Swift observations of ZTF18abukavn/AT2018gep
ATel #12032; S. Schulze (WIS), A. Y. Q. Ho (Caltech), A. A. Miller (Northwestern) on behalf of the Zwicky Transient Facility collaboration
on 11 Sep 2018; 20:07 UT
Credential Certification: Adam Miller (amiller@astro.caltech.edu)
Subjects: Optical, Ultra-Violet, X-ray, Supernovae, Transient
We report on UV/optical and X-ray observations of ZTF18abukavn/AT2018gep (Ho et al., ATel #12030) with the Neil Gehrels Swift Observatory (Gehrels et al. 2004). Observations started at 2018-09-09.59 UTC. We measured the brightness of the transient using an aperture with a radius of 3'':
JD | Filter | Magnitude
2458371.0941 | UVW2 | 15.49 ± 0.06
2458371.1625 | UVW2 | 15.37 ± 0.06
2458371.1013 | UVM2 | 15.73 ± 0.05
2458371.1669 | UVM2 | 15.60 ± 0.05
2458371.0893 | UVW1 | 15.84 ± 0.05
2458371.1577 | UVW1 | 15.73 ± 0.05
2458371.0908 | U | 16.37 ± 0.06
2458371.1591 | U | 16.21 ± 0.06
2458371.0917 | B | 16.68 ± 0.06
2458371.1601 | B | 16.59 ± 0.06
2458371.0965 | V | 16.99 ± 0.11
2458371.1649 | V | 16.61 ± 0.09
The magnitudes are reported in the AB system and are not corrected for reddening. The reported measurements include flux from the host galaxy, though we expect the total host contribution to be small based on GALEX and SDSS observations obtained prior to the discovery of AT2018gep.
Swift/XRT observations were carried out in photon-counting mode. We analyzed the data using http://www.swift.ac.uk/user_objects/. No source was detected at the position of AT2018gep. We infer a limit of 0.003 ct/s (3 sigma confidence). Assuming a Galactic column density of n(H) ~ 1.1 E20 cm^-2, a redshift of 0.033, and a power-law spectrum with photon index = 2, this count rate corresponds to an unabsorbed flux limit of ~9.8 E-14 erg cm^-2 s^-1 in the bandpass from 0.3-10 keV. At the distance of AT2018gep this corresponds to a 0.3-10 keV luminosity L < 2.5e41 erg s^-1.
ZTF is a project led by PI S. R. Kulkarni at Caltech (see ATEL #11266), and includes IPAC; WIS, Israel; OKC, Sweden; JSI/UMd, USA; UW,USA; DESY, Germany; NRC, Taiwan; UW Milwaukee, USA and LANL USA. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. Alert distribution service provided by DIRAC@UW. Alert filtering is being undertaken by the GROWTH marshal system, supported by NSF PIRE grant 1545949.