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Title: Unveiling the Nature of the Unidentified Gamma-ray Sources IV: The Swift Catalog of Potential X-ray Counterparts

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1092770
Report Number(s):
SLAC-PUB-15741
DOE Contract Number:
AC02-76SF00515
Resource Type:
Journal Article
Resource Relation:
Journal Name: Submitted to Astrophysical Journal
Country of Publication:
United States
Language:
English
Subject:
ASTRO

Citation Formats

Paggi, A., /Smithsonian Astrophys. Observ., Massaro, F., /SLAC /KIPAC, Menlo Park, D'Abrusco, R., Smith, H.A., /Smithsonian Astrophys. Observ., Masetti, N., /IASF, Bologna, Giroletti, M., /INAF-IRA, Bologna, Tosti, G., /Perugia U., Funk, S., and /SLAC /KIPAC, Menlo Park. Unveiling the Nature of the Unidentified Gamma-ray Sources IV: The Swift Catalog of Potential X-ray Counterparts. United States: N. p., 2013. Web.
Paggi, A., /Smithsonian Astrophys. Observ., Massaro, F., /SLAC /KIPAC, Menlo Park, D'Abrusco, R., Smith, H.A., /Smithsonian Astrophys. Observ., Masetti, N., /IASF, Bologna, Giroletti, M., /INAF-IRA, Bologna, Tosti, G., /Perugia U., Funk, S., & /SLAC /KIPAC, Menlo Park. Unveiling the Nature of the Unidentified Gamma-ray Sources IV: The Swift Catalog of Potential X-ray Counterparts. United States.
Paggi, A., /Smithsonian Astrophys. Observ., Massaro, F., /SLAC /KIPAC, Menlo Park, D'Abrusco, R., Smith, H.A., /Smithsonian Astrophys. Observ., Masetti, N., /IASF, Bologna, Giroletti, M., /INAF-IRA, Bologna, Tosti, G., /Perugia U., Funk, S., and /SLAC /KIPAC, Menlo Park. Thu . "Unveiling the Nature of the Unidentified Gamma-ray Sources IV: The Swift Catalog of Potential X-ray Counterparts". United States. doi:. https://www.osti.gov/servlets/purl/1092770.
@article{osti_1092770,
title = {Unveiling the Nature of the Unidentified Gamma-ray Sources IV: The Swift Catalog of Potential X-ray Counterparts},
author = {Paggi, A. and /Smithsonian Astrophys. Observ. and Massaro, F. and /SLAC /KIPAC, Menlo Park and D'Abrusco, R. and Smith, H.A. and /Smithsonian Astrophys. Observ. and Masetti, N. and /IASF, Bologna and Giroletti, M. and /INAF-IRA, Bologna and Tosti, G. and /Perugia U. and Funk, S. and /SLAC /KIPAC, Menlo Park},
abstractNote = {},
doi = {},
journal = {Submitted to Astrophysical Journal},
number = ,
volume = ,
place = {United States},
year = {Thu Sep 12 00:00:00 EDT 2013},
month = {Thu Sep 12 00:00:00 EDT 2013}
}
  • A significant fraction (∼30%) of the high-energy γ-ray sources listed in the second Fermi Large Area Telescope (LAT) catalog are still of unknown origin, having not yet been associated with counterparts at lower energies. To investigate the nature of these enigmatic sources, we present an extensive search of X-ray sources lying in the positional uncertainty region of a selected sample of these unidentified gamma-ray sources (UGSs) that makes use of all available observations performed by the Swift X-ray Telescope before 2013 March 31, available for 205 UGSs. To detect the fainter sources, we merged all the observations covering the Fermimore » LAT positional uncertainty region at a 95% level of confidence of each UGS. This yields a catalog of 357 X-ray sources, finding candidate X-ray counterparts for ∼70% of the selected sample. In particular, 25% of the UGSs feature a single X-ray source within their positional uncertainty region, while 45% have multiple X-ray sources. For each X-ray source, we also looked in the corresponding Swift UVOT merged images for optical and ultraviolet counterparts, also performing source photometry. We found ultraviolet-optical correspondences for ∼70% of the X-ray sources. We searched several major radio, infrared, optical, and ultraviolet surveys for possible counterparts within the positional error of the sources in the X-ray catalog to obtain additional information on their nature. Applying the kernel density estimation technique to infrared colors of Wide-Field Infrared Survey Explorer counterparts of our X-ray sources we select six γ-ray blazar candidates. In addition, comparing our results with previous analyses, we select 11 additional γ-ray blazar candidates.« less
  • About one-third of the {gamma}-ray sources listed in the second Fermi Large Area Telescope catalog (2FGL) have no firmly established counterpart at lower energies and so are classified as unidentified gamma-ray sources (UGSs). Here, we propose a new approach to find candidate counterparts for the UGSs based on the 325 MHz radio survey performed with the Westerbork Synthesis Radio Telescope in the northern hemisphere. First, we investigate the low-frequency radio properties of blazars, the largest known population of {gamma}-ray sources; then we search for sources with similar radio properties combining the information derived from the Westerbork Northern Sky Survey (WENSS)more » with those of the NRAO Very Large Array Sky Survey. We present a list of candidate counterparts for 32 UGSs with at least one counterpart in the WENSS. We also performed an extensive research in the literature to look for infrared and optical counterparts of the {gamma}-ray blazar candidates selected using the low-frequency radio observations to confirm their nature. On the basis of our multifrequency research, we identify 23 new {gamma}-ray blazar candidates out of the 32 UGSs investigated. Comparison with previous results on the UGSs is also presented. Finally, we speculate on the advantages of using low-frequency radio observations to associate UGSs and to search for {gamma}-ray pulsar candidates.« less