TITLE: GCN CIRCULAR NUMBER: 35808 SUBJECT: Transient EPW20240219aa: Kp-band imaging observations with NIRES DATE: 24/02/26 21:05:11 GMT FROM: Viraj Karambelkar at Indian Inst of Tech,Bombay <karambelkarvraj21197@gmail.com> Viraj Karambelkar (Caltech), Tomas Ahumada (Caltech), Mansi Kasliwal (Caltech) We observed the location of the X-ray flare EPW20240219aa (Zhang et al., ATel #16463; Zhang et al., GCN #35773) in the near-infrared K prime-band (Kp) with the NIRES acquisition camera on the Keck II telescope starting UTC 2024-02-25T05:12:12.45. We obtained four 300 second exposures that covered the locations of the VLA radio sources # 1-6 reported in GCN #35788. The Kp-band observations reached a depth of ~19.5 mag (Vega). We use an archival Ks-band image of the field from the UKIRT Galactic Plane Survey (Lucas et al. 2008) to calibrate the NIRES images. The depth of the UKIRT image is ~19 mag (Vega). We detect sources at the locations of the VLA sources #1, 2, 3 and 6 in the NIRES image. VLA-1 : We detect a source with m_Kp ~ 19 mag (Vega) that is ~0.8 arcsec offset from the VLA position reported in GCN #35788. The source is also marginally visible in the archival UKIRT image (which is shallower than the new NIRES image.) VLA-2 has m_Kp ~ 17 mag (Vega) and appears as an extended source in the NIRES as well as archival UKIRT image. There is no substantial variation between the two epochs. VLA-3 has m_Kp ~ 19 mag (Vega) and is not detected in the archival image (limit ~19 mag). VLA-4 and VLA-5 are not detected in our images. VLA-6 is clearly detected as an extended source in both the NIRES and archival images. As reported in GCN #35803, this source does not show any variations, and is likely a galaxy unrelated to the transient. VLA-7 was not covered by our observations. In addition to these, we do not detect any new sources in the NIRES observations. VLA-3 is the most promising source in terms of association with the X-ray transient. We encourage further follow-up. View this GCN Circular online at https://gcn.nasa.gov/circulars/35808. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...