Unraveling the nature of unidentified high galactic latitude FERMI/LAT gamma-ray sources with Suzaku

K. Maeda, J. Kataoka, T. Nakamori, L. Stawarz, R. Makiya, T. Totani, C. C. Cheung, D. Donato, N. Gehrels, P. Saz Parkinson, Y. Kanai, N. Kawai, Y. Tanaka, R. Sato, T. Takahashi, Y. Takahashi

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Abstract

Here we report on the results of deep X-ray follow-up observations of four unidentified γ-ray sources detected by the Fermi/LAT instrument at high Galactic latitudes using the X-ray Imaging Spectrometers on board the Suzaku satellite. All of the studied objects were detected with high significance during the first three months of Fermi/LAT operation and subsequently better localized in the first Fermi/LAT catalog (1FGL). For some of them, possible associations with pulsars and active galaxies have subsequently been discussed, and our observations provide an important contribution to this debate. In particular, a bright X-ray point source has been found within the 95% confidence error circle of 1FGLJ1231.1-1410. The X-ray spectrum of the discovered Suzaku counterpart of 1FGLJ1231.1-1410 is well fitted by a blackbody with an additional power-law component. This supports the recently claimed identification of this source with a millisecond pulsar PSRJ1231-1411. For the remaining three Fermi objects, on the other hand, the X-ray observations performed are less conclusive. In the case of 1FGLJ1311.7-3429, two bright X-ray point sources were found within the LAT 95% error circle. Even though the X-ray spectral and variability properties for these sources were robustly assessed, their physical nature and relationship with the γ-ray source remain uncertain. Similarly, we found several weak X-ray sources in the field of 1FGLJ1333.2+5056, one coinciding with the high-redshift blazar CLASSJ1333+5057. We argue that the available data are consistent with the physical association between these two objects, although the large positional uncertainty of the γ-ray source hinders a robust identification. Finally, we have detected an X-ray point source in the vicinity of 1FGLJ2017.3+0603. This Fermi object was recently suggested to be associated with a newly discovered millisecond radio pulsar PSRJ2017+0603, because of the spatial coincidence and the detection of the γ-ray pulsations in the light curve of 1FGLJ2017.3+0603. Interestingly, we have detected the X-ray counterpart of the high-redshift blazar CLASSJ2017+0603, located within the error circle of the γ-ray source, while we were only able to determine an X-ray flux upper limit at the pulsar position. All in all, our studies indicate that while a significant fraction of unidentified high Galactic latitude γ-ray sources is related to the pulsar and blazar phenomena, associations with other classes of astrophysical objects are still valid options.

Original languageEnglish
Article number103
JournalAstrophysical Journal
Volume729
Issue number2
DOIs
Publication statusPublished - 2011 Mar 10

Keywords

  • X-rays: general
  • galaxies: active
  • gamma rays: general
  • pulsars: general
  • radiation mechanisms: non-thermal

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Maeda, K., Kataoka, J., Nakamori, T., Stawarz, L., Makiya, R., Totani, T., Cheung, C. C., Donato, D., Gehrels, N., Saz Parkinson, P., Kanai, Y., Kawai, N., Tanaka, Y., Sato, R., Takahashi, T., & Takahashi, Y. (2011). Unraveling the nature of unidentified high galactic latitude FERMI/LAT gamma-ray sources with Suzaku. Astrophysical Journal, 729(2), [103]. https://doi.org/10.1088/0004-637X/729/2/103