We have investigated the field around the radio-quiet $gamma$-ray pulsar, PSR J2021+4026, with a ~140 ks XMM-Newton observation and a ~56 ks archival Chandra data. Through analyzing the pulsed spectrum, we show that the X-ray pulsation is purely ther
mal in nature which suggests the pulsation is originated from a hot polar cap with $Tsim3times10^{6}$ K on the surface of a rotating neutron star. On the other hand, the power-law component that dominates the pulsar emission in the hard band is originated from off-pulse phases, which possibly comes from a pulsar wind nebula. In re-analyzing the Chandra data, we have confirmed the presence of bow-shock nebula which extends from the pulsar to west by ~10 arcsec. The orientation of this nebular feature suggests that the pulsar is probably moving eastward which is consistent with the speculated proper motion by extrapolating from the nominal geometrical center of the supernova remnant (SNR) G78.2+2.1 to the current pulsar position. For G78.2+2.1, our deep XMM-Newton observation also enables a study of the central region and part of the southeastern region with superior photon statistics. The column absorption derived for the SNR is comparable with that for PSR J2021+4026, which supports their association. The remnant emission in both examined regions are in an non-equilibrium ionization state. Also, the elapsed time of both regions after shock-heating is apparently shorter than the Sedov age of G78.2+2.1. This might suggest the reverse shock has reached the center not long ago. Apart from PSR J2021+4026 and G78.2+2.1, we have also serendipitously detected an X-ray flash-like event XMM J202154.7+402855 from this XMM-Newton observation.
We present a short Chandra observation that confirms a previous unidentified extended X-ray source, G308.3-1.4, as a new supernova remnant (SNR) in the Milky Way. Apart from identifying its SNR nature, a bright X-ray point source has also been discov
ered at the geometrical center. Its X-ray spectral properties are similar to those of a particular class of neutron star known as central compact objects (CCOs). On the other hand, the optical properties of this counterpart suggests it to be a late-type star. Together with the interesting ~ 1.4 hours X-ray periodicity found by Chandra, this system can possibly provide the first direct evidence of a compact binary survived in a supernova explosion.
We report the results from a detailed analysis of an archival XMM-Newton observation of the X-ray source XGPS-I J183251-100106, which has been suggested as a promising magnetic cataclysmic variable candidate based on its optical properties. A single
periodic signal of 1.5 hrs is detected from all EPIC cameras on board XMM-Newton. The phase-averaged X-ray spectrum can be well-modeled with a thermal bremsstrahlung of a temperature kT~50 keV. Both X-ray spectral and temporal behavior of this system suggest it as a eclipsing cataclysmic variable of AM Herculis (or polar) type.
ROSAT all-sky survey (RASS) data have provided another window to search for supernova remnants (SNRs). In reexamining this data archive, a list of unidentified extended X-ray objects have been suggested as promising SNR candidate. However, most of th
ese targets have not yet been fully explored by the state-of-art X-ray observatories. For selecting a pilot target for a long-term identification campaign, we have observed the brightest candidate, G308.3-1.4, with Chandra X-ray observatory. An incomplete shell-like X-ray structure which well-correlated with the radio shell emission at 843 MHz has been revealed. The X-ray spectrum suggests the presence of a shock-heated plasma. All these evidences confirm G308.3-1.4 as a SNR. The brightest X-ray point source detected in this field-of-view is also the one locates closest to the geometrical center of G308.3-1.4, which has a soft spectrum. The intriguing temporal variability and the identification of optical/infrared counterpart rule out the possibility of an isolated neutron star. On the other hand, the spectral energy distribution from Ks band to R band suggests a late-type star. Together with a putative periodicity of sim1.4 hrs, the interesting excesses in V, B bands and H-alpha suggest this source as a promising candidate of a compact binary survived in a supernova explosion (SN).
