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Discovery of PSR J1849-0001, a 38.5 ms Pulsar Powering IGR J18490-0000/HESS J1849-000

ATEL # 3057; E. V. Gotthelf, J. P. Halpern (Columbia U.), R. Terrier, F. Mattana (CNRS/APC Université Paris 7)
on 30 Nov 2010; 14:26 UT
Password Certification: Jules Halpern (

Subjects: X-ray, Gamma Ray, Neutron Stars, Pulsars, Supernova Remnants

We have detected highly significant X-ray pulsations in a series of pointings with the Rossi X-ray Timing Explorer Proportional Counter Array at the putative pulsar/PWN IGR J18490-0000 = HESS J1849-000 = XMMU J184901.6-000117 (Terrier et al. 2008, AIPC, 1085, 312). The single-peaked pulse profile has a modulation of 4.5% including background. We identify PSR J1849-0001 with these high-energy counterparts based on the compatibility of its pulsed 2-20 keV flux with the flux of XMMU J184901.6-000117, and the morphological properties of the XMM-Newton source: point-like with faint extended emission. X-ray detections by the Swift XRT (Rodriguez et al. 2008, ApJ, 482, 731) and the Chandra HRC (Ratti et al. 2010, MNRAS, 408, 1866) also indicate a steady source with no optical/IR counterpart.

A preliminary phase-connected ephemeris from 73 ks of RXTE observations spanning 2010 November 25-29 yields barycentric P = 0.03851893151(31) s and P-dot = (1.40+/-0.18)E-14 s/s at epoch MJD 55525.62. Derived pulsar parameters are: spin-down power 9.6E36 erg/s, surface dipole magnetic field strength 7.4E11 G, and characteristic age 44 kyr. The XMM-Newton spectrum of the pulsar obtained on 2006 April 3 is fitted with power-law of photon index Gamma = 1.12+/-0.14, column density NH = (4.0+/-0.6)E22 cm-2, and flux F(2-10 keV) = 4.64E-12 erg/cm2/s. The INTEGRAL/IBIS spectrum is fitted by Gamma = 1.7+/-0.3 and F(20-100 keV) = (20+/-3) E-12 erg/cm2/s. These properties resemble those of the dozen other spin-powered pulsars detected by INTEGRAL (Mattana et al. 2009, AIPC, 1126, 259; Renaud et al. 2010, ApJ, 716, 663). Assuming a location in the Scutum spiral arm tangent region at a d = 7 kpc, the 0.35-10 TeV flux of HESS J1849-000, ~2.2E-12 erg/cm2/s, is 0.13% of the spin-down luminosity of PSR J1849-0001, similar to other middle-aged pulsars. The ratio of the PWN's TeV to keV flux indicates a system that is just transitioning from synchrotron X-ray to inverse Compton gamma-ray domination.

Observations belonging to our RXTE Cycle 14 program to discover and time this pulsar are continuing in 2010 December. These will refine the ephemeris and associated quantities, and will be reported in a paper currently in preparation. We thank the RXTE project for making the time available for this program, and the mission planners for carefully scheduling the observations.

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