Hard X-ray timing and spectral properties of PSR B0540-69 (original) (raw)
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Pulse profile stability of the Crab pulsar
Research in Astronomy and Astrophysics, 2011
We present an X-ray timing analysis of the Crab pulsar, PSR B0531+21, using the archival RXT E data. We have investigated the stability of the Crab pulse profile, in soft (2−20 keV) and hard (30−100 keV) X-ray energies, over the last decade of RXT E operation. The analysis includes measurement of the separation between the two pulse peaks; and intensity and the widths of the two peaks. We did not find any significant time dependency in the pulse shape. The two peaks are stable in phase, intensity and widths, for the last ten years. The first pulse is relatively stronger at soft X-rays. The first pulse peak is narrower than the second peak, in both, soft-and hard X-ray energies. Both the peaks show a slow rise and a steeper fall. The ratio of the pulsed photons in the two peaks is also constant in time.
Nustarobservations of the Young, Energetic Radio Pulsar PSR B1509–58
The Astrophysical Journal, 2016
We report on Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of the young rotation-powered radio pulsar PSR B1509−59 in the supernova remnant MSH 15−52. We confirm the previously reported curvature in the hard X-ray spectrum, showing that a log parabolic model provides a statistically superior fit to the spectrum compared with the standard power law. The log parabolic model describes the NuSTAR data, as well as previously published γ-ray data obtained with COMPTEL and AGILE, all together spanning 3 keV through 500 MeV. Our spectral modelling allows us to constrain the peak of the broadband high energy spectrum to be at 2.6±0.8 MeV, an improvement of nearly an order of magnitude in precision over previous measurements. In addition, we calculate NuSTAR spectra in 26 pulse phase bins and confirm previously reported variations of photon indices with phase. Finally, we measure the pulsed fraction of PSR B1509−58 in the hard X-ray energy band for the first time. Using the energy resolved pulsed fraction results, we estimate that the pulsar's off-pulse emission has a photon index value between 1.26 and 1.96. Our results support a model in which the pulsar's lack of GeV emission is due to viewing geometry, with the X-rays originating from synchrotron emission from secondary pairs in the magnetosphere.
The young pulsar PSR B0540-69.3 and its synchrotron nebula in the optical and X-rays
Astronomy & Astrophysics, 2004
The young PSR B0540-69 (B0540) 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 previously published HST/FOS data are significantly higher than suggested by broadband groundbased UBVRI photometry. Using our ESO/VLT/FORS1 spectral observations and HST/WFPC2 archival images we show that the old HST and new VLT spectral data are >50% contaminated by the Pulsar Wind Nebula (PWN) and that this is the reason for the above mentioned difference. We find that the broadband HST spectrum for the range 3300-8000 A is clearly non- thermal and has a negative spectral index of 1.07(+0.20/-0.19). This is dif- ferent from the almost flat spectrum of the Crab pulsar. The PWN of B0540 shows a clear asymmetry of the surface brightness distribution along the major axis of the PWN torus-like structure with respect to the pulsar position, also seen in Chandra X-ray images. This can be linked to the asymmetry of the surrounding SN ejecta. We find no significant spectral index variation over the PWN. Using HST archival images we estimate the proper motion of B0540 to be 4.9+/-2.3 mas/yr, i.e. a transverse velocity of 1190+/-560 km/s along the southern jet of the PWN. This can make PSR B0540 the third pulsar with a proper motion aligned with the jet axis of its PWN, which poses constraints on pulsar kick models. We discuss the interstellar absorption toward B0540 including the contributions from the Milky Way, LMC and the supernova ejecta, and compare unabsorbed multi- wavelength spectra of B0540 and the Crab pulsar, and their PWNs. Compared with the Crab, B0540 and its PWN show a significant depression in the optical range.
The Crab pulsar in the 0.75-30 MeV range as seen by CGRO COMPTEL
Astronomy and Astrophysics, 2001
We present the time-averaged characteristics of the Crab pulsar in the 0.75-30 MeV energy window using data from the imaging Compton Telescope COMPTEL aboard the Compton Gamma-Ray Observatory (CGRO) collected over its 9 year mission. Exploiting the exceptionally long COMPTEL exposure on the Crab allowed us to derive significantly improved COMPTEL spectra for the Crab nebula and pulsar emissions, and for the first time to accurately determine at low-energy γ-rays the pulse profile as a function of energy. These timing data, showing the well-known main pulse and second pulse at a phase separation of ∼ 0.4 with strong bridge emission, are studied together with data obtained at soft/hard X-ray energies from the ROSAT HRI, BeppoSAX LECS, MECS and PDS, at soft γ-rays from CGRO BATSE and at high-energy γ-rays from CGRO EGRET in order to obtain a coherent high-energy picture of the Crab pulsar from 0.1 keV up to 10 GeV. The morphology of the pulse profile of the Crab pulsar is continuously changing as a function of energy: the intensities of both the second pulse and the bridge emission increase relative to that of the first pulse for increasing energies up to ∼ 1 MeV. Over the COMPTEL energy range above 1 MeV an abrupt morphology change happens: the first pulse becomes again dominant over the second pulse and the bridge emission loses significance such that the pulse profile above 30 MeV is similar to the one observed at optical wavelengths. A pulse-phase-resolved spectral analysis performed in 7 narrow phase slices consistently applied over the 0.1 keV-10 GeV energy interval shows that the pulsed emission can empirically be described with 3 distinct spectral components: i) a power-law emission component (1 keV-5 GeV; photon index 2.022 ± 0.014), present in the phase intervals of the two pulses; ii) a curved spectral component required to describe soft (< ∼ 100 keV) excess emission present in the same pulse-phase intervals; iii) a broad curved spectral component reflecting the bridge emission from 0.1 keV to ∼ 10 MeV. This broad spectral component extends in phase over the full pulse profile in an approximately triangular shape, peaking under the second pulse. Recent model calculations for a three-dimensional pulsar magnetosphere with outer magnetospheric gap acceleration by Cheng et al. (2000) appear at present most successful in explaining the above complex high-energy characteristics of the Crab pulsar.
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.
AGILE OBSERVATIONS OF THE "SOFT" GAMMA-RAY PULSAR PSR B1509-58
2010
We present the results of new AGILE observations of PSR B1509-58 performed over a period of ∼2.5 years following the detection obtained with a subset of the present data. The modulation significance of the lightcurve above 30 MeV is at a 5σ confidence level and the lightcurve is similar to those found earlier by COMPTEL up to 30 MeV: a broad asymmetric first peak reaching its maximum 0.39 ± 0.02 cycles after the radio peak plus a second peak at 0.94 ± 0.03. The gamma-ray spectral energy distribution of the pulsed flux detected by COMP-TEL and AGILE is well described by a power-law (photon index α = 1.87±0.09)
The near-UV pulse profile and spectrum of the pulsar PSR B0656+14
Astronomy and Astrophysics, 2005
We have observed the middle-aged pulsar PSR B0656+14 with the prism and the NUV MAMA detector of the Space Telescope Imaging Spectrograph (STIS) to measure the pulsar spectrum and periodic pulsations in the near-ultraviolet (NUV). The pulsations are clearly detected, double-peaked and very similar to the optical pulse profile. The NUV pulsed fraction is 70 ± 12%. The spectral slope of the dereddened phase-integrated spectrum in the ∼ 1800 − 3200Å range is ∼ αν = 0.35 ± 0.5 which together with the high pulse fraction indicates a non-thermal origin for the NUV emission. The total flux in the range ∼ 1700 − 3400Å is estimated to be 3.4 ± 0.3 × 10 −15 erg s −1 cm −2 when corrected for E(B − V ) = 0.03 mag. At a distance of 288 pc this corresponds to a luminosity LNUV = 3.4 × 10 28 erg s −1 assuming isotropy of the emission. We compare the NUV pulse profile with observations from radio to gamma-rays. The first NUV sub-pulse is in phase with the gamma-ray pulse marginally detected with EGRET, while the second NUV sub-pulse is similar both in shape and in phase with the non-thermal pulse in hard X-rays. This indicates a single origin of the non-thermal emission in the optical-NUV and in the X-rays. This is also supported by the observed NUV spectral slope, which is compatible with a blackbody plus power-law fit extended from the X-ray range, but dominated by the power-law component in most of the NUV range.
A Multiwavelength Study of PSR B0628−28: The First Overluminous Rotation‐powered Pulsar?
The Astrophysical Journal, 2005
The ROSAT source RX J0630.8−2834 was suggested by positional coincidence to be the X-ray counterpart of the pulsar PSR B0628−28. This association, however, was regarded to be unlikely based on the computed energetics of the putative X-ray counterpart. In this paper we report on multi-wavelength observations of PSR B0628−28 made with the ESO/NTT observatory in La Silla, the Lovell telescope at Jodrell Bank and XMM-Newton. Although the optical observations do not detect any counterpart of RX J0630.8−2834 down to a limiting magnitude of V=26.1 mag and B=26.3 mag, XMM-Newton observations finally confirm it to be the pulsar's X-ray counterpart by detecting X-ray pulses with the radio pulsar's spin-period. The X-ray pulse profile is not sinusoidal but characterized by a two component pulse profile, consisting of a broad peak with a second narrow pulse leading the main pulse by ∼ 144 • . The fraction of pulsed photons is (39 ± 6)% with no strong energy dependence in the XMM-Newton bandpass. The pulsar's X-ray spectrum is well described by a power law with photon index α = 2.63 +0.23 −0.15 . A composite Planckian plus power law spectral model yields an interesting alternative which formally describes the observed energy spectrum equally well. Inferred from best fits are a blackbody temperature of ∼ 1.7 × 10 6 K and a projected blackbody radius of ∼ 69 +30 −25 m, yielding a thermal flux contribution of ∼ 20% within the 0.1 − 2.4 keV band. The pulsar's spin-down to X-ray energy conversion efficiency as obtained from the single power law spectral model is ∼ 16%, aumming the distance inferred from the radio dispersion measure. If confirmed, PSR B0628−28 would be the first X-ray over-luminous rotation-powered pulsar identified among all ∼ 1400 radio pulsars known today. The emission beam geometry of PSR B0628−28 is
2005
The ROSAT source RX J0630.8−2834 was suggested by positional coincidence to be the X-ray counterpart of the pulsar PSR B0628−28. This association, however, was regarded to be unlikely based on the computed energetics of the putative X-ray counterpart. In this paper we report on multi-wavelength observations of PSR B0628−28 made with the ESO/NTT observatory in La Silla, the Lovell telescope at Jodrell Bank and XMM-Newton. Although the optical observations do not detect any counterpart of RX J0630.8−2834 down to a limiting magnitude of V=26.1 mag and B=26.3 mag, XMM-Newton observations finally confirm it to be the pulsar’s X-ray counterpart by detecting X-ray pulses with the radio pulsar’s spin-period. The X-ray pulse profile is not sinusoidal but characterized by a two component pulse profile, consisting of a broad peak with a second narrow pulse leading the main pulse by ∼ 144. The fraction of pulsed photons is (39± 6)% with no strong energy dependence in the XMM-Newton bandpass. Th...
The X-ray properties of the energetic pulsar PSR J1838-0655
Monthly Notices of The Royal Astronomical Society, 2009
We present and interpret several new X-ray features of the X-ray pulsar PSR J1838-0655. The X-ray data are obtained from the archival data of CHANDRA, RXTE}, and SUZAKU. We combine all these X-ray data and fit the spectra with different models. We find that the joint spectra are difficult to fit with a single power law; a broken power-law model with a break at around 6.5 keV can improve the fit significantly. The photon index changes from Gamma\GammaGamma = 1.0 (below 6.5 keV) to Gamma\GammaGamma = 1.5 (above 6.5 keV); this indicates a softer spectral behaviour at hard X-rays. The X-ray flux at 2-20 keV is found to be 1.6x10^{-11} ergs cm^{-2} s^{-1}. The conversion efficiency from the spin-down luminosity is ~ 0.9% at 0.8-10 keV, which is much higher than that (~ 10^{-3}% - 10^{-4}%) of the pulsars that show similar timing properties. We discuss non-thermal radiation mechanisms for the observed high X-ray conversion efficiency and find that emission from the magnetosphere of a greatly inclined rotator is the most favorable interpretation for the conversion rate and the pulse profiles at X-ray bands. A line feature close to 6.65 keV is also detected in the spectra of SUZAKU/XIS; it might be the K$_\alpha$ emission of highly ionised Fe surrounding the pulsar.