Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Kilonova constraints for the LIGO/Virgo/KAGRA neutron star merger candidate S250206dm: GW-MMADS observations

Lei Hu, Tomás Cabrera, Antonella Palmese, James Freeburn, Mattia Bulla, Igor Andreoni, Xander J. Hall, Brendan O'Connor, Ariel Amsellem, Clécio R. Bom, Malte Busmann, Jennifer Fabà, Julius Gassert, Sena Kalabalik, Keerthi Kunnumkai, Daniel Gruen, Luidhy Santana-Silva, André Santos, Tomás Ahumada, Jonathan Carney, Michael W. Coughlin, Xingzhuo Chen, K. E. Saavik Ford, Daniel E. Holz, Mansi M. Kasliwal, Ignacio Magaña Hernandez, Cassidy Mihalenko, Rosalba Perna, Arno Riffeser, Christoph Ries, Lena Schnappinger, Michael Schmidt, Julian Sommer, Sarah Teague, Pablo Vega, Olga Volchansky, Lifan Wang, Yajie Zhang

TL;DR

The paper investigates kilonova constraints for the LIGO/Virgo/KAGRA BHNS candidate S250206dm using the GW-MMADS program, combining wide-field and galaxy-targeted optical/NIR follow-up across DECam, SOAR, Wendelstein, and T80-South. Through image differencing, forced photometry, and rigorous candidate vetting, no kilonova counterpart is identified, enabling competitive limits on KN models relative to GW170817. The study demonstrates that mass-gap BHNS events in O4 can yield meaningful multimessenger constraints and informs strategies for future high-precision localization campaigns and follow-up planning in the era of advanced GW detectors.

Abstract

Gravitational wave (GW) neutron star mergers with an associated electromagnetic counterpart constitute powerful probes of binary evolution, the production sites of heavy elements, general relativity, and the expansion of the universe. Only a handful of candidate GW binary mergers during the fourth LIGO/Virgo/KAGRA observing run (O4) so far are believed to include a neutron star. We present optical-near infrared follow-up observations of the candidate neutron-star black hole GW merger S250206dm. This is the first high-significance mass gap neutron star-black hole candidate observed by multiple GW detectors (thus having a significantly smaller sky localization than one-detector events), offering the first opportunity to effectively follow up a GW event of this kind. Our GW MultiMessenger Astronomy DECam Survey (GW-MMADS) campaign consisted of a wide-field search using the Dark Energy Camera (DECam) and T80-South (T80S), as well as galaxy-targeted observations using the Southern Astrophysical Research (SOAR) imager and the Wendelstein 2.1m 3-channel camera. No viable kilonova counterpart was found in our observations. We use our observation depths to place competitive constraints on kilonova models similar to or brighter than the GW170817 kilonova AT 2017gfo within our observed fields, ruling out 100\% of such models with SOAR galaxy-targeted observations and $\sim43$\% (48\%) with DECam (DECam and T80S).

Kilonova constraints for the LIGO/Virgo/KAGRA neutron star merger candidate S250206dm: GW-MMADS observations

TL;DR

The paper investigates kilonova constraints for the LIGO/Virgo/KAGRA BHNS candidate S250206dm using the GW-MMADS program, combining wide-field and galaxy-targeted optical/NIR follow-up across DECam, SOAR, Wendelstein, and T80-South. Through image differencing, forced photometry, and rigorous candidate vetting, no kilonova counterpart is identified, enabling competitive limits on KN models relative to GW170817. The study demonstrates that mass-gap BHNS events in O4 can yield meaningful multimessenger constraints and informs strategies for future high-precision localization campaigns and follow-up planning in the era of advanced GW detectors.

Abstract

Gravitational wave (GW) neutron star mergers with an associated electromagnetic counterpart constitute powerful probes of binary evolution, the production sites of heavy elements, general relativity, and the expansion of the universe. Only a handful of candidate GW binary mergers during the fourth LIGO/Virgo/KAGRA observing run (O4) so far are believed to include a neutron star. We present optical-near infrared follow-up observations of the candidate neutron-star black hole GW merger S250206dm. This is the first high-significance mass gap neutron star-black hole candidate observed by multiple GW detectors (thus having a significantly smaller sky localization than one-detector events), offering the first opportunity to effectively follow up a GW event of this kind. Our GW MultiMessenger Astronomy DECam Survey (GW-MMADS) campaign consisted of a wide-field search using the Dark Energy Camera (DECam) and T80-South (T80S), as well as galaxy-targeted observations using the Southern Astrophysical Research (SOAR) imager and the Wendelstein 2.1m 3-channel camera. No viable kilonova counterpart was found in our observations. We use our observation depths to place competitive constraints on kilonova models similar to or brighter than the GW170817 kilonova AT 2017gfo within our observed fields, ruling out 100\% of such models with SOAR galaxy-targeted observations and \% (48\%) with DECam (DECam and T80S).

Paper Structure

This paper contains 11 sections, 1 figure.

Table of Contents

  1. Introduction
  2. Observations
  3. Galaxy-targeted Search with SOAR/Goodman
  4. Galaxy-targeted Search with Wendelstein
  5. DECam Search
  6. T80-South search
  7. Candidates
  8. Candidates from SOAR/Goodman
  9. Candidates from Wendelstein
  10. Candidates from DECam
  11. Candidates from T80-South

Figures (1)

  • Figure 1: Localization region of S250206dm overlapped with the footprints of GW-MMADS follow-up observations. The upper and lower inset panels show zoomed-in views of two lobes of the LVK skymap with high probability, located in the Northern and Southern Hemispheres, respectively. For reference, we also overlay in gray the sky tiles in the northern lobe used for ZTF observations of S250206dm (Ahumada et al., in prep.).