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

Research output: Contribution to journalArticlepeer-review

48 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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