Continued Swift observations of the flat spectrum radio quasar PKS 1127-14

ATel #14280; Filippo D'Ammando (INAF-IRA Bologna)
on 18 Dec 2020; 18:07 UT
Credential Certification: Filippo D'Ammando (dammando@ira.inaf.it)

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Following the initial Swift observations of the flat spectrum radio quasar PKS 1127-14 at redshift z = 1.184 (Wilkes 1986, MNRAS, 218, 331), after the gamma-ray flare detected by Fermi-LAT, and performed on 2020 December 13 (ATel #14265), further Swift observations were obtained on December 15 and 17.

Swift-XRT data were taken in Photon Counting mode for a net exposure of about 1.6 ksec and 1.9 ksec on December 15 and 17, respectively. The X-ray spectrum (0.3-10 keV) observed on 2020 December 15 and 17 can be fit by an absorbed power law model with a HI column density consistent with the Galactic value in the direction of the source (n_H = 3.5 x 10^20 cm^-2, Ben Bekhti N. et al., 2016, A&A, 594, A116) and a photon index of 1.1 +/- 0.2 and 1.2 +/- 0.2, comparable within the uncertainties to the photon index observed on December 13. The corresponding (observed) 0.3-10 keV fluxes are (9.3+/-0.9) x10^-12 erg cm^-2 s^-1 and (8.4 +/- 0.7) x10^-12 erg cm^-2 s^-1, respectively, indicating a flux level only slightly lower than the flux on December 13, but still high.

Simultaneous Swift-UVOT observations were performed on 2020 December 15 and 17. The measured magnitudes in optical and UV bands show a brightness level similar to what is observed on December 13 (see table below).

Band	2020-12-15	2020-12-17
V	16.75 +/- 0.11	16.71 +/- 0.09
B	17.13 +/- 0.08	17.02 +/- 0.07
U	16.05 +/- 0.05	16.04 +/- 0.06
W1	15.84 +/- 0.07	15.77 +/- 0.07
M2	15.92 +/- 0.08	15.95 +/- 0.07
W2	16.18 +/- 0.07	16.15 +/- 0.07

In consideration of the ongoing activity of this source, confirmed also by the Swift observations, we encourage further multi-wavelength observations.

We would like to thank the Swift Team for making these observations possible, in particular B. Sbarufatti as the Swift Observatory Duty Scientist.