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We present high-cadence photometric and spectroscopic observations of SN~2020jfo in ultraviolet and optical/near-infrared bands starting from $\sim 3$ to $\sim 434$ days after the explosion, including the earliest data with the 10.4\,m GTC. SN~2020jfo is a hydrogen-rich Type II SN with a relatively short plateau duration ($67.0 \pm 0.6$ days). When compared to other Type II supernovae (SNe) of similar or shorter plateau lengths, SN~2020jfo exhibits a fainter peak absolute $V$-band magnitude ($M_V = -16.90 \pm 0.34$ mag). SN~2020jfo shows significant H$\alpha$ absorption in the plateau phase similar to that of typical SNe~II. The emission line of stable [Ni~II] $\lambda$7378, mostly seen in low-luminosity SNe~II, is very prominent in the nebular-phase spectra of SN~2020jfo. Using the relative strengths of [Ni~II] $\lambda$7378 and [Fe~II] $\lambda$7155, we derive the Ni/Fe production (abundance) ratio of 0.08--0.10, which is $\sim 1.5$ times the solar value. The progenitor mass of SN~2020jfo from nebular-phase spectral modelling and semi-analytical modelling falls in the range of 12--15\,$M_\odot$. Furthermore, semi-analytical modelling suggests a massive H envelope in the progenitor of SN~2020jfo, which is unlikely for SNe~II having short plateaus., Comment: 20 pages (plus 5 pages appendix), 19 figures, Accepted for publication in MNRAS

In this letter, we present recent observations from the Hubble Space Telescope of the interacting transient, SN 2016jbu, at +5 years. We find no evidence for any additional outburst from SN 2016jbu, and the optical source has now faded significantly below the progenitor magnitudes from early 2016. Similar to recent observations of SN 2009ip and SN 2015bh, SN 2016jbu has not undergone a significant change in colour over the past 2 years, suggesting that there is a lack of on-going dust formation. We find SN 2016jbu is fading slower than that expected from radioactive nickel, but faster than the decay of SN 2009ip. The late time light curve displays a non-linear decline and follows on from a re-brightening event that occurred $\sim$8 months after peak brightness, suggesting CSM interaction continues to dominate SN 2016jbu. While our optical observations are plausibly consistent with a surviving, hot, dust-enshrouded star, this would require an implausibly large dust mass. These new observations suggest that SN 2016jbu is a genuine, albeit strange, supernova, and we discuss the plausibility of a surviving binary companion., Comment: 5 pages, 4 figures, submitted to A&A letters

This note presents an initial survey design for the Nancy Grace Roman High-latitude Time Domain Survey. This is not meant to be a final or exhaustive list of all the survey strategy choices, but instead presents a viable path towards achieving the desired precision and accuracy of dark energy measurements using Type Ia supernovae (SNe Ia). We describe a survey strategy that use six filters (RZYJH and F) and the prism on the Roman Wide Field Instrument. This survey has two tiers, one "wide" which targets SNe Ia at redshifts up to 1 and one "deep" targeting redshifts up to 1.7; for each, four filters are used (with Y and J used in both tiers). We propose one field each in the north and south continuous viewing zones, and expect to obtain high-quality distances of $\sim$12,000 SNe Ia with $\sim$5,000 at z > 1. We propose a wide-tier area of $\sim$19 deg$^2$ and a deep tier of $\sim$5 deg$^2$. Exposure times range from 100 s to 900 s for imaging and 900 s to 3600 s for the prism. These exposure times would reach $\sim$25.5 mag and $\sim$26.5 mag for the wide and deep tiers respectively, with deep co-add stacks reaching $\sim$28 mag and $\sim$29 mag. The total survey spans two years, with a total allocation time of six months, and a cadence of $\sim$5 days., Comment: A report to NASA from the Roman Supernova Science Investigation Teams