Optical and near-infrared observations of PKS 0735+178
ATel #15136; Elina Lindfors (FINCA), Talvikki Hovatta (FINCA), Tapio Pursimo (NOT), Viktoria Pinter (NOT), Stephen Warren (Imperial), Thomas Andradi-Brown (Imperial), Zhang-Liang Xie (MPIA), Eduardo Banados (MPIA), Dino Fugazza (INAF Brera), Emilio Molinari (INAF Cagliari)
on 23 Dec 2021; 17:02 UT
Credential Certification: Elina Lindfors (elilin@utu.fi)
Subjects: Infra-Red, Optical, AGN, Blazar, Quasar
We have performed optical and near-infrared observations of the BL Lac object PKS 0735+178 following the strong activity observed in radio (ATel #15105), optical
(ATel #15098), X-rays (ATel #15102, #15109, #15130) and gamma-rays (ATel #15099, #15129), which were triggered by the source proximity to the IceCube
event IC211208A (GCN #31191) and the Baikal-GVD detection of a neutrino from the same region (ATel #15112).
The observations were performed between Dec 15 and 19 with the Rapid Eye Mount (REM) telescope at La Silla, Chile and the Nordic Optical Telescope (NOT) at La Palma, Spain.
The NOT observations were made using NOTCam. Standard IRAF data reduction (flat field correction with twilight flats + combining dithered images) was carried out and differential photometry was performed. The brightness was estimated against three nearby 2MASS stars K-magnitudes between 10.9 and 11.9 (marked C, C1 and C2 in the finding chart available here: https://users.utu.fi/kani/1m/finding_charts/PKS_0735+178_map.html). The standard deviation of the zero point was 0.02 mag. We find that PKS 0735+17 had the following K-band magnitudes
on 2021-12-16T07:20 Ks=11.57+-0.02 and on 2021-12-18T06:45 Ks=11.62+-0.03.
The REM observations were made using both REMIR (K-filter) and ROS2 (g,r,i,z filters) cameras. Standard IRAF data reduction was carried out and differential photometry was performed. In K-band the brightness was estimated against the same 2MASS stars as above, but the standard deviation of the zero point was 0.06mag. In g,r,i and z filters, the brightness was estimated using three nearby Pan-STARRS stars (marked C4, B and C7 in the finding chart available here: https://users.utu.fi/kani/1m/finding_charts/PKS_0735+178_map.html).
We find that PKS 0735+17 had the following magnitudes:
K-band:
2021-12-15T05:50 K=11.46+-0.07
2021-12-16T05:51 K=11.50+-0.12
2021-12-17T05:51 K=11.53+-0.07
2021-12-18T05:51 K=11.58+-0.07
z-band:
2021-12-15T05:50 z=14.35+-0.04
2021-12-16T05:51 z=14.46+-0.03
2021-12-17T05:51 z=14.49+-0.07
2021-12-18T05:51 z=14.41+-0.1
2021-12-19T05:55 z=14.54+-0.1
i-band:
2021-12-15T05:50 i=14.61+-0.02
2021-12-16T05:51 i=14.50+-0.04
2021-12-17T05:51 i=14.57+-0.03
2021-12-18T05:51 i=14.56+-0.1
2021-12-19T05:55 i=14.70+-0.03
r-band:
2021-12-15T05:50 r=14.77+-0.013
2021-12-16T05:51 r=14.80+-0.02
2021-12-17T05:51 r=14.86+-0.014
2021-12-18T05:51 r=14.75+-0.03
2021-12-19T05:55 r=14.91+-0.03
g-band:
2021-12-15T05:50 g=14.98+-0.02
2021-12-16T05:51 g=14.98+-0.02
2021-12-17T05:51 g=15.19+-0.02
2021-12-18T05:51 g=15.08+-0.04
2021-12-19T05:55 g=15.16+-0.04
