NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Spectral and Timing Nature of the Symbiotic X-Ray Binary 4U 1954+319: The Slowest Rotating Neutron Star in AN X-Ray Binary SystemThe symbiotic X-ray binary (SyXB) 4U 1954+319 is a rare system hosting a peculiar neutron star (NS) and an M-type optical companion. Its approx. 5.4 hr NS spin period is the longest among all known accretion-powered pulsars and exhibited large (is approx. 7%) fluctuations over 8 yr. A spin trend transition was detected with Swift/BAT around an X-ray brightening in 2012. The source was in quiescent and bright states before and after this outburst based on 60 ks Suzaku observations in 2011 and 2012. The observed continuum is well described by a Comptonized model with the addition of a narrow 6.4 keV Fe-K alpha line during the outburst. Spectral similarities to slowly rotating pulsars in high-mass X-ray binaries, its high pulsed fraction (approx. 60%-80%), and the location in the Corbet diagram favor high B-field (approx. greater than 10(exp12) G) over a weak field as in low-mass X-ray binaries. The observed low X-ray luminosity (10(exp33)-10(exp35) erg s(exp−1)), probable wide orbit, and a slow stellar wind of this SyXB make quasi-spherical accretion in the subsonic settling regime a plausible model. Assuming a approx. 10(exp13) G NS, this scheme can explain the approx. 5.4 hr equilibrium rotation without employing the magnetar-like field (approx. 10(exp16) G) required in the disk accretion case. The timescales of multiple irregular flares (approx. 50 s) can also be attributed to the free-fall time from the Alfv´en shell for a approx. 10(exp13) G field. A physical interpretation of SyXBs beyond the canonical binary classifications is discussed.
Document ID
20150010753
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Enoto, Teruaki
(High Energy AstroPhysics Association Ehime, Japan)
Sasano, Makoto
(Tokyo Univ. Japan)
Yamada, Shin'Ya
(High Energy AstroPhysics Association Ehime, Japan)
Tamagawa, Toru
(High Energy AstroPhysics Association Ehime, Japan)
Makishima, Kazuo
(Tokyo Univ. Japan)
Pottschmidt, Katja
(Maryland Univ. Baltimore, MD, United States)
Marcu, Diana
(Maryland Univ. Baltimore, MD, United States)
Corbet, Robin H. D.
(Maryland Univ. Baltimore, MD, United States)
Fuerst, Felix
(California Inst. of Tech. Pasadena, CA, United States)
Wilms, Jorn
(Erlangen-Nuernberg Univ. Bamberg, Germany)
Date Acquired
June 15, 2015
Publication Date
April 24, 2014
Publication Information
Publication: The Astrophysical Journal
Publisher: The American Astronomical Society
Volume: 786
Issue: 2
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN23866
Funding Number(s)
CONTRACT_GRANT: NNG06EO90A
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
accretion disks aEuro" binaries: symbiotic aEuro" magnetic fields aEuro" stars:
accretion
No Preview Available