TITLE: GCN CIRCULAR NUMBER: 36705 SUBJECT: LIGO/Virgo S240615dg: GRANDMA/FRAM-CTA-N Observations DATE: 24/06/19 21:54:37 GMT FROM: Dalya Akl at American Uni. SHJ dalyaakl.d@gmail.com

D. Akl (AUS), M. Masek (FZU), C. Andrade (UMN), E. G. Elhosseiny (NRIAG), H. Peng (THU), L. Wang, A. Iskandar (XAO), S. Antier (OCA), S. Karpov (FZU), M. Coughlin (UMN), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), D. Turpin (CEA-Saclay/Irfu), N. Guessoum (AUS), T. Pradier (Unistra/IPHC), M. Prouza (FZU), on behalf of the GRANDMA collaboration:

We performed tiled observations of the LIGO/VIRGO event S240615dg (GCN 36669) with the 25 cm f/6.3 FRAM-CTA-N telescope located at Observatorio del Roque de los Muchachos, La Palma, Spain.

Observations were conducted from 2024-06-17T02:57:12.758 to 2024-06-17T04:09:15.193, 1.64 days after the GW trigger time. We obtained a total of 34 images in the Johnson R band, acquiring 2 consecutive 2-minute long exposures at the individual pointings in the table below, for a total of 4080 seconds. Using the Bibly Skymap as a reference, the observations covered 3.5 square degrees of the localization, corresponding to ~34.7% of the probability enclosed in the localization region.

Our low latency analysis (Karpov et al. 2021) did not reveal any significant candidate down to the limits listed in the table below (5 sigma, AB system).

+------------+-------------+---------+----------+-----------+--------------+ | T-T0 (hr) | MJD | Ra | Dec | Exposure | Lim.Mag. | |------------+-------------+---------+----------+-----------+--------------| | 39.35 | 60478.12306 | 6.79245 | 45.00000 | 120 | 17.13 | | 39.38 | 60478.12452 | 6.79245 | 45.00000 | 120 | 17.33 | | 39.42 | 60478.12609 | 8.02744 | 45.00000 | 120 | 17.23 | | 39.46 | 60478.12755 | 8.02744 | 45.00000 | 120 | 17.24 | | 39.49 | 60478.12913 | 8.28319 | 46.74757 | 120 | 17.22 | | 39.53 | 60478.13059 | 8.28319 | 46.74757 | 120 | 17.25 | | 39.57 | 60478.13216 | 7.00885 | 46.74757 | 120 | 17.10 | | 39.60 | 60478.13362 | 7.00885 | 46.74757 | 120 | 17.21 | | 39.64 | 60478.13520 | 8.71972 | 45.43689 | 120 | 17.27 | | 39.67 | 60478.13666 | 8.71972 | 45.43689 | 120 | 17.17 | | 39.71 | 60478.13823 | 6.22837 | 45.43689 | 120 | 17.07 | | 39.75 | 60478.13969 | 6.22837 | 45.43689 | 120 | 17.13 | | 39.78 | 60478.14128 | 8.85764 | 46.31068 | 120 | 17.16 | | 39.82 | 60478.14273 | 8.85764 | 46.31068 | 120 | 17.00 | | 39.86 | 60478.14431 | 6.32689 | 46.31068 | 120 | 17.06 | | 39.89 | 60478.14577 | 6.32689 | 46.31068 | 120 | 17.14 | | 39.93 | 60478.14734 | 6.17496 | 45.00000 | 120 | 17.16 | | 39.97 | 60478.14880 | 6.17496 | 45.00000 | 120 | 17.31 | | 40.00 | 60478.15038 | 8.92035 | 46.74757 | 120 | 17.33 | | 40.04 | 60478.15184 | 8.92035 | 46.74757 | 120 | 17.37 | | 40.08 | 60478.15341 | 8.64494 | 45.00000 | 120 | 17.43 | | 40.11 | 60478.15487 | 8.64494 | 45.00000 | 120 | 17.40 | | 40.15 | 60478.15642 | 7.35945 | 44.56311 | 120 | 17.42 | | 40.18 | 60478.15788 | 7.35945 | 44.56311 | 120 | 17.43 | | 40.22 | 60478.15946 | 6.37168 | 46.74757 | 120 | 17.52 | | 40.26 | 60478.16092 | 6.37168 | 46.74757 | 120 | 17.54 | | 40.29 | 60478.16251 | 7.71429 | 47.18447 | 120 | 17.35 | | 40.33 | 60478.16397 | 7.71429 | 47.18447 | 120 | 17.46 | | 40.37 | 60478.16555 | 6.74617 | 44.56311 | 120 | 17.53 | | 40.40 | 60478.16701 | 6.74617 | 44.56311 | 120 | 17.49 | | 40.44 | 60478.16859 | 9.40767 | 45.87379 | 120 | 17.24 | | 40.48 | 60478.17005 | 9.40767 | 45.87379 | 120 | 17.24 | | 40.51 | 60478.17163 | 8.35714 | 47.18447 | 120 | 17.42 | | 40.55 | 60478.17309 | 8.35714 | 47.18447 | 120 | 17.42 | +------------+-------------+---------+----------+-----------+--------------+

Our observations were coordinated through Skyportal (https://skyportal-icare.ijclab.in2p3.fr/).

GRANDMA (Global Rapid Advanced Network Devoted to the Multi-messenger Addicts) is a network of robotic telescopes connected all over the world with both photometry and spectrometry capabilities for Time- domain Astronomy (https://grandma.lal.in2p3.fr/). Details on the FRAM telescopes are available on the GRANDMA web pages or at https://grandma.ijclab.in2p3.fr/fram/

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