Swift observation of a new gamma-ray source associated with 1WHSP J104516.2+275133

ATel #12924; Sara Buson (U. Wuerzburg, Germany; UMBC, USA), Simone Garrappa (DESY Zeuthen, Germany), Andrea Gokus (U. Wuerzburg and Remeis Observatory/ECAP, Germany), Gregory Sivakoff (U. Alberta, Canada), M. Santander (U. Alabama, USA), A. Keivani (Columbia U., USA)
on 11 Jul 2019; 21:49 UT
Credential Certification: Sara Buson (sara.buson@gmail.com)

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In GCN Circular #24989 we reported the discovery of a new high-energy (>10GeV) gamma-ray source with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The gamma-ray source is positionally consistent with the blazar 1WHSP J104516.2+275133 (aka SDSS J104516.30+275133.4), and is located in the vicinity of the high-energy IC190704A neutrino event (GCN #24981).

Target of opportunity observations of 1WHSP J104516.2+275133 field were performed with the The Neil Gehrels Swift Observatory on 2019 July 8 and 10, for a total XRT exposure of approximately 3.7 ksec. Swift-XRT data were taken in Photon Counting mode. Assuming a photon index of Gamma=2 and an HI column density consistent with the Galactic value in the direction of the source (n_H = 7.8 x 10^20 cm^-2, Kalberla et al. 2005, A&A, 440, 775), we find an intrinsic 0.5-10 keV flux of approximately (1.3 +/- 0.7) x 10^-13 erg cm^-2 s^-1. This flux observed on 2019 July 8/10 is comparable to the (2.8+/-1.1) x 10^-13 erg cm^-2 s^-1 0.1-2.4 keV absorbed flux observed by ROSAT observations from 1990 November 14 to 16 (Boller et al. 2016, A&A, 588, A103).

Simultaneous Swift-UVOT observations were performed on 2019 July 8/10 in six UVOT filters. Magnitude values are given below, which have been corrected for Galactic extinction using values from Schlafly & Finkbeiner 2011 (ApJ 737, 103). The U band magnitude is comparable to the SDSS u-band magnitude reported in the 7th SDSS release (Abazajian et al. 2009, ApJS, 182, 2, 543-558).

B: 19.4 +/- 0.3

M2: 18.7 +/- 0.3

U: 19.6 +/- 0.5

W1: 19.3 +/- 0.3

W2: 19.5 +/- 0.2

V: >17.9 (no detection)

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