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Chandra Observations of NuSTAR Serendipitous Sources near the Galactic Plane

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posted on 2019-08-20, 12:17 authored by JA Tomsick, GB Lansbury, F Rahoui, J Aird, DM Alexander, M Clavel, A Cuturilo, FM Fornasini, J Hong, L Klindt, D Stern
The Nuclear Spectroscopic Telescope Array (NuSTAR) serendipitous survey has already uncovered a large number of active galactic nuclei (AGNs), providing new information about the composition of the cosmic X-ray background. For AGNs off the Galactic plane, it has been possible to use existing X-ray archival data to improve source localizations, identify optical counterparts, and classify the AGNs with optical spectroscopy. However, near the Galactic plane, better X-ray positions are necessary to achieve optical or near-IR identifications due to the higher levels of source crowding. Thus, we have used observations with the Chandra X-ray Observatory to obtain the best possible X-ray positions. With eight observations, we have obtained coverage for 19 NuSTAR serendips within 12° of the plane. One or two Chandra sources are detected within the error circle of 15 of the serendips, and we report on these sources and search for optical counterparts. For one source (NuSTAR J202421+3350.9), we obtained a new optical spectrum and detected the presence of hydrogen emission lines. The source is Galactic, and we argue that it is likely a cataclysmic variable. For the other sources, the Chandra positions will enable future classifications in order to place limits on faint Galactic populations, including high-mass X-ray binaries and magnetars.


This work made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). Data from Chandra were also used, and the work on serendipitous NuSTAR sources is partially funded by Chandra grants GO5-16154X and GO6-17135X. This work has made use of data from the European Space Agency (ESA) mission Gaia, processed by the Gaia Data Processing and Analysis Consortium (DPAC). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This research had made use of the SIMBAD database and the VizieR catalog access tool, CDS, Strasbourg, France as well as the VISTA and WISE databases and publicly available images from PanSTARRS, SDSS, and IPHAS.



The Astrophysical Journal, 2018, 869:171 (16pp)

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