Comparative Direct Analysis of Type Ia Supernova Spectra. III. Premaximum

Branch, David; Troxel, M. A.; Jeffery, David J.; Hatano, K.; Musco, Miriam; Parrent, J.; Baron, Edward; Dang, Leann Chau; Casebeer, D.; Hall, Nicholas R.

doi:10.1086/520553

Cited by 26 publications

(28 citation statements)

References 67 publications

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“…Finally, in section §5, we give a summary and conclusions. A comparison with synthetic spectra using SYNOW (Branch et al 2007) is presented in Paper II (Vallely et al 2015).…”

Section: Introductionmentioning

confidence: 99%

SN 2014J at M82 – I. A middle-class Type Ia supernova by all spectroscopic metrics

Galbany

Moreno-Raya

Ruiz‐Lapuente

et al. 2016

Mon. Not. R. Astron. Soc.

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We present the intensive spectroscopic follow up of the type Ia supernova (SN Ia) 2014J in the starburst galaxy M82. Twenty-seven optical spectra have been acquired from January 22 nd to September 1 st 2014 with the Isaac Newton (INT) and William Herschel (WHT) Telescopes. After correcting the observations for the recession velocity of M82 and for Milky Way and host galaxy extinction, we measured expansion velocities from spectral line blueshifts and pseudo-equivalent width of the strongest features in the spectra, which gives an idea on how elements are distributed within the ejecta. We position SN 2014J in the Benetti (2005)

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“…Finally, in section §5, we give a summary and conclusions. A comparison with synthetic spectra using SYNOW (Branch et al 2007) is presented in Paper II (Vallely et al 2015).…”

Section: Introductionmentioning

confidence: 99%

SN 2014J at M82 – I. A middle-class Type Ia supernova by all spectroscopic metrics

Galbany

Moreno-Raya

Ruiz‐Lapuente

et al. 2016

Mon. Not. R. Astron. Soc.

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“…In subsequent studies with larger optical spectroscopic samples, 20−30% of the pre-maximum spectra were found to show C ii signatures (Thomas et al 2011a;Parrent et al 2011;Folatelli et al 2012;Silverman & Filippenko 2012). Several of these studies noted, however, that this fraction represents a lower limit because noise, line overlap, and the phase at which the SNe Ia were observed could affect the C ii detection (e.g., Branch et al 2007;Folatelli et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Strong near-infrared carbon in the Type Ia supernova iPTF13ebh

Hsiao

Burns

Contreras

et al. 2015

A&A

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We present near-infrared (NIR) time-series spectroscopy, as well as complementary ultraviolet (UV), optical, and NIR data, of the Type Ia supernova (SN Ia) iPTF13ebh, which was discovered within two days from the estimated time of explosion. The first NIR spectrum was taken merely 2.3 days after explosion and may be the earliest NIR spectrum yet obtained of a SN Ia. The most striking features in the spectrum are several NIR C i lines, and the C i λ1.0693 µm line is the strongest ever observed in a SN Ia. Interestingly, no strong optical C ii counterparts were found, even though the optical spectroscopic time series began early and is densely cadenced. Except at the very early epochs, within a few days from the time of explosion, we show that the strong NIR C i compared to the weaker optical C ii appears to be general in SNe Ia. iPTF13ebh is a fast decliner with ∆m 15 (B) = 1.79 ± 0.01, and its absolute magnitude obeys the linear part of the width-luminosity relation. It is therefore categorized as a "transitional" event, on the fast-declining end of normal SNe Ia as opposed to subluminous/91bg-like objects. iPTF13ebh shows NIR spectroscopic properties that are distinct from both the normal and subluminous/91bg-like classes, bridging the observed characteristics of the two classes. These NIR observations suggest that composition and density of the inner core are similar to that of 91bg-like events, and that it has a deep-reaching carbon burning layer that is not observed in more slowly declining SNe Ia. There is also a substantial difference between the explosion times inferred from the early-time light curve and the velocity evolution of the Si ii λ0.6355 µm line, implying a long dark phase of ∼4 days.

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“…It may be that there is actually one continuous opacity gradient with v e < 1000 km s −1 . Either way, a possible interpretation of this result is that the density profile of SN 2012fr is steeper than most SNe, which are usually well-fitted with a single Si II component with v e ≥ 1000 km s −1 (Branch et al , 2007. This is an odd conclusion to reach, considering our earlier deduction that the region containing Si II may be shell-like.…”

Section: Density Modeling In Phoenixmentioning

confidence: 75%

“…At epochs prior to maximum light, HV Ca II H&K tends to dominate, producing strong absorption features in the 3500 − 4000Å wavelength region. These features usually become weak by maximum light and are replaced at post-maximum phases by the Calcium Infrared Triplet (Ca IR3), which forms in the 8000 − 8500Å region (Branch et al 2007). Typically, Ca II H&K forms in two distinct components: a high-velocity detached component, with the detached component fading by maximum light and a photospheric component.…”

Section: Spectroscopic Peculiarities Of Sn 2012frmentioning

confidence: 99%

“…The global fitting parameters and line optical depths used in our fits are given in Table 1. Although T exec can be set for each ion, we held it fixed at 10000 K for all ions up to day +1 and 7000K after that, to reduce the size of parameter space, as was done in Branch et al (2007) and Branch et al (2008). We constrained T bb to 16000 or 15000 K at all phases (except at day −15, for which T bb = 7000 K, and at day +18, for which T bb = 9000 K), although previous studies have shown that this parameter is not physically meaningful, because Type Ia's are not even approximately true blackbodies and SYNOW only treats line scattering.…”

Section: Synowmentioning

confidence: 99%

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Investigating the Unusual Spectroscopic Time Evolution in SN 2012fr^∗

Cain

Baron

Phillips

et al. 2018

ApJ

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The type Ia supernova (SN) 2012fr displayed an unusual combination of its Si II λλ5972, 6355 features. This includes the ratio of their pseudo equivalent widths, placing it at the border of the Shallow Silicon (SS) and Core Normal (CN) spectral subtype in the Branch diagram, while the Si IIλ6355 expansion velocities places it as a High-Velocity (HV) object in the Wang et al. spectral type that most interestingly evolves slowly, placing it in the Low Velocity Gradient (LVG) typing of Benetti et al. Only 5% of SNe Ia are HV and located in the SS+CN portion of the Branch diagram and less than 10% of SNe Ia are both HV and LVG. These features point towards SN 2012fr being quite unusual, similar in many ways to the peculiar SN 2000cx. We modeled the spectral evolution of SN 2012fr to see if we could gain some insight into its evolutionary behavior. We use the parameterized radiative transfer code SYNOW to probe the abundance stratification of SN 2012fr at pre-maximum, maximum, and post-maximum light epochs. We also use a grid of W7 models in the radiative transfer code PHOENIX to probe the effect of different density structures on the formation of the Si II λ6355 absorption feature at post-maximum epochs. We find that the unusual features observed in SN 2012fr are likely due to a shell-like density enhancement in the outer ejecta. We comment on possible reasons for atypical Ca II absorption features, and suggest that they are related to the Si II features.

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Comparative Direct Analysis of Type Ia Supernova Spectra. III. Premaximum

Cited by 26 publications

References 67 publications

SN 2014J at M82 – I. A middle-class Type Ia supernova by all spectroscopic metrics

SN 2014J at M82 – I. A middle-class Type Ia supernova by all spectroscopic metrics

Strong near-infrared carbon in the Type Ia supernova iPTF13ebh

Investigating the Unusual Spectroscopic Time Evolution in SN 2012fr^∗

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Comparative Direct Analysis of Type Ia Supernova Spectra. III. Premaximum

Cited by 26 publications

References 67 publications

SN 2014J at M82 – I. A middle-class Type Ia supernova by all spectroscopic metrics

SN 2014J at M82 – I. A middle-class Type Ia supernova by all spectroscopic metrics

Strong near-infrared carbon in the Type Ia supernova iPTF13ebh

Investigating the Unusual Spectroscopic Time Evolution in SN 2012fr∗

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Investigating the Unusual Spectroscopic Time Evolution in SN 2012fr^∗