HARD X-RAY EMISSION FROM SH 2-104: A NuSTAR SEARCH FOR GAMMA-RAY COUNTERPARTS

• Published in: The Astrophysical journal 2016-07, Vol.826 (1), p.25-25
• Main Authors: Gotthelf, E. V., Mori, K., Aliu, E., Paredes, J. M., Tomsick, J. A., Boggs, S. E., Christensen, F. E., Craig, W. W., Hailey, C. J., Harrison, F. A., Hong, J. S., Rahoui, F., Stern, D., Zhang, W. W.
• Format: Article
• Language: English
• Subjects: Astronomia de raigs X; Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPLEXES; EMISSION; Estels de neutrons; GALAXY CLUSTERS; GAMMA RADIATION; Gamma rays; H II regions; HARD X RADIATION; ISM: individual objects (Sh 2-104, MGRO J2019+37, 3XMM J201744.7+365045, VER J2019+368); NEBULAE; NEUTRON STARS; PULSARS; pulsars: individual (NuSTAR J201744.3+364812); PULSATIONS; Raigs gamma; SPECTRA; stars: neutron; STELLAR WINDS; X ray sources; X rays; X-ray astronomy; XMM (spacecraft)
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/0004-637X/826/1/25

ABSTRACT We present NuSTAR hard X-ray observations of Sh 2-104, a compact H ii region containing several young massive stellar clusters (YMSCs). We have detected distinct hard X-ray sources coincident with localized VERITAS TeV emission recently resolved from the giant gamma-ray complex MGRO J2019+37 in the Cygnus region. Fainter, diffuse X-rays coincident with the eastern YMSC in Sh2-104 likely result from the colliding winds of a component star. Just outside the radio shell of Sh 2-104 lies 3XMM J201744.7+365045 and a nearby nebula, NuSTAR J201744.3+364812, whose properties are most consistent with extragalactic objects. The combined XMM-Newton and NuSTAR spectrum of 3XMM J201744.7+365045 is well-fit to an absorbed power-law model with cm−2 and a photon index . Based on possible long-term flux variation and the lack of detected pulsations (≤43% modulation), this object is likely a background active galactic nucleus rather than a Galactic pulsar. The spectrum of the NuSTAR nebula shows evidence of an emission line at E = 5.6 keV, suggesting an optically obscured galaxy cluster at z = 0.19 0.02 (d = 800 Mpc) and LX = 1.2 × 1044 erg s−1. Follow-up Chandra observations of Sh 2-104 will help identify the nature of the X-ray sources and their relation to MGRO J2019+37. We also show that the putative VERITAS excess south of Sh 2-104, is most likely associated with the newly discovered Fermi pulsar PSR J2017+3625 and not the H ii region.