SN 2014J at M82 – I. A middle-class Type Ia supernova by all spectroscopic metrics (original) (raw)
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Supernova 2014J at M82 – II. Direct analysis of a middle-class Type Ia supernova
Monthly Notices of the Royal Astronomical Society, 2016
We analyse a time series of optical spectra of SN 2014J from almost two weeks prior to maximum to nearly four months after maximum. We perform our analysis using the SYNOW code, which is well suited to track the distribution of the ions with velocity in the ejecta. We show that almost all of the spectral features during the entire epoch can be identified with permitted transitions of the common ions found in normal supernovae (SNe) Ia in agreement with previous studies. We show that 2014J is a relatively normal SN Ia. At early times the spectral features are dominated by Si II, S II, Mg II, and Ca II. These ions persist to maximum light with the appearance of Na I and Mg I. At later times iron-group elements also appear, as expected in the stratified abundance model of the formation of normal Type Ia SNe. We do not find significant spectroscopic evidence for oxygen, until 100 d after maximum light. The +100 d identification of oxygen is tentative, and would imply significant mixing of unburned or only slight processed elements down to a velocity of 6000 kms −1. Our results are in relatively good agreement with other analyses in the infrared. We briefly compare SN 2011fe to SN 2014J and conclude that the differences could be due to different central densities at ignition or differences in the C/O ratio of the progenitors.
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.
Monthly Notices of the Royal Astronomical Society, 2008
As part of the European Supernova Collaboration we obtained extensive photometry and spectroscopy of the type Ia SN 2002dj covering epochs from 11 days before to nearly two years after maximum. Detailed optical and near-infrared observations show that this object belongs to the class of the high-velocity gradient events as indicated by Si, S and Ca lines. The light curve shape and velocity evolution of SN 2002dj appear to be nearly identical to SN 2002bo. The only significant difference is observed in the optical to near-IR colours and a reduced spectral emission beyond 6500Å. For high-velocity gradient Type Ia supernovae, we tentatively identify a faster rise to maximum, a more pronounced inflection in the V and R light curves after maximum and a brighter, slower declining late-time B light curve as common photometric properties of this class of objects. They also seem to be characterized by a different colour and colour evolution with respect to "normal" SNe Ia. The usual light curve shape parameters do not distinguish these events. Stronger, more blueshifted absorption features of intermediate-mass elements and lower temperatures are the most prominent spectroscopic features of Type Ia supernovae displaying high velocity gradients. It appears that these events burn more intermediate-mass elements in the outer layers. Possible connections to the metallicity of the progenitor star are explored.
Exploring the optical behaviour of a Type Iax supernova SN 2014dt
Monthly Notices of the Royal Astronomical Society, 2017
We present optical photometric (up to ∼410 d since Bmax) and spectroscopic (up to ∼157 d since Bmax) observations of a Type Iax supernova (SN) 2014dt located in M61. SN 2014dt is one of the brightest and closest (D ∼ 20 Mpc) discovered Type Iax SN. It best matches the light-curve evolution of SN 2005hk and reaches a peak magnitude of MB ∼ −18.13 ± 0.04 mag with Δm15 ∼ 1.35 ± 0.06 mag. The early spectra of SN 2014dt are similar to other Type Iax SNe, whereas the nebular spectrum at 157 d is dominated by narrow emission features with less blending as compared to SNe 2008ge and 2012Z. The ejecta velocities are between 5000 and 1000 km s−1, which also confirms the low-energy budget of Type Iax SN 2014dt compared to normal Type Ia SNe. Using the peak bolometric luminosity of SN 2005hk, we estimate the 56Ni mass of ∼0.14 M⊙. The striking similarity between SN 2014dt and SN 2005hk implies that a comparable amount of 56Ni would have been synthesized in the explosion of SN 2014dt.
Optical and NIR observations of the nearby type Ia supernova SN 2014J
Monthly Notices of the Royal Astronomical Society, 2016
Optical and NIR observations of the Type Ia supernova SN 2014J in M82 are presented. The observed light curves are found to be similar to normal Type Ia supernovae (SNe Ia), with a decline rate parameter m 15 (B) = 1.08 ± 0.03. The supernova reached B-band maximum on JD 2456690.14, at an apparent magnitude m B (max) = 11.94. The optical spectra show a red continuum with deep interstellar Na I absorption, but otherwise resemble those of normal SNe Ia. The Si II λ6355 feature indicates a velocity of ∼12 000 km s −1 at B-band maximum, which places SN 2014J at the border of the normal velocity and high velocity group of SNe Ia. The velocity evolution of SN 2014J places it in the Low Velocity Gradient subclass, whereas the equivalent widths of Si II features near B-band maximum place it at the border of the core normal and Broad Line subclasses of SNe Ia. An analytic model fit to the bolometric light curve indicates that a total of ∼1.3 M was ejected in the explosion, and the ejected 56 Ni mass M Ni ∼ 0.6 M. The low [Fe III] λ4701 to [Fe II] λ5200 ratio in the nebular spectra of SN 2014J hints towards clumpiness in the ejecta. Optical broad-band, linear polarimetric observations of SN 2014J obtained on four epochs indicate an almost constant polarization (P R ∼2.7 per cent; θ ∼ 37 •), which suggests that the polarization signal is of interstellar origin.
Spectroscopy of Type Ia supernovae by the Carnegie Supernova Project
2013
This is the first release of optical spectroscopic data of low-redshift Type Ia supernovae (SNe Ia) by the Carnegie Supernova Project including 604 previously unpublished spectra of 93 SNe Ia. The observations cover a range of phases from 12 days before to over 150 days after the time of B-band maximum light. With the addition of 228 near-maximum spectra from the literature we study the diversity among SNe Ia in a quantitative manner. For that purpose, spectroscopic parameters are employed such as expansion velocities from spectral line blueshifts, and pseudo-equivalent widths (pW ). The values of those parameters at maximum light are obtained for 78 objects, thus providing a characterization of SNe Ia that may help to improve our understanding of the properties of the exploding systems and the thermonuclear flame propagation. Two objects, namely SNe 2005M and 2006is, stand out from the sample by showing peculiar Si II and S II velocities but otherwise standard velocities for the rest of the ions. We further study the correlations between spectroscopic and photometric parameters such as light-curve decline rate and color. In agreement with previous studies, we find that the pW of Si II absorption features are very good indicators of light-curve decline rate. Furthermore, we demonstrate that parameters such as pW 2 (Si II 4130) and pW 6 (Si II 5972) provide precise calibrations of the peak B-band luminosity with dispersions of ≈0.15 mag. In the search for a secondary parameter in the calibration of peak luminosity for SNe Ia, we find a ≈2-3-σ correlation between B-band Hubble residuals and the velocity at maximum light of S II and Si II lines.
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.
The Spectroscopic Diversity of Type Ia Supernovae
2012
We present 2603 spectra of 462 nearby Type Ia supernovae (SN Ia) obtained during 1993-2008 through the Center for Astrophysics Supernova Program. Most of the spectra were obtained with the FAST spectrograph at the FLWO 1.5m telescope and reduced in a consistent manner, making data set well suited for studies of SN Ia spectroscopic diversity. We study the spectroscopic and photometric properties of SN Ia as a function of spectroscopic class using the classification schemes of Branch et al. and Wang et al. The width-luminosity relation appears to be steeper for SN Ia with broader lines. Based on the evolution of the characteristic Si II 6355 line, we propose improved methods for measuring velocity gradients, revealing a larger range than previously suspected, from ~0 to ~400 km/s/day considering the instantaneous velocity decline rate at maximum light. We find a weaker and less significant correlation between Si II velocity and intrinsic B-V color at maximum light than reported by Fol...
Monthly Notices of the Royal Astronomical Society, 2013
We present optical UBVRI photometry and medium-resolution spectroscopy of a transitional Type Ia supernova, SN 2009an, over the period −6 to ∼+150 d from the B maximum. With a m 15 (B) = 1.514 ± 0.132, SN 2009an declines faster than normal Type Ia events, but slower than the fast-declining, low-luminosity 1991bg-like events. The B-band absolute magnitude at maximum is −19.02 ± 0.20. The peak bolometric luminosity indicates that 0.41 M of 56 Ni was synthesized during the explosion. The pre-maximum and early post-maximum spectral evolution of SN 2009an is very similar to that in the transitional Type Ia SN 2004eo. Highvelocity features in the Ca II near-infrared triplet are seen during the early phases. Similar to the other few objects belonging to this class, SN 2009an exhibits a higher value (∼0.4) of the Si II line ratio R(Si II). The velocity gradient of the Si II 6355 Å line in the post-maximum epoch (v = 60 km s −1 d −1) is at the boundary between the low-velocity-gradient and high-velocitygradient groups.
Exploring the spectroscopic diversity of Type Ia supernovae
Monthly Notices of the Royal Astronomical Society, 2006
The velocities and equivalent widths of a set of absorption features are measured for a sample of 28 well-observed Type Ia Supernovae covering a wide range of properties. The values of these quantities at maximum are obtained through inter-/extrapolation and plotted against the decline rate, and so are various line ratios. The SNe are divided according to their velocity evolution into the three classes defined by Benetti et al. (2005): LVG, HVG, and FAINT. It is found that all LVG have approximately uniform velocites at B maximum, while the FAINT SNe have values that decrease with increasing ∆m 15 (B), and the HVG have a large spread. The EW s of the Fe-dominated features are approximately constant in all SNe, while those of Intermediate Mass Elements lines have larger values for intermediate decliners and smaller values for brighter and FAINT SNe. The HVG SNe have stronger Si II 6355Å lines, with no correlation with ∆m 15 (B). It is also shown that the Si II 5972Å EW and three EW ratios, including one analogous to the R(Si II) ratio of Nugent et al. (1995), are good spectroscopic indicators of luminosity. The data suggest that all LVG have approximately constant kinetic energy, since burning to IME extends to similar velocities. The FAINT SNe may have somewhat lower energies. The large velocities and EW s of the IME lines in the HVG appear correlated with each other, but are not correlated with the presence of high velocity features in the Ca II IR triplet in the earliest spectra for the SNe for which such data exist.