The X-ray properties of the energetic pulsar PSR J1838-0655 (original) (raw)
Related papers
The Astrophysical Journal, 2010
We present results from two observations of the wind-accreting X-ray pulsar 4U 1907+09 using the Suzaku observatory. The broadband time-averaged spectrum allows us to examine the continuum emission of the source and the cyclotron resonance scattering feature at ∼19 keV. Additionally, using the narrow CCD response of Suzaku near 6 keV allows us to study in detail the Fe K bandpass and to quantify the Fe Kβ line for this source for the first time. The source is absorbed by fully-covering material along the line of sight with a column density of N H ∼ 2 × 10 22 cm −2 , consistent with a wind accreting geometry, and a high Fe abundance (∼ 3 − 4 × solar). Time and phase-resolved analyses allow us to study variations in the source spectrum. In particular, dips found in the 2006 observation which are consistent with earlier observations occur in the hard X-ray bandpass, implying a variation of the whole continuum rather than occultation by intervening material, while a dip near the end of the 2007 observation occurs mainly in the lower energies implying an increase in N H along the line of sight, perhaps indicating clumpiness in the stellar wind.
The two-component X-ray spectrum of the 6.4 S pulsar 1E 1048.1-5937
Astronomy and Astrophysics, 1998
The 6.4 s X-ray pulsar 1E 1048.1-5937 was observed by BeppoSAX in 1997 May. This source belongs to the class of "anomalous" pulsars which have pulse periods in range 5-11 s, show no evidence of optical or radio counterparts, and exhibit long-term increases in pulse period. The phase-averaged 0.5-10 keV spectrum can be described by an absorbed power-law and blackbody model. The best-fit photon index is 2.5±0.2 and the blackbody temperature and radius are 0.64±0.01 keV and 0.59 ± 0.02 km (for a distance of 3 kpc), respectively. The detection of blackbody emission from this source strengthens the similarity with two of the more well studied "anomalous" pulsars, 1E 2259+586 and 4U 0142+614. There is no evidence for any phase dependent spectral changes. The pulse period of 6.45026 ± 0.00001 s implies that 1E 1048.1-5937 continues to spin-down, but at a slower rate than obtained from the previous measurements in 1994 and 1996.
Astrophysical Journal, 2011
The Large Area Telescope (LAT) onboard the Fermi satellite opened a new era for pulsar astronomy, detecting gamma-ray pulsations from more than 60 pulsars, ~40% of which are not seen at radio wavelengths. One of the most interesting sources discovered by LAT is PSR J0357+3205, a radio-quiet, middle-aged (tau_C ~0.5 Myr) pulsar standing out for its very low spin-down luminosity (Erot ~6x10^33 erg/s), indeed the lowest among non-recycled gamma-ray pulsars. A deep X-ray observation with Chandra (0.5-10 keV), coupled with sensitive optical/infrared ground-based images of the field, allowed us to identify PSR J0357+3205 as a faint source with a soft spectrum, consistent with a purely non-thermal emission (photon index Gamma=2.53+/-0.25). The absorbing column (NH=8+/-4x10^20 cm^-2) is consistent with a distance of a few hundred parsecs. Moreover, the Chandra data unveiled a huge (9 arcmin long) extended feature apparently protruding from the pulsar. Its non-thermal X-ray spectrum points to synchrotron emission from energetic particles from the pulsar wind, possibly similar to other elongated X-ray tails associated with rotation-powered pulsars and explained as bow-shock pulsar wind nebulae (PWNe). However, energetic arguments, as well as the peculiar morphology of the diffuse feature associated with PSR J0357+3205 make the bow-shock PWN interpretation rather challenging.
Exploring the X-Ray and Γ-Ray Properties of the Redback Millisecond Pulsar PSR J1723–2837
The Astrophysical Journal, 2014
We have investigated the X-ray and γ−ray properties of the redback millisecond pulsar PSR J1723-2837 with XMM-Newton, Chandra and Fermi. We have discovered the X-ray orbital modulation of this binary system with the minimum that coincides with the phases of radio eclipse. The X-ray emission is clearly non-thermal in nature which can be well described by a simple power-law with a photon index of ∼ 1.2. The phase-averaged luminosity is ∼ 9 × 10 31 erg/s in 0.3-10 keV which consumes ∼ 0.2% of the spin-down power. We have detected the γ−ray emission in 0.1 − 300 GeV from this system at a significance of ∼ 6σ for the first time. The γ−rays in this energy range consumes ∼ 2% of the spindown power and can be modeled by a power-law with a photon index of ∼ 2.6. We discuss the high energy properties of the new redback in the context of an intrabinary shock model.
A Chandra X-Ray Observation of the Binary Millisecond Pulsar PSR J1023+0038
Astrophysical Journal, 2011
We present a Chandra X-Ray Observatory ACIS-S variability, spectroscopy, and imaging study of the peculiar binary containing the millisecond pulsar J1023+0038. The X-ray emission from the system exhibits highly significant (12.5σ) large-amplitude (factor of two to three) orbital variability over the five consecutive orbits covered by the observation, with a pronounced decline in the flux at all energies at superior conjunction. This can be naturally explained by a partial geometric occultation by the secondary star of an X-ray-emitting intrabinary shock, produced by the interaction of outflows from the two stars. The depth and duration of the eclipse imply that the intrabinary shock is localized near or at the surface of the companion star and close to the inner Lagrangian point. The energetics of the shock favor a magnetically dominated pulsar wind that is focused into the orbital plane, requiring close alignment of the pulsar spin and orbital angular momentum axes. The X-ray spectrum consists of a dominant non-thermal component and at least one thermal component, likely originating from the heated pulsar polar caps, although a portion of this emission may be from an optically thin "corona." We find no evidence for extended emission due to a pulsar wind nebula or bow shock down to a limiting luminosity of L X <~ 3.6 × 1029 erg s-1 (0.3-8 keV), <~ 7 × 10-6 of the pulsar spin-down luminosity, for a distance of 1.3 kpc and an assumed power-law spectrum with photon index Γ = 1.5.
The Astrophysical Journal, 2013
We present X-ray observations of the "redback" eclipsing radio millisecond pulsar and candidate radio pulsar/X-ray binary transition object PSR J1723-2837. The X-ray emission from the system is predominantly non-thermal and exhibits pronounced variability as a function of orbital phase, with a factor of ∼2 reduction in brightness around superior conjunction. Such temporal behavior appears to be a defining characteristic of this variety of peculiar millisecond pulsar binaries and is likely caused by a partial geometric occultation by the main-sequence-like companion of a shock within the binary. There is no indication of diffuse X-ray emission from a bow shock or pulsar wind nebula associated with the pulsar. We also report on a search for point source emission and γ-ray pulsations in Fermi Large Area Telescope data using a likelihood analysis and photon probability weighting. Although PSR J1723-2837 is consistent with being a γ-ray point source, due to the strong Galactic diffuse emission at its position a definitive association cannot be established. No statistically significant pulsations or modulation at the orbital period are detected. For a presumed detection, the implied γ-ray luminosity is 5% of its spin-down power. This indicates that PSR J1723-2837 is either one of the least efficient γ-ray producing millisecond pulsars or, if the detection is spurious, the γ-ray emission pattern is not directed towards us.
Studies of high-energy pulsars: The special case of PSR J1849-0001
Nuclear and Particle Physics Proceedings, 2018
We present the results from the data analysis of the XMM-Newton observation (53.6 ks) on PSR J1849-0001. We studied in detail the X-ray emission of this pulsar and we found extended emission (up to ≈ 100 arcsec) from the Pulsar Wind Nebula (PWN), confirming that this is a case of a Pulsar/PWN system and strengthening the evidence that X-ray, hard X-ray and TeV gamma-ray sources are manifestations of the same system. Another important result of our study is the clear evidence that the X-ray PWN of PSR J1849-0001 is asymmetric.
arXiv (Cornell University), 2023
The X-ray pulsar RX J0440.9+4431 went through a giant outburst in 2022 and reached a record-high flux of 2.3 Crab, as observed by Swift/BAT. We study the evolution of different spectral and timing properties of the source using NICER observations. The pulse period is found to decrease from 208 s to 205 s, and the pulse profile evolves significantly with energy and luminosity. The hardness ratio and hardness intensity diagram (HID) show remarkable evolution during the outburst. The HID turns towards the diagonal branch from the horizontal branch above a transition (critical) luminosity, suggesting the presence of two accretion modes. Each NICER spectrum can be described using a cutoff power law with a blackbody component and a Gaussian at 6.4 keV. At higher luminosities, an additional Gaussian at 6.67 keV is used. The observed photon index shows negative and positive correlations with X-ray flux below and above the critical luminosity, respectively. The evolution of spectral and timing parameters suggests a possible change in the emission mechanism and beaming pattern of the pulsar depending on the spectral transition to sub-and super-critical accretion regimes. Based on the critical luminosity, the magnetic field of the neutron star can be estimated in the order of 10 12 or 10 13 G, assuming different theoretical models. Moreover, the observed iron emission line evolves from a narrow to a broad feature with luminosity. Two emission lines originating from neutral and highly ionized Fe atoms were evident in the spectra around 6.4 keV and 6.67 keV (higher luminosities).
The Astrophysical Journal, 2011
The Large Area Telescope (LAT) onboard the Fermi satellite opened a new era for pulsar astronomy, detecting γ-ray pulsations from more than 60 pulsars, ∼ 40% of which are not seen at radio wavelengths. One of the most interesting sources discovered by LAT is PSR J0357+3205, a radio-quiet, middle-aged (τ C ∼ 0.5 Myr) pulsar standing out for its very low spin-down luminosity (Ė rot ∼ 6×10 33 erg s −1 ), indeed the lowest among non-recycled γ-ray pulsars. A deep X-ray observation with Chandra (0.5-10 keV), coupled with sensitive optical/infrared ground-based images of the field, allowed us to identify PSR J0357+3205 as a faint source with a soft spectrum, consistent with a purely non-thermal emission (photon index Γ = 2.53 ± 0.25). The absorbing column (N H = 8 ± 4 × 10 20 cm −2 ) is consistent with a distance of a few hundred parsecs. Moreover, the Chandra data unveiled a huge (9 arcmin long) extended feature apparently protruding from the pulsar. Its non-thermal X-ray spectrum points to synchrotron emission from energetic particles from the pulsar wind, possibly similar to other elongated X-ray tails associated with rotation-powered pulsars and explained as bow-shock pulsar wind nebulae (PWNe). However, energetic arguments, as well as the peculiar morphology of the diffuse feature associated with PSR J0357+3205 make the bow-shock PWN interpretation rather challenging.
Soft and Hard X-Ray Emissions from the Anomalous X-Ray Pulsar 4U 0142+61 Observed with Suzaku
Publications of the Astronomical Society of Japan, 2011
The anomalous X-ray pulsar 4U 0142+61 was observed with Suzaku on 2007 August 15 for a net exposure of ∼100 ks, and was detected in a 0.4 to ∼ 70 keV energy band. The intrinsic pulse period was determined as 8.68878 ± 0.00005 s, in agreement with an extrapolation from previous measurements. The broadband Suzaku spectra enabled a first simultaneous and accurate measurement of the soft and hard components of this object by a single satellite. The former can be reproduced by two blackbodies, or slightly better by a resonant cyclotron scattering model. The hard component can be approximated by a power-law of photon index Γ h ∼ 0.9 when the soft component is represented by the resonant cyclotron scattering model, and its high-energy cutoff is constrained as > 180 keV. Assuming an isotropic emission at a distance of 3.6 kpc, the unabsorbed 1-10 keV and 10-70 keV luminosities of the soft and hard components are calculated as 2.8 × 10 35 erg s −1 and 6.8 × 10 34 erg s −1 , 1 respectively. Their sum becomes ∼ 10 3 times as large as the estimated spin-down luminosity. On a time scale of 30 ks, the hard component exhibited evidence of variations either in its normalization or pulse shape.