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GCN Circular 35027

Subject
LIGO/Virgo/KAGRA S231113bw: GROWTH-India coverage and upper limits
Date
2023-11-14T16:38:00Z (6 months ago)
From
Anirudh Salgundi <salgundi.anirudh@gmail.com>
Via
Web form
R. Kumar, A. Salgundi, R. Sharma, G. Waratkar, A. Suresh, Y. Wagh, A. Arya, V. Swain, D. Raman, T. Roychowdhury, V. Bhalerao (IIT Bombay), S. Barway, G. C. Anupama (IIA), R. Norboo (IAO)

We followed up the sky localisation of the gravitational wave trigger S231113bw (GCN 35016) with the 0.7m GROWTH-India Telescope (GIT). We obtained multiple 300-sec exposures in the r' filter starting at 2023-11-13T20:38:43.52 UT, 34.4 minutes after the LVK trigger. We prioritised our observations based on galaxies in the localisation region, using the NASA/IPAC Extragalactic Database (NED, Cook et al., 2023). We obtained 39 images covering 18 sq deg, with a median depth of 20.27. Based on the "bayestar.multiorder.fits,2" skymap our images have a 1.23% probability of containing the true source.

Data were processed using the GIT pipeline (Kumar et al., 2022). The pipeline performed image subtraction with the ZOGY (Zackay et al., 2016) algorithm, and resultant images were scanned to find transients. Where available, PanSTARRS images (Chambers et al., 2016) were used as references for image subtraction. In other fields (marked with ^), we looked for new point sources absent in the GSC2.3 catalog (Lasker et al., 2008). We rejected a few candidates that were coincident with field stars and minor planets. We did not find any suitable kilonova or transient candidate in our data. 

The detailed observation log is:

| Tile ID | RA (deg) | Dec (deg) | Lim Mag (AB) |

|  4573   |  77.062  |  -25.51   |     20.44    |
|  1410   |  81.537  |  -30.41   |     20.27    |
|  1854   |  81.796  |  -29.71   |     20.24    |
|  530    |  80.178  |  -31.81   |     19.94    |
|  62104  |  255.824 |   69.00   |     19.28    |
|  9803   |  69.433  |  -17.81   |     20.94    |
|  6915   |  73.605  |  -22.01   |     20.04    |
|  4115   |  79.910  |  -26.21   |     20.27    |
|  2298   |  79.639  |  -29.01   |     20.34    |
|  2745   |  77.514  |  -28.31   |     20.51    |
|  5502   |  75.469  |  -24.11   |     20.26    |
|  3653   |  77.286  |  -26.91   |     20.72    |
|  2753   |  83.903  |  -28.31   |     19.99    |
|  60221  |  246.237 |   62.70   |     19.86    |
|  5038   |  77.506  |  -24.81   |     20.74    |
|  60678  |  245.466 |   64.10   |     19.55    |
|  16286  |  65.409  |  -8.71    |     19.62    |
|  5035   |  75.184  |  -24.81   |     20.74    |
|  10293  |  69.880  |  -17.11   |     20.41    |
|  13264  |  67.764  |  -12.91   |     19.39    |
|  6441   |  73.911  |  -22.71   |     20.53    |
|  969    |  81.274  |  -31.11   |     19.91    |
|  2746   |  78.311  |  -28.31   |     20.51    |
|  22422  |  62.539  |  -0.31    |     20.08    |
|  4112   |  77.563  |  -26.21   |     20.37    |
|  1413   |  83.979  |  -30.41   |     20.40    |
|  7871   |  73.588  |  -20.61   |     20.79    |
|  968    |  80.453  |  -31.11   |     20.09    |
|  8832   |  70.746  |  -19.21   |     20.67    |
|  63242  |  270.732 |   73.90   |     18.59    |
|  6442   |  74.673  |  -22.71   |     20.66    |
|  63241^ |  268.179 |   73.91   |     18.63    |
|  4113   |  78.348  |  -26.21   |     20.70    |
|  15273  |  65.673  |  -10.11   |     21.00    |
|  4570   |  74.729  |  -25.51   |     20.53    |
|  16795  |  65.989  |  -8.01    |     19.81    |
|  63404  |  336.108 |   74.60   |     20.18    |
|  61723^ |  248.747 |   67.60   |     19.36    |
|  10296  |  72.084  |  -17.11   |     19.54    |


The magnitudes are calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction.

The GROWTH India Telescope (GIT; Kumar et al., 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.
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