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Post Info TOPIC: PSR J1357-6429 and PSR J1048-5832
Blobrana


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PSR J1357-6429
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Title: Optical observations of PSR J1357-6429 field
Authors: Aida Kirichenko, Andrey Danilenko, Ronald E. Mennickent, George Pavlov, Yury Shibanov, Sergey Zharikov, Dmitry Zyuzin

PSR J1357-6429 is a Vela-like radio pulsar that has been recently detected with Chandra and Fermi, which, like Vela, powers a compact X-ray pulsar wind nebula and X-ray-radio plerion associated with an extended TeV source. We present our deep optical observations with the Very Large Telescope to search for an optical counterpart of the pulsar and its nebula. We detected a point-like source in V, R, and I bands whose position is in agreement with the X-ray position of the pulsar, and whose colours are distinct from those of ordinary stars. The tentative optical luminosity and efficiency of the source are similar to those of the Vela pulsar, which also supports the optical identification. However, the source spectrum is unusually steep, with a spectral index of about 5, which is not typical of optical pulsars. The source offset from the radio position of PSR J1357-6429, which is in line with the corresponding offset of the X-ray position, implies the pulsar transverse velocity of 1600-2000 km/s at the distance of 2-2.5 kpc, making it the fastest moving pulsar known.

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Blobrana


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Title: Possible optical counterpart of PSR J1357--6429
Authors: A. Danilenko, A. Kirichenko, R. E. Mennickent, G. Pavlov, Yu. Shibanov, S. Zharikov, D. Zyuzin

PSR J1357--6429 is a Vela-like radio pulsar that has been recently detected in X-rays and gamma-rays. It powers a compact tail-like X-ray pulsar wind nebula and X-ray-radio plerion associated with an extended TeV source HESS J1356--645. We have performed deep optical observations with the VLT to search for an optical counterpart of the pulsar and its nebula. A point-like source has been detected in V, R, and I bands whose centre position is within the 1-sigma error circle of the X-ray position of the pulsar, and whose colours are distinct from those of ordinary stars. We consider it as a candidate optical counterpart of the pulsar. If it is indeed the counterpart, its 5-sigma offset from the radio pulsar position, measured about 9 yr earlier, implies the transverse velocity of the pulsar in the range of 1600--2000 km s^{-1} at the distance of 2--2.5 kpc, making it the fastest moving pulsar known. The direction of the estimated proper motion coincides with the extension of the pulsar's X-ray tail, suggesting that this is a jet. The tentative optical luminosity and efficiency of the pulsar are similar to those of the Vela pulsar, which also supports the optical identification. However, the candidate shows an unusually steep dereddened flux increase towards the infrared with a spectral index of about 5, not typical for optical pulsars. It implies a strong double-knee spectral break in the pulsar emission between the optical and X-rays. The reasons for the spectral steepness are unclear. It may be caused by a possible nebula knot projected to the jet and strongly overlapped with the pulsar, as is observed for the Crab, where the knot has the spectrum significantly steeper than that of the pulsar. We find no other signs of the pulsar nebula in the optical. Alternatively, the detected source can be a faint AGN, not seen yet in other spectral domains.

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Blobrana


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Posts: 131433
Date:
PSR J1357-6429 and PSR J1048-5832
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Title: VLT observations of the two Fermi pulsars PSR J1357-6429 and PSR J1048-5832
Authors: R. P. Mignani, A. Shearer, A. De Luca, P. Moran, S. Collins, M. Marelli

Optical observations of pulsars are crucial to study the neutron star properties, from the structure and composition of the interior, to the properties and geometry of the magnetosphere. Historically, X and gamma-ray observations have paved the way to the pulsar optical identifications. The launch of Fermi opened new perspectives in the optical-to-gamma-ray studies of neutron stars, with the detection of more than 80 pulsars. Here, we aim to search for optical emission from two Fermi pulsars which are interesting targets on the basis of their spin-down age, energetics, and distance: PSR J1357-6429and PSR J1048-5832. The two pulsars and their pulsar wind nebulae (PWNe) are also detected in X-rays by Chandra and XMM. No deep optical observations of these two pulsars have been reported so far. We used multi-band optical images (V,R,I) taken with the VLT and available in the European Southern Observatory (ESO) archive to search for, or put tight constraints to, their optical emission. We re-assessed the positions of the two pulsars from the analyses of all the available Chandra observations and the comparison with the published radio coordinates. For PSR J1357-6429, this yielded a tentative proper motion mu=0.17±0.055 "/yr (70±15 deg position angle). We did not detect candidate counterparts to PSR J1357-6429 and PSR J1048-5832 down to V~27 and ~27.6, respectively, although for the former we found a possible evidence for a faint, unresolved object at the Chandra position. Our limits imply an efficiency in converting spin-down power into optical luminosity <7x10^{-7} and <6x10^{-6}, respectively, possibly close to that of the Vela pulsar.

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