53686125
Type-I bursts within outbursts of IGR J17473-2721
Aims. Two outbursts were observed by RXTE in the history of the atoll source IGR J17473-2721. During the most recent outburst in 2008, the source showed a complete series of spectral states/transitions. The neutron star system was prolific in type-I X-ray bursts, and we investigate them in the context of complete outbursts evolution. Methods. A total exposure of similar to 309 ks was collected by RXTE during the two outbursts of IGR J17473-2721. We carried out a systematic search for type-I bursts in this data set. For each burst found, we investigated the burst profile, the peak flux, and their dependence on the accretion rate along the evolution of the outbursts. Results. Eighteen type-I X-ray bursts were found from IGR J17473-2721: two from the outburst in 2005 and the other 16 from the recent outburst in 2008. Among them, 3 bursts show photospheric radius expansion ( PRE). The distance to the source is estimated as 6.4 kpc with a 15% uncertainty based on the three bursts that show PRE. In the recent outburst, there are 6 bursts showing up in the low/hard state prior to the state transition to a high/soft state, 3 bursts at the end phase of the high/soft state, and 7 in the following low/hard state. The blackbody radius of these bursts presents a variety of interesting features. We find that, at the end of the recent outburst, the profile of the blackbody radius is anti-correlated with the blackbody temperature and the burst flux. The durations of the type-I burst are found to correlate with the Eddington ratio and to have two parallel evolution groups. Along the decreasing Eddington ratio, the burst duration decreases and ends in each group the PRE bursts occurred. This provides new clues to the type-I bursts in the context of outbursts for atoll XRBs.
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.
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.
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.
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.
43759506
Bounds on the CP asymmetry in b --> sgamma decays.
We have measured the CP asymmetry A(CP) identical with[gamma(b-->sgamma)-gammab-->sgamma)]/[gamma(b-->sgamma)+gamma(b-->sgamma)] to be A(CP) = (-0.079+/-0.108+/-0.022) (1.0+/-0.030), implying that, at 90% confidence level, A(CP) lies between -0.27 and +0.10. These limits rule out some extreme non-standard-model predictions, but are consistent with most, as well as with the standard model.
118350998
Next-to-leading order QCD predictions for graviton and photon associated production in the Large Extra Dimensions model at the LHC
We present the calculations of the complete next-to-leading order (NLO) QCD corrections to the inclusive total cross sections for the Kaluza-Klein (KK) graviton and photon associated production process pp{yields}{gamma}G{sub KK}+X in the large extra dimensions model at the LHC. We show that the NLO QCD corrections in general enhance the total cross sections and reduce the dependence of the total cross sections on the factorization and renormalization scales. When jet veto is considered, the NLO corrections reduce the total cross sections. We also calculate some important differential cross sections for this process at NLO: the missing transverse momentum distribution, the transverse momentum distribution, and the pseudorapidity distribution of photon.
118387840
Dynamical axion field in topological magnetic insulators
Axions are hypothetical particles that might play an important part in particle physics, astrophysics and cosmology. So far they have eluded observation, but theoretical work now predicts that axion physics might be explored in condensed-matter systems known as topological insulators.
118660389
TWO-PHASE ICM IN THE CENTRAL REGION OF THE RICH CLUSTER OF GALAXIES A1795: A JOINT CHANDRA, XMM-NEWTON, AND SUZAKU VIEW
Based on a detailed analysis of the high-quality Chandra, XMM-Newton, and Suzaku data of the X-ray bright cluster of galaxies A1795, we report clear evidence for a two-phase intracluster medium (ICM) structure, which consists of a cool (with a temperature T-c approximate to 2.0-2.2 keV) and a hot (T-h approximate to 5.0-5.7 keV) component that coexist and dominate the X-ray emission at least in the central 80 kpc. A third weak emission component (T-3 approximate to 0.8 keV) is also detected within the innermost 144 kpc and is ascribed to a portion of interstellar medium of the cD galaxy. Deprojected spectral analysis reveals flat radial temperature distributions for both the hot phase and cool phase components. These results are consistent with the ASCA measurements reported by Xu et al. and resemble the previous findings for the Centaurus Cluster. By analyzing the emission measure ratio and gas metal abundance maps created from the Chandra data, we find that the cool phase component is more metal-enriched than the hot phase one in the 50-100 kpc region, which agrees with that found in M87. The coexistence of the cool phase and hot phase ICM cannot be realized by bubble uplifting from active galactic nuclei (AGNs) alone. Instead, the two-phase ICM properties are better reconciled with a cD corona model. In this model, the cool phase may be ascribed to the plasmas confined in magnetic loops, which are surrounded by the intruding hot phase ICM and have been polluted by metals synthesized in the cD galaxy. AGN feedback energy released in the innermost 10 kpc can serve as the heating source to prevent the loop-interior gas from cooling down to temperatures much lower than the observed value. The total gravitating mass profile exhibits a hierarchical structure, regardless of the ICM temperature modeling.
119035074
X-Ray Properties of the Point Source Population in the Spiral Galaxy NGC 5055 （M63） with Chandra
Using Chandra ACIS S3 data we studied the X-ray properties of low-and high-mass X-ray binary populations in the nearby spiral galaxy NGC 5055. A total of 43 X-ray point sources were detected within two effective radii, with 31 sources located on the disk and the rest 12 sources in the bulge. The resolved point sources dominate the X-ray emission of the galaxy, accounting for about 80% of the total counts in 0.3–10 keV. From spectral fittings we calculated the 0.3–10.0 keV luminosities of all the detected X-ray point sources and found that they span a wide range from a few times 1037 erg s−1 to over 1039 erg s−1. After compensating for incompleteness at the low luminosity end, we found that the corrected XLF of the bulge population is well fitted with a broken power-law with a break at 1.57+0.21−0.20×1038 erg s−1, while the profile of the disk population's XLF agrees with a single power-law distribution of slope 0.93+0.07−0.06. The disk population is significantly richer at 2×1038 erg s−1 than the bulge population, indicating that the disk may have undergone relatively recent, strong starbursts that significantly increased the HMXB population, although ongoing starbursts are also observed in the nuclear region. Similar XLF profiles of the bulge and disk populations were found in M81. However, in most other spiral galaxies different patterns of spatial variation of the XLF profiles from the bulge to the disk have been observed, indicating that the star formation and evolution history may be more complex than we have expected.