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Observations of a large flare in GX 1+4 with the Compton gamma ray observatoryThe pulsating X-ray binary GX 1+4 (4U 1728-24) was observed by Oriented Scintillation Spectrometer Experiment (OSSE) onboard the Compton Gamma Ray Observatory (CGRO) from 9 to 21 September 1993 as a target of oppurtunity after Burst and Transient Source Experiment (BATSE) had detected the onset of a large flare by the greatly increased pulsed flux at the period of approximately 2 min. The total flux in the 40-100 keV range as observed by the OSSE reached its maximum of 83 mCrab on 14/15 September, after which it fell sharply to about 31 mCrab within 2 days. The spectrum is well described by thermal type spectra. The characteristic temperature of the average OSSE spectrum for a thermal Bremsstrahlung model is kT = (35.5 +/- 0.5) keV. A single power law can be ruled out. There is evidence for a hardening of the spectrum with decreasing intensity at the end of the flare. The barycentric pulse period was (120.567 +/- 0.005) s on 5 September. The average spin-down rate as taken from the standard BATSE analysis was dP/dt = 0.0105 s/day, and constant over the time of the flare. A further target of oppurtunity (TOO) observation with the ROSAT Position Sensitive Proportional Counter (PSPC) on 18 September led to the first detection of the source with a reflecting X-ray telescope and to a signifcantly improved position: RA(2000) = 17h 32m 2.1s and DEC(2000) = -24 deg 44 min 44 sec. This position 3.5 sec from V2116 Oph, with a 90% error radius of 8 sec is the most accurate so far obtained with an X-ray instrument, thus confirming the identification with the suspected stellar counterpart.
Document ID
19950044480
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Staubert, R.
(Univ. Tubingen Tubingen, Germany)
Maisack, M.
(Univ. Tubingen Tubingen, Germany)
Kendziorra, E.
(Univ. Tubingen Tubingen, Germany)
Draxler, T.
(Univ. Tubingen Tubingen, Germany)
Finger, M. H.
(NASAMSFC, Huntsville, AL US, United States)
Fishman, G. J.
(NASAMSFC, Huntsville, AL US, United States)
Strickman, M. S.
(Naval Research Laboratory, Washington, DC US, United States)
Starr, C. H.
(Naval Research Laboratory, Washington, DC US, United States)
Date Acquired
August 16, 2013
Publication Date
May 1, 1995
Publication Information
Publication: Advances in Space Research
Volume: 15
Issue: 5
ISSN: 0273-1177
Subject Category
Astronomy
Accession Number
95A76079
Funding Number(s)
CONTRACT_GRANT: DARA-50-OR-9204
Distribution Limits
Public
Copyright
Other

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