2025ApJ...994L..45F

Query : 2025ApJ...994L..45F

2025ApJ...994L..45F - Astrophys. J., 994, L45 (2025/December-1)

Optimizing Kilonova Searches: A Case Study of the Type IIb SN 2025ulz in the Localization Volume of the Low-significance Gravitational Wave Event S250818k.

FRANZ N., SUBRAYAN B., KILPATRICK C.D., HOSSEINZADEH G., SAND D.J., ALEXANDER K.D., FONG W.-F., CHRISTY C.T., PEARSON J., LASKAR T., HSU B., RASTINEJAD J., LUNDQUIST M.J., BERGER E., BOSTROEM K.A., BOM C.R., DARC P., GURWELL M., HOSTLER SCHIMPF S., KEATING G.K., NOEL P., RANSOME C., RAO R., SANTANA-SILVA L., SANTOS A.S., SHRESTHA M., ANCHE R., ANDREWS J.E., BORTHAKUR S., BUTLER N.R., COPPEJANS D.L., DALY P.N., DANIEL K.J., DUFFELL P.C., EFTEKHARI T., FIELDS C.E., GAGLIANO A.T., GOLAY W.W., GRICHENER A., HAMDEN E.T., HIRAMATSU D., KUMAR H., MANIKANTAN V., MARGUTTI R., PASCHALIDIS V., PATERSON K., REICHART D.E., RENZO M., SALMAS K., SCHROEDER G., SMITH N., SPEKKENS K., STRADER J., TRILLING D.E., VIEIRA N., WEINER B. and WILLIAMS P.K.G.

Abstract (from CDS):

Kilonovae, the ultraviolet/optical/infrared counterparts to binary neutron star mergers, are an exceptionally rare class of transients. Optical follow-up campaigns are plagued by contaminating transients, which may mimic kilonovae but do not receive sufficient observations to measure the full photometric evolution. In this work, we present an analysis of the multiwavelength dataset of supernova (SN) 2025ulz, a proposed kilonova candidate following the low-significance detection of gravitational waves originating from the potential binary neutron star merger S250818k. Despite an early rapid decline in brightness, our multiwavelength observations of SN 2025ulz reveal that it is a type IIb SN. As part of this analysis, we demonstrate the capabilities of a novel quantitative scoring algorithm to determine the likelihood that a transient candidate is a kilonova, based primarily on its three-dimensional location and light-curve evolution. We also apply our scoring algorithm to other transient candidates in the localization volume of S250818k and find that, at all times after the discovery of SN 2025ulz, there are ≥4 candidates with a score comparable to SN 2025ulz, indicating that the kilonova search may have benefited from the additional follow-up of other candidates. During future kilonova searches, this type of scoring algorithm will be useful to rule out contaminating transients in real time, optimizing the use of valuable telescope resources.

Journal keyword(s): Core-collapse supernovae - Supernovae - Gravitational wave astronomy - Gravitational waves - Gravitational wave sources - Time domain astronomy

Status at CDS : Large table(s) will be appraised for possible ingestion in VizieR.

Simbad objects: 16

Full paper

View the references in ADS

Number of rows : 16

N	Identifier	Otype	ICRS (J2000) RA	ICRS (J2000) DEC	Mag B	Mag V	Mag R	Mag I	Sp type	#ref 1850 - 2026	#notes
1	SN 2016gkg	SN*	01 34 14.46	-29 26 25.0					SNII	126	0
2	SN 2011fu	SN*	02 08 21.40	+41 29 12.3					SNII	74	1
3	SN 2024abfo	SN*	03 57 25.622	-46 11 07.67					SNII	8	0
4	SN 2017jgh	SN*	09 02 56.736	+12 03 04.27					SNIIb	15	0
5	SN 1993J	SN*	09 55 24.77476	+69 01 13.7026	10.8	12.0			SNIIb	1507	1
6	SN 2022hnt	SN*	11 36 59.754	+55 09 50.25					SNIIb	6	0
7	SN 2013df	SN*	12 26 29.33	+31 13 38.3					SNIIb	142	1
8	SN 2008ax	SN*	12 30 40.80	+41 38 16.1	23.6	23.5	14.1	22.6	SNIIb	295	1
9	GrW 170817	GWE	13 09 48.0850	-23 22 53.343					~	2683	0
10	SN 2011dh	SN*	13 30 05.10555	+47 10 10.9227					SNIIb	445	1
11	SN 2020bio	SN*	13 55 37.687	+40 28 39.15					SNIIb	12	0
12	SDSS J155154.16+305409.3	G	15 51 54.16496	+30 54 09.4270					~	2	0
13	SN 2025ulz	SN*	15 51 54.201	+30 54 08.67					SNIIb	6	0
14	SN 2025uso	SN*	16 16 57.433	+35 03 20.81					SNIIb	3	0
15	SN 2024uwq	SN*	20 24 36.770	-43 40 10.13					SNIIb	6	0
16	SN 2011ei	SN*	20 34 22.62	-31 58 23.6					SNIIb	51	1

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