TITLE: GCN CIRCULAR NUMBER: 34759 SUBJECT: LIGO/Virgo/KAGRA S230917af: GRAWITA wide-field observations DATE: 23/09/22 14:53:25 GMT FROM: Paolo D'Avanzo at INAF-OAB pda.davanzo@gmail.com

P. D'Avanzo (INAF-OAB), A. Reguitti (INAF-OAB / INAF-OAPd), L. Tomasella (INAF-OAPd), E. Cappellaro (INAF-OAPd), F. Onori (INAF-OAAb), F. De Luise (INAF-OAAb), L. Tartaglia (INAF-OAAb), R. Brivio (INAF-OAB), M. Ferro (INAF-OAB), V. D’Elia (ASI/SSDC), E. Brocato (INAF-OAAb) report on behalf ot the GRAWITA collaboration:

We carried out follow-up observations of the LIGO/Virgo/KAGRA GW trigger S230917af with the Schmidt telescopes sited in the INAF Asiago and Campo Imperatore observatories (Italy).

Observations from Asiago have been carried out starting on 2023-09-19 at 00:44:52 UT (~ 1.61 days after the GW trigger) with the Clear, g and r filters. A second epoch has been carried out starting on 2023-09-19 at 21:14:12 UT (~ 2.47 days after the GW trigger) with the r filter. These observations covered ~ 86% of the localisation region of the low significance X-ray burst detected by MAXI (Negoro et al., GCN Circ. 34723) and the position of sources S230917af_X3, S230917af_X4 and S230917af_X6 detected by Swift/XRT (Evans et al., GCN Circ. 34736). Preliminary analysis, which includes image subtraction between the two epochs obtained in the r band, does not show evidence for promising candidate counterparts. The typical 3sigma limiting AB magnitudes are r ~ 21 mag and r ~ 22 mag for the first and second epoch, respectively.

Observations from Campo Imperatore have have been carried out starting on 2023-09-19 at 20:14:33 UT (~ 2.42 days after the GW trigger) with the g and r filters. These observations covered ~ 86% of the localisation region of the low significance X-ray burst detected by MAXI and the position of sources S230917af_X3, S230917af_X4 and S230917af_X6 detected by Swift/XRT. Preliminary analysis, which includes image subtraction with the images obtained in the first Asiago epoch, does not show evidence for promising candidate counterparts. The typical 3sigma limiting AB magnitudes are g ~ 21.4 mag and r ~ 20.8 mag.

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