PSPC Data Research Articles

A census with ROSAT of low-luminosity X-ray sources in globular clusters

I analyze 101 observations from the ROSAT archive to search for X-ray sources in or near 55 globular clusters. New sources are found in the cores of NGC 362 (a double source), NGC 6121 (marginally significant), NGC 6139, and NGC 6266; and outside the cores of NGC 6205, NGC 6352 and NGC 6388. More accurate positions are determined for the X-ray sources in some ten clusters. The improved position for the source in NGC 6341 excludes the suggested ultraviolet counterpart. It is shown that one of the two sources reported near the core of NGC 6626 is spurious, as is the detection of a pulsar period in the PSPC data of this cluster; the central source is resolved in three sources. One source reported previously in NGC 6304 is demoted to an upper limit. For 20 cluster cores better upper limits to the X-ray luminosity are obtained. From a statistical analysis I argue that several sources outside the cluster cores may well belong to the clusters. All spectral energy distributions observed so far are relatively soft, with bremsstrahlung temperatures 0.9 keV; there is evidence however that bremsstrahlung spectra do not correctly describe the spectra. The X-ray luminosity per unit mass for the cluster as a whole does not depend on the concentration; the luminosity per unit mass for the core may increase with the cluster concentration.

The X-Ray Structure of the Supernova Remnant 3C 400.2

Abstract We present here the results of an X-ray study of the supernova remnant 3C 400.2 (G53.6$-$2.2) using the ASCA data. 3C 400.2 has an unusual morphology at radio wavelengths, suggesting two SNRs superposed along the same line of sight, whereas its X-ray emission is known to be centrally peaked. We investigated the X-ray spectral variation across the remnant using the ASCA GIS and the ROSAT PSPC data. The X-ray spectra can be well fitted by thin thermal plasma models. However, there is no significant variation in the temperature and the ionization parameter across the remnant. We conclude that it is a single SNR rather than two overlapping SNRs. The centrally peaked X-ray morphology and the thin thermal emission with nearly cosmic abundances indicate that 3C 400.2 belongs to a class of “mixed-morphology SNRs”. We found that the physical parameters of 3C 400.2 are similar to those of other mixed-morphology SNRs. The morphology of 3C 400.2 can be explained by a supernova explosion occurring near to the edge of an interstellar cloud.

Origin of the Scatter in the X‐Ray Luminosity of Early‐Type Galaxies Observed withROSAT

Statistical properties of X-ray luminosity and temperature are studied for 52 early-type galaxies based on the ROSAT PSPC data. All of the X-ray luminous galaxies show largely extended emission with a radius of a few times 10re, while X-ray faint galaxies do not show such a component. This leads to a division of early-type galaxies into two categories: X-ray extended and X-ray compact galaxies. Except for a few galaxies in dense cluster environments, the luminosity and temperature of X-ray compact galaxies are well explained by a kinematical heating of the gas supplied by stellar mass loss. In contrast, X-ray extended galaxies indicate large scatter in the X-ray luminosity. We discuss the notion that X-ray extended galaxies are the central objects of large potential structures and that the presence or absence of this potential is the main origin of the large scatter in the X-ray luminosity.

On the Integrated Spectrum of the X-Ray Binaries and the Origin of Soft X-Ray Emission from the Bulge of M31

Using ROSAT PSPC data, we have performed several tests aimed at understanding the origin of the soft X-ray spectral component detected from the bulge of M31. We find that a significant soft component in the spectrum of the bulge is spatially correlated with the unresolved X-ray emission near the core of M31, which is probably a hot interstellar medium or perhaps a population of multiple faint sources. For the first time, we extracted the spectrum of this unresolved emission, by removing point sources dominating the integral spectrum of the bulge, and found it to be responsible for most of the soft excess. A soft spectral component is not at all needed to fit the point-source spectrum that remains after subtracting the unresolved emission. The integral spectra of bright point sources, both inside and outside of the M31 bulge, can be fitted with a single power law in the ROSAT band. Our analysis rules out the previous suggestion that all bulge emission in M31 may be generated by low-mass X-ray binaries (Irwin & Bregman).

Mass Models and Sunyaev‐Zeldovich Effect Predictions for a Flux‐Limited Sample of 22 Nearby X‐Ray Clusters

We define a 90% complete, volume-limited sample of 31 z<0.1 x-ray clusters and present a systematic analysis of public ROSAT PSPC data on 22 of these objects. Our efforts are undertaken in support of the Penn/OVRO SZE survey, and to this end we present predictions for the inverse Compton optical depth towards all 22 of these clusters. We have performed detailed Monte Carlo simulations to understand the effects of the cluster profile uncertainties on the SZE predictions given the OVRO 5.5-meter telescope beam and switching patterns; we find that the profile uncertainties are one of the least significant components of our error budget for SZE-based distance measurements. We also present baryonic masses and baryon mass fractions derived under the assumption of hydrostatic equilibrium for these 22 clusters. The mean baryonic mass fraction within R_500 \sim 500 h^-1 kpc is (7.02 \pm 0.28) x 10^-2 h^-3/2, or (19.8 \pm 0.8) x 10^-2 for h=0.5. We confirm the Allen et al. (1993) claim of an excess absorbing column density towards Abell 478, but do not find similar anomalies in the other 21 clusters in our sample. We also find some evidence for an excess of soft counts in the ROSAT PSPC data. A measurement of H_o using these models and OVRO SZE determinations will be presented in a second paper.

Oxygen Absorption in M87: Evidence for a Warm+Hot Interstellar Medium

We present a reanalysis of the ROSAT PSPC data within the central 100 kpc of M87 to search for intrinsic oxygen absorption similar to that recently measured in several galaxies and groups. Since M87 is the brightest nearby galaxy or cluster possessing an average temperature (~2 keV) within the PSPC bandpass, it is the ideal target for this study. Using a spatial-spectral deprojection analysis we find the strongest evidence to date for intrinsic oxygen absorption in the hot gas of a galaxy, group, or cluster. Single-phase plasma models modified by intervening Galactic absorption cannot fit the 0.2-2.2 keV PSPC data as they underpredict the 0.2-0.4 keV region and overpredict the 0.5-0.8 keV region where the emission and absorption residuals are obvious upon visual inspection of the spectral fits. These absorption and emission features are significant out to the largest radii investigated. Since the excess emission between 0.2-0.4 keV rules out intrinsic absorption from cold gas or dust, the most reasonable model for the excess emission and absorption features is warm, collisionally ionized gas with a temperature of ~106 K. Simple multiphase models (cooling flow, two phases) modified by both intervening Galactic absorption and by a single oxygen edge provide good fits and yield temperatures and Fe abundances of the hot gas that agree with previous determinations by ASCA and SAX. The multiphase models of M87 inferred from the PSPC can account for the excess EUV emission observed with EUVE and the excess X-ray absorption inferred from Einstein and ASCA data above 0.5 keV. This evidence for a multiphase warm+hot interstellar medium in M87 essentially confirms the original detection by Canizares et al. within the central ~2' using the Einstein FPCS. Although the total mass of the warm gas implied by the oxygen absorption is consistent with the matter deposited by a cooling flow, the suppression of the mass deposition rate and the distortion of the X-ray isophotes in the region where the radio emission is most pronounced suggest some feedback effect from the active galactic nucleus on the cooling gas.

The X‐Ray–faint Early‐Type Galaxy NGC 4697

We analyze archival ROSAT HRI, ROSAT PSPC, and ASCA data of the X-ray faint early-type galaxy NGC4697. The joint ROSAT PSPC + ASCA spectrum is fit by a two-component thermal model, a MEKAL model with kT_{MEKAL}=0.26^{+0.04}_{-0.03} keV with low metallicity and a bremsstrahlung model with kT_{BREM}=5.2^{+3.0}_{-1.6} keV. A similar model was found to fit the spectra of another faint early-type galaxy (NGC4382) and the bulge of M31. We interpret this soft emission as a combination of emission from a soft component of low mass X-ray binaries (LMXBs) and from a low temperature interstellar medium, although the relative contributions of the two components could not be determined. Twelve point sources were identified within 4' of NGC4697, of which 11 are most likely LMXBs associated with the galaxy. The soft X-ray colors of four of the LMXBs in NGC4697 support the claim that LMXBs possess a soft spectral component. Finally, we present a simulation of what we believe the Chandra data of NGC4697 will look like.

X-ray analysis of the cluster 3C 129

The cluster 3C 129 is classified as a rich cluster. An analysis of the properties of the cluster 3C 129 from ROSAT PSPC and HRI, Einstein IPC, and EXOSAT ME observations is presented. The mean temperature from a joint fit of the ROSAT PSPC and EXOSAT ME data is 5.5(±0.2) keV. The luminosity is 0.6×1044 erg s−1 in 0.2–2.4 keV and 2.7×1044 erg s−1 in 0.2–10 keV. We find a cooling flow with a rate of ∼84 M⊙ yr−1. The central gas density is 6×10−3 cm−3, and the ICM mass is 3.6×1013 M⊙. The total cluster mass is ∼5×1014 M⊙. The X-ray morphology shows an east–west elongation, which is evidence for a recent merger event. The radio source 3C 129.1 is located near the X-ray centre. Another cluster member galaxy (the radio galaxy 3C 129) is a prototype of head-tailed radio galaxies, and is located in the west part of the cluster. The tail points along the gradient of intracluster gas pressure. There are no significant point X-ray sources associated with the AGNs of the two radio galaxies.

Iron Gradients in Cooling Flow Galaxies and Groups

Previous studies of the Fe abundances in the hot gas of galaxies and groups have reported conflicting results with most studies finding very subsolar Fe abundances that disagree with standard theory. To investigate the possible role of Fe abundance gradients on these measurements we present deprojection analysis of the ROSAT PSPC data of 10 of the brightest cooling flow galaxies and groups. The PSPC allows for spatially resolved spectral analysis on a half-arcminute scale, and interesting constraints on both the temperatures and Fe abundances are possible because the ~1 keV temperatures of these systems are well matched to the bandpass of the PSPC. In nine out of 10 systems we find clear evidence that the Fe abundance decreases with increasing radius: ZFe ≈ 1-several Z☉ within the central radial bin (r ≲ 10 kpc), which decreases to ZFe ~ 0.5 Z☉ at the largest radii examined (r ~ 50-100 kpc). The Fe abundances (and temperatures) are consistent with the average values for these systems that we obtained in our previous analyses of the ASCA data using multitemperature models, which confirms that previous inferences of very subsolar Fe abundances from ASCA arise from the incorrect assumption of isothermal gas and not the presence of Fe abundance gradients. We discuss why this "Fe bias" affects much more seriously the measurements of ZFe from ASCA data than from ROSAT data. We show that the Fe abundance profiles for these galaxies and groups are consistent with a gasdynamical model where the gas is enriched by stellar ejecta and supernovae in the "solar supernova proportion," the stars formed with a Galactic initial mass function, and the gas is diluted by mixing with primordial gas at large radii.

Diffuse X-ray emission from late-type galaxy haloes

Current theories of galaxy formation predict that spiral galaxies are embedded in a reservoir of hot gas. This gas is able to cool on to the galaxy, replenishing cold gas that is consumed by star formation. Estimates of the X-ray luminosity emitted in the cooling region suggest a bolometric luminosity of the order of 10 × 1041 erg s−1 in massive systems. We have used ROSAT PSPC data to search for extended X-ray emission from the haloes of three nearby, massive, late-type galaxies: NGC 2841, 4594 and 5529. We infer 95 per cent upper limits on the bolometric X-ray luminosities of the haloes of NGC 2841, 4594 and 5529 of 0.4, 1.2 and 3.8 × 1041 erg s−1 respectively. Thus, the true luminosity lies well below the straightforward theoretical prediction. We discuss this discrepancy and suggest a number of ways in which the theoretical model might be brought into agreement with the observational results. A possible solution is that the gravitational potentials of the dark matter haloes of these galaxies are weaker than assumed in the current model. Alternatively, the present-day accretion may be substantially less than is required on average to build the disc over the Hubble time. Our results are, however, based on only three galaxies, none of which is ideal for this kind of study. A larger data set is required to explore this important problem further.

ASCA and ROSAT observations of supersoft X-ray sources

Energy spectra of four luminous supersoft X-ray sources (SSS) are investigated combining the ASCA SIS and the ROSAT PSPC data. We found that the energy spectra of the SSS are commonly reproduced by a blackbody continuum model superposed with sharp edge-like structures. Despite of several years intervals between the ASCA and ROSAT observations, differences of the best-fit parameters are found to be small. This indicates that X-ray emission from these four SSS are rather stable. The blackbody temperature and the edge energies show large differences among the sources, which may reflect differences in the white dwarf mass.

Origin of the Galactic ridge X-ray emission

Origin of the X-ray emission along the Galactic ridge is still an unresolved issue. The ASCA spectra show emission lines of various elements,suggesting thermal emission of thin hot plasmas in non-equilibrium ionization. If they are Galactic-scale diffuse plasmas, their energy density is too high to be contained in the Galactic plane. The energy loss rate due to a consequent plasma outflow is ∼1043 erg s—1 for which no energy source is readily found. Despite a large difference in brightness, the spectrum of the emission from the Galactic center region is found to be strikingly similar, essentially identical, to that of the Galactic ridge emission. Because of the same physical properties, the emissions from both regions are most probably of a single origin. Then, the interpretation in terms of multiple diffuse plasma components of non-equilibrium ionization seems implausible, since there is no reason that the degree of ionization is the same for these two regions of orders of magnitude different electron densities. In view of these problems in the diffuse plasma origin, we revisit the possibility of discrete source origin, with use of the ROSAT archival PSPC data for the Galactic ridge. In total 19 sources are detected in the 0.7—2 keV range above a threshold of ∼10—14 erg cm—2s—1 in 0.5—2 keV, corresponding to a surface density of ∼105sources sr—1. Basedon a model calculation, the observed result requires a class of hardsource with LX ∼ 1029—30 erg s—1 andas abundant as the coronal sources to account for the ridge emission. Such a class of source is not known.

Radial Temperature Profiles of X‐Ray–emitting Gas within Clusters of Galaxies

Previous analyses of ASCA data of clusters of galaxies have found conflicting results regarding the slope of the temperature profile of the hot X-ray gas within clusters, mainly because of the large, energy-dependent point-spread function (PSF) of the ASCA mirrors. We present a summary of all ASCA-determined cluster temperature profiles found in the literature and find a discrepancy in the radial temperature trend of clusters based on which PSF-correction routine is used. This uncertainty in the cluster temperature profile in turn can lead to large uncertainties in the amount of dark matter in clusters. In this study, we have used ROSAT PSPC data to obtain independent relative temperature profiles for 26 clusters, most of which have had their temperature profiles determined by ASCA. Our aim is not to measure the actual temperature values of the clusters but to use X-ray color profiles to search for a hardening or softening of the spectra as a function of radius for comparison to ASCA-derived profiles. The radial color profiles indicate that outside of the cooling flow region, the temperature profiles of clusters are in general constant. Within 35% of the virial radius, we find that a temperature drop of 20% at 10 keV and 12% at 5 keV can be ruled out at the 99% confidence level. A subsample of non-cooling flow clusters shows that the condition of isothermality applies at very small radii too, although cooling gas complicates this determination in the cooling flow cluster subsample. The colors predicted from the temperature profiles of a series of hydrodynamical cluster simulations match the data very well, although they cannot be used to discriminate among different cosmologies. An additional result is that the color profiles show evidence for a central peak in metallicity in low-temperature clusters.

X-ray evidence for multiphase hot gas with solar abundances in the brightest elliptical galaxies

We examine whether isothermal models of the hot gas can successfully describe the ASCA and ROSAT spectra of NGC 1399, 4472, 4636 and 5044, which are among the brightest elliptical galaxies in X-rays. Broad-band spectral fitting of the ASCA SIS and GIS data accumulated within a radius of ∼5 arcmin for each galaxy shows that isothermal models (which also include a component for discrete sources) are unable to fit the SIS data near 1 keV, although a marginal fit for NGC 4636 is obtained if the relative abundances of several elements with respect to Fe are allowed to depart substantially from their solar values. In addition, these isothermal models typically fail to produce the large equivalent widths of the Kα line blends of Si and S that are measured independently of the Fe L emission lines. Two-temperature models provide substantially better broad-band fits to both the SIS and GIS data of each galaxy with the relative abundances (except for NGC 4636) fixed at their solar values. A simple multiphase cooling flow model fits nearly as well as the two-temperature model for NGC 1399, 4472 and 5044. The multiphase models also predict more accurately the Si and S equivalent widths and the ratios of Si xiv/xiii and S xvi/xv than the isothermal models. From detailed comparison of broad-band fits to the ASCA data of these ellipticals using the MEKAL and Raymond-Smith plasma codes, we determine that the MEKAL plasma code (as expected) is significantly more accurate for the important energies ∼0.7–1.4 keV, and the small residuals in the Fe L region for the best-fitting multiphase models imply that remaining inaccuracies in the MEKAL code are insufficient to change qualitatively the results for data of the present quality. Using various approaches, we find that the temperature gradients inferred from the ROSAT PSPC data of these galaxies, especially for NGC 1399 and 5044, are inconsistent with the isothermal models obtained from fitting the ASCA data within a single aperture, but are very consistent with the multiphase models. Therefore, models that assume isothermal gas within r∼5 arcmin are inconsistent with the ASCA and ROSAT PSPC data of these elliptical galaxies. Simple two-temperature models and multiphase cooling flows provide much better descriptions of these data sets with Fe abundances of ∼1–2 solar and (except for NGC 4636) relative abundances fixed at their solar values. We discuss the implications of these nearly solar abundances.

Outer Regions of the Cluster Gaseous Atmospheres

We present a systematic study of the hot gas distribution in the outer regions of regular clusters using ROSAT PSPC data. Outside the cooling flow region, the beta-model describes the observed surface brightness closely, but not precisely. Between 0.3 and 1 virial radii, the profiles are characterized by a power law with slope, expressed in terms of the beta parameter, in the range beta=0.65 to 0.85. The values of beta in this range of radii are typically larger by ~0.05 than those derived from the global fit. There is a mild trend for the slope to increase with temperature, from ~0.68 for 3 keV clusters to ~0.8 for 10 keV clusters; however, even at high temperatures there are clusters with flat gas profiles, 0.7. Our values of beta at large radius are systematically higher, and the trend of beta with temperature is weaker than was previously found; the most likely explanation is that earlier studies were affected by an incomplete exclusion of the central cooling flow regions. For our regular clusters, the gas distribution at large radii is quite close to spherically symmetric and this is shown not to be an artifact of the sample selection. The gas density profiles are very similar when compared in the units of cluster virial radius. The radius of fixed mean gas overdensity 1000 (corresponding to the dark matter overdensity 200 for Omega=0.2) shows a tight correlation with temperature, R~T**0.5, as expected from the virial theorem for clusters with the universal gas fraction. At a given temperature, the rms scatter of the gas overdensity radius is only ~7% which translates into a 20% scatter of the gas mass fraction, including statistical scatter due to measurement uncertainties.

Optical and X-ray variability in the least luminous active galactic nucleus, NGC 4395

We report the detection of optical and X-ray variability in the least luminous known Seyfert galaxy, NGC 4395. Between 1996 July and 1997 January the featureless continuum changed by a factor of 2, which is typical of more luminous AGN. The largest variation was seen at shorter wavelengths, so that the spectrum became `harder' during higher activity states. During the same period, the broad emission-line flux changed by ∼ 20-30 per cent. In a one-week optical broad-band monitoring programme, a 20 per cent change was seen between successive nights. The difference in flux observed between the spectroscopy of 1996 July and the broad-band observations implies variation by a factor of 3 at 4400 A in just one month. In the same period, the spectral shape changed from a power law with spectral index α∼ 0 (characteristic of quasars) to a spectral index α∼ 2 (as observed in other dwarf AGN). ROSAT HRI and PSPC archive data show a variable X-ray source coincident with the Galactic nucleus. A change in X-ray flux by a factor ∼ 2 in 15 d has been observed. When compared with more luminous AGN, NGC 4395 appears to be very X-ray quiet. The hardness ratio obtained from the PSPC data suggests that the spectrum could be absorbed. We also report the discovery of weak Ca II K absorption, suggesting the presence of a young stellar cluster providing of the order of 10 per cent of the blue light. The stellar cluster may be directly observed as a diffuse component in Hubble Space Telescope (HST ) optical imaging. Using HST UV archive data, together with the optical and X-ray observations, we examine the spectral energy distribution for NGC 4395 and discuss the physical conditions implied by the nuclear activity under the standard AGN model. When in the low state, the extrapolated UV continuum is insufficient to explain the observed broad emission lines. This could be explained by intrinsic variability or absorption or may imply an extra heating source for the broad-line region. The observations can be explained either by an accreting massive black hole emitting at about 10-3LEdd or by a single old compact supernova remnant with an age of 50 to 500 yr generated by a small nuclear starburst.

BeppoSAX observations of 2-Jy lobe-dominated broad-line sources -- I. The discovery of a hard X-ray component

We present new BeppoSAX LEGS, MECS and PDS observations of five lobe-dominated, broad-line active galactic nuclei selected from the 2-Jy sample of southern radio sources. These include three radio quasars and two broad-line radio galaxies. ROSAT PSPC data, available for all the objects, are also used to constrain the spectral shape better in the soft X-ray band. The collected data cover the energy range 0.1-10 keV, reaching similar to 50 keV for one source (Pictor A), The main result from the spectral fits is that all sources have a hard X-ray spectrum with energy index alpha(x) similar to 0.75 in the 2-10 keV range. This is at variance with the situation at lower energies where these sources exhibit steeper spectra. Spectral breaks Delta alpha(x) similar to 0.5 at 1-2 keV characterize in fact the overall X-ray spectra of our objects. The flat, high-energy slope is very similar to that displayed by flat-spectrum/core-dominated quasars, which suggests that the same emission mechanism (most likely inverse Compton) produces the hard X-ray spectra in both classes. Finally, a tweak) thermal component is also present at low energies in the two broad-line radio galaxies included in our study.

A Detailed Analysis of the Dynamical State of the Cluster of Galaxies A2218 in X‐Rays

We reanalyze ROSAT PSPC and HRI data of the cluster of galaxies A2218 in order to investigate its dynamical state. To reveal the cluster's substructure in X-rays, we construct symmetric cluster models by fitting a two-dimensional isothermal β-model, which we subsequently subtract from the original data. Study of the remaining structures and their significance gives new insight into existing substructure, and therefore indications concerning the dynamical state of the cluster, which has not yet been clearly visualized in X-rays. The present analysis enables us not only to qualitatively determine the dynamical state of the clusters, but also to draw conclusions about the significance of existing substructure in giving real numbers. A2218 reveals significant structure after the subtraction, providing clear evidence that it is going through a merger phase. The X-ray morphology is in agreement with the surface mass density map obtained by analysis based on weak lensing. The subgroup falling in the center of A2218 is most likely on its first infall.

Extreme Ultraviolet and Optical Observations of The AM Herculis Type Cataclysmic Variable V884 Herculis (RX J1802.1+1804)

ABSTRACTWe observed V884 Herculis (RX J1802.1+1804), during a high accretion state, from 1997 September 17–22 UT using the Extreme Ultraviolet Explorer (EUVE) satellite. Simultaneously, multiple ground‐based optical telescopes obtained photometric observations. Although the EUV flux was too low for spectral study, the light curve from the Deep Survey instrument provides useful information on the system geometry. The phased, folded EUV light curve shows a brief total eclipse similar to previous ROSAT PSPC data followed by a broad dip. The optical light curve shows a lower amplitude of variability and a smoother structure. The similarity of the optical light curves on all six nights, along with previous magnetic measurements, and the coincidence of the periods determined from the optical and EUVE data, confirm the synchronism of this system and its classification as an AM Her type magnetic cataclysmic variable. Doppler tomography of 1995 high state spectra reveals a short, ballistic accretion stream with little emission from an irradiated secondary star. An optical light curve obtained in 1998 June shows the system during a lowered accretion state, with a mean magnitude that is ∼1.5 mag fainter than the high state. The low state light curve displays a smaller amplitude of orbital variation but only slight changes in accretion geometry. A spectrum obtained 15 days later shows that the optical continuum had returned to a high state, although the line strengths appear different from past high states.

X-Ray Pulsations from the Central Source in Puppis A

There are several supernova remnants that contain unresolved X-ray sources close to their centers, presumably radio-quiet neutron stars. To prove that these objects are indeed neutron stars, to understand the origin of their X-ray radiation, and to explain why they are radio quiet, one should know their periods and period derivatives. We searched for pulsations of the X-ray flux from the radio-quiet neutron star candidate RX J0822-4300 near the center of the Puppis A supernova remnant observed with the ROSAT PSPC and HRI. A standard timing analysis of the separate PSPC and HRI data sets does not allow one to detect the periodicity unequivocally. However, a thorough analysis of the two observations separated by 4.56 yr enabled us to find a statistically significant period of P 75.3 ms and its derivative 1.49 × 10-13 s s-1. The corresponding characteristic parameters of the neutron star—age τ = P/(2) = 8.0 kyr, magnetic field B = 3.4 × 1012 G, and rotational energy loss Ė = 1.4 × 1037 ergs s-1—are typical for young radio pulsars. Since the X-ray radiation has a thermal-like spectrum, its pulsations may be due to a nonuniform temperature distribution over the neutron star surface caused by anisotropy of the heat conduction in the strongly magnetized crust.