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Register a new userEvidence for surface cooling emission in the XMM-Newton spectrum of the X-ray pulsar PSR B2334+61
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Katherine E. McGowan
Publication date
2005
fields
Physics
and research's language is
English
Authors
Katherine E. McGowan
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We report on the first XMM-Newton observation of the Vela-like pulsar PSR B2334+61. Spectral analysis reveals soft X-ray emission, with the bulk of the photons emitted at energies below ~1.5 keV. We find that the spectrum has a thermal origin and is well-fitted with either a blackbody or a magnetized, pure H atmospheric model. In the latter case, for a neutron star with a radius of 13 km and a magnetic field of 10e13 G, the best-fit gives an hydrogen column density nH = 0.33 x 10^22 cm^-2 and an effective temperature T_eff^infinity = 0.65 x 10^6 K, as measured at Earth. A comparison of the surface temperature of PSR B2334+61 obtained from this fit with cooling curves favor a medium mass neutron star with M ~ 1.45 solar masses or M ~ 1.6 solar masses, depending on two different models of proton superfluidity in the interior. We do not detect any pulsed emission from the source, and determine an upper limit of 5% for the modulation amplitude of the emission on the pulsars radio frequency.
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Seven years of pulse time-of-arrival measurements have been collected from observations of the young pulsar PSR B2334+61 using the Nanshan radio telescope of Urumqi Observatory. A phase-connected solution has been obtained over the whole data span, 2002 August to 2009 August. This includes a very large glitch that occurred between 2005 August 26 and September 8 (MJDs 53608 and 53621). The relative increase in rotational frequency for this glitch, $Delta u_{g}/ u~sim~20.5times10^{-6}$, is the largest ever seen. Although accounting for less than 1% of the glitch, there were two well-defined exponential decay terms with time constants of 21 and 147 days respectively. There was also a large long-term increase in the spindown rate with $Deltadot u_p/dot u sim 0.011$ at the time of the glitch. A highly significant oscillation with a period of close to one year is seen in the post-glitch residuals. It is very unlikely that this can be accounted for by a pulsar position error or proper motion -- it appears to result from effects interior to the neutron star. Implications of these results for pulsar glitch models are discussed.
With a spin frequency of 707 Hz, PSR J0952-0607 is the second fastest spinning pulsar known. It was discovered in radio by LOFAR in 2017 at an estimated distance of either 0.97 or 1.74 kpc and has a low-mass companion with a 6.42 hr orbital period. We report discovery of the X-ray counterpart of PSR J0952-0607 using XMM-Newton. The X-ray spectra can be well-fit by a single power law model (Gamma = 2.5) or by a thermal plus power law model (kTeff = 40 eV and Gamma = 1.4). We do not detect evidence of variability, such as that due to orbital modulation from pulsar wind and companion star interaction. Because of its fast spin rate, PSR J0952-0607 is a crucial source for understanding the r-mode instability, which can be an effective mechanism for producing gravitational waves. Using the high end of our measured surface temperature, we infer a neutron star core temperature of ~10^7 K, which places PSR J0952-0607 within the window for the r-mode to be unstable unless an effect such as superfluid mutual friction damps the fluid oscillation. The measured luminosity limits the dimensionless r-mode amplitude to be less than ~1x10^-9.
We report on the XMM-Newton observations of the 143 ms pulsar PSR J0538+2817. We present evidence for the first detections of pulsed X-rays from the source at a frequency which is consistent with the predicted radio frequency. The pulse profile is broad and asymmetric, with a pulse fraction of 18 +/- 3%. We find that the spectrum of the source is well-fit with a blackbody with T^{infty} = (2.12^{+0.04}_{-0.03}) x 10^6 K and N_{H} = 2.5 x 10^21 cm^{-2}. The radius determined from the model fit of 1.68 +/- 0.05 km suggests that the emission is from a heated polar cap. A fit to the spectrum with an atmospheric model reduces the inferred temperature and hence increases the radius of the emitting region, however the pulsar distance determined from the fit is then smaller than the dispersion distance.
Using XMM we detect faint unresolved X-ray emission from the Compact Steep Spectrum radio galaxy 3C303.1. We detect a thermal component at kT = 0.8 keV which seems likely to be produced in the ISM of the host galaxy. There is evidence for a second component in the spectrum whose nature is currently ambiguous. Plausible hypotheses for the second component include (1) hot gas shocked by the expansion of the radio source, and (2) Synchrotron self-Compton emission from the southern radio lobe if the magnetic field is below the equipartition value by a factor of about 3.5.
We report on a 25 ks observation of the 8.7 s anomalous X-ray pulsar 4U~0142+61 with the High Energy Transmission Grating Spectrometer (HETGS) on the Chandra X-ray Observatory. The continuum spectrum is consistent with previous measurements and is well fit by an absorbed power-law + blackbody with photon index Gamma=3.3+/-0.4 and kT=0.418+/-0.013 keV. No evidence was found for emission or absorption lines, with an upper limit of ~50 eV on the equivalent width of broad features in the 2.5-13 A (0.95-5.0 keV) range and an upper limit of ~10 eV on the equivalent width of narrow features in the 4.1-17.7 A (0.7-3.0 keV) range. If the source is a magnetar, then the absence of a proton cyclotron line strongly constrains magnetar atmosphere models and hence the magnetic field strength of the neutron star. We find no strong features that are indicative of cyclotron absorption for magnetic field strengths of (1.9-9.8)x10^{14} G. This is still consistent with the dipole field strength of B=1.3x10^{14} G (at the polar cap) estimated from the pulsars spindown.
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