Blue Large-Amplitude Pulsators and Other Short-Period Variable Stars in OGLE-IV Fields of the Outer Galactic Bulge
J. Borowicz1, P. Pietrukowicz1, J. Skowron1, I. Soszyński1, A. Udalski1, M.K. Szymański1, K. Ulaczyk2, R. Poleski1, S. Kozłowski1, P. Mróz1, D.M. Skowron1, K. Rybicki1,3, P. Iwanek1, M. Wrona1, M. Gromadzki1 and M.J. Mróz1
1 Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
2 Department of Physics, University of Warwick, Coventry CV4 7AL, UK
3 Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel
Received: April 1, 2024
ABSTRACT
In this work, we search the OGLE-IV outer Galactic bulge fields
for short-period variable objects. The investigation focuses on
unexplored timescales roughly below one hour in an area containing about
700 million stellar sources down to I≈20 mag. We concentrate
mainly on Blue Large-Amplitude Pulsators (BLAPs), which represent a
recently discovered enigmatic class of short-period hot subluminous
stars. We find 33 BLAPs in the period range from 7.5 min to
66.5 min. Thirty-one of them are new discoveries, which increases the
number of known stars of this class to over one hundred. Additional
eighteen objects with pulsation-like light curve shapes and periods
ranging from 17.3 min to 53.7 min are presented. Very likely, these are
δSct/SX Phe-type stars, but some of them could be pulsating hot
subdwarfs or BLAPs. We also report on the detection of five eclipsing
binary systems with orbital periods between 61.2 min and 121.9 min and
three mysterious variable objects with I-band amplitudes larger
than 0.9 mag. A spectroscopic follow-up would help in the final
classification of the variables.
Key words:
Stars: oscillations - Stars: variables: general - binaries: eclipsing
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