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

doi:10.1086/491698

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

Research output: Contribution to journal › Article › peer-review

8 Citations (Scopus)

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 language	English
Pages (from-to)	L65-L68
Journal	Astrophysical Journal
Volume	631
Issue number	1 II
DOIs	https://doi.org/10.1086/491698
Publication status	Published - 2005 Sep 20
Externally published	Yes

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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

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.",

author = "Yoshitomo Maeda and Aya Kubota and Yoshihito Kobayashi and Akiharu Itoh and Hideyo Kunieda and Yuichi Terashima and Yohko Tsuboi",

year = "2005",

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T1 - A search for X-rays from the long-duration microlensing event MACHO-96-BLG-5

AU - Maeda, Yoshitomo

AU - Kubota, Aya

AU - Kobayashi, Yoshihito

AU - Itoh, Akiharu

AU - Kunieda, Hideyo

AU - Terashima, Yuichi

AU - Tsuboi, Yohko

PY - 2005/9/20

Y1 - 2005/9/20

N2 - 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.

AB - 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.

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

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