Swift observations of long X-ray flaring activity from the blazar PKS 0903-57

ATel #15094; Raj Prince (CFT, Poland)
on 8 Dec 2021; 23:00 UT
Credential Certification: Aditi Agarwal (aditiagarwal.phy@gmail.com)

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Following the event of flux enhancement in blazar, PKS 0903-57 at gamma-ray by Fermi-LAT (Atel #15057) and X-ray by Swift-XRT (Atel #15058), we performed target of opportunity observations using Swift on November 28, December 02, and 06, 2021.

Swift observed the source in photon counting mode on November 28 and December 02 & 06, accumulating 1 ks of exposure. Preliminary analysis suggests that the source spectrum in the energy range 0.3-10 keV could be modeled with an absorbed power-law, using a fixed Galactic Hydrogen column density of 2.6 X 10^21 cm^-2 (HI4PI Collaboration 2016, A&A, 594, 116). On November 28, the X-ray data in the 0.3-10keV band resulted in a flux of (4.92+/-0.74) X 10^-12 erg cm^-2 s^-1, with a photon index of 1.57+/-0.52. On December 02, the estimated flux was increased to (7.41+/-0.89) X 10^-12 erg cm^-2 s^-1, with a photon index of 1.79+/-0.48. The estimated flux using the observation of December 06 is (6.93+/-0.89) X 10^-12 erg cm^-2 s^-1 with a photon index of 1.98+/-0.56. Compared with the Swift activity reported on November 23 (Atel #15058), the fluxes are almost similar within the errorbar, suggesting long-term flaring activity in X-ray. The X-ray fluxes in 0.3-10 keV on November 12, 15, and 18 were estimated as (7.3 +/- 0.7)e-12, (5.5 +/- 0.6)e-12, and (8.1 +/- 0.7)e-12 erg cm^-2 s^-1, respectively. The estimated fluxes from November 12 to December 06 show a long flaring activity in X-ray.

We also performed simultaneous Swift/UVOT observations. The estimated uncorrected magnitudes are, B=15.71 +/- 0.04, U=16.63 +/- 0.05, V=15.01 +/- 0.05, W1=17.48 +/- 0.07, M2=18.39 +/- 0.10, and W2=18.32 +/- 0.07 on November 28. The source brighten up a bit on Decemebr 06 with magnitudes, B=15.32 +/- 0.04, U=16.09 +/- 0.04, V=14.78 +/- 0.05, W1=16.92 +/- 0.06, M2=17.62 +/- 0.08, and W2=17.53 +/- 0.06, suggesting a increase activity in optical-UV also. Simultaneous to the X-ray and optical-UV activity, a high energy activity in gamma-ray is also reported by AGILE (Atel #15086) with integrated flux F(>100 MeV) = (3.4 +/- 0.9) x 10^-6 photons/cm^2/s observed between 2021-12-03 08:00 UT and 2021-12-05 08:00 UT, suggesting the multi-wavelength activity in the source.

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

We further acknowledge the commitment of the Swift Team, Observatory Duty Scientists, and PI, who made these observations possible.