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Post Info TOPIC: PSR J1906+0746
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RE: PSR J1906+0746
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Title: The Binary Companion of Young, Relativistic Pulsar J1906+0746
Author: Joeri van Leeuwen (1,2), Laura Kasian (3), Ingrid H. Stairs (3), D. R. Lorimer, F. Camilo, S. Chatterjee, I. Cognard, G. Desvignes, P. C. C. Freire, G. H. Janssen, M. Kramer, A. G. Lyne, D. J. Nice, S. M. Ransom, B. W. Stappers, J. M. Weisberg ((1) ASTRON, (2) U. Amsterdam, (3) UBC)

PSR J1906+0746 is a young pulsar in the relativistic binary with the second-shortest known orbital period, of 3.98 hours. We here present a timing study based on five years of observations, conducted with the 5 largest radio telescopes in the world, aimed at determining the companion nature. Through the measurement of three post-Keplerian orbital parameters we find the pulsar mass to be 1.291(11) M_sol, and the companion mass 1.322(11) M_sol respectively. These masses fit well in the observed collection of double neutron stars, but are also compatible with other white dwarfs around young pulsars such as J1906+0746. Neither radio pulsations nor dispersion-inducing outflows that could have further established the companion nature were detected. We derive an HI-absorption distance, which indicates that an optical confirmation of a white dwarf companion is very challenging. The pulsar is fading fast due to geodetic precession, limiting future timing improvements. We conclude that young pulsar J1906+0746 is likely part of a double neutron star, or is otherwise orbited by an older white dwarf, in an exotic system formed through two stages of mass transfer.

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Title: Chandra observation of the relativistic binary J1906+0746
Authors: O. Kargaltsev, G. G. Pavlov

PSR J1906+0746 is a 112-kyr-old radio pulsar in a tight relativistic binary with a compact high-mass companion, at the distance of about 5 kpc. We observed this unique system with the Chandra ACIS detector for 31.6 ks. Surprisingly, not a single photon was detected within the 3" radius from the J1906+0746 radio position. For a plausible range of hydrogen column densities, n_H=(0.5-1) x10^{22} cm^{-2}, the nondetection corresponds to the 90% upper limit of (3-5) x10^{30} erg s^{-1} on the unabsorbed 0.5-8 keV luminosity for the power-law model with Gamma=1.0-2.0, and ~10^{32} erg s^{-1} on the bolometric luminosity of the thermal emission from the NS surface. The inferred limits are the lowest known for pulsars with spin-down properties similar to those of PSR J1906+0746. We have also tentatively detected a puzzling extended structure which looks like a tilted ring with a radius of 1.6' centred on the pulsar. The measured 0.5-8 keV flux of the feature, 3.1 x10^{-14} erg cm^{-2} s^{-1}, implies an unabsorbed luminosity of 1.2 x10^{32} erg s^{-1} (4.5 x10^{-4} of the pulsar's spin-down power). Although all conventional interpretations of the ring appear to be problematic, the pulsar-wind nebula with an unusually underluminous pulsar remains the most viable interpretation.

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