AstroNote 2021-92

We observed the field of the AT2021gca/ZTF21aapkbav (AstroNote 2021-89, Andreoni et al.) as part of the Kinder survey. We used the Lulin One-meter Telescope at Lulin Observatory, Taiwan, to obtain images in g, r, i, and z filters. 

Observations started at 14:29 UT on 20 of March 2021 (MJD = 59293.604), 1.17 days after the last observed with ZTF. The images were taken under a various seeing conditions 3".2 and at an average airmass of 1.5. 

We subtracted the SDSS template of this field with our raw images, and derived the following preliminary magnitudes and 2-sigma limits (all in the AB system):

g > 20.58 mag,
r = 20.70 +/- 0.10 mag,
i = 20.78 +/- 0.19 mag,
z > 19.53 mag.

Given magnitudes are calibrated against SDSS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.008 mag in the direction of the counterpart (Schlafly & Finkbeiner 2011). 

Comparing with the ZTF r-band discovery magnitude on 59290.391, the r-band declines ~0.3 mag per day, which is consistent with the estimation by Andreoni et al.  

The "Kinder" (kilonova finder) project aims to find fast evolving objects such as kilonovae. We use the 0.4m-SLT at the Lulin Observatory in Taiwan to obtain images for new, nearby (< 100 Mpc) transients found by the ATLAS project (Smith et al. 2020, 2020arXiv200309052S). By comparing with ATLAS latest magnitudes, we can track their photometric evolution and seek for rapidly fading events. We will report our host-subtracted photometry from our real-time observations measured by using the SNOoPY pipeline (http://sngroup.oapd.inaf.it/ecsnoopy.html) to the WISeREP.