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We present optical and near-infrared observations of SN~2022crv, a stripped envelope supernova in NGC~3054, discovered within 12 hrs of explosion by the Distance Less Than 40 Mpc Survey. We suggest SN~2022crv is a transitional object on the continuum between SNe Ib and SNe IIb. A high-velocity hydrogen feature ($\sim$$-$20,000 -- $-$16,000 $\rm km\,s^{-1}$) was conspicuous in SN~2022crv at early phases, and then quickly disappeared around maximum light. By comparing with hydrodynamic modeling, we find that a hydrogen envelope of $\sim 10^{-3}$ \msun{} can reproduce the behaviour of the hydrogen feature observed in SN~2022crv. The early light curve of SN~2022crv did not show envelope cooling emission, implying that SN~2022crv had a compact progenitor with extremely low amount of hydrogen. The analysis of the nebular spectra shows that SN~2022crv is consistent with the explosion of a He star with a final mass of $\sim$4.5 -- 5.6 \msun{} that has evolved from a $\sim$16 -- 22 \msun{} zero-age main sequence star in a binary system with about 1.0 -- 1.7 \msun{} of oxygen finally synthesized in the core. The high metallicity at the supernova site indicates that the progenitor experienced a strong stellar wind mass loss. In order to retain a small amount of residual hydrogen at such a high metallicity, the initial orbital separation of the binary system is likely larger than $\sim$1000~$\rm R_{\odot}$. The near-infrared spectra of SN~2022crv show a unique absorption feature on the blue side of He I line at $\sim$1.005~$\mu$m. This is the first time that such a feature has been observed in a Type Ib/IIb, and could be due to \ion{Sr}{2}. Further detailed modelling on SN~2022crv can shed light on the progenitor and the origin of the mysterious absorption feature in the near infrared., Comment: 33 pages, 23 figures, submitted to ApJ

We report on analysis using the James Webb Space Telescope (JWST) to identify a candidate progenitor star of the Type II-plateau supernova SN 2022acko in the nearby, barred spiral galaxy NGC 1300. To our knowledge, our discovery represents the first time JWST has been used to localize a progenitor system in pre-explosion archival Hubble Space Telescope (HST) images. We astrometrically registered a JWST NIRCam image from 2023 January, in which the SN was serendipitously captured, to pre-SN HST F160W and F814W images from 2017 and 2004, respectively. An object corresponding precisely to the SN position has been isolated with reasonable confidence. That object has a spectral energy distribution (SED) and overall luminosity consistent with a single-star model having an initial mass possibly somewhat less than the canonical 8 Msun theoretical threshold for core collapse (although masses as high as 9 Msun for the star are also possible); however, the star's SED and luminosity are inconsistent with that of a super-asymptotic giant branch star which might be a forerunner of an electron-capture SN. The properties of the progenitor alone imply that SN 2022acko is a relatively normal SN II-P, albeit most likely a low-luminosity one. The progenitor candidate should be confirmed with follow-up HST imaging at late times, when the SN has sufficiently faded. This potential use of JWST opens a new era of identifying SN progenitor candidates at high spatial resolution., Comment: 8 pages, substantial changes from v1, to appear in MNRAS

We present high cadence optical and ultraviolet observations of the Type II supernova (SN), SN 2022jox which exhibits early spectroscopic high ionization flash features of \ion{H}{1}, \ion{He}{2}, \ion{C}{4}, and \ion{N}{4} that disappear within the first few days after explosion. SN 2022jox was discovered by the Distance Less than 40 Mpc (DLT40) survey $\sim$0.75 days after explosion with followup spectra and UV photometry obtained within minutes of discovery. The SN reached a peak brightness of M$_V \sim$ $-$17.3 mag, and has an estimated $^{56}$Ni mass of 0.04 M$_{\odot}$, typical values for normal Type II SNe. The modeling of the early lightcurve and the strong flash signatures present in the optical spectra indicate interaction with circumstellar material (CSM) created from a progenitor with a mass loss rate of $\dot{M} \sim 10^{-3}-10^{-2}\ M_\odot\ \mathrm{yr}^{-1}$. There may also be some indication of late-time CSM interaction in the form of an emission line blueward of H$\alpha$ seen in spectra around 200 days. The mass-loss rate is much higher than the values typically associated with quiescent mass loss from red supergiants, the known progenitors of Type II SNe, but is comparable to inferred values from similar core collapse SNe with flash features, suggesting an eruptive event or a superwind in the progenitor in the months or years before explosion., Comment: ApJ, accepted 2024 Feb 14

A thermonuclear explosion triggered by a helium-shell detonation on a carbon-oxygen white dwarf core has been predicted to have strong UV line blanketing at early times due to the iron-group elements produced during helium-shell burning. We present the photometric and spectroscopic observations of SN 2016dsg, a sub-luminous peculiar Type I SN consistent with a thermonuclear explosion involving a thick He shell. With a redshift of 0.04, the $i$-band peak absolute magnitude is derived to be around -17.5. The object is located far away from its host, an early-type galaxy, suggesting it originated from an old stellar population. The spectra collected after the peak are unusually red, show strong UV line blanketing and weak O I $\lambda$7773 absorption lines, and do not evolve significantly over 30 days. An absorption line around 9700-10500 \AA is detected in the near-infrared spectrum and is likely from the unburnt helium in the ejecta. The spectroscopic evolution is consistent with the thermonuclear explosion models for a sub-Chandrasekhar mass white dwarf with a thick helium shell, while the photometric evolution is not well described by existing models., Comment: accepted for publication in ApJ

We present photometric and spectroscopic observations of the nearby ($D\approx28$ Mpc) interacting supernova (SN) 2019esa, discovered within hours of explosion and serendipitously observed by the Transiting Exoplanet Survey Satellite (TESS). Early, high cadence light curves from both TESS and the DLT40 survey tightly constrain the time of explosion, and show a 30 day rise to maximum light followed by a near constant linear decline in luminosity. Optical spectroscopy over the first 40 days revealed a highly reddened object with narrow Balmer emission lines seen in Type IIn supernovae. The slow rise to maximum in the optical lightcurve combined with the lack of broad H$\alpha$ emission suggest the presence of very optically thick and close circumstellar material (CSM) that quickly decelerated the supernova ejecta. This CSM was likely created from a massive star progenitor with an $\dot{M}$ $\sim$ 0.3 M$_{\odot}$ yr$^{-1}$ lost in a previous eruptive episode 3--4 years before eruption, similar to giant eruptions of luminous blue variable stars. At late times, strong intermediate-width Ca II, Fe I, and Fe II lines are seen in the optical spectra, identical to those seen in the superluminous interacting SN 2006gy. The strong CSM interaction masks the underlying explosion mechanism in SN 2019esa, but the combination of the luminosity, strength of the H$\alpha$ lines, and mass loss rate of the progenitor all point to a core collapse origin., Comment: Submitted to ApJ 2022 May 21

We present optical photometry and spectroscopy of the Type II supernova ASASSN-14jb, together with VLT MUSE IFU observations of its host galaxy and a nebular-phase spectrum. This SN, in the nearby galaxy ESO 467-G051 ($z=0.006$), was discovered and followed-up by the All Sky Automated Survey for SuperNovae (ASAS-SN). We present LCOGTN $BVgri$ and $Swift$ $w2m1w1ubv$ optical and near-UV/optical light curves and several optical spectra in the early photospheric phase. ASASSN-14jb exploded $\sim 2$ kpc above the star-forming disk of ESO 467-G051, an edge-on disk galaxy. The large projected distance from the disk and non-detection of any H II region in a 1.4 kpc radius in projection are in conflict with the standard environment of core-collapse supernova progenitors and suggests the possible scenario that the progenitor received a kick in a binary interaction. Our analysis yields $D=25\pm 1$ Mpc, $M(^{56}Ni) = 0.0210 \pm 0.0025$ M$_\odot$, $E_{exp}\approx 0.25 \times 10^{51}$ ergs, $M_{ej}\approx 6$ M$_\odot$, and progenitor $R_* = 580 \pm 28$ R$_\odot$, which seems to be consistent with the sub-Solar metallicity of $0.3 \pm 0.1$ Z$_\odot$ derived from the SN spectrum. The nebular spectrum constrains $M_{prog} \simeq 10-12 $ M$_{\odot}$. We discuss the low oxygen abundance of the host galaxy derived from the MUSE data, $12+\log{(O/H)} = 8.27^{+0.16}_{-0.20}$ (O3N2 strong line method), and compare it with the supernova spectra, which is also consistent with a sub-Solar metallicity progenitor. We finally discuss the possible scenarios for the unusual environment for ASASSN-14jb and conclude that either the in-situ star formation or a runaway would imply a low mass progenitor, agreeing with our estimate from the supernova nebular spectrum. We show that the detailed study of the environment can agree with the stronger constrains of the transient observations. (abridged), Comment: 24 pages, submitted to A&A

We present optical photometry and spectroscopy of the Type II supernova ASASSN-14jb, together with VLT MUSE IFU observations of its host galaxy and a nebular-phase spectrum. This SN, in the nearby galaxy ESO 467-G051 ($z=0.006$), was discovered and followed-up by the All Sky Automated Survey for SuperNovae (ASAS-SN). We present LCOGTN $BVgri$ and $Swift$ $w2m1w1ubv$ optical and near-UV/optical light curves and several optical spectra in the early photospheric phase. ASASSN-14jb exploded $\sim 2$ kpc above the star-forming disk of ESO 467-G051, an edge-on disk galaxy. The large projected distance from the disk and non-detection of any H II region in a 1.4 kpc radius in projection are in conflict with the standard environment of core-collapse supernova progenitors and suggests the possible scenario that the progenitor received a kick in a binary interaction. Our analysis yields $D=25\pm 1$ Mpc, $M(^{56}Ni) = 0.0210 \pm 0.0025$ M$_\odot$, $E_{exp}\approx 0.25 \times 10^{51}$ ergs, $M_{ej}\approx 6$ M$_\odot$, and progenitor $R_* = 580 \pm 28$ R$_\odot$, which seems to be consistent with the sub-Solar metallicity of $0.3 \pm 0.1$ Z$_\odot$ derived from the SN spectrum. The nebular spectrum constrains $M_{prog} \simeq 10-12 $ M$_{\odot}$. We discuss the low oxygen abundance of the host galaxy derived from the MUSE data, $12+\log{(O/H)} = 8.27^{+0.16}_{-0.20}$ (O3N2 strong line method), and compare it with the supernova spectra, which is also consistent with a sub-Solar metallicity progenitor. We finally discuss the possible scenarios for the unusual environment for ASASSN-14jb and conclude that either the in-situ star formation or a runaway would imply a low mass progenitor, agreeing with our estimate from the supernova nebular spectrum. We show that the detailed study of the environment can agree with the stronger constrains of the transient observations. (abridged), Comment: 24 pages, submitted to A&A