Optical-uv spectrum and proper motion of the middle-aged pulsar b1055-52 - Astrophysics > High Energy Astrophysical PhenomenaReport as inadecuate




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Abstract: PSRB1055-52 is a middle-aged ~535 kyr radio, X-ray, and gamma-ray pulsarshowing X-ray thermal emission from the neutron star NS surface. A candidateoptical counterpart to PSRB1055-52 was proposed by Mignani and coworkers basedon Hubble Space Telescope HST observations performed in 1996, in one spectralband only. We report on HST observations of this field carried out in 2008, infour spectral bands. The astrometric and photometric analyses of these dataconfirm the identification of the proposed candidate as the pulsar-s opticalcounterpart. Similarly to other middle-aged pulsars, its optical-UV spectrumcan be described by the sum of a power-law PLO component, presumably emittedfrom the pulsar magnetosphere, and a Rayleigh-Jeans RJ component emitted fromthe NS surface. The spectral index of the PLO component, alpha O=1.05+-0.34,is larger than for other pulsars with optical counterparts. The RJ component,with the brightness temperature TO=0.66+-0.10 d 350**2 R O,13**-2 MK whered 350 and R O,13 are the distance to the pulsar in units of 350 pc and theradius of the emitting area in units of 13 km, shows a factor of 4 excess withrespect to the extrapolation of the X-ray thermal component into theUV-optical. This hints that the RJ component is emitted from a larger, colderarea, and suggests that the distance to the pulsar is smaller than previouslythought. From the absolute astrometry of the HST images we measured the pulsarcoordinates with a position accuracy of 0.15-. From the comparison withprevious observations we measured the pulsar proper motion, mu = 42+-5 mas-yr,which corresponds to a transverse velocity V t = 70+-8 d 350 km-s.



Author: R. P. Mignani Mullard Space Science Laboratory, University College London, G. G. Pavlov Department of Astronomy and Astrophysics,

Source: https://arxiv.org/







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