TITLE:   GCN CIRCULAR
NUMBER:  38122
SUBJECT: EP241107a: OHP/T193 photometric and spectroscopic observations
DATE:    24/11/08 01:33:32 GMT
FROM:    Christophe Adami at LAM <christophe.adami@lam.fr>

C. Adami (LAM/Pytheas/AMU), M. Dennefeld (IAP/CNRS/Sorbonne U.), A. Coleiro (APC), S. Basa 
(LAM/Pytheas/AMU), E. Le Floc'h (CEA Paris-Saclay) report on behalf of a larger collaboration

We first performed imaging of the field of EP241107a (Zhou et al. GCN38112, Odeh et al. GCN 38115,
Chao Wu et al. GCN 38116, Lipunov et al. GCN 38117, Mohan et al. GCN 38118, Busmann et al. GCN 
38120) with MISTRAL mounted on the 1.93 m telescope at Observatoire du Haute Provence (OHP, France).
The imaging observations consisted of 3x300s exposures in r-band. We have a very clear detection 
of the transient object. Using as reference field stars from the Pan-STARRS catalogue in a 1 arcmin
radius around the target, we determine a preliminar magnitude of r(AB) = 19.8 +/- 0.05 mag at a 
mean date of 2024-11-07T21:15 UT, ~7 hours after the burst, in good agreement with other reported 
measurements.

We immediately after took two spectra of the object using the MISTRAL blue grism (end of data
collection at 2024-11-07T22:40). Our spectra cover the wavelength range 4200-8100A at a resolution 
of R~700 and consist of one exposure of 900 seconds and an exposure of 1800sec. A red continuum is 
clearly detected from 5200A onwards, but with low signal to noise ratio. A single emission line can be 
marginally seen at ~5350A observed wavelength on the 2D spectrum.
If identified as [OII] 3727A, this would imply a redshift of 0.4355 for the galaxy suggested by Odeh 
et al.  This however needs confirmation, as other  emission lines then expected would fall in 
regions polluted by night sky emission.

We acknowledge the excellent support from Observatoire de Haute-Provence and in particular Jean 
Pierre Troncin for the MISTRAL observations and Neda Heidari.