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Discovery of the 18.7-Second Accreting Pulsar GRO J1948+32

Chakrabarty, Deepto and Koh, Towsian and Bildsten, Lars and Prince, Thomas A. and Finger, Mark H. and Wilson, Robert B. and Pendleton, Geoffrey N. and Rubin, Bradley C. (1995) Discovery of the 18.7-Second Accreting Pulsar GRO J1948+32. Astrophysical Journal, 446 . pp. 826-831. ISSN 0004-637X. doi:10.1086/175839.

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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 11948 + 32 has been localized to within 10 deg^2 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 γ = 2.65 ± 0.15 (assuming photon flux density d N/ dE α E^(-γ) 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 35d < P_(orb) < 70d; orbital radius 75 It-sec < α_x sin i < 300 It-sec, eccentricity e < 0.25, spin frequency derivative 5 x 10^(-13) Hz s^(-1) < v < 2.5 x 10^(-11) Hz s^(-1), X-ray mass function 0.5 M_⊙ <f_x( M ) < 5 M_⊙ . As the stellar type of the mass-providing companion is still not known for this source, we briefly speculate on the nature of mass transfer in this system.

Item Type:Article
Related URLs:
URLURL TypeDescription
Chakrabarty, Deepto0000-0001-8804-8946
Prince, Thomas A.0000-0002-8850-3627
Additional Information:© 1995. The American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1994 August 23; accepted 1994 December 27. We thank referee, Ocker C. de Jager, for a careful reading of the manuscript and I. Neill Reed for arranging a Palomar Schmidt plate observation of the region during the outburst. John Chiu developed many of the BATSE spectral fitting tools used at Caltech. This work was funded in part by NASA grant NAG 5-1458. D. C. was supported by a NASA GSRP fellowship, grant NGT-51184. L. B. was supported by Caltech's Lee A. DuBridge Fellowship, funded by the Weingart Foundation; and by a NASA Compton Fellowship, grant NAG 5-2666.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
NASANAG 5-1458
Lee A. DuBridge FellowshipUNSPECIFIED
Weingart FoundationUNSPECIFIED
NASA Compton FellowshipNAG 5-2666
Subject Keywords:pulsars: individual: (GRO 11948 + 32) -pulsars: individual : (GRO 12014 + 34) ­ X-rays: stars
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory1995-08
Record Number:CaltechAUTHORS:20140612-112707881
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46241
Deposited By: Deborah Miles
Deposited On:12 Jun 2014 22:27
Last Modified:10 Nov 2021 17:23

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