrared mean disk surface brightnesses are compared in a sample of nearby spirals observed by ISOCAM. This shows that, in spiral disks, dust emission at 7 and 15 microns provides a reasonable star formation tracer. The…
The yellow hypergiant star V509 Cas is currently undergoing an extreme phase of evolution. Having experienced eruptive mass-loss outbursts in the 20th century, the star's effective temperature reached record high values in the early 2000s.…
The observed multi-GeV gamma-ray emission from the solar disk --- sourced by hadronic cosmic rays interacting with gas, and affected by complex magnetic fields --- is not understood. Utilizing an improved analysis of the Fermi-LAT data that…
We present the results of our monitoring program to study the long-term variability of the Halpha line in high-mass X-ray binaries. We have carried out the most complete optical spectroscopic study of the global properties of high-mass…
We investigate how the empirical properties of hot X-ray-emitting gas in a sample of seven starburst and three normal edge-on spiral galaxies (a sample which covers the full range of star-formation intensity found in disk galaxies)…
We report the discovery of a hard-thermal (T ~ 130 MK) and variable X-ray emission from the Be star HD 157832, a new member of the puzzling class of gamma-Cas-like Be/X-ray systems. Recent optical spectroscopy reveals the presence of a…
We present the results of medium resolution (Delta v = 60 km/s) spectropolarimetric observations across Halpha of a sample of B[e] and Herbig Be objects. A change in linear polarization across Halpha is detected in a large fraction of the…