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We present 35 ks Chandra ACIS observations of the 42 Myr old radio pulsar PSR B1451-68. A point source is detected 0".32±0".73 from the expected radio pulsar position. It has ~200 counts in the 0.3-8 keV energy range. We identify this point source as the X-ray counterpart of the radio pulsar. PSR B1451-68 is located close to a Two Micron All Sky Survey point source for which we derive 7% as the upper limit on the flux contribution to the measured pulsar X-ray flux. The pulsar spectrum can be described by either a power-law model with photon index Γ = 2.4-0.3+0.4 and a unrealistically high absorbing column density NH = (2.5-1.3+1.2) x 1021 cm-2, or by a combination of a kT = 0.35-0.07+0.12 keV blackbody and a Γ = 1.4±0.5 power-law component for NHDM = 2.6 x 1020 cm-2, estimated from the pulsar dispersion measure. At the parallactic, a Lutz-Kelker bias corrected distance of 480 pc, the non-thermal X-ray luminosities in the 0.3-8 keV energy band are either L0.3-8keVnonth = (11.3±1.7) x 1029 erg s-1 or L0.3-8k eVnonth = (5.9-5.0+4.9 x 1029 erg s-1, respectively. This corresponds to non-thermal X-ray efficiencies of either η0.3-8k eVnonth = L0.3-8k eVnonth/E ~ 5 x 10-3 or 3 x 10-3, respectively. [ABSTRACT FROM AUTHOR]

Candidate supernova remnants (SNRs) G23.5+0.1 and G25.5+0.0 were observed by XMM-Newton in the course of a snapshot survey of plerionic and composite SNRs in the Galactic plane. In the field of G23.5+0. I, we detected an extended source, ~3' in diameter, which we tentatively interpret as a pulsar wind nebula (PWN) of the middle-aged radio pulsar B1830-08 (J1833-0827; P = 85.3 ms, τ = 147 kyr, Ė = 5.8 x 1035 erg s-1, d = 5.7 kpc), with the PWN luminosity L0.2-10keV ≈ 5 X 1033 erg s-1 ≈ 8 x 10-3 Ė. The pulsar is not resolved in the EPIC images. Our analysis suggests an association between PSR B 1830-08 and the surrounding diffuse radio emission. If the radio emission is due to the SNR, then the pulsar must be significantly younger than its characteristic age. Alternatively. the radio emission may come from a relic PWN. The field also contains SGR 1833-0832 and another middle-aged pulsar B 1829-08 (J1832-0827; P = 647 ms, τ = 161 kyr, Ė = 9.3 x 1033 erg s-1, d = 4.7 kpc), none of which are detected in our observation. In the field of G25.5+0.0, which contains the extended TeV source HESS J1837-069, we detected the recently discovered young high-energy pulsar J1838-0655 (P = 70.5 ms, τ = 23 kyr, Ė = 5.5 x 1036 erg s-1) embedded in a PWN with extent of 1.'3. The unabsorbed pulsar + PWN luminosity is L2-11 keV ≈ 2 X 1034 erg s-1 ≈ 4 x 10-3/Ė at an assumed distance of 7 kpc. We also detected another PWN candidate (AX J1837.3-0652) with an extent oft and unabsorbed luminosity L2-10keV ≈ 4 x 1033 erg s-1 at d = 7 kpc. The third X-ray source, located within the extent of the HESS J1837-069, has a peculiar extended radio counterpart, possibly a radio galaxy with a double nucleus or a microquasar. We did not find any evidence of the SNR emission in the G25.5+0.0 field. We provide detailed multiwavelength analysis and identifications of other field sources and discuss robustness of the G25.5+0.0 and G23.5+0.1 classifications as SNRs. [ABSTRACT FROM AUTHOR]

High-magnetic-field pulsars represent an important class of objects for studying the relationship between magnetars and radio pulsars. Here we report on four Chandra observations of the high-magnetic-field pulsar J 1718-3718 (B = 7.4 × 1013 G) taken in 2009 as well as a reanalysis of 2002 Chandra observations of the region. We also report an improved radio position for this pulsar based on ATCA observations. We detect X-ray pulsations at the pulsar's period in the 2009 data, with a pulsed fraction of 52% ± 13% in the 0.8-2.0 keV band. We find that the X-ray pulse is aligned with the radio pulse. The data from 2002 and 2009 show consistent spectra and fluxes: a merged overall spectrum is well fit by a blackbody of temperature 186-18+19 eV, slightly higher than predicted by standard cooling models; however, the best-fit neutron star atmosphere model is consistent with standard cooling. We find the bolometric luminosity Lbb∞ = 4-2+5 × 1032 erg s-1 ~ 0.3 E for a distance of 4.5 kpc. We compile measurements of the temperatures of all X-ray-detected high-B pulsars as well as those of low-B radio pulsars and find evidence for the former being hotter on average than the latter. [ABSTRACT FROM AUTHOR]

We report on XMM-Newton EPIC observations of the young pulsar J2022+3842, with a characteristic age of 8.9 kyr. We detected X-ray pulsations and found the pulsation period P ≈ 48.6 ms, and its derivative , which is two times larger than previously reported values. The pulsar exhibits two very narrow (FWHM ∼1.2 ms) X-ray pulses each rotation, separated by ≈0.48 of the period, with a pulsed fraction of ≈0.8. Using the correct values of P and , we calculate the pulsar's spin-down power erg s–1 and magnetic field B = 2.1 × 1012 G. The pulsar spectrum is well modeled with a hard power-law (PL) model (photon index Γ = 0.9 ± 0.1, hydrogen column density nH = (2.3 ± 0.3) × 1022 cm–2). We detect a weak off-pulse emission, which can be modeled with a softer PL (Γ ≈ 1.7 ± 0.7), that is poorly constrained because of contamination in the EPIC-pn timing mode data. The pulsar's X-ray efficiency in the 0.5-8 keV energy band, , is similar to those of other pulsars. The XMM-Newton observation did not detect extended emission around the pulsar. Our re-analysis of ChandraX-ray Observatory archival data shows a hard, Γ ≈ 0.9 ± 0.5, spectrum and a low efficiency, ηPWN ∼ 2 × 10–5(D/10 kpc)2, for the compact pulsar wind nebula, unresolved in the XMM-Newton images. [ABSTRACT FROM AUTHOR]

We report on an X-ray observation of the 166 Myr old radio pulsar J0108–1431 with XMM-Newton. The X-ray spectrum can be described by a power-law model with a relatively steep photon index Γ ≈ 3 or by a combination of thermal and non-thermal components, e.g., a power-law component with fixed photon index Γ = 2 plus a blackbody component with a temperature of kT = 0.11 keV. The two-component model appears more reasonable considering different estimates for the hydrogen column density NH. The non-thermal X-ray efficiency in the single power-law model is , higher than in most other X-ray-detected pulsars. In the case of the combined model, the non-thermal and thermal X-ray efficiencies are even higher, . We detected X-ray pulsations at the radio period of P ≈ 0.808 s with significance of ≈7σ. The pulse shape in the folded X-ray light curve (0.15-2 keV) is asymmetric, with statistically significant contributions from up to five leading harmonics. Pulse profiles at two different energy ranges differ slightly: the profile is asymmetric at low energies, 0.15-1 keV, while at higher energies, 1-2 keV, it has a nearly sinusoidal shape. The radio pulse peak leads the 0.15-2 keV X-ray pulse peak by ▵ϕ = 0.06 ± 0.03. [ABSTRACT FROM AUTHOR]

We report on the analysis of two XMM-Newton observations of the recently discovered soft gamma repeater Swift J1834.9–0846, taken in 2005 September and one month after the source went into outburst on 2011 August 7. We performed timing and spectral analyses on the point source as well as on the extended emission. We find that the source period is consistent with an extrapolation of the Chandra ephemeris reported earlier and the spectral properties remained constant. The source luminosity decreased to a level of 1.6 × 1034 erg s–1 following a decay trend of ∝t–0.5. Our spatial analysis of the source environment revealed the presence of two extended emission regions around the source. The first (region A) is a symmetric ring around the point source, starting at 25″ and extending to ∼50″. We argue that region A is a dust scattering halo. The second (region B) has an asymmetrical shape extending between 50″ and 150″, and is detected both in the pre- and post-outburst data. We argue that this region is a possible magnetar wind nebula (MWN). The X-ray efficiency of the MWN with respect to the rotation energy loss is substantially higher than those of rotation-powered pulsars: . The higher efficiency points to a different energy source for the MWN of Swift J1834.9–0846, most likely bursting activity of the magnetar, powered by its high magnetic field, B = 1.4 × 1014 G. [ABSTRACT FROM AUTHOR]