TITLE: GCN CIRCULAR NUMBER: 39785 SUBJECT: LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn DATE: 25/03/19 17:15:20 GMT FROM: Hsin-Yu Chen at The University of Texas at Austin hsinyu@austin.utexas.edu

Hsin-Yu Chen (UT Austin), Greg Zeimann (UT McDonald Observatory), J. Craig Wheeler (UT Austin), and Jozsef Vinko (Konkoly Observatory) report on behalf of the LIGHETR Collaboration:

We conducted targeted follow-up observations of AT 2025azn (Hosseinzadeh et al., GCN 39191), a potential electromagnetic counterpart to the LIGO/Virgo/KAGRA gravitational-wave event S250206dm (LVK Collaboration, GCN 39175), using the Low Resolution Spectrograph (LRS2) on the Hobby-Eberly Telescope (HET) [1].

The observations were carried out 9 to 14 days after the gravitational-wave event and consisted of two 1800s exposures with LRS2-R (covering 650–842 nm and 818–1050 nm) and two 1800s exposures with LRS2-B (covering 370–470 nm and 460–700 nm) [2].

Our preliminary analysis did not reveal any emission beyond that of the host galaxy. Further analysis is ongoing.

[1] Bustamante Rosell et al, ApJ (2023) [2] Chonis et al, Proceedings of the SPIE (2014)

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