Significant optical decay and brightening in blazar PKS 0735+17 coincident with IceCube-211208A

ATel #15100; K. Zhirkov, V. Lipunov, E. Gorbovskoy, P. Balanutsa, A. Kuznetsov, O. Gress, G. Antipov, D. Vlasenko, N. Tiurina, D. Zimnukhov, V. Senik, V. Topolev, A. Chasovnikov, E. Minkina, V. Grinshpun, D. Cheryasov, Ya. Kechin, Ya. Kechin, T. Pogrosheva, V. Shumkov (Lomonosov MSU), R. Rebolo, M. Serra(IAC), D. A. H. Buckley (SAAO), N. M. Budnev (ISU, API), R. Podesta, C. Lopez, F. Podesta, C. Francile (OAFA), A. Tlatov, D. Dormidontov (KSS, Pulkovo observatory), A. Gabovich (BSPU)
on 10 Dec 2021; 11:15 UT
Credential Certification: Nataly Tyurina (tiurina@sai.msu.ru)

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MASTER Global Robotic Net (Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L)
reports on the significant optical decay and brightening in a blazar PKS 0735+17
and on a significant detection of a lower limit on the degree of linear polarization.

In Atel #15098 we reported on the high optical state of PKS 0735+17.
To confirm whether or not this object might be the source of IceCube-2112108A we conducted follow-up observations at MASTER-IAC, MASTER-SAAO, MASTER-OAFA and MASTER-Kislovodsk.

After analyzing our observations we discovered that PKS 0735+17 significantly decayed 4 days before the neutrino and brightened to the past level several hours after the neutrino with no significant variability afterwards.

Considering that TXS 0506+056, source of IceCube-170922A, showed a similar picture (Lipunov et al, ApJL, 896, L19, 2020) albeit in a shorter timescale(several hours), it is likely that PKS 0735+17 is a source of IceCube-211208A.

Polarization observations were made by MASTER-IAC during the night of 2021-12-10. We report on a significant detection of a lower limit on the degree of linear polarization .

Judging from these and from the detection of enhanced emission from the blazar by Fermi-LAT(Atel #15099) we conclude that the BL Lac object PKS 0735+17 is a likely source of IceCube-211208A even though it is slightly outside the 90% of the localization error-box (GCN #31191 , https://gcn.gsfc.nasa.gov/other/icecube_211208A.gcn3).

Multiwavelength observations are highly encouraged.

MASTER Global Robotic Net