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We report deep radio observations of nearby Type Ia Supernovae (SNe Ia) with the electronic Multi-Element Radio Linked Interferometer Net-work (e-MERLIN), and the Australia Telescope Compact Array (ATCA). No detections were made. With…

We report deep EVN and eMERLIN observations of the Type Ia SN 2014J in the nearby galaxy M 82. Our observations represent, together with JVLA observations of SNe 2011fe and 2014J, the most sensitive radio studies of Type Ia SNe ever. By…

We present and discuss the radio observations of 27 Type Ia supernovae (SNe Ia) observed over two decades with the Very Large Array. No SN Ia has been detected so far in the radio, implying a very low density for any possible circumstellar…

On August 24 (UT) the Palomar Transient Factory (PTF) discovered PTF11kly (SN 2011fe), the youngest and most nearby type Ia supernova (SN Ia) in decades. We followed this event up in the radio (centimeter and millimeter bands) and X-ray…

We report on Expanded Very Large Array (EVLA) observations of the Type IIb supernova 2011dh, performed over the first 100 days of its evolution and spanning 1-40 GHz in frequency. The radio emission is well-described by the self-similar…

Type Ia supernovae (SNe) serve as a fundamental pillar of modern cosmology, owing to their large luminosity and a well-defined relationship between light-curve shape and peak brightness. The precision distance measurements enabled by SNe Ia…

Since April 2000, a program using the ESO/VLT/UVES to search for early circumstellar signatures from nearby supernovae has been conducted. Until now, two Type Ia supernovae have been observed, SNe 2000cx and 2001el. Here we report on…

Searching for the presence of circumstellar material is currently the only direct way to discriminate between the different types of possible progenitor systems for Type Ia supernovae. We have therefore looked for narrow H-alpha in a…

We present deep Hubble Space Telescope imaging of the nearby Type Ia supernova (SN Ia) 2011fe obtained 11.5yr after explosion. No emission is detected at the SN location to a $1\sigma$ ($3\sigma$) limit of ${F555W > 30.2 \;(29.0)}~$mag, or…

We present deep Chandra X-ray observations of two nearby Type Ia supernovae, SN 2017cbv and SN 2020nlb, which reveal no X-ray emission down to a luminosity $L_X$$\lesssim$5.3$\times$10$^{37}$ and $\lesssim$5.4$\times$10$^{37}$ erg s$^{-1}$…

We have considered 53 Type Ia supernovae (SNe Ia) observed by the Swift X-Ray Telescope (XRT). None of the SNe Ia are individually detected at any time or in stacked images. Using these data and assuming that the SNe Ia are a homogeneous…

Using the Hubble Space Telescope (HST) and the Large Binocular Telescope, we followed the evolution of the Type Ia supernova (SN Ia) 2011fe for an unprecedented 1840 days past $B$-band maximum light and over a factor of $7$ million in flux.…

We present a generalized analytic formalism for the inverse Compton X-ray emission from hydrogen-poor supernovae and apply this framework to SN2011fe using Swift-XRT, UVOT and Chandra observations. We characterize the optical properties of…

Searching for the presence of a circumstellar medium is a direct observational way to discriminate between different types of progenitor systems for Type Ia supernovae. We have modeled whether such gas may give rise to detectable emission,…

Despite intense scrutiny, the progenitor system(s) that gives rise to Type Ia supernovae remains unknown. The favored theory invokes a carbon-oxygen white dwarf accreting hydrogen-rich material from a close companion until a thermonuclear…

We present early time high-resolution (VLT/UVES) and late time low-resolution (VLT/FORS) optical spectra of the normal type Ia supernova, SN 2001el. The high-resolution spectra were obtained at -9 and -2 days to allow the detection of…

We present X-ray and radio observations of what may be the closest type Iax supernova (SN) to date, SN 2014dt (d=12.3-19.3 Mpc) and provide tight constraints on the radio and X-ray emission. We infer a specific radio luminosity of <…

Deep X-ray observations of the post-explosion environment around the very nearby Type Ia SN\,2014J (Dl=3.5 Mpc) reveal no X-ray emission down to a luminosity L<7x10^{36} erg/s (0.3-10 keV) at t~20 days after the explosion. We interpret this…

Searches for circumstellar material around Type Ia supernovae (SNe Ia) are one of the most powerful tests of the nature of SN Ia progenitors, and radio observations provide a particularly sensitive probe of this material. Here we report…

The explosion of a Type Ia supernova, SN 2011ef, in the nearby Pinwheel galaxy (M101 at 6.4 Mpc) provides an opportunity to study pre-explosion images and search for the progenitor, which should consist of a white dwarf (WD), possibly…