Early Blue Excess from the Type Ia Supernova 2017cbv

2017 ◽  
Vol 14 (S339) ◽  
pp. 47-49
Author(s):  
G. Hosseinzadeh
Keyword(s):  
Light Curve ◽  
Standard Type ◽  
Circumstellar Material ◽  
Type Ia Supernova ◽  
Unusual Distribution ◽  
Photometric Observations ◽  
Type Ia ◽  
Optical Light Curve ◽  
Ia Supernovae

AbstractThis paper presented very early, high-cadence photometric observations of the nearby Type Ia SN 2017cbv. The light-curve is unique in that during the first five days of observations it has a blue bump in the U, B, and g bands which is clearly resolved by virtue of our photometric cadence of 5.7 hr during that time span. We modelled the light-curve as the combination of an early shock of the supernova ejecta against a non-degenerate companion star plus a standard Type Ia supernova component. Our best-fit model suggested the presence of a subgiant star 56 R⊙ from the exploding white dwarf, although that number is highly model-dependent. While the model matches the optical light-curve well, it over-predicts the flux expected in the ultraviolet bands. That may indicate that the shock is not a blackbody, perhaps because of line blanketing in the UV. Alternatively, it could point to another physical explanation for the optical blue bump, such as interaction with circumstellar material or an unusual distribution of the element Ni. Early optical spectra of SN 2017cbv show strong carbon absorption as far as day –13 with respect to maximum light, suggesting that the progenitor system contained a significant amount of unburnt material. These results for SN 2017cbv illustrate the power of early discovery and intense follow-up of nearby supernovæ for resolving standing questions about the progenitor systems and explosion mechanisms of Type Ia supernovæ.

scholarly journals A type Ia supernova at the heart of superluminous transient SN 2006gy

Science ◽  
2020 ◽  
Vol 367 (6476) ◽  
pp. 415-418 ◽  
Author(s):  
Anders Jerkstrand ◽  
Keiichi Maeda ◽  
Koji S. Kawabata
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Supernova Explosion ◽  
Large Mass ◽  
Late Time ◽  
Standard Type ◽  
Circumstellar Material ◽  
Common Envelope ◽  
Type Ia Supernova ◽  
Type Ia

Superluminous supernovae radiate up to 100 times more energy than normal supernovae. The origin of this energy and the nature of the stellar progenitors of these transients are poorly understood. We identify neutral iron lines in the spectrum of one such supernova, SN 2006gy, and show that they require a large mass of iron (≳0.3 solar masses) expanding at 1500 kilometers per second. By modeling a standard type Ia supernova hitting a shell of circumstellar material, we produce a light curve and late-time iron-dominated spectrum that match the observations of SN 2006gy. In such a scenario, common envelope evolution of a progenitor binary system can synchronize envelope ejection and supernova explosion and may explain these bright transients.

scholarly journals ASASSN-18tb: a most unusual Type Ia supernova observed by TESS and SALT

2019 ◽  
Vol 487 (2) ◽  
pp. 2372-2384 ◽  
Author(s):  
P J Vallely ◽  
M Fausnaugh ◽  
S W Jha ◽  
M A Tucker ◽  
Y Eweis ◽  
...  
Keyword(s):  
Light Curve ◽  
Power Law ◽  
Type Ia Supernovae ◽  
Normal Type ◽  
Type Ia Supernova ◽  
Type Ia ◽  
Early Rise ◽  
Ia Supernovae ◽  
Best Fit ◽  
Unusual Type

ABSTRACT We present photometric and spectroscopic observations of the unusual Type Ia supernova ASASSN-18tb, including a series of Southern African Large Telescope spectra obtained over the course of nearly six months and the first observations of a supernova by the Transiting Exoplanet Survey Satellite. We confirm a previous observation by Kollmeier et al. showing that ASASSN-18tb is the first relatively normal Type Ia supernova to exhibit clear broad (∼1000 km s−1) H α emission in its nebular-phase spectra. We find that this event is best explained as a sub-Chandrasekhar mass explosion producing $M_{\mathrm{ Ni}} \approx 0.3\,\, \rm {M}_\odot$. Despite the strong H α signature at late times, we find that the early rise of the supernova shows no evidence for deviations from a single-component power-law and is best fit with a moderately shallow power law of index 1.69 ± 0.04. We find that the H α luminosity remains approximately constant after its initial detection at phase +37 d, and that the H α velocity evolution does not trace that of the Fe iii λ4660 emission. These suggest that the H α emission arises from a circumstellar medium (CSM) rather than swept-up material from a non-degenerate companion. However, ASASSN-18tb is strikingly different from other known CSM-interacting Type Ia supernovae in a number of significant ways. Those objects typically show an H α luminosity two orders of magnitude higher than what is seen in ASASSN-18tb, pushing them away from the empirical light-curve relations that define ‘normal’ Type Ia supernovae. Conversely, ASASSN-18tb exhibits a fairly typical light curve and luminosity for an underluminous or transitional SN Ia, with MR ≈ −18.1 mag. Moreover, ASASSN-18tb is the only SN Ia showing H α from CSM interaction to be discovered in an early-type galaxy.

scholarly journals An investigation of 56Ni shells as the source of early light curve bumps in type Ia supernovae

2020 ◽  
Vol 642 ◽  
pp. A189
Author(s):  
M. R. Magee ◽  
K. Maguire
Keyword(s):  
Light Curve ◽  
Light Curves ◽  
Radioactive Material ◽  
Type Ia Supernovae ◽  
Spectral Evolution ◽  
Strong Suppression ◽  
Shell Models ◽  
Type Ia ◽  
Optical Light Curve ◽  
Ia Supernovae

An excess of flux (i.e. a bump) in the early light curves of type Ia supernovae has been observed in a handful of cases. Multiple scenarios have been proposed to explain this excess flux. Recently, it has been shown that for at least one object (SN 2018oh) the excess emission observed could be the result of a large amount of 56Ni in the outer ejecta (∼0.03 M⊙). We present a series of model light curves and spectra for ejecta profiles containing 56Ni shells of varying masses (0.01, 0.02, 0.03, and 0.04 M⊙) and widths. We find that even for our lowest mass 56Ni shell, an increase of >2 magnitudes is produced in the bolometric light curve at one day after explosion relative to models without a 56Ni shell. We show that the colour evolution of models with a 56Ni shell differs significantly from those without and shows a colour inversion similar to some double-detonation explosion models. Furthermore, spectra of our 56Ni shell models show that strong suppression of flux between ∼3700–4000 Å close to maximum light appears to be a generic feature for this class of model. Comparing our models to observations of SNe 2017cbv and 2018oh, we show that a 56Ni shell of 0.02–0.04 M⊙ can match shapes of the early optical light curve bumps, but the colour and spectral evolution are in disagreement. Our models also predict a strong UV bump that is not observed. This would indicate that an alternative origin for the flux excess is necessary. In addition, based on existing explosion scenarios, producing such a 56Ni shell in the outer ejecta as required to match the light curve shape, without the presence of additional short-lived radioactive material, may prove challenging. Given that only a small amount of 56Ni in the outer ejecta is required to produce a bump in the light curve, such non-monotonically decreasing 56Ni distributions in the outer ejecta must be rare, if they were to occur at all.

scholarly journals Significant luminosity differences of two twin Type Ia supernovae

2019 ◽  
Vol 491 (4) ◽  
pp. 5991-5999 ◽  
Author(s):  
Ryan J Foley ◽  
Samantha L Hoffmann ◽  
Lucas M Macri ◽  
Adam G Riess ◽  
Peter J Brown ◽  
...  
Keyword(s):  
Light Curve ◽  
Spectral Energy Distribution ◽  
Cosmological Parameters ◽  
Spectral Energy ◽  
Type Ia Supernovae ◽  
Curve Shape ◽  
Type Ia ◽  
Optical Light Curve ◽  
Ia Supernovae ◽  
Peak Luminosity

ABSTRACT The Type Ia supernovae (SNe Ia) 2011by, hosted in NGC 3972, and 2011fe, hosted in M101, are optical ‘twins,’ having almost identical optical light-curve shapes, colours, and near-maximum-brightness spectra. However, SN 2011fe had significantly more ultraviolet (UV; 1600 < λ < 2500 Å) flux than SN 2011by before and at peak luminosity. Several theoretical models predict that SNe Ia with higher progenitor metallicity should (1) have additional UV opacity and thus lower UV flux; (2) have an essentially unchanged optical spectral-energy distribution; (3) have a similar optical light-curve shape; and (4) because of the excess neutrons, produce more stable Fe-group elements at the expense of radioactive 56Ni and thus have a lower peak luminosity. Following these predictions, Foley and Kirshner suggested that the difference in UV flux between SNe 2011by and 2011fe was the result of their progenitors having significantly different metallicities. They also measured a large, but insignificant, difference between the peak absolute magnitudes of the SNe (ΔMV, peak = 0.60 ± 0.36 mag), with SN 2011fe being more luminous. We present a new Cepheid-based distance to NGC 3972, substantially improving the precision of the distance measurement for SN 2011by. With these new data, we determine that the SNe have significantly different peak luminosities (ΔMV, peak = 0.335 ± 0.069 mag). Consequently, SN 2011fe produced 38 per cent more 56Ni than SN 2011by, consistent with predictions for progenitor metallicity differences for these SNe, although alternative models may also explain this difference. We discuss how progenitor metallicity differences can contribute to the intrinsic scatter for light-curve-shape-corrected SN luminosities, the use of ‘twin’ SNe for measuring distances, and implications for using SNe Ia for constraining cosmological parameters.

scholarly journals THE GOLDEN STANDARD TYPE Ia SUPERNOVA 2005cf: OBSERVATIONS FROM THE ULTRAVIOLET TO THE NEAR-INFRARED WAVEBANDS

2009 ◽  
Vol 697 (1) ◽  
pp. 380-408 ◽  
Author(s):  
X. Wang ◽  
W. Li ◽  
A. V. Filippenko ◽  
R. J. Foley ◽  
R. P. Kirshner ◽  
...  
Keyword(s):  
Near Infrared ◽  
Standard Type ◽  
Type Ia Supernova ◽  
Type Ia ◽  
Golden Standard

scholarly journals Constraints on the density distribution of type Ia supernovae ejecta inferred from late-time light-curve flattening

2020 ◽  
Vol 493 (4) ◽  
pp. 5617-5624
Author(s):  
Doron Kushnir ◽  
Eli Waxman
Keyword(s):  
Light Curve ◽  
Weighted Average ◽  
Far Infrared ◽  
Average Density ◽  
Light Curves ◽  
Type Ia Supernovae ◽  
Late Time ◽  
Simple Method ◽  
Type Ia ◽  
Ia Supernovae

ABSTRACT The finite time, τdep, over which positrons from β+ decays of 56Co deposit energy in type Ia supernovae ejecta lead, in case the positrons are trapped, to a slower decay of the bolometric luminosity compared to an exponential decline. Significant light-curve flattening is obtained when the ejecta density drops below the value for which τdep equals the 56Co lifetime. We provide a simple method to accurately describe this ‘delayed deposition’ effect, which is straightforward to use for analysis of observed light curves. We find that the ejecta heating is dominated by delayed deposition typically from 600 to 1200 d, and only later by longer lived isotopes 57Co and 55Fe decay (assuming solar abundance). For the relatively narrow 56Ni velocity distributions of commonly studied explosion models, the modification of the light curve depends mainly on the 56Ni mass-weighted average density, 〈ρ〉t3. Accurate late-time bolometric light curves, which may be obtained with JWST far-infrared (far-IR) measurements, will thus enable to discriminate between explosion models by determining 〈ρ〉t3 (and the 57Co and 55Fe abundances). The flattening of light curves inferred from recent observations, which is uncertain due to the lack of far-IR data, is readily explained by delayed deposition in models with $\langle \rho \rangle t^{3} \approx 0.2\, \mathrm{M}_{\odot }\, (10^{4}\, \textrm{km}\, \textrm{s}^{-1})^{-3}$, and does not imply supersolar 57Co and 55Fe abundances.

scholarly journals A Precise Distance Indicator: Type Ia Supernova Multicolor Light‐Curve Shapes

1996 ◽  
Vol 473 (1) ◽  
pp. 88-109 ◽  
Author(s):  
Adam G. Riess ◽  
William H. Press ◽  
Robert P. Kirshner
Keyword(s):  
Light Curve ◽  
Type Ia Supernova ◽  
Type Ia ◽  
Distance Indicator ◽  
Indicator Type

scholarly journals The Hyper Suprime-Cam SSP transient survey in COSMOS: Overview

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Naoki Yasuda ◽  
Masaomi Tanaka ◽  
Nozomu Tominaga ◽  
Ji-an Jiang ◽  
Takashi J Moriya ◽  
...  
Keyword(s):  
Light Curve ◽  
Deep Layer ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Variable Stars ◽  
Photometric Redshifts ◽  
Data Set ◽  
Type Ia ◽  
Strategic Program ◽  
Ia Supernovae

Abstract We present an overview of a deep transient survey of the COSMOS field with the Subaru Hyper Suprime-Cam (HSC). The survey was performed for the 1.77 deg2 ultra-deep layer and 5.78 deg2 deep layer in the Subaru Strategic Program over six- and four-month periods from 2016 to 2017, respectively. The ultra-deep layer reaches a median depth per epoch of 26.4, 26.3, 26.0, 25.6, and 24.6 mag in g, r, i, z, and y bands, respectively; the deep layer is ∼0.6 mag shallower. In total, 1824 supernova candidates were identified. Based on light-curve fitting and derived light-curve shape parameter, we classified 433 objects as Type Ia supernovae (SNe); among these candidates, 129 objects have spectroscopic or COSMOS2015 photometric redshifts and 58 objects are located at z > 1. Our unique data set doubles the number of Type Ia SNe at z > 1 and enables various time-domain analyses of Type II SNe, high-redshift superluminous SNe, variable stars, and active galactic nuclei.

scholarly journals deepSIP: linking Type Ia supernova spectra to photometric quantities with deep learning

2020 ◽  
Vol 496 (3) ◽  
pp. 3553-3571
Author(s):  
Benjamin E Stahl ◽  
Jorge Martínez-Palomera ◽  
WeiKang Zheng ◽  
Thomas de Jaeger ◽  
Alexei V Filippenko ◽  
...  
Keyword(s):  
Deep Learning ◽  
Light Curve ◽  
Data Augmentation ◽  
Data Sets ◽  
Curve Shape ◽  
Learning Standards ◽  
Type Ia Supernova ◽  
Type Ia ◽  
Augmentation Strategy ◽  
Hyperparameter Selection

ABSTRACT We present deepSIP (deep learning of Supernova Ia Parameters), a software package for measuring the phase and – for the first time using deep learning – the light-curve shape of a Type Ia supernova (SN Ia) from an optical spectrum. At its core, deepSIP consists of three convolutional neural networks trained on a substantial fraction of all publicly available low-redshift SN Ia optical spectra, on to which we have carefully coupled photometrically derived quantities. We describe the accumulation of our spectroscopic and photometric data sets, the cuts taken to ensure quality, and our standardized technique for fitting light curves. These considerations yield a compilation of 2754 spectra with photometrically characterized phases and light-curve shapes. Though such a sample is significant in the SN community, it is small by deep-learning standards where networks routinely have millions or even billions of free parameters. We therefore introduce a data-augmentation strategy that meaningfully increases the size of the subset we allocate for training while prioritizing model robustness and telescope agnosticism. We demonstrate the effectiveness of our models by deploying them on a sample unseen during training and hyperparameter selection, finding that Model I identifies spectra that have a phase between −10 and 18 d and light-curve shape, parametrized by Δm15, between 0.85 and 1.55 mag with an accuracy of 94.6 per cent. For those spectra that do fall within the aforementioned region in phase–Δm15 space, Model II predicts phases with a root-mean-square error (RMSE) of 1.00 d and Model III predicts Δm15 values with an RMSE of 0.068 mag.

scholarly journals K2 Observations of SN 2018oh Reveal a Two-component Rising Light Curve for a Type Ia Supernova

2018 ◽  
Vol 870 (1) ◽  
pp. L1 ◽  
Author(s):  
G. Dimitriadis ◽  
R. J. Foley ◽  
A. Rest ◽  
D. Kasen ◽  
A. L. Piro ◽  
...  
Keyword(s):  
Light Curve ◽  
Type Ia Supernova ◽  
Two Component ◽  
Type Ia
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