DA495 - Astronomy News

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Posts: 131433

Date: Sep 4 19:59 2015

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Title: Constraining the parameters of the pulsar wind nebula DA 495 and its pulsar with Chandra and XMM-Newton Author: A. Karpova, D. Zyuzin, A. Danilenko, Yu. Shibanov We present spectral and timing analyses of the X-ray emission from the pulsar wind nebula DA 495 and its central object, J1952.2+2925, suggested to be the pulsar, using archival Chandra and XMM-Newton data. J1952.2+2925 has a pure thermal spectrum which is equally well fitted either by the blackbody model with a temperature of approx 215 eV and an emitting area radius of approx 0.6 km or by magnetized neutron star atmosphere models with temperatures of 80-90 eV. In the latter case the thermal emission can come from the entire neutron star surface which temperature is consistent with standard neutron star cooling scenarios. We place also an upper limit on the J1952.2+2925 nonthermal flux. The derived spectral parameters are generally compatible with published ones based only on the Chandra data, but they are much more accurate due to the inclusion of XMM-Newton data. No pulsations were found and we placed an upper limit for the J1952.2+2925 pulsed emission fraction of 40 per cent. Utilizing the interstellar absorption-distance relation, we estimated the distance to DA 495, which can be as large as 5 kpc if J1952.2+2925 emission is described by the atmosphere models. We compiled possible multi-wavelength spectra of the nebula including radio data; they depend on the spectral model of the central object. Comparing the results with other pulsar plus wind nebula systems we set reasonable constraints on the J1952.2+2925 spin-down luminosity and age. We suggest that the Fermi source 3FGL J1951.6+2926 is the likely gamma-ray counterpart of J1952.2+2925. Read more (1449kb, PDF) __________________

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Posts: 131433

Date: Jul 12 11:21 2008

SNR G065.7+01.2

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Position(2000): RA 19 52 13.70, Dec +29 25 08.0

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Posts: 131433

Date: Jul 8 05:47 2008

DA495	Permalink

Title: DA495 - an aging pulsar wind nebula Authors: R. Kothes, T.L. Landecker, W. Reich, S. Safi-Harb, Z. Arzoumanian We present a radio continuum study of the pulsar wind nebula (PWN) DA 495 (G65.7+1.2), including images of total intensity and linear polarization from 408 to 10550 MHz based on the Canadian Galactic Plane Survey and observations with the Effelsberg 100-m Radio Telescope. Removal of flux density contributions from a superimposed H2 region and from compact extragalactic sources reveals a break in the spectrum of DA 495 at 1.3 GHz, with a spectral index \alpha=-0.45 ± 0.20 below the break and \alpha=-0.87 ± 0.10 above it ({S}_\nu \propto{\nu^{\alpha}}). The spectral break is more than three times lower in frequency than the lowest break detected in any other PWN. The break in the spectrum is likely the result of synchrotron cooling, and DA 495, at an age of ~20,000 yr, may have evolved from an object similar to the Vela X nebula, with a similarly energetic pulsar. We find a magnetic field of ~1.3 mG inside the nebula. After correcting for the resulting high internal rotation measure, the magnetic field structure is quite simple, resembling the inner part of a dipole field projected onto the plane of the sky, although a toroidal component is likely also present. The dipole field axis, which should be parallel to the spin axis of the putative pulsar, lies at an angle of ~50° east of the North Celestial Pole and is pointing away from us towards the south-west. The upper limit for the radio surface brightness of any shell-type supernova remnant emission around DA 495 is \Sigma_{1 GHz} ~ 5.4 x 10^{-23} OAWatt m^{-2} Hz^{-1} sr^{-1} (assuming a radio spectral index of \alpha = -0.5), lower than the faintest shell-type remnant known to date. Read more (486kb, PDF) __________________

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Posts: 131433

Date: Jun 25 09:05 2008

Supernova remnant DA 495	Permalink

Title: Chandra Confirmation of a Pulsar Wind Nebula in DA 495 Authors: Z. Arzoumanian (1), S. Safi-Harb (2), T. L. Landecker (3), R. Kothes (3 and 4), F. Camilo (5) ((1) CRESST/NASA GSFC, (2) University of Manitoba, (3) DRAO Herzberg Institute of Astrophysics, (4) University of Calgary, (5) Columbia University) As part of a multiwavelength study of the unusual radio supernova remnant DA 495, we present observations made with the Chandra X-ray Observatory. Imaging and spectroscopic analysis confirms the previously detected X-ray source at the heart of the annular radio nebula, establishing the radiative properties of two key emission components: a soft unresolved source with a blackbody temperature of 1 MK consistent with a neutron star, surrounded by a nonthermal nebula 40'' in diameter exhibiting a power-law spectrum with photon index Gamma = 1.6±0.3, typical of a pulsar wind nebula. The implied spin-down luminosity of the neutron star, assuming a conversion efficiency to nebular flux appropriate to Vela-like pulsars, is ~10^{35} ergs/s, again typical of objects a few tens of kyr old. Morphologically, the nebular flux is slightly enhanced along a direction, in projection on the sky, independently demonstrated to be of significance in radio polarisation observations; we argue that this represents the orientation of the pulsar spin axis. At smaller scales, a narrow X-ray feature is seen extending out 5'' from the point source, a distance consistent with the sizes of resolved wind termination shocks around many Vela-like pulsars. Finally, we argue based on synchrotron lifetimes in the estimated nebular magnetic field that DA 495 represents a rare pulsar wind nebula in which electromagnetic flux makes up a significant part, together with particle flux, of the neutron star's wind, and that this high magnetisation factor may account for the nebula's low luminosity. Read more (220kb, PDF) __________________

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