VizieR Online Data Catalog: AT 2021loi photometry & sp. follow-up (Makrygianni+, 2023)

We retrieved point-spread function (PSF)-fit photometry of reference-subtracted images from the ZTF forced photometry service from MJD=58194 to MJD=59975 and the Asteroid Terrestrial-impact Last Alert System (ATLAS) forced photometry service from MJD=57232 to MJD=59975 at the position of the transient AT 2021loi. <P />We also obtained optical photometry in the gri bands starting on 2021-Jul-01 with the Las Cumbres Observatory network of 1m telescopes. <P />The location of AT 2021loi was repeatedly observed in the mid-infrared (MIR) regime by the Wide-Field Infrared Survey Explorer (WISE) and its extensions, NEOWISE and the NEOWISE reactivation mission survey (NEOWISE-R; Mainzer+ 2014, J/ApJ/792/30). The measurements were conducted in both the W1 and W2 bands (3.4 and 4.6um, respectively). <P />We initiated near-UV (NUV) follow-up observations (PI: L. Makrygianni) with the Neil Gehrels Swift Observatory Optical/UV Telescope (UVOT). We obtained 23 Swift epochs from 2021 June 21 to 2022 October 11 in all six UVOT filters (uvw2, uvm2, uvw1, U, B, and V). <P />We also used the archival NUV flux measurement from GALEX observations taken on 2006 November 9. <P />The X-ray observations with the X-Ray Telescope (XRT) on Swift were obtained simultaneously with the UVOT observations. We also initiated radio measurements with the Arcminute Microkelvin Imager-Large Array (AMI-LA) and the Karl G. Jansky Very Large Array (VLA). The AMI-LA is a radio interferometer comprised of eight 12.8m diameter antennas producing 28 baselines that extend from 18m up to 110m in length and operate with a 5GHz bandwidth divided into eight channels around a central frequency of 15.5GHz. See Section 3.1.2. <P />We retrieved an archival spectrum of WISEA J010039.62+394230.3, the host galaxy of AT 2021loi, from the fifth data release of the LAMOST survey (LAMOST/DR5) obtained on 2013 December 22. The LAMOST spectrum covers the range 3500-9000Å with a resolution of R=1800. <P />The classification spectrum of AT 2021loi was obtained with the LRIS on Keck I, which covers the wavelength range between 3400 and 10300Å with a resolution of R=600-1000, on 2021 June 7. <P />We initiated a spectroscopic monitoring campaign for AT 2021loi using the FLOYDS spectrograph mounted on the robotic 2m telescope at Haleakala Hawaii (which is also part of the Las Cumbres Observatory network). During the 16 months of spectroscopic monitoring, we obtained 20 spectra. FLOYDS covers the 3500-10000Å range in a single exposure by capturing two spectral orders simultaneously, yielding a spectral resolution of R~400. The exposure time of the spectra varies between 1500 and 1800s, and we have used a slit width of 2". <P />(2 data files)....