Supernova 2014J at M82 – II. Direct analysis of a middle-class Type Ia supernova

We analyze a time series of optical spectra of SN 2014J from almost two weeks prior to maximum to nearly four months after maximum. We perform our analysis using the SYNOW code, which is well suited to track the distribution of the ions with velocity in the ejecta. We show that almost all of the spectral features during the entire epoch can be identified with permitted transitions of the common ions found in normal SNe Ia in agreement with previous studies. We show that 2014J is a relatively normal SN Ia. At early times the spectral features are dominated by Si II, S II, Mg II, and Ca II. These ions persist to maximum light with the appearance of Na I and Mg I. At later times iron-group elements also appear, as expected in the stratified abundance model of the formation of normal type Ia SNe. We do not find significant spectroscopic evidence for oxygen, until 100 days after maximum light. The +100 day identification of oxygen is tentative, and would imply significant mixing of unburned or only slight processed elements down to a velocity of 6,000 km~s−1. Our results are in relatively good agreement with other analyses in the IR. We briefly compare SN 2011fe to SN 2014J and conclude that the differences could be due to different central densities at ignition or differences in the C/O ratio of the progenitors

BVRI Light Curves for 29 Type Ia Supernovae

BVRI light curves are presented for 27 Type Ia supernovae discovered during the course of the Calan/Tololo Survey and for two other SNe Ia observed during the same period. Estimates of the maximum light magnitudes in the B, V, and I bands and the initial decline rate parameter m15(B) are also given.Comment: 17 pages, figures and tables are not included (contact first author if needed), to appear in the Astronomical Journa

The Carnegie Supernova Project I photometry data release of low-redshift stripped envelope supernovae

The first phase of the Carnegie Supernova Project (CSP-I) was a dedicated supernova follow-up program based at the Las Campanas Observatory that collected science data of young, low-redshift supernovae between 2004 and 2009. Presented in this paper is the CSP-I photometric data release of low-redshift stripped-envelope core-collapse supernovae. The data consist of optical (uBgVri) photometry of 34 objects, with a subset of 26 having near-infrared (YJH) photometry. Twenty objects have optical pre-maximum coverage with a subset of 12 beginning at least five days prior to the epoch of B-band maximum brightness. In the near-infrared, 17 objects have pre-maximum observations with a subset of 14 beginning at least five days prior to the epoch of J-band maximum brightness. Analysis of this photometric data release is presented in companion papers focusing on techniques to estimate host-galaxy extinction and the light-curve and progenitor star properties of the sample. The analysis of an accompanying visual-wavelength spectroscopy sample of similar to 150 spectra will be the subject of a future paper.Danish Agency for Science and Technology and Innovation Instrument-center for Danish Astrophysics (IDA) VILLUM FONDEN 13261 NSF PHY-1066293 PHY-1607611 Millennium Center for Supernova Science - Programa Iniciativa Cientifica Milenio del Ministerio de Economia, Fomento y Turismo de Chile P10-064-F US National Science Foundation (NSF) AST-0306969 AST-0607438 AST-0908886 AST-1008343 AST-1211916 AST-1613426 AST-1613455 AST-1613472 TABASGO Foundation Christopher R. Redlich Fund Miller Institute for Basic Research in Scienc

A Hubble diagram of distant type IA supernovae

Artículo de publicaciónWe have constructed Hubble diagrams in B and V for 13 Type Ia supernovae (SNe Ia) found in the course of the Calan/Tololo survey covering an unprecedented range in redshift (0.01 less than Z less than 0.1). As opposed to other published Hubble diagrams, these are solely based on light curves obtained with CCDs, which have been carefully reduced in order to avoid background contamination. Special care was also taken in the extrapolation of peak magnitudes for the SNe that were discovered after maximum light by using five different template light curves representing the range of observed decline rates of SNe Ia. The resulting Hubble diagrams show clear evidence for a distance-dependent dispersion. Although some of the scatter could be due to the peculiar velocities of the host galaxies or to uncorrected dust absorption in the host galaxies, we argue that the dominant source is an intrinsic dispersion in the peak absolute magnitudes of SNe Ia of approximately 0.8 mag in MB and approximately 0.5 mag in MV. If low-luminosity events like SN 1991bg are actually a separate class of supernovae which arise from different progenitors, then the intrinsic dispersion in MB and MV for normal SNe Ia would decrease to approximately 0.3-0.5 mag. This study confirms, in general terms, the finding by Phillips (1993) from a sample of well observed nearby SNe Ia that the absolute B and V magnitudes are correlated with the initial decline rate of the B light curve, although this effect seems to be less pronounced in the Calan/Tololo SNe. Although the number of SNe studied here is relatively small, we find that galaxies having a younger stellar population appear to host the most luminous SNe Ia. We present Hubble diagrams in B and V for the subset of the Calan/Tololo SNe which have decline rates in the range 0.8 less than Delta m15(B) less than 1.5. A dramatic decrease in the scatter in these diagrams is obtained when the data are corrected for the peak luminosity-decline rate relation derived from events in the Phillips sample of nearby SNe Ia covering the same range of decline rates. Using the recently measured Cepheid distance to NGC 5253, a Hubble constant in the range H0 approximately equal to 62-67 km/s/Mpc is calculated when the peak luminosity-decline rate relation is taken into account. The result of ignoring this effect for SN 1972E is to underestimate H0 by approximately 15%

The Standardized Candle Method for Type II Plateau Supernovae

Artículo de publicación ISIIn this paper we study the “standardized candle method” using a sample of 37 nearby (redshift z < 0.06) Type II plateau supernovae having BV RI photometry and optical spectroscopy. An analytic procedure is implemented to fit light curves, color curves, and velocity curves. We find that the V − I color toward the end of the plateau can be used to estimate the host-galaxy reddening with a precision of (AV ) = 0.2 mag. The correlation between plateau luminosity and expansion velocity previously reported in the literature is recovered. Using this relation and assuming a standard reddening law (RV = 3.1), we obtain Hubble diagrams in the BV I bands with dispersions of 0.4 mag. Allowing RV to vary and minimizing the spread in the Hubble diagrams, we obtain a dispersion range of 0.25–0.30 mag, which implies that these objects can deliver relative distances with precisions of 12–14%. The resulting best-fit value of RV is 1.4 ± 0.1

Type II supernovae as distance indicators at near-IR wavelengths

Motivated by the advantages of observing at near-IR wavelengths, we investigate Type II supernovae (SNe II) as distance indicators at those wavelengths through the Photospheric Magnitude Method (PMM). For the analysis, we use BVIJH photometry and optical spectroscopy of 24 SNe II during the photospheric phase. To correct photometry for extinction and redshift effects, we compute total-to-selective broad-band extinction ratios and K-corrections up to z = 0.032. To estimate host galaxy colour excesses, we use the colour-colour curve method with the V-I versus B-V as colour combination. We calibrate the PMM using four SNe II in galaxies having Tip of the Red Giant Branch distances. Among our 24 SNe II, nine are at cz &gt; 2000 km s -1, which we use to construct Hubble diagrams (HDs). To further explore the PMM distance precision, we include into HDs the four SNe used for calibration and oth

The high cadence transient survey (HITS). Compilation and characterization of light–curve catalogs

The High Cadence Transient Survey (HiTS) aims to discover and study transient objects with characteristic timescales between hours and days, such as pulsating, eclipsing and exploding stars. This survey represents a unique laboratory to explore large etendue observations from cadences of about 0.1 days and to test new computational tools for the analysis of large data. This work follows a fully Data Science approach: from the raw data to the analysis and classification of variable sources. We compile a catalog of ∼15 million object detections and a catalog of ∼2.5 million light–curves classified by variability. The typical depth of the survey is 24.2, 24.3, 24.1 and 23.8 in u, g, r and i bands, respectively. We classified all point–like non–moving sources by first extracting features from their light–curves and then applying a Random Forest classifier. For the classification, we used a training set constructed using a combination of cross-matched catalogs, visual inspection, transfer/active learning and data augmentation. The classification model consists of several Random Forest classifiers organized in a hierarchical scheme. The classifier accuracy estimated on a test set is approximately 97%. In the unlabeled data, 3 485 sources were classified as variables, of which 1 321 were classified as periodic. Among the periodic classes we discovered with high confidence, 1 δ–scutti, 39 eclipsing binaries, 48 rotational variables and 90 RR–Lyrae and for the non–periodic classes we discovered 1 cataclysmic variables, 630 QSO, and 1 supernova candidates. The first data release can be accessed in the project archive of HiTSa

THE EXPANDING PHOTOSPHERE METHOD APPLIED TO SN-1992AM AT CZ=14600KM-S

Artículo de publicación ISIWe present photometry and spectroscopy of SN 1992am for five months following its discovery by the Calan/CTIO SN search. These data show SN 1992am to be type II-P, displaying hydrogen in its spectrum and the typical shoulder in its light curve. The photometric data and the distance from our own analysis are used to construct the supernova's bolometric light curve. Using the bolometric light curve, we estimate SN 1992am ejected approximately 0.30. M. of Ni-56, an amount four times larger than that of other well studied SNe II. SN 1992am's; host galaxy lies at a redshift of cz = 14 600 km s-1, making it one of the most distant SNe II discovered, and an important application of the Expanding Photosphere Method. Since z = 0.05 is large enough for redshift-dependent effects to matter, we develop the technique to derive luminosity distances with the Expanding Photosphere Method at any redshift. and apply this method to SN 1992am. The derived distance, D = 180(+30/-25) Mpc, is independent of all other rungs in the extragalactic distance ladder. The redshift of SN 1992am's host galaxy is sufficiently large that uncertainties due to perturbations in the smooth Hubble flow should be smaller than 10%. The Hubble ratio derived from the distance and redshift of this single object is H-0 = 81(+17/-15) km s-1 Mpc-1. In the future, with more of these distant objects, we hope to establish an independent and statistically robust estimate of H-0 based solely on type II supernovae