SRG/eROSITA observation of OI 275 during enhanced gamma-ray activity

ATel #15012; S. Haemmerich (Remeis-Observatory/ECAP, FAU Erlangen), A. Gokus (Remeis-Observatory/ECAP, FAU Erlangen & Uni Wuerzburg), P. Weber (Remeis-Observatory/ECAP, FAU Erlangen), A. Zainab (Remeis-Observatory/ECAP, FAU Erlangen), I. Kreykenbohm (Remeis-Observatory/ECAP, FAU Erlangen), A. Rau (MPE Garching), J. Wilms (Remeis-Observatory/ECAP, FAU Erlangen)
on 3 Nov 2021; 15:37 UT
Credential Certification: Andrea Gokus (andrea.gokus@fau.de)

Tweet

The position of the FSRQ OI 275 (RA = 07:48:35.60, DEC = +24:00:26.24) was scanned by the eROSITA telescope (Predehl et al. 2021, A&A 647, A1) onboard the Russian/German Spectrum-X-Gamma mission (Sunyaev et al. 2021, arxiv:2104.1326) during its fourth ongoing all-sky survey between 2021 October 24 00:58 UTC and 2021 October 27 12:58 UTC. The eROSITA observation coincided with a state of enhanced gamma-ray activity detected by Fermi/LAT (Valverde et al., ATel#15007). 51 counts were collected during a total exposure of 127s.

The observed X-ray spectrum is well described by an absorbed power-law model. Fixing the equivalent neutral hydrogen column density to N_H=5.7 x 10^20 cm^-2 (HI4PI Collaboration, N. Ben Bekhti, et al., 2016, A&A 594, A116) we find a photon index of 2.0 +/- 0.5 and an absorbed 0.3-10 keV flux of (2.0 +/- 0.6) x 10^-12 erg/cm^2/s (all following values use the same band). No significant difference in the count rate between the individual scans could be observed. The average count is (0.39 +/- 0.06) counts/s.

OI 275 was also detected during the first three eROSITA all-sky surveys with the following, higher fluxes:
2020 April 19/20: (2.6 +/- 0.6) x 10^-12 erg/cm^2/s,
2020 October 22: (3.8 +/- 0.7) x 10^-12 erg/cm^2/s, and
2021 April 21: (5.0 +/- 0.6) x 10^-12 erg/cm^2/s.
The spectral shape did not change significantly between the individual visits (photon indices: 2020 April: 1.6 +/- 0.4, 2020 Oct: 1.6 +/- 0.4, 2021 April: 1.61 +/- 0.23). While the FSRQ is quite variable in the X-rays, it seems to be more variable in the gamma-regime.

Multi-wavelength follow-up observations, especially with other X-ray missions, are encouraged in order to study the variability of the source on shorter time-scales.