Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDeep optical observations of the gamma-ray pulsar PSR J0007+7303 in the CTA 1 supernova remnant
552
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The Fermi Large Area Telescope (LAT) discovered the time signature of a radio-silent pulsar coincident with RX J0007.0+7302, a plerion-like X-ray source at the centre of the CTA 1 supernova remnant. The inferred timing parameters of the gamma-ray pulsar PSR J0007+7303 (P=315.8 ms; dot{P}sim3.6 10^{-13} s s^{-1}) point to a Vela-like neutron star, with an age comparable to that of CTA 1. The PSR J0007+7303 low distance (sim 1.4 kpc), interstellar absorption (A_Vsim 1.6), and relatively high energy loss rate (dot{E} sim4.5 10^{35} erg s^{-1}), make it a suitable candidate for an optical follow-up. Here, we present deep optical observations of PSR J0007+7303. The pulsar is not detected in the Gran Telescopio Canarias (GTC) images down to a limit of rsim 27.6 (3 sigma), the deepest ever obtained for this pulsar, while William Herschel Telescope (WHT) images yield a limit of V sim 26.9. Our r-band limit corresponds to an optical emission efficiency eta_{opt}= L_{opt}/dot{E} < 9.4 10^{-8}. This limit is more constraining than those derived for other Vela-like pulsars, but is still above the measured optical efficiency of the Vela pulsar. We compared the optical upper limits with the extrapolation of the XMM-Newton X-ray spectrum and found that the optical emission is compatible with the extrapolation of the X-ray power-law component, at variance with what is observed, e.g. in the Vela pulsar.
rate research
Read More
Prompted by the Fermi LAT discovery of a radio-quiet gamma-ray pulsar inside the CTA 1 supernova remnant, we obtained a 130 ks XMM-Newton observation to assess the timing behavior of this pulsar. Exploiting both the unprecedented photon harvest and the contemporary Fermi LAT timing measurements, a 4.7 sigma single peak pulsation is detected, making PSR J0007+7303 the second example, after Geminga, of a radio-quiet gamma-ray pulsar also seen to pulsate in X-rays. Phase-resolved spectroscopy shows that the off-pulse portion of the light curve is dominated by a power-law, non-thermal spectrum, while the X-ray peak emission appears to be mainly of thermal origin, probably from a polar cap heated by magnetospheric return currents, pointing to a hot spot varying throughout the pulsar rotation.
(Abridged) We conducted new 6cm and 11cm observations of CTA 1 using the Urumqi 25-m and Effelsberg 100-m telescopes. Data at other wavelengths were included to investigate the spectrum and polarisation properties. We obtained new total intensity and polarisation maps at 6cm and 11cm with angular resolutions of 9.5 arcmin and 4.4 arcmin, respectively. We derived a spectral index of alpha=-0.63+/-0.05 based on the integrated flux densities at 408 MHz, 1420 MHz, 2639 MHz, and 4800 MHz. The spectral index map calculated from data at the four frequencies shows a clear steepening of the spectrum from the strong shell emission towards the north-western breakout region with weak diffuse emission. The decrease of the spectral index is up to about 0.3. The RM map derived from polarisation data at 6cm and 11cm shows a sharp transition between positive RMs in the north-eastern and negative RMs in the south-western part of the SNR. We note a corresponding RM pattern of extragalactic sources and propose the existence of a large-diameter Faraday screen in front of CTA 1, which covers the north-eastern part of the SNR. The RM of the Faraday screen is estimated to be about +45 rad/m2. A RM structure function of CTA 1 indicates a very regular magnetic field within the Faraday screen, which is larger than about 2.7 microG in case of 500 pc distance.
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 5$sigma$ 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 Comptel and Agile is well described by a power-law (photon index alpha=1.87+/-0.09) with a remarkable cutoff at E_c=81 +/- 20 MeV, representing the softest spectrum observed among gamma-ray pulsars so far. The pulsar luminosity at E > 1 MeV is $L_{gamma}=4.2^{+0.5}_{-0.2} times10^{35}$ erg/s, assuming a distance of 5.2 kpc, which implies a spin-down conversion efficiency to gamma-rays of $sim 0.03$. The unusual soft break in the spectrum of PSR B1509-58 has been interpreted in the framework of polar cap models as a signature of the exotic photon splitting process in the strong magnetic field of this pulsar. In this interpretation our spectrum constrains the magnetic altitude of the emission point(s) at 3 km above the neutron star surface, implying that the attenuation may not be as strong as formerly suggested because pair production can substitute photon splitting in regions of the magnetosphere where the magnetic field becomes too low to sustain photon splitting. In the case of an outer-gap scenario, or the two pole caustic model, better constraints on the geometry of the emission would be needed from the radio band in order to establish whether the conditions required by the models to reproduce Agile lightcurves and spectra match the polarization measurements.
PSR J0205+6449 is a young ({approx} 5400 years), Crab-like pulsar detected in radio and at X and {gamma}-ray energies and has the third largest spin-down flux among known rotation powered pulsars. It also powers a bright synchrotron nebula detected in the optical and X-rays. At a distance of {approx} 3.2 kpc and with an extinction comparable to the Crab, PSR J0205+6449 is an obvious target for optical observations. We observed PSR J0205+6449 with several optical facilities, including 8m class ground-based telescopes, such as the Gemini and the Gran Telescopio Canarias. We detected a point source, at a significance of 5.5{sigma}, of magnitude i {approx} 25.5, at the centre of the optical synchrotron nebula, coincident with the very accurate Chandra and radio positions of the pulsar. Thus, we discovered a candidate optical counterpart to PSR J0205+6449. The pulsar candidate counterpart is also detected in the g ({approx}27.4) band and weakly in the r ({approx}26.2) band. Its optical spectrum is fit by a power law with photon index {Gamma}0 = 1.9{pm}0.5, proving that the optical emission if of non-thermal origin, is as expected for a young pulsar. The optical photon index is similar to the X-ray one ({Gamma}X = 1.77{pm}0.03), although the optical fluxes are below the extrapolation of the X-ray power spectrum. This would indicate the presence of a double spectral break between the X-ray and optical energy range, at variance with what is observed for the Crab and Vela pulsars, but similar to the Large Magellanic Cloud pulsar PSR B0540-69.
We present an X-ray study of the mixed-morphology supernova remnant CTB 1 (G116.9+0.2) observed with Suzaku. The 0.6-2.0 keV spectra in the northeast breakout region of CTB 1 are well represented by a collisional ionization-equilibrium plasma model with an electron temperature of ~ 0.3 keV, whereas those in the southwest inner-shell region can be reproduced by a recombining plasma model with an electron temperature of ~ 0.2 keV, an initial ionization temperature of ~ 3 keV, and an ionization parameter of ~ 9 $times$ 10$^{11}$ cm$^{-3}$s. This is the first detection of the recombining plasma in CTB 1. The electron temperature in the inner-shell region decreases outwards, which implies that the recombining plasma is likely formed by the thermal conduction via interaction with the surrounding cold interstellar medium. The Ne abundance is almost uniform in the observed regions whereas Fe is more abundant toward the southwest of the remnant, suggesting an asymmetric ejecta distribution. We also detect a hard tail above the 2 keV band that is fitted with a power-law function with a photon index of 2-3. The flux of the hard tail in the 2-10 keV band is ~ 5 $times$ 10$^{-13}$ erg cm$^{-2}$ s$^{-1}$ and is peaked at the center of CTB 1. Its origin is unclear but one possibility is a putative pulsar wind nebula associated with CTB 1.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
