118509207
The 2009 outburst from the new X-ray transient and black-hole candidate XTE J1652-453
We analyse the Rossi X-ray Timing Explorer (RXTE) and Swift observations of the 2009 outburst from a newly discovered transient and black hole candidate XTE J1652-453. The behaviour of the source was observed by RXTE to be a sequence of spectral states that are typical of black-hole X-ray binaries. During the first seven observations, it is determined that the source remains in a high/soft state. This is determined from the spectrum that is dominated by a soft thermal component, which contributes an average of similar to 85 per cent to the X-ray flux at 2-20 keV, and from the hardness similar to 0.1 showing up in the hardness-intensity diagram. For the last 20 observations, the spectral state is classified as low/hard, according to an average hardness of similar to 0.8 and a balance between the thermal and the non-thermal components; a power-law component takes >= 80 per cent of the total 2-20 keV flux. Located in between is an intermediate state that the source might have experienced. The usual relationship between the rms and hardness is also present in the hardness-rms diagram. Throughout the outburst, no quasi-periodic oscillations are found in XTE J1652-453.
16433217
The afterglows of ultraluminous quasars
Quasars represent a brief phase in the life cycle of most massive galaxies, but the evolutionary connection between central black holes and their host galaxies remains unclear. While quasars are active and shining brighter than the Compton-limit luminosity, their radiation heats the surrounding medium to the Compton temperature, forming Compton spheres extending to the Stromgren radius of Fe26+/He2+. After the quasars shut off, their "afterglow" can be detected through three signatures: (1) an extended X-ray envelope, with a characteristic temperature of ~3 × 107 K, (2) Lyα and Lyβ lines and the K edge of Fe26+, and (3) nebulosity from hydrogen and helium recombination emission lines. We discuss the possibility of detecting these signatures using Chandra, the planned X-Ray Evolving Universe Spectroscopy mission, and ground-based optical telescopes. The luminosity and size of quasar afterglows can be used to constrain the lifetime of quasars.
17406200
EVOLUTION OF GASEOUS DISK VISCOSITY DRIVEN BY SUPERNOVA EXPLOSIONS IN STAR-FORMING GALAXIES AT HIGH REDSHIFT
Motivated by Genzel et al.'s observations of high-redshift star-forming galaxies, containing clumpy and turbulent rings or disks, we build a set of equations describing the dynamical evolution of gaseous disks with inclusion of star formation and its feedback. Transport of angular momentum is due to "turbulent" viscosity induced by supernova explosions in the star formation region. Analytical solutions of the equations are found for the initial cases of a gaseous ring and the integrated form for a gaseous disk, respectively. For a ring with enough low viscosity, it evolves in a slow process of gaseous diffusion and star formation near the initial radius. For a high viscosity, the ring rapidly diffuses in the early phase. The diffusion drives the ring into a region with a low viscosity and starts the second phase undergoing pile-up of gas at a radius following the decreased viscosity torque. The third is a sharply decreasing phase because of star formation consumption of gas and efficient transportation of gas inward forming a stellar disk. We apply the model to two z similar to 2 galaxies BX 482 and BzK 6004, and find that they are undergoing a decline in their star formation activity.
119102309
Possible hard X-ray shortages in bursts from KS 1731-260 and 4U 1705-44
Aims. A hard X-ray shortage, implying the cooling of the corona, was observed during bursts of IGR J17473-272, 4U 1636-536, Aql X-1, and GS 1826-238. Apart from these four sources, we investigate here an atoll sample, in which the number of bursts for each source is larger than 5, to explore the possible additional hard X-ray shortage during Rossi X-ray timing explorer (RXTE) era. Methods. According to the source catalog that shows type-I bursts, we analyzed all the available pointing observations of these sources carried out by the RXTE proportional counter array. We grouped and combined the bursts according to their outburst states and searched for the possible hard X-ray shortage while bursting. Results. We found that the island states of KS 1731-260 and 4U 1705-44 show a hard X-ray shortage at significant levels of 4.5 and 4.7σ and a systematic time lag of 0.9 ± 2.1 s and 2.5 ± 2.0 s with respect to the soft X-rays, respectively. While in their banana branches and other sources, we did not find any consistent shortage.
15715110
Suppressed star formation in circumnuclear regions in seyfert galaxies
Feedback from black hole activity is widely believed to play a key role in regulating star formation and black hole growth. A long-standing issue is the relation between star formation and the fueling of the supermassive black holes in active galactic nuclei (AGNs). We compile a sample of 57 Seyfert galaxies to tackle this issue. We estimate the surface densities of gas and star formation rates in circumnuclear regions (CNRs). Comparing them with the well-known Kennicutt-Schmidt (K-S) law, we find that the star formation rates (SFRs) in the CNRs of most Seyfert galaxies are suppressed in this sample. Feedback is suggested to explain the suppressed SFRs.
17396076
INTEGRAL and RXTE/ASM observations on IGR J17098−3628
To probe further the possible nature of the unidentified source IGR J17098-3628, we have carried out a detailed analysis of its long-term time variability as monitored by RXTE/ASM, and of its hard X-ray properties as observed by INTEGRAL. INTEGRAL has monitored this sky region over years and significantly detected IGR J17098-3628 only when the source was in this dubbed active state. In particular, at $\ge$ 20 keV, IBIS/ISGRI caught an outburst in March 2005, lasting for $\sim$5 days with detection significance of 73$\sigma$ (20-40 keV) and with the emission at $ $20 keV) outburst by $\sim$2 days. This resembles the behavior of X-ray novae like XN 1124-683, hence it further suggests a LMXB nature for IGR J17098-3628. While the quality of the ASM data prevents us from drawing any definite conclusions, these discoveries are important clues that, coupled with future observations, will help to resolve the as yet unknown nature of IGR J17098-3628.
13918084
Construction, pattern recognition and performance of the CLEO III LiF-TEA RICH detector
We briefly describe the construction and performance of the LiF-TEA RICH detector constructed for the CLEO III experiment.
118151192
Emissive mechanism of radio flat spectrum on X-ray binaries
We present that the radio emission with flat spectrum in X-ray binaries comes from the synchrotron emission of relativistic electrons in the high energy tail of hot electrons in continuous conical jet. The jet is assumed to be produced by the advection-dominated accretion flow (ADAF) and maintains ion and electron temperatures constant in the case of adiabatic steady conical expansion. The flat spectrum is result of self-absorbed synchrotron emission by relativistic thermal electrons. We find that the critical frequency at which the radiation becomes optically thin declines along the jet. The emission observed at higher frequencies originates at smaller distance, closer to the base of the jet. The highest cut-off frequency of the flat spectrum is at the base of the jet, and is determined by the physics of the ADAF and the position of the jet formation. We assert that it is a characteristic of the ADAF in black hole X-ray binaries that a continuous steady outflow is formed and causes the observed flat spectrum in the low/hard state. The observed synchrotron emission consists of the flat spectral component from the jet and the steep spectral component from the ADAF. The flat spectral component extends from infrared to radio wavelengths, while the steep spectral component with the 2/5 spectral slope extends from infrared to shorter wavelengths, it will be dominated by the thermal emission from companion star.
119230126
The TAOS Project Stellar Variability II. Detection of 15 Variable Stars
The Taiwanese-American Occultation Survey (TAOS) project has collected more than a billion photometric measurements since 2005 January. These sky survey data-covering timescales from a fraction of a second to a few hundred days-are a useful source to study stellar variability. A total of 167 star fields, mostly along the ecliptic plane, have been selected for photometric monitoring with the TAOS telescopes. This paper presents our initial analysis of a search for periodic variable stars from the time-series TAOS data on one particular TAOS field, No. 151 (RA = 17$^{\rm h}30^{\rm m}6\fs$67, Dec = 27\degr17\arcmin 30\arcsec, J2000), which had been observed over 47 epochs in 2005. A total of 81 candidate variables are identified in the 3 square degree field, with magnitudes in the range 8 < R < 16. On the basis of the periodicity and shape of the lightcurves, 29 variables, 15 of which were previously unknown, are classified as RR Lyrae, Cepheid, delta Scuti, SX Phonencis, semi-regular and eclipsing binaries.
1890895
Progress report on new rf breakdown studies in an S-band structure at SLAC
This paper gives a progress report on RF breakdown studies carried out at SLAC on an S-band standing-wave disk-loaded accelerator structure. The structure is the same as described at two earlier conferences but it has been equipped with eight new radial probes and one output port to observe the emission of light, which has not yet been used. The earlier breakdown limit of 144 MV/m equivalent traveling-wave accelerating gradient and 312 MV/m peak surface field has been reached again and possibly exceeded slightly even though the disk iris edges are severely pitted from earlier tests. Using the new probes it has become possible to monitor field emission as a function of azimuthal direction as well as to record the signals generated at the instant of breakdown. Results are given together with some information on the condition of the structure, chemical cleaning and RF processing. The paper ends with the presentation of some speculations and future plans.
15380121
A Puzzling X-Ray Source Found in the Chandra Deep Field-South
In this Letter, we report the detection of an extremely strong X-ray emission line in the 940 ks Chandra ACIS-I spectrum of CXOCDFS J033225.3-274219. The source was identified as a type 1 active galactic nucleus at a redshift of z = 1.617, with a 2.0-10.0 keV rest-frame X-ray luminosity of ~1044 ergs s-1. The emission line was detected at 6.2 keV, with an equivalent width (EW) of 4.4 keV; both quantities refer to the observed frame. In the rest frame, the line is at 16.2 keV with an EW of 11.5 keV. An X-ray emission line at a similar energy (~17 keV, in the rest frame) in PKS 2149-306 was discovered before using ASCA data. We reject the possibility that the line is due to a statistical or instrumental artifact. The line is most likely due to blueshifted Fe K emission from an relativistic outflow, probably an inner X-ray jet, with velocities of the order of ~0.6c-0.7c. Other possible explanations are also discussed.