H$alpha$ Luminosity of ATLAS18qtd Does Not Plateau in the Nebular Phase

We present new spectroscopic and photometric observations of ATLAS18qtd/SN 2018cqj, a fast-declining Type Ia supernova with variable H$alpha$ emission in previously-published nebular phase spectra. ATLAS18qtd is undetected in both spectroscopic and photometric observations which occurred at $sim 540~rm d$ after maximum light and $sim 230~rm d$ after the last H$alpha$ detection. With these new non-detections, we place an upper limit on the H$alpha$ luminosity of $lesssim 1.1times 10^{36}~rm{erg}~rm s^{-1}$ indicating the H$alpha$ flux decreased by a factor of $gtrsim 4$ since the previous detection. This upper limit excludes H$alpha$ emission that plateaus or increases since the previous detection but cannot confirm that the H$alpha$ emission decay rate is equivalent to the supernova decay rate.

The Rise and Fall of ASASSN-18pg: Following a TDE from Early To Late Times

We present nearly 500 days of observations of the tidal disruption event ASASSN-18pg, spanning from 54 days before peak light to 441 days after peak light. Our dataset includes X-ray, UV, and optical photometry, optical spectroscopy, radio observations, and the first published spectropolarimetric observations of a TDE. ASASSN-18pg was discovered on 2018 July 11 by the All-Sky Automated Survey for Supernovae (ASAS-SN) at a distance of $d=78.6$ Mpc, and with a peak UV magnitude of $msimeq14$ it is both one of the nearest and brightest TDEs discovered to-date. The photometric data allow us to track both the rise to peak and the long-term evolution of the TDE. ASASSN-18pg peaked at a luminosity of $Lsimeq2.2times10^{44}$ erg s$^{-1}$, and its late-time evolution is shallower than a flux $propto t^{-5/3}$ power-law model, similar to what has been seen in other TDEs. ASASSN-18pg exhibited Balmer lines and spectroscopic features consistent with Bowen fluorescence prior to peak which remained detectable for roughly 225 days after peak. Analysis of the two-component H$alpha$ profile indicates that, if they are the result of reprocessing of emission from the accretion disk, the different spectroscopic lines may be coming from regions between $sim10$ and $sim60$ light-days from the black hole. No X-ray emission is detected from the TDE and there is no evidence of a jet or strong outflow detected in the radio. Our spectropolarimetric observations give no strong evidence for significant asphericity in the emission region, with the emission region having an axis ratio of at least $sim0.65$.

White Dwarf Variability with gPhoton: Pulsators

We present results from a search for short time-scale white dwarf variability using texttt{gPhoton}, a time-tagged database of textit{GALEX} photon events and associated software package. We conducted a survey of $320$ white dwarf stars in the McCook-Sion catalogue, inspecting each for photometric variability with particular emphasis on variability over time-scales less than $sim 30$ minutes. From that survey, we present the discovery of a new pulsating white dwarf: WD 2246-069. A Ca II K line is found in archival ESO spectra and an IR excess is seen in WISE $W1$ and $W2$ bands. Its independent modes are identified in follow-up optical photometry and used to model its interior structure. Additionally, we detect UV pulsations in four previously known pulsating ZZ Ceti-type (DAVs). Included in this group is the simultaneous fitting of the pulsations of WD 1401-147 in optical, near-ultraviolet and far-ultraviolet bands using nearly concurrent Whole Earth Telescope and textit{GALEX} data, providing observational insight into the wavelength dependence of white dwarf pulsation amplitudes.