Browsing by Author "Corbel, Stéphane"

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Investigating the Mini and Giant Radio Flare Episodes of Cygnus X-3
(2020-12-29) Egron, Elise; Pellizzoni, Alberto; Righini, Simona; Giroletti, Marcello; Koljonen, Karri; Pottschmidt, Katja; Trushkin, Sergei; Lobina, Jessica; Pilia, Maura; Wilms, Joern; Corbel, Stéphane; Grinberg, Victoria; Loru, Sara; Trois, Alessio; Rodriguez, Jérome; Lähteenmäki, A.; Tornikoski, M.; Enestam, Sissi; Järvelä, E.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The microquasar Cygnus X-3 underwent a giant radio flare in 2017 April, reaching a maximum flux of ∼16.5 Jy at 8.5 GHz. We present results from a long monitoring campaign carried out with Medicina at 8.5, 18.6, and 24.1 GHz, parallel to the Metsähovi radio telescope at 37 GHz, from 2017 April 4 to 11. We observe a spectral steepening from α = 0.2 to 0.5 (with S ν ∝ ν α) within 6 hr of the epoch of the flare's peak maximum, and rapid changes in the spectral slope in the following days during brief enhanced emission episodes while the general trend of the radio flux density indicated the decay of the giant flare. We further study the radio orbital modulation of Cyg X-3 emission associated with the 2017 giant flare and with six mini-flares observed in 1983, 1985, 1994, 1995, 2002, and 2016. The enhanced emission episodes observed during the decline of the giant flare at 8.5 GHz coincide with the orbital phase φ ∼ 0.5 (orbital inferior conjunction). On the other hand, the light curves of the mini-flares observed at 15-22 GHz peak at φ ∼, except for the 2016 light curve, which is shifted 0.5 w.r.t. the other ones. We attribute the apparent phase shift to the variable location of the emitting region along the bent jet. This might be explained by the different accretion states of the flaring episodes (the 2016 mini-flare occurred in the hypersoft X-ray state).
A Multiwavelength Study of GRS 1716-249 in Outburst: Constraints on Its System Parameters
(2022-06-01) Saikia, Payaswini; Russell, David M.; Baglio, M. C.; Bramich, D. M.; Casella, Piergiorgio; Trigo, Maria Diaz; Gandhi, Poshak; Jiang, Jiachen; Maccarone, Thomas; Soria, Roberto; Al Noori, Hind; Al Yazeedi, Aisha; Alabarta, Kevin; Belloni, Tomaso; Bel, Marion Cadolle; Ceccobello, Chiara; Corbel, Stéphane; Fender, Rob; Gallo, Elena; Homan, Jeroen; Koljonen, Karri; Lewis, Fraser; Markoff, Sera B.; Miller-Jones, James C.A.; Rodriguez, Jerome; Russell, Thomas D.; Shahbaz, Tariq; Sivakoff, Gregory R.; Testa, Vincenzo; Tetarenko, Alexandra J.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We present a detailed study of the evolution of the Galactic black hole transient GRS 1716-249 during its 2016-2017 outburst at optical (Las Cumbres Observatory), mid-infrared (Very Large Telescope), near-infrared (Rapid Eye Mount telescope), and ultraviolet (the Neil Gehrels Swift Observatory Ultraviolet/Optical Telescope) wavelengths, along with archival radio and X-ray data. We show that the optical/near-infrared and UV emission of the source mainly originates from a multi-temperature accretion disk, while the mid-infrared and radio emission are dominated by synchrotron emission from a compact jet. The optical/UV flux density is correlated with the X-ray emission when the source is in the hard state, consistent with an X-ray irradiated accretion disk with an additional contribution from the viscous disk during the outburst fade. We find evidence for a weak, but highly variable jet component at mid-infrared wavelengths. We also report the long-term optical light curve of the source and find that the quiescent i′ -band magnitude is 21.39 ± 0.15 mag. Furthermore, we discuss how previous estimates of the system parameters of the source are based on various incorrect assumptions, and so are likely to be inaccurate. By comparing our GRS 1716-249 data set to those of other outbursting black hole X-ray binaries, we find that while GRS 1716-249 shows similar X-ray behavior, it is noticeably optically fainter, if the literature distance of 2.4 kpc is adopted. Using several lines of reasoning, we argue that the source distance is further than previously assumed in the literature, likely within 4-17 kpc, with a most likely range of ∼4-8 kpc.