We present spatially resolved X-ray spectroscopy of PSR B1951+32 and its pulsar wind nebula ( PWN ) in supernova remnant (SNR) CTB 80 from a Chandra observation. The Chandra X-ray map clearly reveals various components of a ram-pressure-confined PWN embedded in the SNR ejecta: a point source representing the pulsar, X-ray emission from the bow shock, a luminous X-ray tail, a 30 00 diameter plateau whose northwestern part is absent, and the more diffuse outer X-ray emission. The plateau is closely surrounded by the radio, [O iii], [S ii], and [N ii] shells, and the outer diffuse emission is mostly within the H shells. While the spectra of all the features are well fitted with power-law models, a power-law plus blackbody model can fit the spectrum of the pulsar significantly better than using a power-law model alone. Generally, the spectra of these components obey the trend of steepening from the inside to the outside. However, the edge of the plateau probably has a harder spectrum than the central region of the plateau. The cause of the apparent hard spectrum of the plateau edge is unclear, but we speculate that it might be due to a shock between the PWN and the SNR ejecta. The possible blackbody radiation component from the pulsar has a temperature of 0:13 AE 0:02 keV and an equivalent emitting radius of 2:2 þ1:4 À0:8 (d/2 kpc) km, and is thus probably from the hot spots on the pulsar. We also show in this paper that the blackbody temperature of the entire surface of PSR B1951+32 is much lower than those predicted by the standard neutron star cooling models.
Aims. IGR J19405-3016 is reported in the 3rd IBIS catalog as one of its lowest significance sources (∼4.6σ under an exposure of about 371 ks). This leads to a caveat in multi-wavelength studies, although the source was identified in the optical as a Seyfert 1. The currently available INTEGRAL data on the source have increased to an exposure time of ∼1376 ks, which stimulates us to investigate the reality of this source again by using all the available data from INTEGRAL and Swift/XRT. Methods. We analyzed all available observations carried out by the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) on IGR J19405-3016. The data were processed by using the latest version OSA 7.0. In addition, we analyzed all the available Swift/XRT data on this source. Results. We find that IGR J19405-3016 has a detection significance of ∼9.4σ in the 20-60 keV band during the observational period between March 2003 and March 2008. This confirms a real source detection reported previously. The source position and error location are therefore updated. The source is found to be constant over years at the hard X-rays. We analyzed the Swift/XRT observations on IGR J19405-3016 as well, and find that the spectrum can be fitted with a simple power law model. Over the three XRT observations, the source flux varied by up to 39% from the average, and the spectrum is generally soft. The combined XRT/ISGRI spectrum is well fitted with a simple power law model (photon index 2.11 ± 0.03) with a column density fixed at 8.73 × 10 20 atoms/cm 2 . Such a photon index is consistent with the mean value 1.98 (dispersion 0.27) obtained from Swift/BAT AGN samples at 14-195 keV. The spectral slope of IGR J19405-3016 is softer than the average spectral slope found elsewhere. A similar discrepancy is found with other results regarding Seyfert 1 AGNs. A possible explanation for this simple spectral description may be that the low level of the column density allows for the "true" spectrum to appear at soft X-rays as well.
Aims. IGR J16460+0849 is reported in the 3rd IBIS catalog with the shortest exposure of about 11 ks among all the detected sources, which makes it the most interesting target to be investigated with a deeper exposure. The currently available data have increased to an exposure time of a few hundred ks. This stimulates us to investigate the source again by using all the available data. Methods. We analyze all available observations carried out by the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) on the unidentified source IGR J16460+0849. The data were processed by using the latest version OSA 7.0. In addition we analyze also all the available Swift/XRT data on this source. Results. We find that IGR J16460+0849 has a detection significance of ∼4.4σ in the 20−100 keV band during the observational period between March 2003 and September 2004, when it was exposed by ∼19 ks. Thereafter the source was not detected anymore, despite an additional exposure of ∼271 ks. This suggests a flux variability on a timescale of years. The spectral analysis shows that the IBIS/ISGRI data are well presented by a power-law shape, with a photon index obtained as 1.45 ± 0.86. So far, the source has been detected consistently by IBIS/ISGRI in the subsequent observations and in the adjacent energy bands. We have analyzed the Swift/XRT observations on IGR J16460+0849 as well, and found no source inside the IBIS/ISGRI error circle. The non-detection during the Swift/XRT observation is consistent with the source having a variable nature.
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