51503075
A BAYESIAN METHOD FOR THE INTERCALIBRATION OF SPECTRA IN REVERBERATION MAPPING
Flux calibration of spectra in reverberation mapping (RM) is most often performed by assuming the flux constancy of some specified narrow emission lines, which stem from an extended region that is sometimes partially spatially resolved, in contrast to the point-like broad-line region and the central continuum source. The inhomogeneous aperture geometries used among different observation sets in a joint monitoring campaign introduce systematic deviations to the fluxes of broad lines and central continuum, and intercalibration over these data sets is required. As an improvement to the previous empirical correction performed by comparing the (nearly) contemporaneous observation points, we describe a feasible Bayesian method that obviates the need for (nearly) contemporaneous observations, naturally incorporates physical models of flux variations, and fully takes into account the measurement errors. In particular, it fits all the data sets simultaneously regardless of samplings and makes use of all of the information in the data sets. A Markov Chain Monte Carlo implementation is employed to recover the parameters and uncertainties for intercalibration. Application to the RM data sets of NGC 5548 with joint monitoring shows the high fidelity of our method.
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.
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.
118438022
On the eccentricity distribution of short-period single-planet systems
We apply standard Markov chain Monte Carlo (MCMC) analysis techniques to 50 short-period, single-planet systems discovered with radial velocity technique. We develop a new method for accessing the significance of a non-zero orbital eccentricity, namelyanalysis, which combines the frequentist bootstrap approach with Bayesian analysis of each simulated data set. We find that the eccentricity estimations from theanalysis are generally consistent with the results from both the standard MCMC analysis and previous references. Themethod is particular useful for assessing the significance of small eccentricities. Our results suggest that the current sample size is insufficient to draw robust conclusions about the roles of tidal interaction and perturbations in shaping the eccentricity distribution of short-period single- planet systems. We use a Bayesian population analysis to show that a mixture of analytical distributions is a good approximation of the underlying eccentricity distribution. For short- period planets, we find the most probable values of parameters in the analytical functions given the observed eccentricities. These analytical functions can be used in theoretical investigations or as priors for the eccentricity distribution when analysing short-period planets. As the measurement precision improves and sample size increases, the method can be applied to more complex parametrizations for the underlying distribution of eccentricity for extrasolar planetary systems.
118408584
ON THE SCATTERING ENHANCEMENT OF N V λ1240 EMISSION LINE OF QUASI-STELLAR OBJECTS
The N v emission line of active galactic nuclei shows peculiar behavior in the line-continuum correlation, which may be indicative of an extra line component in addition to that from the normal broad emission line region. In this paper, we investigate possible contribution to the N v emission via resonant scattering of both continuum and Ly alpha in a broad absorption line (BAL) outflow by performing the Sobolev Monte Carlo simulations. The contribution is dependent on the covering factor, optical depth, and velocity profile of the outflow, as well as the equivalent width (EW) of Lya. Adopting model parameters constrained by observations, we find that the measured N v EW in the spectra of non-BAL quasi-stellar objects (QSOs) could have been enhanced by a factor of 1.82-2.73 on average, while there is only moderate absorption of Lya along the BAL outflow direction. Our model can produce a relatively narrow scattering line profile. About 80% of the total scattered flux falls within the central +/- 4500 km s(-1). We find that the resonant scattering can produce a prominent polarized emission line around N v. Both the broad excess emission and the unusually large polarized flux observed around N v in BAL QSOs are considered as strong evidence for the scattering enhancement. Future spectropolarimetric observations and spectroscopic monitoring of luminous QSOs may offer crucial tests for this interpretation, and provide useful information on the physical and geometrical properties of QSO outflows. We argue that the scattering offers a promising and robust process for producing the peculiar behavior of N v emission compared to the other processes proposed previously.
119307857
Determination of the Topology Skeleton of Magnetic Fields in a Solar Active Region
Magnetic topology has been a key to the understanding of magnetic energy release mechanism. Based on observed vector magnetograms, we have determined the three-dimensional (3D) topology skeleton of the magnetic fields in the active region NOAA 10720. The skeleton consists of six 3D magnetic nulls and a network of corresponding spines, fans, and null-null lines. For the first time, we have identified a spiral magnetic null in Sun's corona. The magnetic lines of force twisted around the spine of the null, forming a `magnetic wreath' with excess of free magnetic energy and resembling observed brightening structures at extra-ultraviolet (EUV) wavebands. We found clear evidence of topology eruptions which are referred to as catastrophic changes of topology skeleton associated with a coronal mass ejection (CME) and an explosive X-ray flare. These results shed new lights on the structural complexity and its role in explosive magnetic activity. The concept of flux rope has been widely used in modelling explosive magnetic activity, although their observational identity is rather obscure or, at least, lacking of necessary details up to date. We suggest that the magnetic wreath associated with the 3D spiral null is likely an important class of the physical entity of flux ropes.
415448
Measurements of direct CP violation, CPT symmetry, and other parameters in the neutral kaon system
The authors present precision measurements of the direct CP violation parameter, Re({epsilon}{prime}/{epsilon}), the kaon parameters, {Delta}m and {tau}{sub S}, and the CPT tests, {phi}{sub {+-}} and {Delta}{phi}, in neutral kaon decays. These results are based on the full dataset collected by the KTeV experiment at Fermi National Accelerator Laboratory during 1996, 1997, and 1999. This dataset contains {approx} 15 million K {yields} {pi}{sup 0}{pi}{sup 0} decays and {approx} 69 million K {yields} {pi}{sup +}{pi}{sup -} decays. They describe significant improvements to the precision of these measurements relative to previous KTeV analyses. They find Re({epsilon}{prime}/{epsilon}) = [19.2 {+-} 1.1(stat) {+-} 1.8(syst)] x 10{sup -4}, {Delta}m = (5265 {+-} 10) x 10{sup 6} hs{sup -1}, and {tau}{sub S} = (89.62 {+-} 0.05) x 10{sup -12} s. They measure {phi}{sub {+-}} = (44.09 {+-} 1.00){sup o} and {Delta}{phi} = (0.29 {+-} 0.31){sup o}; these results are consistent with CPT symmetry.
123856190
Existence of a proton halo in Al-23 and its significance
Reaction cross section sigma(R) of proton-rich isotones (N = 10) near Al-23 and Al isotopes (Al23-28) on C target have been measured at intermediate energies around 30 MeV/nucleon. An abnormal increase of the experimental sigma(R) is observed for Al-23 and it suggests that there is an anomalously large matter rms radius in Al-23. Together with the very weakly binding of the last proton (S-p = 0.125 MeV), it indicates that there is a proton halo in Al-23. This conclusion is also supported by the difference factor d which is deduced from the measured and theoretical sigma(R) in the Glauber or Boltzmann-Uehling-Uhlenbeck model and is used for the manifest of halo phenomena. The theoretical calculation based,on the relativistic density dependent Hartree model shows that there is a proton halo when the last proton is in the 2s(1/2) orbit in Al-23. The significance of the proton halo in Al-23 is discussed.