A search for X-rays from the long-duration microlensing event MACHO-96-BLG-5

Yoshitomo Maeda, Aya Kubota, Yoshihito Kobayashi, Akiharu Itoh, Hideyo Kunieda, Yuichi Terashima, Yohko Tsuboi

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Abstract

MACHO-96-BLG-5 was a microlensing event of exceptionally long duration, lasting ∼800 days, which is suggestive of a stellar-mass black hole for the lens. With a 9.8 ks Chandra ACIS-S observation, we detected no X-ray events associated with the position of MACHO-96-BLG-5. An upper limit is estimated as 4.6 counts at the 99% confidence level. By assuming an absorbed power law spectrum with a photon index Γ = 1.4-2.0, the upper limit on the 0.3-8 keV luminosity is estimated as (7-8) × 1029 ergs s-1 at an assumed distance of 1 kpc. The corresponding Eddington ratio is (8-9) × 10-10 for a black hole of 6 M. The luminosity is lower than observed for quiescent black hole binaries in our Galaxy and is consistent with a scenario, previously suggested by Bennett et al., in which the lens for MACHO-96-BLG-5 is an isolated stellar-mass black hole, although other possibilities are not ruled out.

Original languageEnglish
JournalAstrophysical Journal
Volume631
Issue number1 II
DOIs
Publication statusPublished - 2005 Sep 20
Externally publishedYes

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massive compact halo objects
stellar mass
erg
power law
x rays
luminosity
lenses
confidence
galaxies
photons
index

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Maeda, Y., Kubota, A., Kobayashi, Y., Itoh, A., Kunieda, H., Terashima, Y., & Tsuboi, Y. (2005). A search for X-rays from the long-duration microlensing event MACHO-96-BLG-5. Astrophysical Journal, 631(1 II). https://doi.org/10.1086/491698

A search for X-rays from the long-duration microlensing event MACHO-96-BLG-5. / Maeda, Yoshitomo; Kubota, Aya; Kobayashi, Yoshihito; Itoh, Akiharu; Kunieda, Hideyo; Terashima, Yuichi; Tsuboi, Yohko.

In: Astrophysical Journal, Vol. 631, No. 1 II, 20.09.2005.

Research output: Contribution to journalArticle

Maeda, Y, Kubota, A, Kobayashi, Y, Itoh, A, Kunieda, H, Terashima, Y & Tsuboi, Y 2005, 'A search for X-rays from the long-duration microlensing event MACHO-96-BLG-5', Astrophysical Journal, vol. 631, no. 1 II. https://doi.org/10.1086/491698
Maeda, Yoshitomo ; Kubota, Aya ; Kobayashi, Yoshihito ; Itoh, Akiharu ; Kunieda, Hideyo ; Terashima, Yuichi ; Tsuboi, Yohko. / A search for X-rays from the long-duration microlensing event MACHO-96-BLG-5. In: Astrophysical Journal. 2005 ; Vol. 631, No. 1 II.
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