Discovery of an unidentified Fermi object as a black widow-like millisecond pulsar

A. K.H. Kong*, R. H.H. Huang, K. S. Cheng, J. Takata, Y. Yatsu, C. C. Cheung, D. Donato, L. C.C. Lin, J. Kataoka, Y. Takahashi, K. Maeda, C. Y. Hui, P. H.T. Tam

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

49 Citations (Scopus)


The Fermi γ-ray Space Telescope has revolutionized our knowledge of the γ-ray pulsar population, leading to the discovery of almost 100 γ-ray pulsars and dozens of γ-ray millisecond pulsars (MSPs). Although the outer-gap model predicts different sites of emission for the radio and γ-ray pulsars, until now all of the known γ-ray MSPs have been visible in the radio. Here we report the discovery of a "radio-quiet" γ-ray-emitting MSP candidate by using Fermi, Chandra, Swift, and optical observations. The X-ray and γ-ray properties of the source are consistent with known γ-ray pulsars. We also found a 4.63 hr orbital period in optical and X-ray data. We suggest that the source is a black widow-like MSP with a 0.1 M late-type companion star. Based on the profile of the optical and X-ray light curves, the companion star is believed to be heated by the pulsar while the X-ray emissions originate from pulsar magnetosphere and/or from intrabinary shock. No radio detection of the source has been reported yet, and although no γ-ray/radio pulsation has been found we estimate that the spin period of the MSP is 3-5 ms based on the inferred γ-ray luminosity.

Original languageEnglish
Article numberL3
JournalAstrophysical Journal Letters
Issue number1
Publication statusPublished - 2012 Mar 1


  • X-rays: stars
  • binaries: close
  • gamma rays: stars
  • pulsars: general
  • stars: individual (1FGL J2339.7-0531, SDSS J233938.74-053305.2)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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