Early and late time VLT spectroscopy of SN 2001el - progenitor constraints for a type Ia supernova (original) (raw)
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Hydrogen and helium in the spectra of Type Ia supernovae
Monthly Notices of the Royal Astronomical Society, 2013
We present predictions for hydrogen and helium emission line luminosities from circumstellar matter around Type Ia supernovae (SNe Ia) using time dependent photoionization modelling. Early high-resolution ESO/Very Large Telescope (VLT) optical echelle spectra of the SN Ia 2000cx were taken before and up to ∼70 d after maximum to probe the existence of such narrow emission lines from the supernova. We detect no such lines, and from our modelling place an upper limit on the mass-loss rate for the putative wind from the progenitor system, M 1.3 × 10 −5 M yr −1 , assuming a speed of 10 km s −1 and solar abundances for the wind. If the wind would be helium-enriched and/or faster, the upper limit onṀ could be significantly higher. In the helium-enriched case, we show that the best line to constrain the mass-loss would be He I λ10 830. In addition to confirming the details of interstellar Na I and Ca II absorption towards SN 2000cx as discussed by Patat et al., we also find evidence for 6613.56 Å diffuse interstellar band absorption in the Milky Way. We also discuss measurements of the X-ray emission from the interaction between the supernova ejecta and the wind and we re-evaluate observations of SN 1992A obtained ∼16 d after maximum by Schlegel & Petre. We find an upper limit ofṀ ∼ 1.3 × 10 −5 M yr −1 which is significantly higher than that estimated by Schlegel & Petre. These results, together with the previous observational work on the normal SNe Ia 1994D and 2001el, disfavour a symbiotic star in the upper mass-loss rate regime (so-called Mira-type systems) from being the likely progenitor scenario for these SNe. Our model calculations are general, and can also be used for the subclass of SNe Ia that do show circumstellar interaction, e.g. the recent PTF 11kx. To constrain hydrogen in late-time spectra, we present ESO/VLT and ESO/New Technology Telescope optical and infrared observations of SNe Ia 1998bu and 2000cx in the nebular phase, 251−388 d after maximum. We see no signs of hydrogen line emission in SNe 1998bu and 2000cx at these epochs, and from the absence of Hα with a width of the order of ∼10 3 km s −1 , we argue from modelling that the mass of such hydrogen-rich gas must be 0.03 M for both supernovae. Comparing similar upper limits with recent models of Pan et al., it seems that hydrogen-rich donors with a separation of 5 times the radius of the donor may be ruled out for the five SNe Ia 1998bu, 2000cx, 2001el, 2005am and 2005cf. Larger separation, helium-rich donors, or a double-degenerate origin for these supernovae seems more likely. Our models have also been used to put the limit on hydrogen-rich gas in the recent SN 2011fe, and for this supernova, a double-degenerate origin seems likely.
THE FIRST MAXIMUM-LIGHT ULTRAVIOLET THROUGH NEAR-INFRARED SPECTRUM OF A TYPE Ia SUPERNOVA
The Astrophysical Journal, 2012
We present the first maximum-light ultraviolet (UV) through near-infrared (NIR) Type Ia supernova (SN Ia) spectrum. This spectrum of SN 2011iv was obtained nearly simultaneously by the Hubble Space Telescope at UV/optical wavelengths and the Magellan Baade telescope at NIR wavelengths. These data provide the opportunity to examine the entire maximum-light SN Ia spectral-energy distribution. Since the UV region of a SN Ia spectrum is extremely sensitive to the composition of the outer layers of the explosion, which are transparent at longer wavelengths, this unprecedented spectrum can provide strong constraints on the composition of the SN ejecta, and similarly the SN explosion and progenitor system. SN 2011iv is spectroscopically normal, but has a relatively fast decline (∆m 15 (B) = 1.69 ± 0.05 mag). We compare SN 2011iv to other SNe Ia with UV spectra near maximum light and examine trends between UV spectral properties, light-curve shape, and ejecta velocity. We tentatively find that SNe with similar light-curve shapes but different ejecta velocities have similar UV spectra, while those with similar ejecta velocities but different light-curve shapes have very different UV spectra. Through a comparison with explosion models, we find that both a solar-metallicity W7 and a zero-metallicity delayed-detonation model provide a reasonable fit to the spectrum of SN 2011iv from the UV to the NIR. Subject headings: supernovae: general -supernovae: individual (SN 2011iv) 1 Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-12592.
Analysis of the Spectrum of the Type V Supernova SN1986J
International Astronomical Union Colloquium
The supernova SN1986j resembles the prototypical Type V supernova SN1961v in the relatively slow ∼1000km/s expansion velocity, the slow light curve, and also in the Hα dominated spectrum. The optical spectrum is similar to the spectra of some novae, and some OB stars with massive winds, being characteristic of a nebular plasma at about 1010cm−3 and 104K. What makes SN1986j exceptional is its tremendous radio luminosity, the brightest radio supernova observed to date. The radio emission indicates the presence of a massive circumstellar wind, with which the SN ejecta are now colliding. Since the cooling time of the optically emitting gas is about an hour, a heat source is required to power the light curve. Shocks moving back into the ejecta offer a natural heat source, and account quantitatively for the observed luminosity and spectral character of SN1986j. The large Hα/Hβ ratio is attributed to trapping of Ly α, which pumps the n = 2 level of hydrogen, causing a finite optical depth ...
Comparative Direct Analysis of Type Ia Supernova Spectra. III. Premaximum
A comparative study of spectra of 21 Type Ia supernovae (SNe Ia) obtained about one week before maximum light, and 8 spectra obtained 11 or more days before maximum, is presented. To a large extent the premaximum spectra exhibit the defining characteristics of the four groups defined in Paper II (corenormal, broad-line, cool, and shallow-silicon). Comparisons with SYNOW synthetic spectra show that all strong features and most weak ones can be accounted for in a plausible way. The issues of detached high-velocity features, the possible ubiquity of carbon clumps, the maximum detectable ejecta velocities, and the possibility of blueshifted emission-line peaks are discussed.
We present the spectral evolution, light curve, and corresponding interpretation for the "normal-bright" Type Ia Supernova 2005cg discovered by ROTSE-IIIc. The host is a low-luminosity (M r = −16.75), blue galaxy with strong indications of active star formation and an environment similar to that expected for SNe Ia at high redshifts. Early-time (t ∼ −10 days) optical spectra obtained with the HET reveal an asymmetric, triangularshaped Si II absorption feature at about 6100 Å with a sharp transition to the continuum at a blue shift of about 24,000 km s −1 . By 4 days before maximum, the Si II absorption feature becomes symmetric with smoothly curved sides. Similar Si II profile evolution has previously been observed in other supernovae, and is predicted by some explosion models, but its significance has not been fully recognized. Although the spectra predicted by pure deflagration and delayed detonation models are similar near maximum light, they predict qualitatively different chemical abundances in the outer layers and thus give qualitatively different spectra at the earliest phases. The Si line observed in SN 2005cg at early times requires the presence of burning products at high velocities and the triangular shape is likely to be formed in an extended region of slowly declining Si abundance that characterizes delayed detonation models. The spectra show a high-velocity Ca II IR feature that coincides in velocity space with the Si II cutoff. This supports the interpretation that the Ca II is formed when the outer layers of the SN ejecta sweep up about 5 × 10 −3 M ⊙ of material within the progenitor system. We compare our results with other "Branch-normal" SNe Ia with early time spectra, namely SN 2003du, 1999ee and 1994D. Although the expansion velocities based on their Si II absorption minima differ, all show triangular-shaped profiles and velocity cutoffs between 23,000 and 25,000 km s −1 , which are consistent with the Doppler shifts of their respective high-velocity Ca II IR features. SN 1990N-like objects, however, showed distinctly different behavior that may suggest separate progenitor sub-classes.
The Astrophysical Journal, 2008
SN 2006tf is the third most luminous supernova (SN) discovered so far, after SN 2005ap and SN 2006gy. SN 2006tf is valuable because it provides a link between two regimes: (1) luminous type IIn supernovae powered by emission directly from interaction with circumstellar material (CSM), and (2) the most extremely luminous SNe where the CSM interaction is so optically thick that energy must diffuse out from an opaque shocked shell. As SN 2006tf evolves, it slowly transitions from the second to the first regime as the clumpy shell becomes more porous. This link suggests that the range in properties of the most luminous SNe is largely determined by the density and speed of hydrogen-rich material ejected shortly before they explode. The total energy radiated by SN 2006tf was at least 7 × 10 50 ergs. If the bulk of this luminosity came from the thermalization of shock kinetic energy, then the star needs to have ejected ∼18 M ⊙ in the 4-8 yr before core collapse, and another 2-6 M ⊙ in the decades before that. A Type Ia explosion is therefore excluded. From the Hα emission-line profile, we derive a blast-wave speed of 2,000 km s −1 that does not decelerate, and from the narrow P Cygni absorption from pre-shock gas we deduce that the progenitor's wind speed was ∼190 km s −1. This is reminiscent of the wind speeds of luminous blue variables (LBVs), but not of red supergiants or Wolf-Rayet stars. We propose that like SN 2006gy, SN 2006tf marked the death of a very massive star that retained a hydrogen envelope until the end of its life, and suffered extreme LBV-like mass loss in the decades before it exploded.
Comparative Direct Analysis of Spectra of Type Ia Supernovae. I. SN 1994D
Arxiv preprint astro-ph/ …, 2005
As the first step in a comprehensive, comparative, direct analysis of the spectra of Type Ia supernovae (SNe Ia), we use the parameterized supernova synthetic-spectrum code, Synow, to interpret 26 spectra of the well-observed SN 1994D. Our results are consistent with the traditional view that the composition structure (element abundance fractions versus ejection velocity) is radially stratified. We find that resonance-scattering features due to permitted lines of Ca II, Na I, and Fe II persist to more than 100 days after explosion. The fitting parameters for SN 1994D, together with those to be determined for other SNe Ia, will provide an internally consistent quantification of the spectroscopic diversity among SNe Ia, and shed light on how the various manifestations of observational diversity are related to their physical causes.
On the source of the late-time infrared luminosity of SN 1998S and other Type II supernovae
Monthly Notices of The Royal Astronomical Society, 2004
We present late-time near-infrared (NIR) and optical observations of the type IIn SN 1998S. The NIR photometry spans 333-1242 days after explosion, while the NIR and optical spectra cover 333-1191 days and 305-1093 days respectively. The NIR photometry extends to the M'-band (4.7 mu), making SN 1998S only the second ever supernova for which such a long IR wavelength has been detected. The shape and evolution of the H alpha and HeI 1.083 mu line profiles indicate a powerful interaction with a progenitor wind, as well as providing evidence of dust condensation within the ejecta. The latest optical spectrum suggests that the wind had been flowing for at least 430 years. The intensity and rise of the HK continuum towards longer wavelengths together with the relatively bright L' and M' magnitudes shows that the NIR emission was due to hot dust newly-formed in supernovae may provide the ejecta and/or pre-existing dust in the progenitor circumstellar medium (CSM). [ABRIDGED] Possible origins for the NIR emission are considered. Significant radioactive heating of ejecta dust is ruled out, as is shock/X-ray-precursor heating of CSM dust. More plausible sources are (a) an IR-echo from CSM dust driven by the UV/optical peak luminosity, and (b) emission from newly-condensed dust which formed within a cool, dense shell produced by the ejecta shock/CSM interaction. We argue that the evidence favours the condensing dust hypothesis, although an IR-echo is not ruled out. Within the condensing-dust scenario, the IR luminosity indicates the presence of at least 0.001 solar masses of dust in the ejecta, and probably considerably more. Finally, we show that the late-time intrinsic (K-L') evolution of type II supernovae may provide a useful tool for determining the presence or absence of a massive CSM around their progenitor stars.
Spectrum Analysis of Type IIb Supernova 1996cb
We analyze a time series of optical spectra of SN 1993J-like supernova 1996cb, from 14 days before maximum to 86 days after that, with a parameterized supernova synthetic-spectrum code SYNOW. Detailed line identification are made through fitting the synthetic spectra to observed ones. The derived photospheric velocity, decreasing from 11, 000 km s −1 to 3, 000 km s −1 , gives a rough estimate of the ratio of explosion kinetic energy to ejecta mass, i.e. E/M ej ∼ 0.2 − 0.5 × 10 51 ergs/M ej (M ⊙ ). We find that the minimum velocity of hydrogen is ∼ 10, 000 km s −1 , which suggests a small hydrogen envelope mass of ∼ 0.02 − 0.1 M ej , or 0.1 − 0.2 M ⊙ if E is assumed 1 × 10 51 ergs. A possible Ni II absorption feature near 4000Å is identified throughout the epochs studied here and is most likely produced by primordial nickel. Unambiguous Co II features emerge from 16 days after maximum onward, which suggests that freshly synthesized radioactive material has been mixed outward to a velocity of at least 7, 000 km s −1 as a result of hydrodynamical instabilities. Although our synthetic spectra show that the bulk of the blueshift of [O I] λ5577 net emission, as large as ∼ 70Å at 9 days after maximum, is attributed to line blending, a still considerable residual ∼ 20Å remains till the late phase. It may be evidence of clumpy or large-scale asymmetric nature of oxygen emission region.
The Astrophysical Journal, 2018
We present detailed ultraviolet, optical and near-infrared light curves of the Type Ia supernova (SN) 2012fr, which exploded in the Fornax cluster member NGC 1365. These precise high-cadence light curves provide a dense coverage of the flux evolution from −12 to +140 days with respect to the epoch of Bband maximum (t Bmax). Supplementary imaging at the earliest epochs reveals an initial slow, nearly linear rise in luminosity with a duration of ∼2.5 days, followed by a faster rising phase that is well reproduced by an explosion model with a moderate amount of 56 Ni mixing in the ejecta. From an analysis of the light curves, we conclude: (i) explosion occurred < 22 hours before the first detection of the supernova, (ii) the rise time to peak bolometric (λ > 1800Å) luminosity was 16.5 ± 0.6 days, (iii) the supernova suffered little or no hostgalaxy dust reddening, (iv) the peak luminosity in both the optical and nearinfrared was consistent with the bright end of normal Type Ia diversity, and (v) 0.60 ± 0.15 M of 56 Ni was synthesized in the explosion. Despite its normal luminosity, SN 2012fr displayed unusually prevalent high-velocity Ca II and Si II absorption features, and a nearly constant photospheric velocity of the Si II λ6355 line at ∼12,000 km s −1 beginning ∼5 days before t Bmax. Other peculiarities in the early phase photometry and the spectral evolution are highlighted. SN 2012fr also adds to a growing number of Type Ia supernovae hosted by galaxies with direct Cepheid distance measurements.