The Swift serendipitous survey in deep XRT GRB fields (SwiftFT)
Simonetta PuccettiM. CapalbiP. GiommiM. PerriG. StrattaLeonardo AngeliniD. N. BurrowsS. CampanaG. ChincariniG. CusumanoN. GehrelsA. MorettiJohn NousekJ. P. OsborneG. Tagliaferri
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Abstract:
We searched for X-ray serendipitous sources in over 370 Swift-XRT fields centered on gamma ray bursts detected between 2004 and 2008 and observed with total exposures ranging from 10 ks to over 1 Ms. This defines the Swift Serendipitous Survey in deep XRT GRB fields, which is quite broad compared to existing surveys (~33 square degrees) and medium depth, with a faintest flux limit of 7.2e-16 erg cm^-2 s^-1 in the 0.5 to 2 keV energy range. The survey has a high degree of uniformity thanks to the stable point spread function and small vignetting correction factors of the XRT, moreover is completely random on the sky as GRBs explode in totally unrelated parts of the sky. In this paper we present the sample and the X-ray number counts of the high Galactic-latitude sample, estimated with high statistics over a wide flux range (i.e., 7.2e-16 to ~5e-13 erg cm^-2 s^-1 in the 0.5-2 keV band and 3.4e-15 to ~6e-13 erg cm^-2 s^-1 in the 2-10 keV band). We detect 9387 point-like sources, while 7071 point-like sources are found at high Galactic-latitudes (i.e. >=20 deg). The large number of detected sources resulting from the combination of large area and deep flux limits make this survey a new important tool for investigating the evolution of AGN. In particular, the large area permits finding rare high-luminosity objects like QSO2, which are poorly sampled by other surveys, adding precious information for the luminosity function bright end. The high Galactic-latitude logN-logS relation is well determined over all the flux coverage, and it is nicely consistent with previous results at 1 sigma confidence level. By the hard X-ray color analysis, we find that the Swift Serendipitous Survey in deep XRT GRB fields samples relatively unobscured and mildly obscured AGN, with a fraction of obscured sources of ~37% (~15%) in the 2-10 (0.3-3 keV) band.Keywords:
Vignetting
Swift
We construct and examine the pulsar luminosity function using the new list which includes data for 1328 radio pulsars. In this work, the luminosity function for 1400 MHz is constructed for the rst time. We also present an improved luminosity function for 400 MHz. The luminosity functions at 400 and 1400 MHz are compared. Also, the luminosity functions excluding the binary millisecond pulsars and the pulsars with low magnetic elds are constructed. It is found that the new luminosity function is considerably atter in the low luminosity part for 400 MHz. 1400 HMz luminosity values of radio pulsars together with upper limits of 1400 MHz luminosity for anomalous X-ray pulsars and dim radio quiet neutron stars are presented as a function of both characteristic age and magnetic eld. The implications of the pulsar luminosity function for these new kinds of neutron star are discussed.
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The influence of photometrically unresolved binaries on the luminosity function is studied. Assuming that the local luminosity function (LF) reflects a distribution of unresolved binaries under different assumptions on the properties of a set of unresolved binaries, the coresponding luminosity functions of their components is constructed. It is found that the effect depends on the distribution of the component mass ratio q, and differs for different portions of the LF. For brighter stars (M V < 6 m) the effect is small. Around the LF maximum (M V 13 m) it is strongest in the case when both components are of similar mass. The most prominent difference was found in the region of the faintest stars (M V 20 m ), where the effect is strongest if low-q systems are frequent
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Chi-squared analysis of the combined BATSE/PVO peak flux distribution places constraints on the luminosity function of gamma-ray bursts in a Λ=0, Ω0=1 Friedmann cosmology with a non-evolving density distribution. The analysis indicates that the minimum burst luminosity, the maximum burst luminosity, or both, are constrained, with the opposite end of the luminosity function often unconstrained. For this cosmological model, a non-zero width of the intrinsic luminosity function is preferred, but luminosity functions are forbidden that let many bursts from an extremely broad luminosity range be observed.
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We present the X-ray luminosity function of AGN in three energy bands (Soft: 0.5-2 keV, Hard: 2-10 keV and Ultrahard: 4.5-7.5 keV). We have used the XMS survey along with other highly complete flux-limited deeper and shallower surveys for a total of 1009, 435 and 119 sources in the Soft, Hard and Ultrahard bands, respectively. We have modeled the intrinsic absorption of the Hard and Ultrahard sources (NH function) and computed the intrinsic X-ray luminosity function in all bands using a Maximum Likelihood fit technique to an analytical model. We find that the X-ray luminosity function (XLF) is best described by a Luminosity-Dependent Density Evolution (LDDE) model. Our results show a good overall agreement with previous results in the Hard band, although with slightly weaker evolution. Our model in the Soft band present slight discrepancies with other works in this band, the shape of our present day XLF being significantly flatter. We find faster evolution in the AGN detected in the Ultrahard band than those in the Hard band. The fraction of absorbed AGN in the Hard and Ultrahard bands is dependent on the X-ray luminosity. We find evidence of evolution of this fraction with redshift in the Hard band but not in the Ultrahard band, possibly due to the low statistics. Our best-fit XLF shows that the high-luminosity AGN are fully formed earlier than the less luminous AGN. The latter sources account for the vast majority of the accretion rate and mass density of the Universe, according to an anti-hierarchical black hole growth scenario.
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Abstract We present the X-ray luminosity function (XLF) of the Antennae galaxies based on 8 observation performed with Chandra . We detect between 37 and 49 sources in each observation. After combining all observations we detect a total of 120 sources down to a limiting luminosity of ~ 2 x 10 37 erg s –1 . Comparison between the XLFs of the individual observations shows that they are not affected by source variability. The cumulative XLF of the coadded observations is well represented by a single power-law with a slope of ~ –0.5.
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Several types of extragalactic high-energy transients have been discovered, which include high-luminosity and low-luminosity long-duration gamma-ray bursts (GRBs), short-duration GRBs, supernova shock breakouts (SBOs), and tidal disruption events (TDEs) without or with an associated relativistic jet. In this paper, we apply a unified method to systematically study the redshift-dependent event rate densities and the global luminosity functions (GLFs; ignoring redshift evolution) of these transients. We introduce some empirical formulae for the redshift-dependent event rate densities for different types of transients and derive the local specific event rate density, which also represents its GLF. Long GRBs (LGRBs) have a large enough sample to reveal features in the GLF, which is best charaterized as a triple power law (PL). All the other transients are consistent with having a single-power-law (SPL) LF. The total event rate density depends on the minimum luminosity, and we obtain the following values in units of Gpc−3 yr−1: for high-luminosity LGRBs above 1050 erg s−1; for low-luminosity LGRBs above 5 × 1046 erg s−1; and above 1050 erg s−1 for short GRBs with three different merger delay models (Gaussian, lognormal, and PL); above 1044 erg s−1 for SBOs, for normal TDEs above 1044 erg s−1; and above 1048 erg s−1 for TDE jets as discovered by Swift. Intriguingly, the GLFs of different kinds of transients, which cover over 12 orders of magnitude, are consistent with an SPL with an index of −1.6.
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