GCN Circular 25372

T.-W. Chen (MPE), A. Nicuesa Guelbenzu (TLS Tautenburg), M. Fraser (UCD), J. Bolmer (MPE), T. Schweyer (MPE), A. Rau (MPE), S. Klose (TLS Tautenburg), L Salmon (UCD), S. J. Smartt (QUB), A. J. Levan (Radboud Univ), and Paolo D'Avanzo (INAF-OAB) report for a larger collaboration:

We observed 36 galaxies within the 90% error volume of S190814bv (LVC GCN 25324
Not found
 
 
) simultaneously in g'r'i'z'JHKs with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). Observations were obtained on 15 August 2019 between 04:39 and 10:16 UT, 7.5 hours after the GW event. Galaxies were selected from the HOGWARTS code (https://gwtool.watchertelescope.ie/). For each galaxy we obtained on avarage 2.1 min in the optical bands and 3.9 min in the NIR bands. Observations were performed under seeing conditions varying from 1".0 to 2".3 with an average seeing of 1".4, and at an airmass ranging from 1.0 to 1.4 with an average airmass of 1.1. According to these conditions, the typical 3-sigma detection limit in the r' band is 21.3 mag and 19.8 mag in J (all in the AB system).

Visual inspection of the r' and J-band images shows no apparent candidates in any of the images in comparison to archival imaging from Pan-STARRS, DSS and WISE. Although we caution that fainter candidates close to their hosts could be missed in such an inspection. 

The locations of the galaxies observed are
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No.     RA (J2000)        Dec (J2000)
1        10.676272        -21.774082
2        10.242757        -22.083128
3        13.192388        -22.975018
4        11.781363        -24.370647
5        23.594837        -32.835316
6        23.018082        -33.802876
7        12.180364        -23.561686
8        13.806392        -26.321253
9        10.666405        -21.800196
10        23.089487        -31.092321
11        12.364808        -26.538301
12        24.334146        -33.330853
13        14.254662        -23.837297
14        21.229847        -30.621069
15        10.862282        -22.189581
16        13.704722        -26.371256
17        22.342892        -32.849354
18        20.766964        -31.095718
19        11.442945        -25.920193
20        9.807239        -22.102215
21        10.639115        -22.866308
22        23.877426        -32.970612
23        12.25617        -23.811317
24        22.93853        -32.415623
25        12.441799        -26.443037
26        12.120861        -22.147444
27        9.920177        -22.196348
28        11.870618        -25.440655
29        10.91611        -21.659298
30        22.549915        -32.903667
31        11.472051        -23.772461
32        11.543399        -24.650192
33        12.666141        -26.813395
34        12.320091        -26.219179
35        13.804421        -24.044033
36        22.145348        -32.296467
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Note: we re-observed those galaxies (numbers 3, 6, 8, 15, 23 and 29) on 16 August 2019 with GROND, in order to obtain one magnitude deeper images to confirm some possible marginally detected sources taken on 15 August. None of these sources were still detected or convincing though, and we hence do not consider them as genuine sources. 

We acknowledge excellent help in obtaining these data from Angela Hempel and R��gis Lachaume on La Silla.