DISCOVERY OF THE 18.7 SECOND ACCRETING X-RAY PULSAR GRO J1948+ 32 DEEPTO CI-IAKRABARTY, 1 TowsIAN K011, LARs BILDSTEN, 2 AND THOMAS A. PRINCE

Abstract:

We have detected an 18.7 s accreting X-ray pulsar in the Cygnus region, using the BATSE large-area detectors on the Compton Gamma Ray Observatory. GRO J1948+ 32 has been localized to within 10 degz using a method we developed for positioning weak pulsed sources with BATSE. During the 33 day outburst, the phase-averaged 20-75 keV pulsed flux rose from 25 mCrab to 50 mCrab over 10 days and then decayed below our detection _threshold over nearly 25 days. A photon spectral index of y= 2.65 i 0.15 (assuming photon flux density dN/dE oc E 7’) was measured during a bright interval. The observed modulation of the neutron star’s pulse frequency is suggestive of orbital variation over less than one orbit cycle. Assuming a constant spin frequency derivative over the outburst, we can place the following individual 95% confidence limits on each of the pulsar parameters: orbital period 35 ‘< Pm,< 70 …

Año de publicación:

1995

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