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Title: The First Simultaneous X-Ray/Radio Detection of the First Be/BH System MWC 656
Author: Ribó Gomis, Marc
Munar i Adrover, Pere
Paredes i Poy, Josep Maria
Marcote Martin, Benito
Iwasawa, Kazushi
Moldón Vara, Francisco Javier
Casares, J.
Migliari, Simone
Paredes Fortuny, Xavier
Keywords: Forats negres (Astronomia)
Estels binaris de raigs X
Black holes (Astronomy)
X-ray binaries
Issue Date: 1-Feb-2017
Publisher: Institute of Physics (IOP)
Abstract: MWC 656 is the first known Be/black hole (BH) binary system. Be/BH binaries are important in the context of binary system evolution and sources of detectable gravitational waves because they are possible precursors of coalescing neutron star/BH binaries. X-ray observations conducted in 2013 revealed that MWC 656 is a quiescent high-mass X-ray binary (HMXB), opening the possibility to explore X-ray/radio correlations and the accretion/ejection coupling down to low luminosities for BH HMXBs. Here we report on a deep joint Chandra/VLA observation of MWC 656 (and contemporaneous optical data) conducted in 2015 July that has allowed us to unambiguously identify the X-ray counterpart of the source. The X-ray spectrum can be fitted with a power law with Γ ~ 2, providing a flux of sime4 × 10−15 erg cm−2 s−1 in the 0.5-8 keV energy range and a luminosity of LX sime 3 × 1030 erg s−1 at a 2.6 kpc distance. For a 5 M⊙ BH this translates into sime5 × 10−9 LEdd. These results imply that MWC 656 is about 7 times fainter in X-rays than it was two years before and reaches the faintest X-ray luminosities ever detected in stellar-mass BHs. The radio data provide a detection with a peak flux density of 3.5 ± 1.1 μJy beam−1. The obtained X-ray/radio luminosities for this quiescent BH HMXB are fully compatible with those of the X-ray/radio correlations derived from quiescent BH low-mass X-ray binaries. These results show that the accretion/ejection coupling in stellar-mass BHs is independent of the nature of the donor star.
Note: Reproducció del document publicat a:
It is part of: Astrophysical Journal Letters, 2017, vol. 835, num. 2
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ISSN: 2041-8205
Appears in Collections:Articles publicats en revistes (Institut de Ciències del Cosmos (ICCUB))
Articles publicats en revistes (Física Quàntica i Astrofísica)

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