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Register a new userDetection of Pulsed X-ray Emission from XMM-Newton Observations of PSR J0538+2817
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Added by
Katherine E. McGowan
Publication date
2003
fields
Physics
and research's language is
English
Authors
Katherine E. McGowan
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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.
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We present the results of two XMM-Newton observations of Jupiter carried out in 2003 for 100 and 250 ks (or 3 and 7 planet rotations) respectively. X-ray images from the EPIC CCD cameras show prominent emission from the auroral regions in the 0.2 - 2.0 keV band: the spectra are well modelled by a combination of emission lines, including most prominently those of highly ionised oxygen (OVII and OVIII). In addition, and for the first time, XMM-Newton reveals the presence in both aurorae of a higher energy component (3 - 7 keV) which is well described by an electron bremsstrahlung spectrum. This component is found to be variable in flux and spectral shape during the Nov. 2003 observation, which corresponded to an extended period of intense solar activity. Emission from the equatorial regions of Jupiters disk is also observed, with a spectrum consistent with that of solar X-rays scattered in the planets upper atmosphere. Jupiters X-rays are spectrally resolved with the RGS which clearly separates the prominent OVII contribution of the aurorae from the OVIII, FeXVII and MgXI lines, originating in the low-latitude disk regions of the planet.
We present results of timing observations of the 143-ms pulsar J0538+2817 that provide a proper motion measurement which clearly associates the pulsar with the supernova remnant S147. We measure a proper motion of 67$_{-22}^{+48}$ mas yr$^{-1}$, implying a transverse velocity of $v= 385^{+260}_{-130}$ km s$^{-1}$. We derive an age of the pulsar and S147 of only $30pm4$ kyr which is a factor of 20 times less than the pulsars characteristic age of $tau_c = 620$ kyr. This age implies an initial spin period of $P_0=139$ ms, close to the present pulse period and a factor of several larger than what is usually inferred for birth periods. Implications for recent X-ray detections of this pulsar are discussed.
We report on the XMM-Newton observations of the young, 102 ms pulsar PSR B1706-44. We have found that both a blackbody plus power-law and a magnetized atmospheric model plus power-law provide an excellent fit to the EPIC spectra. The two scenarios are therefore indistinguishable on a statistical basis, although we are inclined to prefer the latter on physical grounds. In this case, assuming a source distance of ~2.3 kpc, the size of the region responsible for the thermal emission is R~13 km, compatible with the surface of a neutron star. A comparison of the surface temperature of PSR B1706-44 obtained from this fit with cooling curves favor a medium mass neutron star with M~1.45 solar masses or M~1.59 solar masses, depending on two different models of proton superfluidity in the interior. The large collecting area of XMM-Newton allows us to resolve a substructure in the broad soft X-ray modulation detected by Chandra, revealing the presence of two separate peaks with pulsed fractions of 7 +/- 4% and 15 +/- 3%, respectively.
We have detected pulsed X-ray emission from the fastest millisecond pulsar known, PSR B1937+21 (P=1.558 msec), with ASCA. The pulsar is detected as a point source above $sim 1.7$ keV, with no indication of nebulosity. The source flux in the 2--10 keV band is found to be $f = (3.7pm 0.6) times 10^{-13}$ erg s$^{-1}$ cm$^{-2}$, which implies an isotropic luminosity of $L_{rm x} = 4 pi D^2 f sim (5.7pm 1.0) times 10^{32} ~(D/3.6 {rm kpc})^2$ erg s$^{-1}$, where D is the distance, and an X-ray efficiency of $sim 5 times 10^{-4}$ relative to the spin-down power of the pulsar. The pulsation is found at the period predicted by the radio ephemeris with a very narrow primary peak, the width of which is about 1/16 phase ($sim 100 mu$s), near the time resolution limit ($61 mu$s) of the observation. The instantaneous flux in the primary peak (1/16 phase interval) is found to be ($4.0pm 0.8) times 10^{-12}$ erg s$^{-1}$ cm$^{-2}$. Although there is an indication for the secondary peak, we consider its statistical significance too low to claim a definite detection. The narrow pulse profile and the detection in the 2--10 keV band imply that the X-ray emission is caused by the magnetospheric particle acceleration. Comparison of X-ray and radio arrival times of pulses indicates, within the timing errors, that the X-ray pulse is coincident with the radio interpulse.
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.
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