Optical Microlensing by Primordial Black Holes with IACTs

Discussion timeslot (ZOOM-Meeting): 20. July 2021 - 12:00
ZOOM-Meeting URL: https://desy.zoom.us/j/96969970711
ZOOM-Meeting ID: 96969970711
ZOOM-Meeting Passcode: ICRC2021
Corresponding Session: https://icrc2021-venue.desy.de/channel/40-Dark-Matter-Indirect-Detection-and-Cosmological-Substructures-DM/81
Live-Stream URL: https://icrc2021-venue.desy.de/livestream/Discussion-07/8

Abstract:
'Primordial black holes (PBHs), hypothesized to be the result of density fluctuations during the early universe, are candidates for dark matter. When microlensing background stars, they cause a transient apparent enhancement of the flux. Measuring these signals with optical telescopes is a powerful method to constrain the PBH abundance in the range of $10^{-11},M_{odot}$ to $10^{1},M_{odot}$. Especially for galactic stars, the finiteness of the sources needs to be taken into account. In previous studies of galactic fields, this reduces the average event duration proportional to the black hole mass $langle t_erangle propto m_{PBH}$ for masses $ smaller 10^{-9},M_{odot}$ leading to an expected duration of $mathcal{O}(mathrm{s})$ for $ m_{PBH}approx 10^{-11},M_{odot}$. A fast sampling speed of the instrument could enable the detection of low mass PBHs. Current limits are set with sampling speeds of 2 minutes to 24 hours. Ground-based Imaging Atmospheric Cherenkov telescopes (IACTs) are optimized to detect the $sim$ns long optical Cherenkov signals induced by atmospheric air showers. As shown recently, their large mirror area allows the detection of fast ($ll 1,$s) optical transient signals such as asteroid occultations. We investigate whether optical observations by IACTs can contribute to extending microlensing limits to the unconstrained mass range $M_{PBH} smaller 10^{-11}M_odot$. Therefore we discuss the limiting factors to perform these searches for each telescope type. We calculate the number of expected detectable microlensing events in the relevant mass range for the current and next-generation IACTs considering realistic source parameters.'

Authors: Konstantin Johannes Pfrang | Tarek Hassan | Elisa Pueschel
Indico-ID: 466
Proceeding URL: https://pos.sissa.it/395/495