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X-ray Follow-ups of XSS J12270-4859: A Low-mass X-ray Binary with Gamma-ray Fermi-LAT AssociationContext. XSS J1227.0-4859 is a peculiar, hard X-ray source recently positionally associated to the Fermi-LAT source 1FGL J1227.9- 4852/2FGL J1227.7-4853. Multi-wavelength observations have added information on this source, indicating a low-luminosity lowmass X-ray binary (LMXB), but its nature is still unclear. Aims. To progress in our understanding, we present new X-ray data from a monitoring campaign performed in 2011 with the XMM-Newton, RXTE, and Swift satellites and combine them with new gamma-ray data from the Fermi and AGILE satellites. We complement the study with simultaneous near-UV photometry from XMM-Newton and with previous UV/optical and near-IR data. Methods. We analysed the temporal characteristics in the X-rays, near-UV, and gamma rays and studied the broad-band spectral energy distribution from radio to gamma rays. Results. The X-ray history of XSS J1227 over 7 yr shows a persistent and rather stable low-luminosity (6 × 1033 d2 1 kpcerg s−1) source, with flares and dips being peculiar and permanent characteristics. The associated Fermi-LAT source 2FGL J1227.7-4853 is also stable over an overlapping period of 4.7 yr. Searches for X-ray fast pulsations down to msec give upper limits to pulse fractional amplitudes of 15−25% that do not rule out a fast spinning pulsar. The combined UV/optical/near-IR spectrum reveals a hot component at approximately 13 kK and a cool one at approximately 4.6 kK. The latter would suggest a late-type K2−K5 companion star, a distance range of 1.4−3.6 kpc, and an orbital period of 7-9 h. A near-UV variability (6 h) also suggests a longer orbital period than previously estimated. Conclusions. The analysis shows that the X-ray and UV/optical/near-IR emissions are more compatible with an accretion-powered compact object than with a rotational powered pulsar. The X-ray to UV bolometric luminosity ratio could be consistent with a binary hosting a neutron star, but the uncertainties in the radio data may also allow an LMXB black hole with a compact jet. In this case, it would be the first associated with a high-energy gamma-ray source.
Document ID
20140002696
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.1051/0004-6361/201220393
Authors
deMartino, D. (Osservatorio Astronomico, Capodimonte Naples, Italy)
Belloni, T. (Osservatorio Astronomico di Brera Merate, Italy)
Falanga, M. (International Space Science Inst. Bern, Switzerland)
Papitto, A. (Consejo Superior de Investigaciones Cientificas Barcelona, Spain)
Motta, S. (Osservatorio Astronomico di Brera Merate, Italy)
Pellizzoni, A. (Osservatorio Astronomico di Cagliari Capoterra, Italy)
Evangelista, Y. (Istituto di Astrofisica e Planetologia Spaziale (INAF-IAPS) Rome, Italy)
Piano, G. (Istituto di Astrofisica e Planetologia Spaziale (INAF-IAPS) Rome, Italy)
Masetti, N. (Istituto di Astrofisica Spaziale e Fisica Cosmica (INAF-IASF) Bologna, Italy)
Mouchet, M. (CEA Saclay, Service d'Astrophysique Gif-sur-Yvette, France)
Mukai, K. (Maryland Univ. Baltimore County Baltimore, MD, United States)
Possenti, A. (Osservatorio Astronomico di Cagliari Capoterra, Italy)
Date Acquired
April 3, 2014
Publication Date
February 1, 2013
Publication Information
Publication: Astronomy and Astrophyics
Volume: 550
Subject Category
Astronomy
Report/Patent Number
GSFC-E-DAA-TN8686
Funding Number(s)
CONTRACT_GRANT: ASI/INAF/-I/009/10/0
CONTRACT_GRANT: NNG06EO9A
CONTRACT_GRANT: iLINK2011-0303
CONTRACT_GRANT: ITN 215212
CONTRACT_GRANT: SGR2009- 811
CONTRACT_GRANT: AYA2012-39303
Distribution Limits
Public
Copyright
Public Use Permitted.

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