### Abstract

We discuss the potential of the gravitational microlensing method as a unique tool to detect unambiguous signals caused by intermediate-mass black holes in globular clusters. We select clusters near the line of sight to the Galactic bulge and the Small Magellanic Cloud, estimate the density of background stars for each of them, and carry out simulations in order to estimate the probabilities of detecting the astrometric signatures caused by black hole lensing. We find that for several clusters, the probability of detecting such an event is significant with available archival data from the Hubble Space Telescope. Specifically, we find that M 22 is the cluster with the best chances of yielding an intermediate-mass black hole (IMBH) detection via astrometric microlensing. If M 22 hosts an IMBH of mass 10^{5} M_{⊙}, then the probability that at least one star will yield a detectable signal over an observational baseline of 20 years is ~86 per cent, while the probability of a null result is around 14 per cent. For an IMBH of mass 10^{6} M_{⊙}, the detection probability rises to >99 per cent. Future observing facilities will also extend the available time baseline, improving the chance of detections for the clusters we consider.

Original language | English |
---|---|

Pages (from-to) | 2025-2035 |

Number of pages | 11 |

Journal | Monthly Notices of the Royal Astronomical Society |

Volume | 460 |

Issue number | 2 |

DOIs | |

Publication status | Published - 2016 |

Externally published | Yes |

### Fingerprint

### Keywords

- Globular clusters: general
- Gravitational lensing: micro
- Stars: black holes

### ASJC Scopus subject areas

- Astronomy and Astrophysics
- Space and Planetary Science

### Cite this

*Monthly Notices of the Royal Astronomical Society*,

*460*(2), 2025-2035. https://doi.org/10.1093/mnras/stw1137

**Searching for intermediate-mass black holes in globular clusters with gravitational microlensing.** / Kains, N.; Bramich, D. M.; Sahu, K. C.; Calamida, A.

Research output: Contribution to journal › Article

*Monthly Notices of the Royal Astronomical Society*, vol. 460, no. 2, pp. 2025-2035. https://doi.org/10.1093/mnras/stw1137

}

TY - JOUR

T1 - Searching for intermediate-mass black holes in globular clusters with gravitational microlensing

AU - Kains, N.

AU - Bramich, D. M.

AU - Sahu, K. C.

AU - Calamida, A.

PY - 2016

Y1 - 2016

N2 - We discuss the potential of the gravitational microlensing method as a unique tool to detect unambiguous signals caused by intermediate-mass black holes in globular clusters. We select clusters near the line of sight to the Galactic bulge and the Small Magellanic Cloud, estimate the density of background stars for each of them, and carry out simulations in order to estimate the probabilities of detecting the astrometric signatures caused by black hole lensing. We find that for several clusters, the probability of detecting such an event is significant with available archival data from the Hubble Space Telescope. Specifically, we find that M 22 is the cluster with the best chances of yielding an intermediate-mass black hole (IMBH) detection via astrometric microlensing. If M 22 hosts an IMBH of mass 105 M⊙, then the probability that at least one star will yield a detectable signal over an observational baseline of 20 years is ~86 per cent, while the probability of a null result is around 14 per cent. For an IMBH of mass 106 M⊙, the detection probability rises to >99 per cent. Future observing facilities will also extend the available time baseline, improving the chance of detections for the clusters we consider.

AB - We discuss the potential of the gravitational microlensing method as a unique tool to detect unambiguous signals caused by intermediate-mass black holes in globular clusters. We select clusters near the line of sight to the Galactic bulge and the Small Magellanic Cloud, estimate the density of background stars for each of them, and carry out simulations in order to estimate the probabilities of detecting the astrometric signatures caused by black hole lensing. We find that for several clusters, the probability of detecting such an event is significant with available archival data from the Hubble Space Telescope. Specifically, we find that M 22 is the cluster with the best chances of yielding an intermediate-mass black hole (IMBH) detection via astrometric microlensing. If M 22 hosts an IMBH of mass 105 M⊙, then the probability that at least one star will yield a detectable signal over an observational baseline of 20 years is ~86 per cent, while the probability of a null result is around 14 per cent. For an IMBH of mass 106 M⊙, the detection probability rises to >99 per cent. Future observing facilities will also extend the available time baseline, improving the chance of detections for the clusters we consider.

KW - Globular clusters: general

KW - Gravitational lensing: micro

KW - Stars: black holes

UR - http://www.scopus.com/inward/record.url?scp=84983041961&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84983041961&partnerID=8YFLogxK

U2 - 10.1093/mnras/stw1137

DO - 10.1093/mnras/stw1137

M3 - Article

AN - SCOPUS:84983041961

VL - 460

SP - 2025

EP - 2035

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 2

ER -