Swift-XRT follow-up analysis of unidentified hard X-ray sources: Searching for soft X-ray counterparts of unidentified hard X-ray sources
| Authors | |
|---|---|
| Year of publication | 2024 |
| Type | Article in Periodical |
| Magazine / Source | Astronomy and Astrophysics |
| MU Faculty or unit | |
| Citation | |
| web | https://doi.org/10.1051/0004-6361/202348401 |
| Doi | http://dx.doi.org/10.1051/0004-6361/202348401 |
| Keywords | methods: data analysis; catalogs; X-rays: general |
| Description | Context. It has been established that the sources contributing to the cosmic X-ray background (CXB) emission are mainly nearby active galactic nuclei (AGNs), in particular those that are obscured. Thus, it is important to fully identify the hard X-ray sky source population to accurately characterize the individual contribution of different AGNs to the overall CXB emission. Aims. We present a follow-up analysis of all 218 sources marked as unidentified in our previous revision of the third release of the Palermo Swift-BAT hard X-ray catalog (3PBC) based on our multifrequency classification scheme. These 218 sources were classified as unidentified in our previous analyses because they lacked an assigned low-energy counterpart. Methods. We searched for soft X-ray counterparts of these 218 3PBC sources in archival Swift-XRT observations obtained between January 1, 2005, and August 1, 2018. In particular, we found 1213 archival Swift-XRT observations for 192 of the 218 unidentified sources. Results. We find 93 possible Swift-XRT counterparts within the Swift-BAT positional uncertainty regions. They correspond to 73 3PBC sources, 60 of which have only a single Swift-XRT detection; the rest have multiple detections. We present all the detected possible counterparts of the as-of-yet-unidentified hard X-ray sources to the community as a catalog for future spectroscopic follow-up targets, together with a short catalog of our classification of the ten sources for which there were available spectra. |
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