arXiv subjects

B. J. Shappee

Publications and source records attributed to B. J. Shappee.

At least 19 recordsLinked to original sources

arXiv2026

The type Ia supernova 2023vjh: a peculiar 1991bg-like SN with unusually faint light curves

We present observations of the 1991bg-like type Ia supernova (SN) 2023vjh, associated with the elliptical galaxy MCG+04-10-013. Its light-curve shape parameters ($\Delta m_{15}(B)=1.89 \pm 0.01$ mag and $s_{BV} = 0.45 \pm 0.03$), together with its spectroscopic evolution, place it firmly within the class of fast-declining, subluminous SNe Ia. The near-peak spectra show prominent features of Si II, Ca II, and Ti II, consistent with a cool photosphere, and place SN 2023vjh within the "cool" and extreme cool regions on the classification diagrams. In addition, the three late-phase near-infrared (NIR) spectra display the Ca II NIR triplet, Fe II, and Co II absorptions, but no obvious $H$-band break. Although SN 2023vjh falls in the same regions of the classification diagrams as other well-studied 91bg-like events, it shows some deviation within this class. In particular, it is systematically fainter than predicted by explosion models and fainter than other well-studied 91bg-like SNe. Light-curve fitting and color-based analyses indicate a relatively large reddening ($E(B-V)_{host}\sim$ 0.2 - 0.35 mag), which is unusual for 91bg-like SNe. Yet, the lack of detectable Na I D absorption in its spectra, along with its large projected distance from the center of its passive host galaxy (6.8 kpc), suggests that interstellar extinction along the line of sight is minimal. SN 2023vjh appears to be fainter than typical 91bg-like SNe, and it could be affected by circumstellar material (CSM). Comparisons with explosion models and alternative extinction prescriptions show that including CSM-like extinction improves agreement in the blue bands, but residual discrepancies in the $i$-band may reflect limitations in the model.

astro-ph.HE↗

arXiv2026

The Enigmatic Type Icn Supernova 2024abvb Located ~22 kpc from Its Host Galaxy

We report multiwavelength observations of the highly offset (~22.4 kpc) SN 2024abvb, the sixth Type Icn supernova to date. With a peak magnitude of Mr = -19.55 +/- 0.11 mag, it is among the most luminous in the existing sample and shows similar colours and decline rates to other SNe Icn. The early optical spectra show a blue continuum with narrow C II features (vFWHM ~ 2000 km s^-1), consistent with a typical wind velocity of a Wolf-Rayet star. The absence of C III lambda 5696 emission at the time of explosion is consistent with a Type Ibn supernova; however, the lack of narrow He lines in both the optical and near-infrared spectra supports a SNe Icn classification. Unlike the majority of SNe Icn, we do not detect broad features in the late-time (7-21 days relative to o-band peak) spectral phase of SN 2024abvb. Semi-analytical modelling of the light curves shows that it can be reproduced by ~2.6 Msun of SN ejecta interacting with ~0.3 Msun of circumstellar material (CSM), both larger than other SNe Icn but consistent with rapidly evolving SNe Ibn. The metallicity at the SN location is significantly lower than the global metallicity of its host galaxy, suggesting that line-driven mass loss required to strip the progenitor of its H and He envelopes was likely inefficient. We estimate the star-formation-rate history at the location of SN 2024abvb and find that it lies at the bottom ~5th percentile among SESNe hosts, inconsistent with a Wolf-Rayet progenitor. Based on its spectral features, local and host environment properties, and host-galaxy offset, we favour an 8-10 Msun star stripped by a compact companion as the progenitor, with a sufficient runaway velocity to reach the observed offset.

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arXiv2025

University of Hawaii 88-inch Telescope Observations of the Interstellar Comet 3I/ATLAS: Spectrophotometric Blue-Sensitive Spectral Time Series Spanning Two Months from Discovery

Interstellar objects are the ejected building blocks of other solar systems. As such, they enable the acquisition of otherwise inaccessible information about nascent extrasolar systems. The discovery of the third interstellar object, 3I/ATLAS, provides an opportunity to explore the properties of a small body from another solar system and to compare it to the small bodies in our own. To that end, we present spectrophotometric observations of 3I/ATLAS taken using the SuperNova Integral Field Spectrograph on the University of Hawaii 2.2-m telescope. Our data includes the earliest $\lambda\leq3800$ A spectrum of 3I/ATLAS, obtained $\sim$12.5 hours after the discovery announcement. Later spectra confirm previously reported cometary activity, including Ni and CN emission. The data show wavelength-varying spectral slopes ($S\approx($0\%-29\%)/1000 A, depending on wavelength range) throughout the pre-perihelion ($r_h=4.4$-$2.5$ au) approach of 3I/ATLAS. We perform synthetic photometry on our spectra and find 3I/ATLAS shows mostly stable color evolution over the period of our observations, with $g-r$ colors ranging from $\sim$0.69-0.75 mag, $r-i$ colors ranging from $\sim$0.26-0.30 mag, and $c-o$ colors ranging from $\sim$0.50-0.55 mag. Ongoing post-perihelion observations of 3I/ATLAS will provide further insight into its potentially extreme composition.

astro-ph.EP↗

arXiv2025

Spatial Profiles of 3I/ATLAS CN and Ni Outgassing from Keck/KCWI Integral Field Spectroscopy

Cometary activity from interstellar objects provides a unique window into the environs of other stellar systems. We report blue-sensitive integral field unit spectroscopy of the interstellar object 3I/ATLAS from the Keck-II-mounted Keck Cosmic Web Imager on August 24, 2025 UT. We confirm previously reported CN and Ni outgassing, and present, for the first time, the radial profiles of Ni and CN emission in 3I/ATLAS. We find a characteristic $e$-folding radius of $593.7\pm14.8$ km for Ni and $841.0\pm15.4$ km for CN; this suggests that the Ni emission is more centrally concentrated in the nucleus of the comet and favors hypotheses involving easily dissociated species such as metal carbonyls or metal-polycyclic-aromatic-hydrocarbon molecules. Additional integral field spectroscopy after perihelion will offer a continued opportunity to determine the evolution of the radial distributions of species in interstellar comet 3I/ATLAS.

astro-ph.EP↗

arXiv2025

JWST Observations of SN 2024ggi II: NIRSpec Spectroscopy and CO Modeling at 285 and 385 Days Past the Explosion

We present James Webb Space Telescope (JWST) NIRSpec observations of SN~2024ggi, spanning wavelengths of 1.7--5.5 micron at +285.51 and +385.27 days post-explosion. These nebular spectra are dominated by asymmetric emission lines from atomic species including H, Ca, Ar, C, Mg, Ni, Co, and Fe, indicative of an aspherical explosion. The other strong features are molecular CO vibrational bands from the fundamental and first overtone. We introduce a novel, data-driven approach using non-LTE 3D radiative transfer simulations to model the CO emission with high fidelity. This method enables us to constrain the three-dimensional CO distribution and its radial temperature structure. CO formation is found to occur prior to day +285, with subsequent evolution characterized by progressive evaporation. The CO mass decreases from approximately 8.7 to 1.3*E-3 Mo, while the average temperature drops from about 2900 K to 2500 K. Concurrently, the CO distribution transitions from nearly homogeneous to highly clumped (density contrast increasing from fc=1.2 to 2). The minimum velocity of the CO-emitting region remains nearly constant (v1 = 1200 to 1100 km/s), significantly above the receding photosphere velocity (v(ph) = 500 km/s), suggesting the photosphere resides within Si-rich layers. However, the temperature profile indicates that only a narrow zone reaches the conditions necessary for SiO formation. Due to a lack of observational constraints, SiO clumping is not modeled, and thus, synthetic SiO profiles for mass estimates are not highlighted. We discuss the implications of these findings for dust formation processes in SN~2024ggi.

astro-ph.SR↗

arXiv2025

Pan-STARRS follow-up of the gravitational-wave event S250818k and the lightcurve of SN 2025ulz

Kilonovae are the scientifically rich, but observationally elusive, optical transient phenomena associated with compact binary mergers. Only a handful of events have been discovered to date, all through multi-wavelength (gamma ray) and multi-messenger (gravitational wave) signals. Given their scarcity, it is important to maximise the discovery possibility of new kilonova events. To this end, we present our follow-up observations of the gravitational-wave signal, S250818k, a plausible binary neutron star merger at a distance of $237 \pm 62$ Mpc. Pan-STARRS tiled 286 and 318 square degrees (32% and 34% of the 90% sky localisation region) within 3 and 7 days of the GW signal, respectively. ATLAS covered 65% of the skymap within 3 days, but with lower sensitivity. These observations uncovered 47 new transients; however, none were deemed to be linked to S250818k. We undertook an expansive follow-up campaign of AT 2025ulz, the purported counterpart to S250818k. The griz-band lightcurve, combined with our redshift measurement ($z = 0.0849 \pm 0.0003$) all indicate that SN 2025ulz is a SN IIb, and thus not the counterpart to S250818k. We rule out the presence of a AT 2017gfo-like kilonova within $\approx 27$% of the distance posterior sampled by our Pan-STARRS pointings ($\approx 9.1$% across the total 90% three-dimensional sky localisation). We demonstrate that early observations are optimal for probing the distance posterior of the three-dimensional gravitational-wave skymap, and that SN 2025ulz was a plausible kilonova candidate for $\lesssim 5$ days, before ultimately being ruled out.

astro-ph.HE↗

arXiv2025

Supernova rates and luminosity functions from ASAS-SN II: 2014-2017 core-collapse supernovae and their subtypes

The volumetric rates and luminosity functions (LFs) of core-collapse supernovae (ccSN) and their subtypes are important for understanding the cosmic history of star formation and the buildup of ccSN products. To estimate these rates, we use data of nearby ccSNe discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) from 2014--2017, when all observations were made in the $V$-band. The sample is composed of 174 discovered or recovered events, with high spectroscopic completeness from followup observations. This allows us to obtain a statistically precise and systematically robust estimate of nearby rates for ccSNe and their subtypes. The volumetric rates are estimated by correcting the observed number of events for the survey completeness, which was estimated through injection recovery simulations using ccSN light curves. We find a total volumetric rate for ccSNe of $7.0^{+1.0}_{-0.9} \times 10^{-5} \ \textrm{yr}^{-1} \ \textrm{Mpc}^{-3} \ h^{3}_{70}$, at a median redshift of 0.0149, for absolute magnitudes at peak $M_{V,peak} \leq -14$ mag. This result is in agreement with previous local volumetric rates. We obtain volumetric rates for the different ccSN subtypes (II, IIn, IIb, Ib, Ic, Ibn, and Ic-BL), and find that the relative fractions of Type II, stripped-envelope, and interacting ccSNe are $63.2\%$, $32.3\%$, and $4.4\%$, respectively. We also estimate a volumetric rate for superluminous SNe of $1.5^{+4.4}_{-1.1} \ \textrm{yr}^{-1} \ \textrm{Gpc}^{-3} \ h^{3}_{70}$, corresponding to a fraction of $0.002\%$ of the total ccSN rate. We produce intrinsic $V$-band LFs of ccSNe and their subtypes, and show that ccSN rates steadily decline for increasing luminosities. We further investigate the specific ccSN rate as a function of their host galaxy stellar mass, and find that the rate decreases with increasing stellar mass, with significantly higher rates at lower mass galaxies.

astro-ph.HE↗

arXiv2025

JWST Observations of SN 2023ixf II: The Panchromatic Evolution Between 250 and 720 Days After the Explosion

We present the nebular phase spectroscopic and photometric observations of the nearby hydrogen-rich core-collapse supernova (CC-SN) 2023ixf, obtained through our JWST programs. These observations, combined with ground-based optical and near-infrared spectra, cover +252.67 - 719.96 d, creating a comprehensive, panchromatic time-series dataset spanning 0.32 - 30$\mu$m. In this second paper of the series, we focus on identifying key spectral emission features and tracking their evolution through the nebular phase. The JWST data reveal hydrogen emission from the Balmer to Humphreys series, as well as prominent forbidden lines from Ne, Ar, Fe, Co, and Ni. NIRSpec observations display strong emission from the first overtone and fundamental bands of carbon monoxide, which weaken with time as the ejecta cools and dust emission dominates. The spectral energy distribution shows a clear infrared excess emerging by +252.67 d peaking around 10.0$\mu$m, with a secondary bump at 18.0$\mu$m developing by +719.96 d. We suggest that this evolution could arises from multiple warm dust components. In upcoming papers in this series, we will present detailed modeling of the molecular and dust properties. Overall, this dataset significantly advances our understanding of the mid-infrared properties of CC-SNe, providing an unprecedented view of their late-time line, molecule, and dust emission.

astro-ph.SR↗

arXiv2025

A Systematic Search for Big Dippers in ASAS-SN

Dipper stars are extrinsically variable stars with deep dimming events due to extended, often dusty, structures produced by a wide range of mechanisms such as collisions, protoplanetary evolution or stellar winds. ASAS-SN has discovered 12 dipper-like objects as part of its normal operations. Here we systematically search the $\sim 5.1$ million ASAS-SN targets with $13<g<14$~mag for dippers with $\Delta g\ge0.3$~mag to identify 4 new candidates. We also discover 15 long-period eclipsing binary candidates. We characterized the 19 new and 12 previously discovered objects using the ASAS-SN light curves and archival multi-wavelength data. We divide them into three categories: long-period eclipsing binaries with a single eclipse (13 total), long-period eclipsing binaries with multiple eclipses (7 total) and dipper stars with dust or disk occultations (11 total).

astro-ph.SR↗

arXiv2025

JWST Observations of SN 2024ggi I: Interpretation and Model Comparison of the Type II Supernova 2024ggi at 55 days Past Explosion

We present panchromatic 0.4-21 microns observations of the nearby (about 7.2 Mpc) Type II supernova 2024ggi, obtained during the plateau phase at about 55 d past explosion. Our dataset includes JWST spectra spanning 1.7-14 microns, MIR imaging at 7.7 and 21 microns, and near-simultaneous ground-based optical and NIR spectra covering 0.32-1.8 microns. The NIR and MIR spectral features of SN 2024ggi are dominated by HI emission. We present line IDs and a toy PHOENIX/1D model that reproduces the observations well, especially the continuum redward of 0.9 microns We compare SN 2024ggi to SN 2022acko and SN 2023ixf, two other Type II supernovae that were also observed by JWST, and highlight key similarities and differences in their spectral features. No evidence for a MIR excess or dust is found at these epochs, with the model matching the observed flux out to 21 microns. We discuss the model's shortcomings, focusing on the density profile, which suppresses line blanketing and produces features in the optical that are too narrow. Our results show the power of panchromatic studies in both exploring the nature of the SN ejecta and constraining detailed models of SNe.

astro-ph.SR↗

arXiv2025

JWST Observations of SN 2023ixf I: Completing the Early Multi-Wavelength Picture with Plateau-phase Spectroscopy

We present and analyze panchromatic (0.35--14 $\mu$m) spectroscopy of the Type II supernova 2023ixf, including near- and mid-infrared spectra obtained 33.6 days after explosion during the plateau-phase, with the James Webb Space Telescope (JWST). This is the first in a series of papers examining the evolution of SN 2023ixf with JWST spanning the initial 1000 days after explosion, monitoring the formation and growth of molecules and dust in ejecta and surrounding environment. The JWST infrared spectra are overwhelmingly dominated by H lines, whose profiles reveal ejecta structures, including flat tops, blue notches, and red shoulders, unseen in the optical spectra. We characterize the nature of these structures, concluding that they likely result from a combination of ejecta geometry, viewing angle, and opacity effects. We find no evidence for the formation of dust precursor molecules such as carbon-monoxide (CO), nor do we observe an infrared excess attributable to dust. These observations imply that the detections of molecules and dust in SN 2023ixf at later epochs arise either from freshly synthesized material within the ejecta or circumstellar material at radii not yet heated by the supernova at this epoch.

astro-ph.HE↗

arXiv2025

ASASSN-24fw: An 8-month long, 4.1 mag, optically achromatic and polarized dimming event

We discuss ASASSN-24fw, a 13th-magnitude star that optically faded by $\Delta g = 4.12 \pm 0.02$ mag starting in September 2024 after over a decade of quiescence in ASAS-SN. The dimmimg lasted $\sim$8 months before returning to quiescence in late May 2025. The spectral energy distribution (SED) before the event is that of a pre-main sequence or a modestly evolved F star with some warm dust emission. The shape of the optical SED during the dim phase is unchanged and the optical and near-infrared spectra are those of an F star. The SED and the dilution of some of the F star infrared absorption features near minimum suggest the presence of a $\sim$0.25$M_\odot$ M dwarf binary companion. The 43.8 year period proposed by Nair & Denisenko (2024) appears correct and is probably half the precession period of a circumbinary disk. The optical eclipse is nearly achromatic, although slightly deeper in bluer filters, $\Delta (g-z)=0.31\pm0.15$ mag, and the $V$ band emission is polarized by up to 4%. The materials most able to produce such small optical color changes and a high polarization are big ($\sim$20 $\mu$m) carbonaceous or water ice grains. Particle distributions dominated by big grains are seen in protoplanetary disks, Saturn-like ring systems and evolved debris disks. We also carry out a survey of occultation events, finding 46 additional systems, of which only 7 (4) closely match $\varepsilon$ Aurigae (KH 15D), the two archetypes of stars with long and deep eclipses. The full sample is widely distributed in an optical color-magnitude diagram, but roughly half show a mid-IR excess. It is likely many of the others have cooler dust since it seems essential to produce the events.

astro-ph.SR↗

arXiv2025

The Hawaii Infrared Supernova Study (HISS): Spectroscopic Data Release 1

We present the first data release of the Hawaii Infrared Supernova Study (\textit{HISS}), consisting of a large sample of near-infrared (NIR) spectra, $0.7 - 2.5 \mathrm{\mu m}$, obtained with the Keck-II/NIRES and IRTF/SpeX spectrographs. This sample is comprised of 90 NIR spectra of 48 transient events, spanning from hours after explosion to $\geq + 350$ days. Acquired over three years (2021-2024), this data release includes 17 Type Ia SNe, 15 Type II SNe, 8 Stripped Envelope SNe, 6 interacting SNe, 1 TDE, and 1 SLSN-I. These spectra were all systematically reduced using either the \textsc{Python}-based reduction code \textsc{Pypeit} or the \textsc{IDL}-based \textsc{Spextool} and constitute one of the largest NIR samples of transients available to the astrophysical community. We show the utility of NIR spectra and identify the key spectral features across multiple types of SNe. We show how both early-time and nebular-phase NIR spectra can be used to investigate the physics of the explosion, and to reveal the properties of the progenitor. With the addition of this dataset, the number of publicly available NIR spectra spanning multiple transient types has been substantially increased. In its next phase, \textit{HISS} will leverage target-of-opportunity spectral observations and NIR imaging from telescopes on Maunakea. Expanding the NIR dataset of SNe is vital to the transient community, particularly in light of the increasing emphasis on the infrared regime following the recent launch of the \textit{James Webb Space Telescope} and the forthcoming launch of the \textit{Nancy Grace Roman Space Telescope}.

astro-ph.HE↗

arXiv2025

Early and Extensive Ultraviolet Through Near Infrared Observations of the Intermediate-Luminosity Type Iax Supernovae 2024pxl

We present ultraviolet (UV) through near-infrared (NIR) photometric and spectroscopic observations of the nearby SN 2024pxl, the third Type Ia supernova (SN Ia) in NGC 6384. SN 2024pxl is a Type Iax supernova (SN Iax) with an intermediate luminosity ($M_r = -16.99\pm0.32$ mag) and an average SN Iax light curve decline rate. SN 2024pxl was discovered $\sim$3 days after first light, and the rising light curve follows a single power law that is inconsistent with significant interaction with a companion star or circumstellar material. Our extensive NIR photometric coverage is comparable to that of the well-observed SNe Iax 2005hk and 2012Z, and we demonstrate that the $J-H$ colors of SNe Iax differ from normal SNe Ia and appear to be more homogeneous as a class. Spectroscopically, we report the earliest-ever NIR spectrum of a SN Iax as measured from maximum light ($t\approx-9$ days): a featureless continuum with similarities to a $\sim$9,000 K blackbody, and the line velocities are consistent with a mixed-ejecta structure, with C, Si, and Fe having similar velocities and velocity evolutions. We find a tentative correlation between the $H$-band break Co II velocity $\sim$20 days post-peak and absolute magnitude, with more luminous SNe Iax showing faster Co II velocities. Our observations suggest that SN 2024pxl resulted from the thermonuclear disruption of a CO white dwarf star that undergoes deflagration burning.

astro-ph.HE↗

arXiv2025

ASASSN-13dn: A Luminous and Double-Peaked Type II Supernova

We present observations of ASASSN-13dn, one of the first supernovae discovered by ASAS-SN, and a new member of the rare group of Luminous Type II Supernovae (LSNe II). It was discovered near maximum light, reaching an absolute magnitude of M$_{v}$ $\sim$ -19 mag, placing this object between normal luminosity type II SNe and superluminous SNe A detailed analysis of the photometric and spectroscopic data of ASASSN-13dn is performed. The spectra are characterized by broad lines, in particular the H$\alpha$ lines where we measure expansion velocities ranging between 14000 - 6000 km s$^{-1}$ over the first 100 days. H$\alpha$ dominates the nebular spectra, and we detect a narrow P-Cygni absorption within the broader emission line with an expansion velocity of 1100 km s$^{-1}$. Photometrically, its light curve shows a re-brightening of $\sim$ 0.6 mag in the $gri$ bands starting at 25$\pm$2 days after discovery, with a secondary peak at $\sim 73$d, followed by an abrupt and nearly linear decay of 0.09 mag d$^{-1}$ for the next 35 days. At later times, after a drop of 4 magnitudes from the second maximum, the light curves of ASASSN-13dn shows softer undulations from 125 to 175 days. We compare ASASSN-13dn with other LSNe II in the literature, finding no match to both light curve and spectroscopic properties. We discuss the main powering mechanism and suggest that interaction between the ejecta and a dense CSM produced by eruptions from an LBV-like progenitor could potentially explain the observations.

astro-ph.SR↗

arXiv2025

Seeing the Outer Edge of the Infant Type Ia Supernova 2024epr in the Optical and Near Infrared

We present optical-to-near-infrared (NIR) photometry and spectroscopy of the Type Ia supernova (SN Ia) 2024epr, including NIR spectra observed within two days of first light. The early-time optical spectra show strong, high-velocity Ca and Si features near rarely-observed velocities at $\sim$0.1$c$, and the NIR spectra show a C I "knee." Despite early-time, high-velocity features, SN 2024epr evolves into a normal SN Ia, albeit with stronger peak-light Ca absorption than other SNe Ia with the same light curve shape. Although we infer a normal decline rate, $\Delta m_{15}(B)=1.09\pm0.12$ mag, from the light-curve rise, SN 2024epr is a Branch "cool" object and has red early-time colors ($g-r\approx0.15$ mag at $-10$ days). The high velocities point to a density enhancement in the outer layers of the explosion, predicted by some models, but thick-shell He-detonation models do not match the smoothly rising light curve or apparent lack of He in our early-time NIR spectra. No current models (e.g., delayed detonation or thin He shell double detonation) appear to reproduce all observed properties, particularly the unusual early-time colors. Such constraints are only possible for SN 2024epr from the earliest optical and NIR observations, highlighting their importance for constraining SN Ia models. Finally, we identify several literature SNe Ia with intermediate mass elements at $\sim$30\,000 km s$^{-1}$ within days after the explosion that evolve into otherwise normal SNe Ia at peak light, suggesting the early-time spectra of SNe Ia may hide a broad diversity of observational characteristics.

astro-ph.HE↗

arXiv2024

Optical and near-infrared photometry of 94 type II supernovae from the Carnegie Supernova Project

Type II supernovae (SNeII) mark the endpoint in the lives of hydrogen-rich massive stars. Their large explosion energies and luminosities allow us to measure distances, metallicities, and star formation rates into the distant Universe. To fully exploit their use in answering different astrophysical problems, high-quality low-redshift data sets are required. Such samples are vital to understand the physics of SNeII, but also to serve as calibrators for distinct - and often lower-quality - samples. We present uBgVri optical and YJH near-infrared (NIR) photometry for 94 low-redshift SNeII observed by the Carnegie Supernova Project (CSP). A total of 9817 optical and 1872 NIR photometric data points are released, leading to a sample of high-quality SNII light curves during the first ~150 days post explosion on a well-calibrated photometric system. The sample is presented and its properties are analysed and discussed through comparison to literature events. We also focus on individual SNeII as examples of classically defined subtypes and outlier objects. Making a cut in the plateau decline rate of our sample (s2), a new subsample of fast-declining SNeII is presented. The sample has a median redshift of 0.015, with the nearest event at 0.001 and the most distant at 0.07. At optical wavelengths (V), the sample has a median cadence of 4.7 days over the course of a median coverage of 80 days. In the NIR (J), the median cadence is 7.2 days over the course of 59 days. The fast-declining subsample is more luminous than the full sample and shows shorter plateau phases. Of the non-standard SNeII highlighted, SN2009A particularly stands out with a steeply declining then rising light curve, together with what appears to be two superimposed P-Cygni profiles of H-alpha in its spectra. We outline the significant utility of these data, and finally provide an outlook of future SNII science.

astro-ph.CO↗

arXiv2024

Citizen ASAS-SN Data Release II: Variable Star Classification Using Citizen Science

We present the second results from Citizen ASAS-SN, a citizen science project for the All-Sky Automated Survey for Supernovae (ASAS-SN) hosted on the Zooniverse platform. Citizen ASAS-SN tasks users with classifying variable stars based on their light curves. We started with 94975 new variable candidates and identified 4432 new variable stars. The users classified the new variables as 841 pulsating variables, 2995 rotational variables, 350 eclipsing binaries, and 246 unknown variables. We found 68% user agreement for user-classified pulsating variables, 51% for rotational variables, and 77% for eclipsing binaries. We investigate user statistics and compare new variables to known variables. We present a sample of variables flagged as interesting or unusual.

astro-ph.SR↗