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GCN Circular 38370

Subject
LIGO/Virgo S241127aj: GRANDMA/FRAM-CTA-N Observations
Date
2024-11-28T19:18:52Z (a month ago)
From
Thomas Hussenot-Desenonges at IJCLab <thomas.hussenot@ijclab.in2p3.fr>
Via
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T. Hussenot-Desenonges (IJCLAB), D. Akl (AUS), M. Coughlin (UMN), M. Molham (NRIAG),  S. Agayeva (Shamakhy Obs.), S. Antier (OCA), C. Andrade (UMN), S. Karpov (FZU), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS), M. Masek (FZU), on behalf of the GRANDMA collaboration:

We performed tiled observations of the LIGO/VIRGO event S241127aj (GCN 38336Loading...
 
 ) 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 2024-11-28T06:05:22 to 2024-11-28T08:21:54, 1.0 day after the GW trigger time. We obtained a total of 23 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 2760 seconds.
The observation plan was constructed to cover 11.8 degrees of the bayestar.multiorder.fits,1 localization, corresponding to ~3.1% of the enclosed probability. The regions of highest localization probability were unfortunately unobservable because of constraints of proximity to the Sun.

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, Vega system):

|        Start time (UTC) |        RA |    DEC | Lim.Mag. | Exposure (seconds)

| 2024-11-28T06:05:22.573 | 189.11392 | -31.62162 | 17.04 | 120
| 2024-11-28T06:07:34.140 | 189.11392 | -31.62162 | 17.03 | 120
| 2024-11-28T06:09:56.133 | 188.46395 | -30.64865 | 16.96 | 120
| 2024-11-28T06:12:07.703 | 188.46395 | -30.64865 | 17.02 | 120
| 2024-11-28T06:14:26.822 | 187.97468 | -31.62162 | 17.19 | 120
| 2024-11-28T06:16:38.420 | 187.97468 | -31.62162 | 17.13 | 120
| 2024-11-28T06:19:00.368 | 189.66443 | -36.48649 | 17.45 | 120
| 2024-11-28T06:21:11.958 | 189.66443 | -36.48649 | 17.46 | 120
| 2024-11-28T06:23:43.572 | 195.42857 | -73.45946 | 17.74 | 120
| 2024-11-28T06:25:55.193 | 195.42857 | -73.45946 | 17.76 | 120
| 2024-11-28T06:28:16.041 | 198.85714 | -73.45946 | 17.73 | 120
| 2024-11-28T06:30:27.649 | 198.85714 | -73.45946 | 17.73 | 120
| 2024-11-28T06:32:48.431 | 192       | -73.45946 | 17.76 | 120
| 2024-11-28T07:11:24.897 | 188.9441  | -29.67568 | 17.72 | 120
| 2024-11-28T07:13:36.499 | 188.9441  | -29.67568 | 17.65 | 120
| 2024-11-28T07:15:56.104 | 189.59248 | -30.64865 | 17.67 | 120
| 2024-11-28T07:18:07.696 | 189.59248 | -30.64865 | 17.53 | 120
| 2024-11-28T07:20:31.567 | 190.25316 | -31.62162 | 17.57 | 120
| 2024-11-28T07:22:43.183 | 190.25316 | -31.62162 | 17.53 | 120
| 2024-11-28T07:25:14.770 | 192       | -73.45946 | 17.64 | 120
| 2024-11-28T07:27:26.342 | 192       | -73.45946 | 17.65 | 120
| 2024-11-28T08:17:43.339 | 188.45638 | -36.48649 | 16.07 | 120
| 2024-11-28T08:19:54.951 | 188.45638 | -36.48649 | 15.87 | 120

All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022), and calibrated using the Gaia DR3 SynPhot catalogue. 
The data are not corrected from Galaxy extinction.


We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023)

GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518).