Searches for pulsar-like candidates from unidentified objects in the Third Catalog of Hard Fermi-LAT Sources with machine learning techniques

C. Y. Hui, Jongsu Lee, K. L. Li, Sangin Kim, Kwangmin Oh, Shengda Luo, Alex P. Leung, A. K.H. Kong, J. Takata, K. S. Cheng

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2 Citations (Scopus)

Abstract

We report the results of searching pulsar-like candidates from the unidentified objects in the Third Catalog of Hard Fermi-LAT Sources (3FHL). Using a machine-learning-based classification scheme with a nominal accuracy of ~98 per cent, we have selected 27 pulsarlike objects from 200 unidentified 3FHL sources for an identification campaign. Using archival data, X-ray sources are found within the γ -ray error ellipses of 10 3FHL pulsar-like candidates. Within the error circles of the much better constrained X-ray positions, we have also searched for the optical/infrared counterparts and examined their spectral energy distributions. Among our shortlisted candidates, the most secure identification is the association of 3FHL J1823.3- 1339 and its X-ray counterpart with the globular cluster Mercer 5. The γ -rays from the source can be contributed by a population of millisecond pulsars residing in the cluster. This makes Mercer 5 as one of the slowly growing hard γ -ray population of globular clusters with emission >10 GeV. Very recently, another candidate picked by our classification scheme, 3FHL J1405.1-6118, has been identified as a new γ -ray binary with an orbital period of 13.7 d. Our X-ray analysis with a short Chandra observation has found a possible periodic signal candidate of ~1.4 h and a putative extended X-ray tail of ~20 arcsec long. Spectral energy distribution of its optical/infrared counterpart conforms with a blackbody of Tbb ~ 40 000 K and Rbb ~ 12 R⊙ at a distance of 7.7 kpc. This is consistent with its identification as an early O star as found by infrared spectroscopy.

Original languageEnglish
Pages (from-to)1093-1109
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Volume495
Issue number1
DOIs
Publication statusPublished - 2020

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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