<i>Chandra</i>Phase‐resolved X‐Ray Spectroscopy of the Crab Pulsar

Weisskopf, Martin C.; O’Dell, Stephen L.; Paerels, F.; Elsner, Ronald F.; Becker, Werner; Tennant, Allyn F.; Swartz, Douglas A.

doi:10.1086/380600

Cited by 76 publications

(62 citation statements)

References 33 publications

(70 reference statements)

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“…Before doing so, it is worth stressing that while we quote values of N H , our measurements are of the neon and magnesium (and oxygen for 4U 0142+61) column densities. Thus, the accuracy with which we can determine columns of a given other element (or dust) depends not only on our statistical uncertainty, but also on the uncertainty on the abundance of that element relative to neon and magnesium (as well as on possible corrections for the extent to which a given element is locked up in optically thick dust; e.g., Wilms et al [2000]; for a general caution on the implications of the set of abundances used, see Weisskopf et al [2004]). …”

Section: Resultsmentioning

confidence: 99%

Extinction Columns and Intrinsic X‐Ray Spectra of the Anomalous X‐Ray Pulsars

Durant

Kerkwijk

2006

ApJ

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The X-ray spectra of anomalous X-ray pulsars have long been fit by smooth, empirical models such as the sum of a blackbody plus a power law. These reproduce the $0.5Y10 keV range well, but fail at lower and higher energies, grossly overpredicting the optical and underpredicting the hard X-ray emission. A poorly constrained source of uncertainty in determining the true, intrinsic spectra, in particular at lower energies, is the amount of interstellar extinction. In previous studies, extinction column densities with small statistical errors were derived as part of the fits of the spectra to simple continuum models. Different choices of model, however, each produced statistically acceptable fits but a wide range of columns. Here we attempt to measure the interstellar extinction in a modelindependent way, using individual absorption edges of the elements O, Fe, Ne, Mg, and Si in X-ray grating spectra taken with XMM-Newton. We find that our inferred equivalent hydrogen column density N H for 4U 0142+61 is a factor of 1.4 lower than the typically quoted value from blackbody plus power-law fits, and is now consistent with estimates based on the dust scattering halo and visual extinction. For three other sources, we find column densities consistent with earlier estimates. We use our measurements to recover the intrinsic spectra of the AXPs empirically, without making assumptions on what the intrinsic spectral shapes ought to be. We find that the power-law components that dominate at higher energies do not extend below the thermal peak.

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Section: Resultsmentioning

confidence: 99%

Extinction Columns and Intrinsic X‐Ray Spectra of the Anomalous X‐Ray Pulsars

Durant

Kerkwijk

2006

ApJ

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“…This plot also shows that O abs is significantly different from solar. Weisskopf et al (2004) report from their Chandra observation of the Crab nebula that, using the abundances from Anders & Grevesse (1989), they find an underabundance of oxygen in the Galactic absorption component of 0.41 ± 0.07. Takei et al (2003) find values in the range from 0.63 ± 0.12 to 0.74 ± 0.14 using a Chandra observation of Cyg X-2.…”

Section: Discussionmentioning

confidence: 99%

X-ray spectroscopy on Abell 478 with XMM-Newton

Plaa

Kaastra

Tamura

et al. 2004

A&A

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Abstract. We report the results from a spatially resolved spectroscopy study with XMM-Newton on the relaxed cluster of galaxies Abell 478. From the EPIC data we extract a temperature profile and radial abundance profiles for Ne, Mg, Si, S, Ca, Fe and Ni. The abundance profiles follow the same trends as observed in other clusters. The spectra of the core of the cluster can be best fitted with a multi-temperature model. We argue that this multi-temperature behavior is mostly due to projection effects, because of the strong temperature gradient in the core. Contributions from other effects, for example, intrinsic temperature stratification cannot be fully excluded. For the first time we measure an underabundance of oxygen in the Galactic absorption component toward a cluster. The measured oxygen abundance in this absorber is about 0.5 times the solar oxygen abundance as determined by Anders & Grevesse (1989).

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“…The low metal content of LMC, and the low MW foreground absorption, make such tests sensitive to any supernova ejecta contribution. X-ray spectral fits to data obtained with Chandra of the Crab pulsar have recently highlighted the importance of the abundance factor (Willingale et al 2001;Weisskopf et al 2004). Using various abundances it was found that the line of sight to the Crab is significantly underabundant in oxygen.…”

Section: Supernova Ejecta Absorptionmentioning

confidence: 99%

The young pulsar PSR B0540-69.3 and its synchrotron nebula in the optical and X-rays

Serafimovich¹,

Shibanov²,

Lundqvist³

et al. 2004

A&A

184

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Abstract. The young PSR B0540-69.3 in the LMC is the only pulsar (except the Crab pulsar) for which a near-UV spectrum has been obtained. However, the absolute flux and spectral index of the HST/FOS spectrum are significantly higher than suggested by previous broad-band time-resolved groundbased UBVRI photometry. To investigate this difference, observations with ESO/VLT/FORS1 and analysis of HST/WFPC2 archival data were done. We show that the HST and VLT spectral data for the pulsar have > ∼ 50% nebular contamination and that this is the reason for the above-mentioned difference. The broadband HST spectrum for the range 3300-8000 Å is clearly nonthermal and has a negative spectral index, F ν ∝ ν −α with α ν = 1.0719 . This is different from the almost flat spectrum of the Crab pulsar, and also steeper than for the previously published broadband photometry of PSR B0540-69.3. We have also studied the spatial variations of the brightness and spectral index of the Pulsar Wind Nebula (PWN) around the pulsar, and find no significant spectral index variation over the PWN. The HST data show a clear asymmetry of the surface brightness distribution along the major axis of the torus-like structure of the PWN with respect to the pulsar position, also seen in Chandra/HRC X-ray images. This is different from the Crab PWN and likely linked to the asymmetry of the surrounding SN ejecta. The HST/WFPC2 archival data have an epoch separation of 4 years, and this allows us to estimate the proper motion of the pulsar. We find a motion of 4.9 ± 2.3 mas yr −1 (corresponding to a transverse velocity of 1190 ± 560 km s −1 ) along the southern jet of the PWN. If this is confirmed at a higher significance level by future observations, this makes PSR B0540-69.3 the third pulsar with a proper motion aligned with the jet axis of its PWN, which poses constraints on pulsar kick models. To establish the multiwavelength spectrum of the pulsar and its PWN, we have included recent Chandra X-ray data, and discuss the soft pulsar X-ray spectrum based on spectral fits including absorption by interstellar gas in the Milky Way, LMC as well as the supernova ejecta. We have compared the multiwavelength spectra of PSR B0540-69.3 and the Crab pulsar, and find that both PSR B0540-69.3 and the Crab pulsar have a weaker flux in the optical than suggested by a low-energy power-law extension of the X-ray spectrum. This optical depression is more severe for PSR B0540-69.3 than for the Crab pulsar. The same trend is seen for the PWNe of the two pulsars, and continues for low energies also out in the radio band. We discuss possible interpretations of this behavior.

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ChandraPhase‐resolved X‐Ray Spectroscopy of the Crab Pulsar

Cited by 76 publications

References 33 publications

Extinction Columns and Intrinsic X‐Ray Spectra of the Anomalous X‐Ray Pulsars

Extinction Columns and Intrinsic X‐Ray Spectra of the Anomalous X‐Ray Pulsars

X-ray spectroscopy on Abell 478 with XMM-Newton

The young pulsar PSR B0540-69.3 and its synchrotron nebula in the optical and X-rays

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