In this scenario the authors showed that the resulting photon spectrum has a spectral break at most at ~1 MeV. However, Aharonian & Vardanian (1985) proposed that this emission has a non-thermal origin related to the development of electromagnetic cascades initiated by particles accelerated to relativistic energies in regions close to the BH, that is, in the accretion disk. The canonical explanation for this hard X-ray emission is inverse Compton scattering of disk photons by hot ( k T e ~ 100 keV) thermal electrons in the inner region of the accretion flow, which is usually referred to as the “corona” ( Shapiro et al. In the HS, instead, the blackbody component is much less luminous, with a 0.1 keV temperature, and most of the energy is emitted in a hard tail component characterized by a ~1.5 photon index and an exponential cutoff at a few hundred keV.
The SS is dominated by the thermal emission peaking at ~1 keV and a steep power-law at higher energies with a photon index Γ ~ 2–3. 2013) intermediate states (IS), and the complete sequence of states is well-represented in a hardness intensity diagram (HID) by the q-shaped track trajectory ( Fender et al. The two main states are joined by short-lived (typically of a few days Grinberg et al. The dominance of one or the other component defines the two main spectral states that the system can display: the soft state (SS) and the hard state (HS). The spectrum of the BH X-ray binaries can be roughly described as the sum of two components: a blackbody-like emission from the geometrically thin and optically thick accretion disk, and a power-law tail, whose origin is still under debate. 2011), it is one of the brightest X-ray sources, and therefore is considered an optimal candidate for the study of the accretion and ejection processes onto a BH system. Located at a distance of 1.86 kpc ( Reid et al. Cygnus X-1 is the only Galactic high-mass XRB for which the compact object has been identified to be a BH. However, this value has been questioned by Ziółkowski (2014), who suggested a range of 25–35 M ⊙. The companion star is the early-type O9.7Iab supergiant HDE 226868 ( Walborn 1973), with a mass of ( 19.2 ± 1.9) M ⊙ ( Orosz et al. The compact object has been identified as a black hole (BH) with ( 14.8 ± 1.0) M ⊙ ( Orosz et al. Key words: accretion, accretion disks / acceleration of particles / gamma rays: general / radiation mechanisms: non-thermal / stars: individual: Cygnus X-1 / X-rays: binariesĬygnus X-1 is an X-ray binary (XRB), that is, a system in which the compact object accretes matter from the companion star. The evidence of flux orbital variability indicates the anisotropic inverse-Compton on stellar photons as the mechanism at work, thus constraining the emission region to a distance 10 11– 10 13 cm from the black hole. We detected GeV emission from Cygnus X-1 and probed that the emission is most likely associated with the relativistic jets. There is a hint of orbital flux variability, with high-energy emission mostly coming around the superior conjunction.Ĭonclusions. The energy spectrum, extending up to ~20 GeV without any sign of spectral break, is well fit by a power-law function with a photon index of 2.3 ± 0.2. The signal is correlated with the hard X-ray flux: the source is observed at high energies only during the hard X-ray spectral state, when the source is known to display persistent, relativistic radio-emitting jets. We report the detection of a signal at ~8 σ statistical significance that is spatially coincident with Cygnus X-1 and has a luminosity of 5.5 × 10 33 erg s -1, above 60 MeV.
#Songster cygnus x1 software
We analyzed 7.5 yr of data by Fermi-LAT with the latest Pass 8 software version. We probe the high-energy ( >60 MeV) emission from the black hole X-ray binary system, Cygnus X-1, and investigate its origin. Galindo 5ġ Max-Planck-Institut fur Kernphysik, PO Box 103980, 69029 Heidelberg, GermanyĮ-mail: Institut de Fisica d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), Campus UAB, 08193 Bellaterra (Barcelona), Spainģ Institute of Space Sciences (CSIC-IEEC), 08193 Barcelona, SpainĤ Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Irelandĥ Universitat de Barcelona, ICC, IEEC-UB, 08028 Barcelona, SpainĪims. Astronomical objects: linking to databases.Including author names using non-Roman alphabets.Suggested resources for more tips on language editing in the sciences Punctuation and style concerns regarding equations, figures, tables, and footnotes
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