Swift observations of 4FGL J1154.0+4037

ATel #15335; S. Baitieri (Uni Bicocca, INAF-OAB), P. Romano, S. Vercellone, L. Foschini (INAF-OAB)
on 18 Apr 2022; 10:44 UT
Credential Certification: Pat Romano (romano@ifc.inaf.it)

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We report the preliminary results of the observations performed by the Neil Gehrels Swift Observatory on the source 4FGL J1154.0+4037 (B3 1151+408, z=0.92512). This source was recently re-classified by Foschini et al 2021 (Univ.,7,372) as a candidate gamma-ray narrow-line Seyfert 1 (g-NLS1). Previoulsy, only an upper limit at 0.02E-11 erg/cm2/s (0.1-2.4 keV) from ROSAT/PSPC was available.

The observation (net exposure about 3.3 ks) took place starting on 2022-04-16 at 06:02:11 (MJD 59685.25152). The source was detected at the following coordinates:

RA/Dec(J2000) = 178.47764, 40.61413 which is equivalent to: RA(J2000) = 11h 53m 54.63s,
Dec(J2000) = +40d 36m 50.9s
with an estimated uncertainty of 3.0 arcsec (radius, 90% confidence), 1.8 arcsec from the radio position of B3 1151+408.

We fit the XRT/PC spectrum (3252 s) with an absorbed power law, and obtained an absorbing column consistent with the Galactic one NHGal =1.70x10^20 cm-2, a photon index of 2.1 (+0.8, -0.3) and an average absorbed flux 3.7(+1.5,-1.3)10^-13 erg/s/cm^2 (0.3-10 keV).

The UVOT observed the field simultaneously with the XRT in the following optical and UV filters:

MJD Filter Magnitude
MJD+/-MJDerr filter mags+/-mags_e (stat) +/-mags_esys (sys)
59685.3292+/-0.0646 V > 19.32
59685.3221+/-0.0656 B > 20.28
59685.5295+/-0.2747 U 19.34+/-0.19 (stat) +/-0.02 (sys)
59685.5274+/-0.2758 W1 19.42+/-0.17 (stat) +/-0.03 (sys)
59685.3318+/-0.0655 M2 19.39+/-0.19 (stat) +/-0.03 (sys)
59685.3253+/-0.0672 W2 19.96+/-0.20 (stat) +/-0.03 (sys)
The magnitudes are not corrected for Galactic extinction.

We warmly thank B. Chenko, the Science Planners, and the Observatory Duty Scientists for having scheduled these observations.