TEMPORAL PROPERTIES OF GX 301-2 OVER A YEAR-LONG OBSERVATION WITH SuperAGILE

Journal Article · Sun Jan 10 04:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/708/2/1663· OSTI ID:21392400

Evangelista, Y; Feroci, M; Costa, E; Del Monte, E; Donnarumma, I; Lapshov, I; Lazzarotto, F; Pacciani, L; Soffitta, P; Argan, A; D'Ammando, F ^[1]; Rapisarda, M ^[2]; Barbiellini, G ^[3]; Boffelli, F; Cattaneo, P W ^[4]; Bulgarelli, A; Di Cocco, G; Fuschino, F ^[5]; Caraveo, P; Chen, A ^[6]

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1. INAF IASF Roma, Via Fosso del Cavaliere 100, I-00133 Roma (Italy)
2. ENEA, Via E. Fermi 45, I-00044 Frascati (Rm) (Italy)
3. INFN Trieste, Padriciano 99, I-34012 Trieste (Italy)
4. INFN Pavia, Via Bassi, 6 I-27100 Pavia (Italy)
5. INAF IASF Bologna, Via Gobetti 101, I-40129 Bologna (Italy)
6. INAF IASF Milano, Via E. Bassini 15, I-20133 Milano (Italy)

We present the long-term monitoring of the high-mass X-ray binary GX 301-2 performed with the SuperAGILE (SA) instrument on-board the Astro-rivelatore Gamma ad Immagini LEggero (AGILE) mission. The source was monitored in the 20-60 keV energy band during the first year of the mission from 2007 July 17 to 2008 August 31, covering about one whole orbital period and three more pre-periastron (PP) passages for a total net observation time of about 3.7 Ms. The SA data set represents one of the most continuous and complete monitoring at hard X-ray energies of the 41.5 days long binary period available to date. The source behavior was characterized at all orbital phases in terms of hard X-ray flux, spectral hardness, spin-period history, pulsed fraction, and pulse shape profile. We also complemented the SA observations with the soft X-ray data of the Rossi X-Ray Timing Explorer/All-Sky Monitor. Our analysis shows a clear orbital modulation of the spectral hardness, with peaks in correspondence with the PP flare and near phase 0.25. The hardness peaks, we found, could be related with the wind-plus-stream accretion model proposed in order to explain the orbital light-curve modulation of GX 301-2. Timing analysis of the pulsar spin period shows that the secular trend of the approx680 s pulse period is consistent with the previous observations, although there is evidence of a slight decrease in the spin-down rate. The analysis of the hard X-ray-pulsed emission also showed a variable pulse shape profile as a function of the orbital phase, with substructures detected near the passage at the periastron, and a clear modulation of the pulsed fraction, which appears in turn strongly anticorrelated with the source intensity.

• OSTI ID: 21392400
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 708; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BARYONS
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
ELECTRONIC CIRCUITS
ELEMENTARY PARTICLES
FERMIONS
HADRONS
HARD X RADIATION
IONIZING RADIATIONS
MODULATION
NEUTRONS
NUCLEONS
PULSARS
PULSE CIRCUITS
PULSE SHAPERS
PULSES
RADIATIONS
SIGNAL CONDITIONERS
SOFT X RADIATION
STARS
X RADIATION