Discovery of a 105 ms X‐Ray Pulsar in Kesteven 79: On the Nature of Compact Central Objects in Supernova Remnants (original) (raw)
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X‐Ray Timing of PSR J1852+0040 in Kesteven 79: Evidence of Neutron Stars Weakly Magnetized at Birth
The Astrophysical Journal, 2007
The 105-ms X-ray pulsar J1852+0040 is the central compact object (CCO) in supernova remnant Kes 79. We report a sensitive upper limit on its radio flux density of 12 µJy at 2 GHz using the NRAO Green Bank Telescope. Timing using the Newton X-Ray Multi-Mirror Mission (XMM-Newton) and the Chandra X-ray Observatory over a 2.4 yr span reveals no significant change in its spin period. The 2σ upper limit on the period derivative leads, in the dipole spin-down formalism, to an energy loss rateĖ < 7 × 10 33 ergs s −1 , surface magnetic field strength B p < 1.5 × 10 11 G, and characteristic age τ c ≡ P/2Ṗ > 8 Myr. This value of τ c exceeds the age of the SNR by 3 orders of magnitude, implying that the pulsar was born spinning at its current period. However, the X-ray luminosity of PSR J1852+0040, L bol ≈ 3 × 10 33 (d/7.1 kpc) 2 ergs s −1 , is a large fraction ofĖ, which challenges the rotation-powered assumption. Instead, its high blackbody temperature kT BB = 0.46 ± 0.04 keV, small blackbody radius R BB ≈ 0.8 km, and large pulsed fraction f p ≈ 80%, may be evidence of accretion onto a polar cap, possibly from a fallback disk made of supernova debris. If B p < 10 10 G, an accretion disk can penetrate the light cylinder and interact with the magnetosphere while resulting torques on the neutron star remain within the observed limits. A weak B-field is also inferred in another CCO, the 424-ms pulsar 1E 1207.4−5209, from its steady spin and soft X-ray absorption lines. We propose this origin of radio-quiet CCOs: the magnetic field, derived from a turbulent dynamo, is weaker if the NS is formed spinning slowly, which enables it to accrete SN debris. Accretion excludes neutron stars born with both B p < 10 11 G and P > 0.1 s from radio pulsar surveys, where B p < 10 11 G is not encountered except among very old (τ c > 40 Myr) or recycled pulsars. Finally, such a CCO, if born in SN 1987A, could explain the non-detection of a pulsar there.
X‐Ray Observations of the High Magnetic Field Radio Pulsar PSR J1814−1744
The Astrophysical Journal, 2000
PSR J1814−1744 is a 4 s radio pulsar with surface dipole magnetic field strength 5.5× 10 13 G, inferred assuming simple magnetic dipole braking. This pulsar's spin parameters are very similar to those of anomalous X-ray pulsars (AXPs), suggesting that this may be a transition object between the radio pulsar and AXP population, if AXPs are isolated, high magnetic field neutron stars as has recently been hypothesized. We present archival X-ray observations of PSR J1814−1744 made with ROSAT and ASCA. X-ray emission is not detected from the position of the radio pulsar. The derived upper flux limit implies an X-ray luminosity significantly smaller than those of all known AXPs. This conclusion is insensitive to the possibility that X-ray emission from PSR J1814−1744 is beamed or that it undergoes modest variability. When interpreted in the context of the magnetar mechanism, these results argue that X-ray emission from AXPs must depend on more than merely the inferred surface magnetic field strength. This suggests distinct evolutionary paths for radio pulsars and AXP, despite their proximity in period-period derivative phase space.
The Astrophysical Journal, 2001
PSR J1119−6127 is a recently discovered 1700-year-old radio pulsar that has a very high inferred surface dipolar magnetic field. We present a detailed analysis of a pointed ASCA observation and archival ROSAT data of PSR J1119−6127 and its surroundings. Both data sets reveal extended emission coincident with the newlydiscovered radio supernova remnant G292.2-0.5, reported in a companion paper by Crawford et al. A hard point source, offset ∼1. ′ 5 from the position of the radio pulsar, is seen with the ASCA GIS. No pulsations are detected at the radio period with a pulsed fraction upper limit of 61% (95% confidence). The limited statistics prevent a detailed spectral analysis, although a power-law model with photon index Γ ≈ 1 − 2 describes the data well. Both the spectral model and derived X-ray luminosity are consistent with those measured for other young radio pulsars, although the spatial offset renders an identification of the source as the X-ray counterpart of the pulsar uncertain.
Astrophysical Journal, 2002
SAX J1808.4-3658 is a unique source being the first Low Mass X-ray Binary showing coherent pulsations at a spin period comparable to that of millisecond radio pulsars. Here we present an XMM-Newton observation of SAX J1808.4-3658 in quiescence, the first which assessed its quiescent luminosity and spectrum with good signal to noise. XMM-Newton did not reveal other sources in the vicinity of SAX J1808.4-3658 likely indicating that the source was also detected by previous BeppoSAX and ASCA observations, even if with large positional and flux uncertainties. We derive a 0.5-10 keV unabsorbed luminosity of L X = 5 × 10 31 erg s −1 , a relatively low value compared with other neutron star soft X-ray transient sources. At variance with other soft X-ray transients, the quiescent spectrum of SAX J1808.4-3658 was dominated by a hard (Γ ∼ 1.5) power law with only a minor contribution ( < ∼ 10%) from a soft black body component. If the power law originates in the shock between the wind of a turned-on radio pulsar and matter outflowing from the companion, then a spin-down to X-ray luminosity conversion efficiency of η ∼ 10 −3 is derived; this is in line with the value estimated from the eclipsing radio pulsar PSR J1740-5340. Within the deep crustal heating model, the faintness of the blackbody-like component indicates that SAX J1808.4-3658 likely hosts a massive neutron star (M > ∼ 1.7 M ⊙ ).
Astronomy and Astrophysics, 2004
We report on the analysis of new X-ray data obtained with XMM-Newton and Chandra from two ROSAT-discovered X-ray dim isolated neutron stars (XDINs). RX J0806.4−4123 was observed with XMM-Newton in April 2003, 2.5 years after the first observation. The EPIC-pn data confirm that this object is an X-ray pulsar with 11.371 s neutron star spin period. The X-ray spectrum is consistent with absorbed black-body emission with a temperature kT = 96 eV and NH = 4·10 19 cm −2 without significant changes between the two observations. Four XMM-Newton observations of RX J0420.0−5022 between December 2002 and July 2003 did not confirm the 22.7 s pulsations originally indicated in ROSAT data, but clearly reveal a 3.453 s period. A fit to the X-ray spectrum using an absorbed black-body model yields kT = 45 eV, the lowest value found from the small group of XDINs and NH = 1.0·10 20 cm −2 . Including a broad absorption line improves the quality of the spectral fits considerably for both objects and may indicate the presence of absorption features similar to those reported from RBS1223, RX J1605.3+3249 and RX J0720.4−3125. For both targets we derive accurate X-ray positions from the Chandra data and present an optical counterpart candidate for RX J0420.0−5022 with B = 26.6±0.3 mag from VLT imaging.
A Detailed X-Ray Investigation of PSR J2021+4026 and the Γ-Cygni Supernova Remnant
The Astrophysical Journal, 2015
We have investigated the field around the radio-quiet γ-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 thermal in nature which suggests the pulsation is originated from a hot polar cap with T ∼ 3 × 10 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.
An XMM-Newton Study of the 401 Hz Accreting Pulsar SAX J1808.4-3658 in Quiescence
Journal of Quaternary Science, 2002
SAX J1808.4-3658 is a unique source being the first Low Mass X-ray Binary showing coherent pulsations at a spin period comparable to that of millisecond radio pulsars. Here we present an XMM-Newton observation of SAX J1808.4-3658 in quiescence, the first which assessed its quiescent luminosity and spectrum with good signal to noise. XMM-Newton did not reveal other sources in the vicinity of SAX J1808.4-3658 likely indicating that the source was also detected by previous BeppoSAX and ASCA observations, even if with large positional and flux uncertainties. We derive a 0.5-10 keV unabsorbed luminosity of L_X=5x10^{31} erg/s, a relatively low value compared with other neutron star soft X-ray transient sources. At variance with other soft X-ray transients, the quiescent spectrum of SAX J1808.4-3658 was dominated by a hard (Gamma~1.5) power law with only a minor contribution (<10%) from a soft black body component. If the power law originates in the shock between the wind of a turned-on radio pulsar and matter outflowing from the companion, then a spin-down to X-ray luminosity conversion efficiency of eta~10^{-3} is derived; this is in line with the value estimated from the eclipsing radio pulsar PSR J1740-5340. Within the deep crustal heating model, the faintness of the blackbody-like component indicates that SAX J1808.4-3658 likely hosts a massive neutronstar (M>1.7 solar masses).
Phase-resolved X-ray spectroscopy of the millisecond pulsar SAX J1808.4−3658
Monthly Notices of the Royal Astronomical Society, 2002
We present new results based on RXTE observations of the millisecond pulsar SAX J1808.4-3658 carried out during the decay of the April 1998 outburst. The X-ray spectrum can be fitted by a two-component model. We interpret the soft component as blackbody emission from a heated spot on the neutron star, and the hard component as coming from Comptonization in plasma heated by the accretion shock as the material collimated by the magnetic field impacts onto the neutron star surface. The hotspot is probably the source of seed photons for Comptonization. The hard component illuminates the disc, giving rise to a reflected spectrum. The amount of reflection indicates that the disc is truncated at fairly large radii (20-40 R g ), consistent with the lack of relativistic smearing of the spectral features. The inferred evolution of the inner radius is not consistent with the magnetic field truncating the disc. Instead it seems more likely that the inner disc radius is set by some much longer time-scale process, most probably connected to the overall evolution of the accretion disc. This disc truncation mechanism would then have to be generic in all low mass accretion rate flows both in disc accreting neutron stars and black hole systems.
Constraints on Neutron Star Properties from X-ray Observations of Millisecond Pulsars
Astrophysical Journal, 2006
We present a model of thermal X-ray emission from hot spots on the surface of a rotating compact star with an unmagnetized light-element atmosphere. An application to ROSAT, Chandra, and XMM-Newton X-ray observations of the nearest known rotation-powered millisecond pulsar (MSP) PSR J0437--4715 reveals that the thermal emission from this pulsar is fully consistent with such a model, enabling constraints
The Astrophysical Journal, 2001
We report the discovery of a young and energetic pulsar in the Parkes multibeam survey of the Galactic plane. PSR J1016−5857 has a rotation period of 107 ms and period derivative of 8.0 × 10 −14 , implying a characteristic age of 21 kyr and spin-down luminosity of 2.6 × 10 36 erg s −1 . The pulsar is located just outside, and possibly interacting with, the shell supernova remnant G284.3−1.8. Archival X-ray data show a source near the pulsar position which is consistent with emission from a pulsar wind nebula. The pulsar is also located inside the error box of the unidentified EGRET source 3EG J1013−5915, for which it represents a plausible counterpart.