ASASSN-25bv: Two Recent, Deep Dimming Events
ATel #17196; B. JoHantgen, D. M. Rowan, K. Z. Stanek, C. S. Kochanek, J. Callahan, S. A. Petz (OSU), B. J. Shappee (Univ. of Hawaii)
on 20 May 2025; 14:46 UT
Credential Certification: Krzysztof Stanek (stanek.32@osu.edu)
Subjects: Optical, Binary, Star, Variables
Using data from the All-Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014, Kochanek et al. 2017, Hart et al. 2023 ) we found a star with two deep dimming events. ASASSN-25bv (RA = 08h58m15.60s, DEC = -43d09m55.26s, d ~ 1.0 kpc, G = 11.8, BP = 12.2, RP =11.2, DR3 source_id =5332048241235589504) is a main sequence star in Gaia DR3 (Gaia Collaboration et al., 2023, A&A, 674, A1) with extinction-corrected absolute magnitude M_G = -0.62 mag and GBP -GRP = -0.18 mag. This is consistent with a main sequence B-star. This star has a RUWE = 5.44, and the Gaia RV amplitude = 24.85 km/s, suggesting it is a binary system. This star was first observed by ASAS-SN on UT 2016-02-02 and it has roughly ~ 10,000 data points at this time.
ASASSN-25bv has a mean g-magnitude of ~12.3 (V ~ 12.0). The first dimming event began around UT 2025-02-03 and lasted for about 27 days. It faded to a depth of g ~ 13.2 on UT 2025-02-14. The egress was observed by TESS in Sector 89, (Ricker et al., 2015, Journal of Astronomical Telescopes, Instruments, and Systems, Volume 1, id. 014003) and has a depth of ~0.6 magnitudes in the TESS T-band. The second event began around UT 2025-04-06 and is currently ongoing. This dip is asymmetric and features a plateau at g-magnitude of ~12.9 that spans roughly from UT 2025-04-10 to UT 2025-04-16. The dip then fell to a g-magnitude of ~13.2 around UT 2025-04-21, where it has remained. The shape of the ASAS-SN light curve is similar to other eclipsing Be-binaries like TT Nor (Rowan et al., 2023, MNRAS, Volume 520, Issue 2)
We thank Las Cumbres Observatory and its staff for their continued support of ASAS-SN. ASAS-SN operations are funded in part by the Gordon and Betty Moore Foundation through grants GBMF5490 and GBMF10501 to the Ohio State University, and Alfred P. Sloan Foundation grant G-2021-14192.
