Thursday, July 25, 2013

1307.6331 (N. Rea et al.)

A strongly magnetized pulsar within grasp of the Milky Way's supermassive black hole    [PDF]

N. Rea, P. Esposito, J. A. Pons, R. Turolla, D. F. Torres, G. L. Israel, A. Possenti, M. Burgay, D. Vigano', R. Perna, L. Stella, G. Ponti, F. Baganoff, D. Haggard, A. Papitto, A. Camero-Arranz, S. Zane, A. Minter, S. Mereghetti, A. Tiengo, R. Schoedel, M. Feroci, R. Mignani, D. Gotz
The center of our Galaxy hosts a supermassive black hole, Sagittarius (Sgr) A*. Young, massive stars within 0.5 pc of SgrA* are evidence of an episode of intense star formation near the black hole a few Myr ago. Some of them might have left behind a young neutron star traveling deep into SgrA*'s gravitational potential. However, no neutron star closer than ~200 parsec from the supermassive black hole has been detected so far. On 2013 April 25, a short X-ray burst was observed from the direction of the Galactic center. Thanks to the superb spatial resolution of the Chandra X-ray Observatory, we could pinpoint the associated, persistent pulsating X-ray source at an angular distance of 2.4+/-0.3 arcsec from SgrA*. Using a series of Chandra and Swift observations we have refined the spin period and its derivative (P=3.7635443(3) and \dot{P}=7.6(2)x10^{-12} s/s), confirmed by radio observations performed with the Green Bank (GBT) and Parkes single dish antennas, that also measured a Dispersion Measure of DM=1750 +/-50 pc cm^{-3}, the highest ever detected for a radio pulsar. We have found that this X-ray source is a young magnetar at only ~0.07-2 pc away from SgrA*, and that with high probability (~90%), it is in a bound orbit around the black hole. The passage of radiation fronts produced by the past activity from the magnetar through the molecular clouds surrounding the Galactic center region might also partially explain the light echoes observed in the Fe fluorescence features.
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