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SUMMARY:Gaia and microlensing - an opportunity for Black Holes search - Kr
 is Rybicki (Warsaw)
DTSTART:20180328T121500Z
DTEND:20180328T124500Z
UID:TALK102607@talks.cam.ac.uk
CONTACT:Dr Nick Bate
DESCRIPTION:It is expected that there are about 500 milions stellar black 
 holes floating in our Galaxy. Not\nmore than 30 are known\, and only in bi
 nary systems. Even though there are some\ncandidates for single ones\, non
 e of them was confirmed yet. Partially it comes from the fact\nthat they a
 re very hard to detect\, but detecting multiple such objects would vastly 
 increase\nour understanding of the latest stages of stellar evolution and 
 the Galaxy structure. The\nperfect tool for measuring the mass of unseen o
 bjects is microlensing\, yet the very special\ncircumstances are needed to
  measure the mass of the lens\, which is the one and only\nparameter which
  allow us to judge weather the object is a single black hole or not.\n\nGa
 ia satellite will give an opportunity to look at microlensing events from 
 the different\nangle. With its exquisite astrometry\, it may be possible t
 o measure not only the\nmagnification of the source\, but also its apparen
 t displacement during the event\, which\nprovides additional information a
 bout the lens properties.\n\nWe consider a possibility of simultaneous obs
 ervation of the microlensing event by the Gaia\nmission from space and the
  OGLE project from the ground. Basing on the example of\nOGLE-ULENS-PAR-02
 \, which is likely a black hole\, we predict that for bright events with\n
 clear parallax signal and Gaia astrometry available for them\, it will be 
 possible to determine\nthe mass of the 10 M⊙ lens with accuracy between 
 few to 15%. We estimate that the rate of\nastrometric microlensing events 
 caused by the stellar-origin black holes is ≈ 4 × 10−7 yr−1\,\nwhic
 h implies\, that after 5 years of Gaia operation and ≈ 5 × 10^6 bright 
 sources in Gaia\, it\nwill be possible to identify few such events in its 
 final catalogues. The talk is based on our\nrecent paper: Rybicki et al. 2
 018 (2018MNRAS.476.2013R).
LOCATION:Sackler Lecture Theatre\, IoA
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