NuSTAR and XMM-Newton observations of the Arches cluster in 2015: fading hard X-ray emission from the molecular cloud



: Krivonos R, Clavel M, Hong J, Mori K, Ponti G, Poutanen J, Rahoui F, Tomsick J, Tsygankov S

Publisher: OXFORD UNIV PRESS

: 2017

: Monthly Notices of the Royal Astronomical Society

: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

: MON NOT R ASTRON SOC

: 468

: 3

: 2822

: 2835

: 14

: 0035-8711

: 1365-2966

DOI: https://doi.org/10.1093/mnras/stx585

: https://academic.oup.com/mnras/article-lookup/doi/10.1093/mnras/stx585

: https://research.utu.fi/converis/portal/detail/Publication/23346022


We present results of long Nuclear Spectroscopic Telescope Array (NuSTAR; 200 ks) and XMM-Newton (100 ks) observations of the Arches stellar cluster, a source of bright thermal (kT similar to 2 keV) X-rays with prominent Fe XXV K alpha 6.7 keV line emission and a nearby molecular cloud, characterized by an extended non-thermal hard X-ray continuum and fluorescent Fe K alpha 6.4 keV line of a neutral or low-ionization state material around the cluster. Our analysis demonstrates that the non-thermal emission of the Arches cloud underwent a dramatic change, with its homogeneous morphology, traced by fluorescent Fe K alpha line emission, vanishing after 2012, revealing three bright clumps. The declining trend of the cloud emission, if linearly fitted, is consistent with half-life decay time of similar to 8 yr. Such strong variations have been observed in several other molecular clouds in the Galactic Centre, including the giant molecular cloud Sgr B2, and point towards a similar propagation of illuminating fronts, presumably induced by the past flaring activity of Sgr A(star). We also detect a significant drop of the equivalent width of the fluorescent Fe Ka line, which could mean either that the new clumps have a different position along the line of sight or that the contribution of cosmic ray has become more dominant.

Last updated on 2024-26-11 at 10:49