Lens parameters for Gaia18cbf - a long gravitational microlensing event in the Galactic plane

June 2022 • 2022A&A...662A..59K

Authors • Kruszyńska, K. • Wyrzykowski, Ł. • Rybicki, K. A. • Maskoliūnas, M. • Bachelet, E. • Rattenbury, N. • Mróz, P. • Zieliński, P. • Howil, K. • Kaczmarek, Z. • Hodgkin, S. T. • Ihanec, N. • Gezer, I. • Gromadzki, M. • Mikołajczyk, P. • Stankevičiūtė, A. • Čepas, V. • Pakštienė, E. • Šiškauskaitė, K. • Zdanavičius, J. • Bozza, V. • Dominik, M. • Figuera Jaimes, R. • Fukui, A. • Hundertmark, M. • Narita, N. • Street, R. • Tsapras, Y. • Bronikowski, M. • Jabłońska, M. • Jabłonowska, A. • Ziółkowska, O.

Abstract • Context. The timescale of a microlensing event scales as a square root of a lens mass. Therefore, long-lasting events are important candidates for massive lenses, including black holes.
Aims: Here, we present the analysis of the Gaia18cbf microlensing event reported by the Gaia Science Alerts system. It exhibited a long timescale and features that are common for the annual microlensing parallax effect. We deduce the parameters of the lens based on the derived best fitting model.
Methods: We used photometric data collected by the Gaia satellite as well as the follow-up data gathered by the ground-based observatories. We investigated the range of microlensing models and used them to derive the most probable mass and distance to the lens using a Galactic model as a prior. Using a known mass-brightness relation, we determined how likely it is that the lens is a main-sequence (MS) star.
Results: This event is one of the longest ever detected, with the Einstein timescale of t_E = 491.41_−84.94^+128.31 days for the best solution and t_E = 453.74_−105.74^+178.69 days for the second best. Assuming Galaxy priors, this translates to the most probable lens masses of M_L = 2.65_−1.48^+5.09 M_⊙ and M_L = 1.71_−1.06^+3.78 M_⊙, respectively. The limits on the blended light suggest that this event was most likely not caused by a MS star, but rather by a dark remnant of stellar evolution.

Full Table A.1 is only and Table A.2 is also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/662/A59

Links

• PREPRINT http://arxiv.org/abs/2111.08337
• POSTSCRIPT https://www.aanda.org/10.1051/0004-6361/202142602/postscript
• ELECTR https://doi.org/10.1051%2F0004-6361%2F202142602
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2022A%26A...662A..59K
• PDF https://www.aanda.org/10.1051/0004-6361/202142602/pdf
• DATA http://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/662/A59