We present optical (UBVRI) and near-infrared (JHK) photometry, along with optical spectra, of the Type Ia supernova SN 2000E in the spiral galaxy NGC 6951. It was discovered by the staff of the Teramo Observatory during the monitoring of the SN 1999el. The observations span a time interval of 234 days in the optical and 134 days in the near-infrared (starting ~16 and ~7 days before maximum B light, respectively). Optical spectra are available from 6 days before maximum B light to 122 days after it. The photometric behavior of SN 2000E is remarkably similar to that of SN 1991T and SN 1992bc: it exhibits a Δm15(B) = 0.94 mag, thus being classifiable as a slow-declining Type Ia supernova (SN) and showing the distinctive features of such a class of objects both in the visible and in the near-infrared. Spectroscopically, SN 2000E appears as a "normal" Type Ia SN, like SN 1990N. We could constrain reddening [E(B-V) ~ 0.5 mag] and distance (μ0 ~ 32.14 mag) using a number of different methods. The bolometric luminosity curve of SN 2000E, which displays a bump at the epoch of the secondary near-infrared peak, allows a determination of the 56Ni mass, amounting to 0.9 M☉.

Optical and Near-Infrared Photometry of the Type Ia Supernova 2000E in NGC 6951

We present a novel technique for fitting restframe I-band light curves on a data set of 42 type la Supernovae (SNe Ia). Using the result of the fit, we construct a Hubble diagram with 26 SNe from the subset at 0.01 < z < 0.1. Adding two SNe at z ∼ 0.5 yields results consistent with a flat Λ-dominated "concordance universe" (ΩM, ΩΛ) = (0.25, 0.75). For one of these, SN 2000fr, new near infrared data are presented. The high redshift supernova NIR data are also used to test for systematic effects in the use of SNe la as distance estimators. A flat, Λ = 0, universe where the faintness of supernovae at z ∼ 0.5 is due to grey dust homogeneously distributed in the intergalactic medium is disfavoured based on the high-z Hubble diagram using this small data-set. However, the uncertainties are large and no firm conclusion may be drawn. We explore the possibility of setting limits on intergalactic dust based on B - I and B - V colour measurements, and conclude that about 20 well measured SNe are needed to give statistically significant results. We also show that the high redshift restframe I-band data points are better fit by light curve templates that show a prominent second peak, suggesting that they are not intrinsically underluminous. © ESO 2005.

/pdf/restframe-i-band-hubble-diagram-for-type-ia-supernovae-up-to-111lgbc9oy.pdf

Restframe I-band Hubble diagram for type Ia supernovae up to redshift z~0.5

We present optical and near-infrared photometry, as well as ground-based optical spectra and Hubble Space Telescope ultraviolet spectra, of the Type Ia supernova (SN) 2001ay. At maximum light the Si II and Mg II lines indicated expansion velocities of 14,000 km s^(–1), while Si III and S II showed velocities of 9000 km s^(–1). There is also evidence for some unburned carbon at 12,000 km s^(–1). SN 2001ay exhibited a decline-rate parameter of Δm_(15)(B) = 0.68 ± 0.05 mag; this and the B-band photometry at t ≳+25 day past maximum make it the most slowly declining Type Ia SN yet discovered. Three of the four super-Chandrasekhar-mass candidates have decline rates almost as slow as this. After correction for Galactic and host-galaxy extinction, SN 2001ay had M_B = –19.19 and M_V = –19.17 mag at maximum light; thus, it was not overluminous in optical bands. In near-infrared bands it was overluminous only at the 2σ level at most. For a rise time of 18 days (explosion to bolometric maximum) the implied ^(56)Ni yield was (0.58 ± 0.15)/α M_☉, with α = L_(max)/E_(Ni) probably in the range 1.0-1.2. The ^(56)Ni yield is comparable to that of many Type Ia SNe. The "normal" 56Ni yield and the typical peak optical brightness suggest that the very broad optical light curve is explained by the trapping of γ rays in the inner regions.

/pdf/the-most-slowly-declining-type-ia-supernova-2001ay-3q3yk81vsl.pdf

THE MOST SLOWLY DECLINING TYPE Ia SUPERNOVA 2001ay

Light curves are the most readily available and most frequently used astrophysical tools for variable phenomena. Supernovae are no exception to this. The information that can be extracted from detailed light and colors curves, together with the detailed study of the spectral evolution, tells us about the progenitor star, the various energy input sources, the explosion environment, material in the line of sight and cosmological effects. Over the past decade we have come to understand the power of detailed light curve studies and how they tie into the exploration of other astrophysical topics.

Optical Light Curves of Supernovae

The use of standard candles for distance measurements is wide spread. Yet, we currently do not know a pure standard candle in astronomy. The concept of standard candles involves not only the secure establishment of a unique luminosity but also a clear observational distinction of the objects as a class. Even Type Ia supernovae, whose maximum luminosity shows amongst the smallest scatter known, need to be normalised to provide accurate distances. Without this normalisation the cosmological claims based on supernovae would not be possible. With a careful normalisation Type Ia supernovae are the best known distance indicators for cosmology to date. This is most easily shown by the small dispersion around the expansion line in the Hubble diagram. Problems with the empirical normalisation remain and a theoretical understanding of this normalisation is missing. This has direct ramifications on systematic uncertainties when deriving cosmological implications from Type Ia supernovae. Improving the understanding of supernova physics is now the prime task to sharpen this tool of observational cosmology. Once the explosion mechanism is revealed a serious discussion of possible evolutionary effects in Type Ia supernovae can start.

Are Type Ia Supernovae Standard Candles

Author(s): Phillips, MM; Krisciunas, K; Suntzeff, NB; Roth, M; Germany, L; Candia, P; Gonzalez, S; Hamuy, M; Freedman, WL; Persson, SE; Nugent, PE; Aldering, G; Conley, A | Abstract: This paper provides a progress report on a collaborative program at the Las Campanas and Cerro Tololo Observatories to observe the near-IR light curves of Type Ia supernovae. We discuss how the morphologies of the JHK light curves change as a function of the decline rate. Evidence is presented which indicates that the absolute magnitudes in the H band have little or no dependence on the decline rate, suggesting that SNe Ia may be nearly perfect cosmological standard candles in the near-IR. A preliminary Hubble diagram in the H band is presented and compared with a similar diagram in V for the same objects. Finally, observations of two peculiar supernovae, 1999ac and 2001ay, are briefly discussed.

/pdf/infrared-light-curves-of-type-ia-supernovae-2zsbmuyv3l.pdf

Infrared light curves of type Ia supernovae

This paper provides a progress report on a collaborative program at the Las Campanas and Cerro Tololo Observatories to observe the near-IR light curves of Type Ia supernovae. We discuss how the morphologies of the JHK light curves change as a function of the decline rate. Evidence is presented which indicates that the absolute magnitudes in the H band have little or no dependence on the decline rate, suggesting that SNe Ia may be nearly perfect cosmological standard candles in the near-IR. A preliminary Hubble diagram in the H band is presented and compared with a similar diagram in V for the same objects. Finally, observations of two peculiar supernovae, 1999ac and 2001ay, are briefly discussed.

/pdf/infrared-light-curves-of-type-ia-supernovae-1p15df8r0y.pdf

M. Roth

Papers

Infrared light curves of type Ia supernovae

Infrared Light Curves of Type Ia Supernovae