Type Iax supernovae (SNe Iax) are the largest known class of peculiar white dwarf SNe, distinct from normal Type Ia supernovae (SNe Ia). The unique properties of SNe Iax, especially their strong photospheric lines out to extremely late times, allow us to model their optical spectra and derive the physical parameters of the longlasting 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 selfconsistent, nearly unaltered deflagration explosion model from Fink et al. using
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Abstract TARDIS , an open source radiativetransfer code. 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 SNe 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 SNe Iax and normal SNe 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, quasisteadystate 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. 
Abstract Here we present 1701 light curves of 1550 unique, spectroscopically confirmed Type Ia supernovae (SNe Ia) that will be used to infer cosmological parameters as part of the Pantheon+ SN analysis and the Supernovae and H 0 for the Equation of State of dark energy distanceladder analysis. This effort is one part of a series of works that perform an extensive review of redshifts, peculiar velocities, photometric calibration, and intrinsicscatter models of SNe Ia. The total number of light curves, which are compiled across 18 different surveys, is a significant increase from the first Pantheon analysis (1048 SNe), particularly at low redshift ( z ). Furthermore, unlike in the Pantheon analysis, we include light curves for SNe with z < 0.01 such that SN systematic covariance can be included in a joint measurement of the Hubble constant ( H 0 ) and the dark energy equationofstate parameter ( w ). We use the large sample to compare properties of 151 SNe Ia observed by multiple surveys and 12 pairs/triplets of “SN siblings”—SNe found in the same host galaxy. Distance measurements, application of bias corrections, and inference of cosmological parameters are discussed in the companion paper by Brout et al., and the determination of H 0 is discussed by Riess et al. These analyses will measure w with ∼3% precision and H 0 with ∼1 km s −1 Mpc −1 precision.more » « less

Abstract We combine our dynamical modeling blackhole mass measurements from the Lick AGN Monitoring Project 2016 sample with measured crosscorrelation time lags and line widths to recover individual scale factors,
f , used in traditional reverberationmapping analyses. We extend our sample by including prior results from Code for AGN Reverberation and Modeling of Emission Lines (caramel ) studies that have utilized our methods. Aiming to improve the precision of blackhole mass estimates, as well as uncover any regularities in the behavior of the broadline region (BLR), we search for correlations betweenf and other AGN/BLR parameters. We find (i) evidence for a correlation between the virial coefficient and blackhole mass, (ii) marginal evidence for a similar correlation between ${\mathrm{log}}_{10}({f}_{\mathrm{mean},\sigma})$ and blackhole mass, (iii) marginal evidence for an anticorrelation of BLR disk thickness with ${\mathrm{log}}_{10}({f}_{\mathrm{rms},\sigma})$ and ${\mathrm{log}}_{10}({f}_{\mathrm{mean},\mathrm{FWHM}})$ , and (iv) marginal evidence for an anticorrelation of inclination angle with ${\mathrm{log}}_{10}({f}_{\mathrm{rms},\mathrm{FWHM}})$ , ${\mathrm{log}}_{10}({f}_{\mathrm{mean},\mathrm{FWHM}})$ , and ${\mathrm{log}}_{10}({f}_{\mathrm{rms},\sigma})$ . Last, we find marginal evidence for a correlation between lineprofile shape, when using the rootmeansquare spectrum, ${\mathrm{log}}_{10}({f}_{\mathrm{mean},\sigma})$ , and the virial coefficient, ${\mathrm{log}}_{10}{(\mathrm{FWHM}/\sigma )}_{\mathrm{rms}}$ , and investigate how BLR properties might be related to lineprofile shape using ${\mathrm{log}}_{10}({f}_{\mathrm{rms},\sigma})$caramel models. 
null (Ed.)ABSTRACT The ejecta velocity is a very important parameter in studying the structure and properties of Type Ia supernovae (SNe Ia) and is a candidate key parameter in improving the utility of SNe Ia for cosmological distance determinations. Here, we study the velocity distribution of a sample of 311 SNe Ia from the kaepora data base. The velocities are derived from the Si ii λ6355 absorption line in optical spectra measured at (or extrapolated to) the time of peak brightness. We statistically show that the observed velocity has a bimodal Gaussian distribution (population ratio 201:110 or 65 per cent:35 per cent) consisting of two groups of SNe Ia: Group I with a lower but narrower scatter ($11\, 000 \pm 700\, \mathrm{km\, s}^{1}$), and Group II with a higher but broader scatter ($12\, 300 \pm 1800\, \mathrm{km\, s}^{1}$). The true origin of the two components is unknown. Naturally, there could exist two intrinsic velocity distributions observed. However, we try to use asymmetric geometric models through statistical simulations to reproduce the observed distribution assuming that all SNe Ia share the same intrinsic distribution. In the two cases we consider, 35 per cent of SNe Ia are considered to be asymmetric in Case 1, and all SNe Ia are asymmetric in Case 2. Simulations for both cases can reproduce the observed velocity distribution but require a significantly large portion ($\gt 35{{\ \rm per\ cent}}$) of SNe Ia to be asymmetric. In addition, the Case 1 result is consistent with recent SNe Ia polarization observations that higher Si ii λ6355 velocities tend to be more polarized.more » « less

Abstract We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from z = 0.001 to 2.26. This work features an increased sample size from the addition of multiple crosscalibrated photometric systems of SNe covering an increased redshift span, and improved treatments of systematic uncertainties in comparison to the original Pantheon analysis, which together result in a factor of 2 improvement in cosmological constraining power. For a flat ΛCDM model, we find Ω M = 0.334 ± 0.018 from SNe Ia alone. For a flat w 0 CDM model, we measure w 0 = −0.90 ± 0.14 from SNe Ia alone, H 0 = 73.5 ± 1.1 km s −1 Mpc −1 when including the Cepheid host distances and covariance (SH0ES), and w 0 = − 0.978 − 0.031 + 0.024 when combining the SN likelihood with Planck constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both w 0 values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a flat w 0 w a CDM universe, and measure w a = − 0.1 − 2.0 + 0.9 from Pantheon+ SNe Ia alone, H 0 = 73.3 ± 1.1 km s −1 Mpc −1 when including SH0ES Cepheid distances, and w a = − 0.65 − 0.32 + 0.28 when combining Pantheon+ SNe Ia with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than onethird of the total uncertainty in the measurement of H 0 and cannot explain the present “Hubble tension” between local measurements and early universe predictions from the cosmological model.more » « less

Abstract We have modeled the velocityresolved reverberation response of the H
β broad emission line in nine Seyfert 1 galaxies from the Lick Active Galactic Nucleus (AGN) Monitoring Project 2016 sample, drawing inferences on the geometry and structure of the lowionization broadline region (BLR) and the mass of the central supermassive black hole. Overall, we find that the Hβ BLR is generally a thick disk viewed at low to moderate inclination angles. We combine our sample with prior studies and investigate lineprofile shape dependence, such as , on BLR structure and kinematics and search for any BLR luminositydependent trends. We find marginal evidence for an anticorrelation between the profile shape of the broad H ${\mathrm{log}}_{10}(\mathrm{FWHM}/\sigma )$β emission line and the Eddington ratio, when using the rms spectrum. However, we do not find any luminositydependent trends, and conclude that AGNs have diverse BLR structure and kinematics, consistent with the hypothesis of transient AGN/BLR conditions rather than systematic trends. 
ABSTRACT We present BVRI and unfiltered (Clear) light curves of 70 strippedenvelope supernovae (SESNe), observed between 2003 and 2020, from the Lick Observatory Supernova Search followup program. Our SESN sample consists of 19 spectroscopically normal SNe Ib, 2 peculiar SNe Ib, six SNe Ibn, 14 normal SNe Ic, 1 peculiar SN Ic, 10 SNe IcBL, 15 SNe IIb, 1 ambiguous SN IIb/Ib/c, and 2 superluminous SNe. Our followup photometry has (on a perSN basis) a mean coverage of 81 photometric points (median of 58 points) and a mean cadence of 3.6 d (median of 1.2 d). From our full sample, a subset of 38 SNe have premaximum coverage in at least one passband, allowing for the peak brightness of each SN in this subset to be quantitatively determined. We describe our data collection and processing techniques, with emphasis toward our automated photometry pipeline, from which we derive publicly available data products to enable and encourage further study by the community. Using these data products, we derive hostgalaxy extinction values through the empirical colour evolution relationship and, for the first time, produce accurate risetime measurements for a large sample of SESNe in both optical and infrared passbands. By modelling multiband light curves, we find that SNe Ic tend to have lower ejecta masses and lower ejecta velocities than SNe Ib and IIb, but higher 56Ni masses.