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Discovery of the 198 s X-ray Pulsar GRO J2058+42

Colleen A. Wilson·Mark H. Finger·B. Alan Harmon·Deepto Chakrabarty·Tod Strohmayer
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Abstract

GRO J2058+42, a transient 198 second x-ray pulsar, was discovered by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory (CGRO), during a "giant" outburst in 1995 September-October. The total flux peaked at about 300 mCrab (20-50 keV) as measured by Earth occultation. The pulse period decreased from 198 s to 196 s during the 46-day outburst. The pulse shape evolved over the course of the outburst and exhibited energy dependent variations. BATSE observed five additional weak outbursts from GRO J2058+42, each with two week duration and peak pulsed flux of about 15 mCrab (20-50 keV), that were spaced by about 110 days. An observation of the 1996 November outburst by the Rossi X-ray Timing Explorer (RXTE) Proportional Counter Array (PCA) localized the source to within a 4\arcmin radius error circle (90 % confidence) centered on R.A. = 20h 59m.0, Decl. = 41 deg 43 arcmin (J2000). Additional shorter outbursts with peak pulsed fluxes of about 8 mCrab were detected by BATSE halfway between the first four 15 mCrab outbursts. The RXTE All-Sky Monitor detected all 8 weak outbursts with approximately equal durations and intensities. GRO J2058+42 is most likely a Be/X-ray binary that appears to outburst at periastron and apastron. No optical counterpart has been identified to date and no x-ray source was present in the error circle in archival ROSAT observations.

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Colleen A. Wilson, Mark H. Finger, B. Alan Harmon, Deepto Chakrabarty, Tod Strohmayer. 1998-02-25. Discovery of the 198 s X-ray Pulsar GRO J2058+42. https://doi.org/10.1086/305677

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