Environmental Dependence of Type Ia Supernovae in Low-Redshift Galaxy Clusters

We present an analysis of 102 type Ia supernovae (SNe Ia) in nearby (z < 0.1), x-ray selected galaxy clusters. This is the largest such sample to date and is based on archival data primarily from ZTF and ATLAS. We divide our SNe Ia into an inner cluster sample projected within $r_{500}$ of the cluster center and an outer cluster sample projected between $r_{500}$ and $2\,r_{500}$. We compare these to field samples of SNe Ia at similar redshifts in both quiescent and star-forming host galaxies. Based on SALT3 fits to the light curves, we find that the inner cluster SNe Ia have a higher fraction of fast-evolving objects (SALT3 $x_1 < -1$) than the outer cluster or field quiescent samples. This implies an intrinsically different population of SNe Ia occurs in inner cluster environments, beyond known correlations based on host galaxy alone. Our cluster samples show a strongly bimodal $x_1$ distribution with a fast-evolving component that dominates the inner cluster objects ($\gtrsim$ 75%) but is just a small fraction of SNe Ia in field star-forming galaxies ($\lesssim$ 10%). We do not see strong evidence for variations in the color (SALT3 $c$) distributions among the samples and find only minor differences in SN Ia standardization parameters and Hubble residuals. We suggest that the age of the stellar population drives the observed distributions, with the oldest populations nearly exclusively producing fast-evolving SNe Ia.Comment: Submitted to AAS journal

Sensitive and Specific Detection of Mycoplasma species by Consensus Polymerase Chain Reaction and Dot Blot Hybridization

Mycoplasmas are highly fastidious bacteria, difficult to culture and slow growing. Many species of mycoplasmas are important pathogens that cause respiratory infection in laboratory animals and that are known to affect experimental results obtained with contaminated animals. The aim of the present study was to develop a sensitive and specific assay for the detection of mycoplasma species. To this end, we developed a polymerase chain reaction and dot blot hybridization assay (PCR/DBH) for detecting mycoplasma DNA and evaluated it for its sensitivity and specificity. Mycoplasma consensus primer pairs were used for the amplification of target DNA. When PCR product was visually detected, the limit of detection of the PCR test was 102 pg of mycoplasma purified DNA. For DBH, the amplified DNA was labeled by incorporation of digoxigenin (DIG). This DIG-labeled probe was capable of detecting 104 pg of purified mycoplasma DNA by DBH. PCR/DBH was more sensitive than PCR or DBH alone and was also very specific. Our PCR/DBH assay can be applied efficiently to confirm the presence of mycoplasma species on clinical samples and to differentiate between mycoplasma species infection and other bacterial infections

A JWST Near- and Mid-Infrared Nebular Spectrum of the Type Ia Supernova 2021aefx

We present JWST near- and mid-infrared spectroscopic observations of the nearby normal Type Ia supernova SN 2021aefx in the nebular phase at $+255$ days past maximum light. Our Near Infrared Spectrograph (NIRSpec) and Mid Infrared Instrument (MIRI) observations, combined with ground-based optical data from the South African Large Telescope (SALT), constitute the first complete optical $+$ NIR $+$ MIR nebular SN Ia spectrum covering 0.3$-$14 $\\mu$m. This spectrum unveils the previously unobserved 2.5$-$5 $\\mu$m region, revealing strong nebular iron and stable nickel emission, indicative of high-density burning that can constrain the progenitor mass. The data show a significant improvement in sensitivity and resolution compared to previous Spitzer MIR data. We identify numerous NIR and MIR nebular emission lines from iron-group elements and as well as lines from the intermediate-mass element argon. The argon lines extend to higher velocities than the iron-group elements, suggesting stratified ejecta that are a hallmark of delayed-detonation or double-detonation SN Ia models. We present fits to simple geometric line profiles to features beyond 1.2 $\\mu$m and find that most lines are consistent with Gaussian or spherical emission distributions, while the [Ar III] 8.99 $\\mu$m line has a distinctively flat-topped profile indicating a thick spherical shell of emission. Using our line profile fits, we investigate the emissivity structure of SN 2021aefx and measure kinematic properties. Continued observations of SN 2021aefx and other SNe Ia with JWST will be transformative to the study of SN Ia composition, ionization structure, density, and temperature, and will provide important constraints on SN Ia progenitor and explosion models

Ultraviolet Spectroscopy and TARDIS Models of the Broad-lined Type-Ic Supernova 2014ad

Few published ultraviolet (UV) spectra exist for stripped-envelope supernovae, and none to date for broad-lined Type Ic supernovae (SN Ic-bl). These objects have extremely high ejecta velocities and are the only supernova type directly linked to gamma-ray bursts (GRBs). Here we present two epochs of HST/STIS spectra of the SN Ic-bl 2014ad, the first UV spectra for this class. We supplement this with 26 new epochs of ground-based optical spectra, augmenting a rich spectral time series. The UV spectra do not show strong features, likely due to high opacity, and are consistent with broadened versions of other SN Ic spectra observed in the UV. We measure Fe II 5169 Angstrom velocities and show that SN 2014ad has even higher ejecta velocities than most SNe Ic both with and without observed GRBs. We construct models of the SN 2014ad UV+optical spectra using TARDIS, a 1D Monte-Carlo radiative-transfer spectral synthesis code. The models fit the data well at multiple epochs in the optical but underestimate the flux in the UV. We find that high densities at high velocities are needed to reproduce the spectra, with $\sim$3 M$_\odot$ of material at $v >$ 22,000 km s$^{-1}$, assuming spherical symmetry. Our nebular line fits suggest a steep density profile at low velocities. Together, these results imply a higher total ejecta mass than estimated from previous light curve analysis and expected from theory. This may be reconciled by a flattening of the density profile at low velocity and extra emission near the center of the ejecta.Comment: 25 pages, 14 figures, submitted to AAS Journal

SN 2019ewu: A Peculiar Supernova with Early Strong Carbon and Weak Oxygen Features from a New Sample of Young SN Ic Spectra

With the advent of high cadence, all-sky automated surveys, supernovae (SNe) are now discovered closer than ever to their dates of explosion. However, young pre-maximum light follow-up spectra of Type Ic supernovae (SNe Ic), probably arising from the most stripped massive stars, remain rare despite their importance. In this paper we present a set of 49 optical spectra observed with the Las Cumbres Observatory through the Global Supernova Project for 6 SNe Ic, including a total of 17 pre-maximum spectra, of which 8 are observed more than a week before V-band maximum light. This dataset increases the total number of publicly available pre-maximum light SN Ic spectra by 25% and we provide publicly available SNID templates that will significantly aid in the fast identification of young SNe Ic in the future. We present detailed analysis of these spectra, including Fe II 5169 velocity measurements, O I 7774 line strengths, and continuum shapes. We compare our results to published samples of stripped supernovae in the literature and find one SN in our sample that stands out. SN 2019ewu has a unique combination of features for a SN Ic: an extremely blue continuum, high absorption velocities, a P-cygni shaped feature almost 2 weeks before maximum light that TARDIS radiative transfer modeling attributes to C II rather than H$\alpha$, and weak or non-existent O I 7774 absorption feature until maximum light.Comment: Submitted to the Astrophysical Journal. 15 pages, 6 figure

Over 500 Days in the Life of the Photosphere of the Type Iax Supernova SN 2014dt

Type Iax supernovae (SN Iax) are the largest known class of peculiar white dwarf supernovae, distinct from normal Type Ia supernovae (SN Ia). The unique properties of SN Iax, especially their strong photospheric lines out to extremely late times, allow us to model their optical spectra and derive physical parameters for the long-lasting photosphere. We present an extensive spectral timeseries, including 21 new spectra, of SN Iax 2014dt from +11 to +562 days after maximum light. We are able to reproduce the entire timeseries with a self-consistent, nearly unaltered deflagration explosion model from Fink et al. (2014) using TARDIS, an open-source radiative transfer code (Kerzendorf & Sim 2014; Kerzendorf et al. 2023). We find that the photospheric velocity of SN 2014dt slows its evolution between +64 and +148 days, which closely overlaps the phase when we see SN 2014dt diverge from the normal spectral evolution of SN Ia (+90 to +150 days). The photospheric velocity at these epochs, ~400$-$1000 km s$^{-1}$, may demarcate a boundary within the ejecta below which the physics of SN Iax and normal SN Ia differ. Our results suggest that SN 2014dt is consistent with a weak deflagration explosion model that leaves behind a bound remnant and drives an optically thick, quasi-steady-state wind creating the photospheric lines at late times. The data also suggest that this wind may weaken at epochs past +450 days, perhaps indicating a radioactive power source that has decayed away.Comment: Accepted to ApJ, 22 pages, 8 figures, 3 table

Serendipitous Nebular-phase JWST Imaging of SN Ia 2021aefx: Testing the Confinement of 56-Co Decay Energy

We present new 0.3-21 micron photometry of SN 2021aefx in the spiral galaxy NGC 1566 at +357 days after B-band maximum, including the first detection of any SN Ia at >15 micron. These observations follow earlier JWST observations of SN 2021aefx at +255 days after the time of maximum brightness, allowing us to probe the temporal evolution of the emission properties. We measure the fraction of flux emerging at different wavelengths and its temporal evolution. Additionally, the integrated 0.3-14 micron decay rate of $\Delta m_{0.3-14} = 1.35 \pm 0.05$ mag/100 days is higher than the decline rate from the radioactive decay of $^{56}$Co of $\sim 1.2$mag/100 days. The most plausible explanation for this discrepancy is that flux is shifting to >14 micron, and future JWST observations of SNe Ia will be able to directly test this hypothesis. However, models predicting non-radiative energy loss cannot be excluded with the present data.Comment: Accepted for publication in ApJL; 11 pages, 4 figures, 2 tables in two-column AASTEX63 forma

Supernova 2018cuf : a type iip supernova with a slow fall from plateau

We present multiband photometry and spectroscopy of SN 2018cuf, a Type IIP ("P"for plateau) supernova (SN) discovered by the Distance Less Than 40 Mpc Survey within 24 hr of explosion. SN 2018cuf appears to be a typical SN IIP, with an absolute V-band magnitude of -16.73 ± 0.32 at maximum and a decline rate of 0.21 ± 0.05 mag/50 days during the plateau phase. The distance of the object was constrained to be 41.8 ± 5.7 Mpc by using the expanding photosphere method. We used spectroscopic and photometric observations from the first year after the explosion to constrain the progenitor of SN 2018cuf using both hydrodynamic light-curve modeling and late-time spectroscopic modeling. The progenitor of SN 2018cuf was most likely a red supergiant of about 14.5 Me that produced 0.04 ± 0.01 Me 56Ni during the explosion. We also found ∼0.07 Me of circumstellar material (CSM) around the progenitor is needed to fit the early light curves, where the CSM may originate from presupernova outbursts. During the plateau phase, high-velocity features at ∼11,000 km s-1 were detected in both the optical and near-infrared spectra, supporting the possibility that the ejecta were interacting with some CSM. A very shallow slope during the postplateau phase was also observed, and it is likely due to a low degree of nickel mixing or the relatively high nickel mass in the SN.Fil: Dong, Yize. University of California at Davis; Estados UnidosFil: Valenti, S.. University of California at Davis; Estados UnidosFil: Bostroem, K. A.. University of California at Davis; Estados UnidosFil: Sand, D. J.. University of Arizona; Estados UnidosFil: Andrews, Jennifer E.. University of Arizona; Estados UnidosFil: Galbany, Lluís. Universidad de Granada; EspañaFil: Jha, Saurabh W.. State University of New Jersey; Estados UnidosFil: Eweis, Youssef. State University of New Jersey; Estados UnidosFil: Kwok, Lindsey. State University of New Jersey; Estados UnidosFil: Hsiao, Eric. Florida State University; Estados UnidosFil: Davis, Scott. Florida State University; Estados UnidosFil: Brown, Peter J.. Texas A&M University; Estados UnidosFil: Kuncarayakti, H.. University of Turku; FinlandiaFil: Maeda, Keiichi. Kyoto University; JapónFil: Rho, Jeonghee. SETI Institute; Estados UnidosFil: Amaro, R. C.. University of Arizona; Estados UnidosFil: Anderson, J. P.. European Southern Observatory Chile; ChileFil: Arcavi, Iair. Universitat Tel Aviv; IsraelFil: Burke, Jamison. University of California; Estados UnidosFil: Dastidar, Raya. Aryabhatta Research Institute of observational sciences; IndiaFil: Folatelli, Gaston. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Haislip, Joshua. University of North Carolina at Chapel Hill; Estados UnidosFil: Hiramatsu, Daichi. University of California; Estados UnidosFil: Hosseinzadeh, Griffin. Harvard-Smithsonian Center for Astrophysics; Estados UnidosFil: Howell, D. Andrew. University of California; Estados UnidosFil: Jencson, J.. University of Arizona; Estados UnidosFil: Kouprianov, Vladimir. University of North Carolina at Chapel Hill; Estados UnidosFil: Lundquist, M.. University of Arizona; Estados UnidosFil: Lyman, J. D.. University of Warwick; Reino UnidoFil: McCully, Curtis. University of California; Estados Unido