The reversible polydisperse Parking Lot Model

We use a new version of the reversible Parking Lot Model to study the compaction of vibrated polydisperse media. The particle sizes are distributed according to a truncated power law. We introduce a self-consistent desorption mechanism with a hierarchical initialization of the system. In this way, we approach densities close to unity. The final density depends on the polydispersity of the system as well as on the initialization and will reach a maximum value for a certain exponent in the power law.Comment: 7 pages, Latex, 12 figure

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

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

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%

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 > 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