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 |
|---|---|
| Journal | Astrophysical Journal |
| Volume | 631 |
| Issue number | 1 II |
| DOIs | |
| Publication status | Published - 2005 Sep 20 |
| Externally published | Yes |
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- Space and Planetary Science
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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 journal › Article
}
TY - JOUR
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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U2 - 10.1086/491698
DO - 10.1086/491698
M3 - Article
VL - 631
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1 II
ER -