VizieR Online Data Catalog: UV-Opt LCs of ASASSN-19bt detected by TESS (Holoien+, 2019)

ASAS-SN is an ongoing project designed to monitor the entire visible sky in an unbiased way with a rapid cadence to discover bright, nearby transients. To accomplish this, we use units hosted by the Las Cumbres Observatory global telescope network (Brown+ 2013PASP..125.1031B) at multiple sites around the globe, each consisting of four 14cm telescopes on a common mount. ASAS-SN expanded in 2017 and currently operates with five units, located in Hawaii, Texas, Chile, and South Africa. In order to maximize the synergy between ASAS-SN and TESS, ASAS-SN monitors the TESS fields at an increased cadence. Located in the TESS CVZ near the South Ecliptic Pole, ASASSN-19bt has been observed by TESS almost constantly since science operations commenced in late July of 2018.

ASASSN-19bt was discovered on 2019 January 29.91 at RAJ2000=07:00:11.41,DEJ2000=-66:02:25.16 in g-band images obtained from the ASAS-SN "Payne-Gaposchkin" unit located in Sutherland, South Africa, and we promptly announced its discovery to the community via the Transient Name Server, which assigned it the designation AT 2019ahk.

We triggered a spectroscopic follow-up observation with the Low-dispersion Survey Spectrograph 3 (LDSS-3) mounted on the Magellan Clay 6.5m telescope on 2019 January 31.20.

We were awarded 17 epochs of target-of-opportunity (TOO) observations from the Neil Gehrels Swift Gamma-ray Burst Mission (Swift), UltraViolet and Optical Telescope (UVOT), and X-ray Telescope (XRT). See Section 2.4 and 2.6.1.

In addition to the ASAS-SN, Swift, and TESS observations, we also obtained photometric observations in the BVri filters from Las Cumbres Observatory 1m telescopes located in Cerro Tololo, Chile, Siding Spring, Australia, and Sutherland, South Africa. See Section 2.5.

We obtained BVgri magnitudes of the host galaxy (2MASXJ07001137-6602251) from the AAVSO Photometric All-Sky Survey Data Release 10 (APASS; Henden et al. 2015), JHKS magnitudes from the Two Micron All-Sky Survey (2MASS), and W1 and W2 measurements from the Wide-field Infrared Survey Explorer (WISE) AllWISE data release. See Section 2.1.

Since the Swift XRT observations showed evidence of weak X-ray emission as the source rose to peak, we requested two deep (41.4ks each) XMM-Newton Observatory TOO observations of the source. The first observation was taken on 2019 March 1 (ObsID: 0831791001, PI: Auchettl), approximately 3.5 days before peak (MJD_XMM1=58543.21), while the second observation was taken on 2019 April 15 (ObsID: 0831791101, PI: Auchettl), approximately 42 days after peak (MJD_XMM2=58589). See Section 2.6.2.

After obtaining our first classification spectrum of ASASSN-19bt, we began a program of spectroscopic follow-up to complement our photometric data set. Our follow-up spectra were obtained with LDSS-3 on the 6.5m Magellan Clay telescope, the Inamori-Magellan Areal Camera and Spectrograph (IMACS) on the 6.5m Magellan-Baade telescope, the Goodman Spectrograph on the Southern Astrophysical Research (SOAR) 4.1m telescope, and the Wide Field Reimaging CCD Camera (WFCCD) mounted on the du Pont 100 inch telescope. These observations (spanning 2019 Jan 31.20 to 2019 Apr 13.09) included seven spectra obtained prior to peak light and four spectra obtained within 3 days of peak light. See Section 2.7.

(1 data file).