Open AccessX‐ray and γ‐ray spectra and variability of the black hole candidate GX 339–4
Author(s) -
Wardziński Grzegorz,
Zdziarski Andrzej A.,
Gierliński Marek,
Eric Grove J.,
Jahoda Keith,
Neil Johnson W.
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.05914.x
Subject(s) - physics , astrophysics , bremsstrahlung , luminosity , spectral line , x ray binary , astronomy , black hole (networking) , accretion (finance) , electron , neutron star , computer network , routing protocol , routing (electronic design automation) , quantum mechanics , galaxy , computer science , link state routing protocol
ABSTRACT We analyse five observations of the X‐ray binary GX 339–4 by the soft γ‐ray OSSE detector on board CGRO simultaneous with either Ginga or RXTE observations. The source was bright during four of them, with the luminosity of L ∼ 10 37 erg s −1 and the spectrum typical for hard states of accreting black holes, and it was in an off state during the fifth one, with L ∼ 10 35 erg s −1 . Our broad‐band spectral fits show the mean electron energy of electrons in the Comptonizing plasma decreasing with increasing luminosity within the hard (bright) state. For the observation with the best statistics at soft γ‐rays, ∼1/4 of energy in the Comptonizing plasma is probably carried by non‐thermal electrons. Then, considering the efficiency of Comptonized hybrid synchrotron emission allows us to obtain an upper limit on the strength of the magnetic field in the X‐ray source. Furthermore, this synchrotron emission is capable of producing the optical spectrum observed in an optically‐high state of GX 339–4. In the off state, the hard X‐ray spectrum is consistent with being dominated by bremsstrahlung. The unusually strong Fe Kα line observed by the RXTE /PCA during that state is found not to be intrinsic to the source but to originate mostly in the Galactic diffuse emission.