arXiv subjects

S. Taubenberger

Publications and source records attributed to S. Taubenberger.

At least 109 records · Page 6Linked to original sources

arXiv2014

Type Ia supernova bolometric light curves and ejected mass estimates from the Nearby Supernova Factory

We present a sample of normal type Ia supernovae from the Nearby Supernova Factory dataset with spectrophotometry at sufficiently late phases to estimate the ejected mass using the bolometric light curve. We measure $^{56}$Ni masses from the peak bolometric luminosity, then compare the luminosity in the $^{56}$Co-decay tail to the expected rate of radioactive energy re- lease from ejecta of a given mass. We infer the ejected mass in a Bayesian context using a semi-analytic model of the ejecta, incorporating constraints from contemporary numerical models as priors on the density structure and distribution of $^{56}$Ni throughout the ejecta. We find a strong correlation between ejected mass and light curve decline rate, and consequently $^{56}$Ni mass, with ejected masses in our data ranging from 0.9-1.4 $M_\odot$. Most fast-declining (SALT2 $x_1 < -1$) normal SNe Ia have significantly sub-Chandrasekhar ejected masses in our fiducial analysis.

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arXiv2014

Underluminous Type II Plateau Supernovae: II. Pointing towards moderate mass precursors

We present new data for five under-luminous type II-plateau supernovae (SNe IIP), namely SN 1999gn, SN 2002gd, SN 2003Z, SN 2004eg and SN 2006ov. This new sample of low-luminosity SNe IIP (LL SNe IIP) is analyzed together with similar objects studied in the past. All of them show a flat light curve plateau lasting about 100 days, an under luminous late-time exponential tail, intrinsic colours that are unusually red, and spectra showing prominent and narrow P-Cygni lines. A velocity of the ejected material below 10^3 km/s is inferred from measurements at the end of the plateau. The 56Ni masses ejected in the explosion are very small (less than 10^-2 solar masses). We investigate the correlations among 56Ni mass, expansion velocity of the ejecta and absolute magnitude in the middle of the plateau, confirming the main findings of Hamuy (2003), according to which events showing brighter plateau and larger expansion velocities are expected to produce more 56Ni. We propose that these faint objects represent the low luminosity tail of a continuous distribution in parameters space of SNe IIP. The physical properties of the progenitors at the explosion are estimated through the hydrodynamical modeling of the observables for two representative events of this class, namely SN 2005cs and SN 2008in. We find that the majority of LL SNe IIP, and quite possibly all, originate in the core-collapse of intermediate mass stars, in the mass range 10-15 solar masses.

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arXiv2013

SN 2009N: Linking normal and subluminous type II-P SNe

We present ultraviolet, optical, near-infrared photometry and spectroscopy of SN 2009N in NGC 4487. This object is a type II-P supernova with spectra resembling those of subluminous II-P supernovae, while its bolometric luminosity is similar to that of the intermediate luminosity SN 2008in. We created SYNOW models of the plateau phase spectra for line identification and to measure the expansion velocity. In the near-infrared spectra we find signs indicating possible weak interaction between the supernova ejecta and the pre-existing circumstellar material. These signs are also present in the previously unpublished near-infrared spectra of SN 2008in. The distance to SN 2009N is determined via the expanding photosphere method and the standard candle method as $D= 21.6 \pm 1.1\,{\mathrm {Mpc}}$. The produced nickel-mass is estimated to be $\sim 0.020 \pm 0.004\,{\mathrm M_\odot}$. We infer the physical properties of the progenitor at the explosion through hydrodynamical modelling of the observables. We find the values of the total energy as $\sim 0.48 \times 10^{51}\, {\mathrm {erg}}$, the ejected mass as $\sim 11.5\,{\mathrm M_\odot}$, and the initial radius as $\sim 287\,{\mathrm R_\odot}$.

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arXiv2013

Optical and near-infrared observations of SN 2011dh - The first 100 days

We present optical and near-infrared (NIR) photometry and spectroscopy of the Type IIb supernova (SN) 2011dh for the first 100 days. We complement our extensive dataset with SWIFT ultra-violet (UV) and Spitzer mid-infrared (MIR) data to build a UV to MIR bolometric lightcurve using both photometric and spectroscopic data. Hydrodynamical modelling of the SN based on this bolometric lightcurve have been presented in Bersten (2012). We find that the absorption minimum for the hydrogen lines is never seen below ~11000 km/s but approaches this value as the lines get weaker. This suggests that the interface between the helium core and hydrogen rich envelope is located near this velocity in agreement with the Bersten et al. (2012) He4R270 ejecta model. Spectral modelling of the hydrogen lines using this ejecta model supports the conclusion and we find a hydrogen mass of 0.01-0.04 solar masses to be consistent with the observed spectral evolution. We estimate that the photosphere reaches the helium core at 5-7 days whereas the helium lines appear between ~10 and ~15 days, close to the photosphere and then move outward in velocity until ~40 days. This suggests that increasing non-thermal excitation due to decreasing optical depth for the gamma-rays is driving the early evolution of these lines. We also provide and discuss pre- and post-explosion observations of the SN site which shows a reduction by 75 percent in flux at the position of the yellow supergiant coincident with SN 2011dh. The B, V and r band decline rates of 0.0073, 0.0090 and 0.0053 mag/day respectively are consistent with the remaining flux being emitted by the SN. Hence we find that the star was indeed the progenitor of SN 2011dh as previously suggested by Maund et al. (2011) and which is also consistent with the results from the hydrodynamical modelling.

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arXiv2013

SN 2010lp---a Type Ia supernova from a violent merger of two carbon--oxygen White Dwarfs

SN 2010lp is a subluminous Type Ia supernova (SN Ia) with slowly-evolving lightcurves. Moreover, it is the only subluminous SN Ia observed so far that shows narrow emission lines of OI in late-time spectra, indicating unburned oxygen close to the centre of the ejecta. Most explosion models for SNe Ia cannot explain the narrow OI emission. Here, we present hydrodynamic explosion and radiative transfer calculations showing that the violent merger of two carbon-oxygen white dwarfs of 0.9 and 0.76 solar masses, respectively, adequately reproduces the early-time observables of SN 2010lp. Moreover, our model predicts oxygen close to the centre of the explosion ejecta, a pre-requisite for narrow OI emission in nebular spectra as observed in SN 2010lp.

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arXiv2013

PESSTO monitoring of SN 2012hn: further heterogeneity among faint type I supernovae

We present optical and infrared monitoring data of SN 2012hn collected by the Public ESO Spectroscopic Survey for Transient Objects (PESSTO). We show that SN 2012hn has a faint peak magnitude (MR ~ -15.7) and shows no hydrogen and no clear evidence for helium in its spectral evolution. Instead, we detect prominent Ca II lines at all epochs, which relates this transient to previously described 'Ca-rich' or 'gap' transients. However, the photospheric spectra (from -3 to +32 d with respect to peak) of SN 2012hn show a series of absorption lines which are unique, and a red continuum that is likely intrinsic rather than due to extinction. Lines of Ti II and Cr II are visible. This may be a temperature effect, which could also explain the red photospheric colour. A nebular spectrum at +150d shows prominent CaII, OI, CI and possibly MgI lines which appear similar in strength to those displayed by core-collapse SNe. To add to the puzzle, SN 2012hn is located at a projected distance of 6 kpc from an E/S0 host and is not close to any obvious starforming region. Overall SN 2012hn resembles a group of faint H-poor SNe that have been discovered recently and for which a convincing and consistent physical explanation is still missing. They all appear to explode preferentially in remote locations offset from a massive host galaxy with deep limits on any dwarf host galaxies, favouring old progenitor systems. SN 2012hn adds heterogeneity to this sample of objects. We discuss potential explosion channels including He-shell detonations and double detonations of white dwarfs as well as peculiar core-collapse SNe.

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arXiv2013

Synthetic light curves and spectra for three-dimensional delayed-detonation models of Type Ia supernovae

In a companion paper, Seitenzahl et al. (2013) presented a set of three-dimensional delayed detonation models for thermonuclear explosions of near-Chandrasekhar mass white dwarfs (WDs). Here, we present multi-dimensional radiative transfer simulations that provide synthetic light curves and spectra for those models. The model sequence explores both changes in the strength of the deflagration phase (controlled by the ignition configuration) and the WD central density. In agreement with previous studies, we find that the strength of the deflagration significantly affects the explosion and the observables. Variations in the central density also have an influence on both brightness and colour, but overall it is a secondary parameter in our set of models. In many respects, the models yield a good match to normal Type Ia supernovae (SNe Ia): peak brightness, rise/decline time scales and synthetic spectra are all in reasonable agreement. There are, however, several differences. In particular, the models are too red around maximum light, manifest spectral line velocities that are a little too high and yield I-band light curves that do not match observations. Although some of these discrepancies may simply relate to approximations made in the modelling, some pose real challenges to the models. If viewed as a complete sequence, our models do not reproduce the observed light-curve width-luminosity relation (WLR) of SNe Ia: all our models show similar B-band decline rates, irrespective of peak brightness. This suggests that simple variations in the strength of the deflagration phase in Chandrasekhar-mass deflagration-to-detonation models do not readily explain the observed diversity of normal SNe Ia. This may imply that some other parameter within the Chandrasekhar-mass paradigm is key to the WLR, or that a substantial fraction of normal SNe Ia arise from an alternative explosion scenario.

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arXiv2013

[OI] 6300,6364 in the nebular spectrum of a subluminous Type Ia supernova

In this letter a late-phase spectrum of SN 2010lp, a subluminous Type Ia supernova (SN Ia), is presented and analysed. As in 1991bg-like SNe Ia at comparable epochs, the spectrum is characterised by relatively broad [FeII] and [CaII] emission lines. However, instead of narrow [FeIII] and [CoIII] lines that dominate the emission from the innermost regions of 1991bg-like SNe, SN 2010lp shows [OI] 6300,6364 emission, usually associated with core-collapse SNe and never observed in a subluminous thermonuclear explosion before. The [OI] feature has a complex profile with two strong, narrow emission peaks. This suggests oxygen to be distributed in a non-spherical region close to the centre of the ejecta, severely challenging most thermonuclear explosion models discussed in the literature. We conclude that given these constraints violent mergers are presently the most promising scenario to explain SN 2010lp.

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arXiv2013

Comparison of progenitor mass estimates for the type IIP SN 2012A

We present the one-year long observing campaign of SN 2012A which exploded in the nearby (9.8 Mpc) irregular galaxy NGC 3239. The photometric evolution is that of a normal type IIP supernova. The absolute maximum magnitude, with MB = -16.23 +- 0.16 mag. SN2012A reached a peak luminosity of about 2X10**42 erg/s, which is brighter than those of other SNe with a similar 56Ni mass. The latter was estimated from the luminosity in the exponential tail of the light curve and found to be M(56Ni) = 0.011 +-0.004 Msun. The spectral evolution of SN 2012A is also typical of SN IIP, from the early spectra dominated by a blue continuum and very broad (~10**4 km/s) Balmer lines, to the late-photospheric spectra characterized by prominent P-Cygni features of metal lines (Fe II, Sc II, Ba II, Ti II, Ca II, Na ID). The photospheric velocity is moderately low, ~3X10**3 km/s at 50 days, for the low optical depth metal lines. The nebular spectrum obtained 394 days after the shock breakout shows the typical features of SNe IIP and the strength of the [O I] doublet suggests a progenitor of intermediate mass, similar to SN 2004et (~15 Msun). A candidate progenitor for SN 2012A has been identified in deep, pre-explosion K'-band Gemini North (NIRI) images, and found to be consistent with a star with a bolometric magnitude -7.08+-0.36 (log L/Lsun = 4.73 +- 0.14$ dex). The magnitude of the recovered progenitor in archival images points toward a moderate-mass 10.5 (-2/+4.5) Msun star as the precursor of SN 2012A. The explosion parameters and progenitor mass were also estimated by means of a hydrodynamical model, fitting the bolometric light curve, the velocity and the temperature evolution. We found a best fit for a kinetic energy of 0.48 foe, an initial radius of 1.8X10**13 cm and ejecta mass of 12.5 Msun.

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arXiv2013

Moderately Luminous type II Supernovae

Core-collapse Supernovae (CC-SNe) descend from progenitors more massive than about 8 Msun. Because of the young age of the progenitors, the ejecta may eventually interact with the circumstellar medium (CSM) via highly energetic processes detectable in the radio, X-ray, ultraviolet (UV) and, sometimes, in the optical domains. In this paper we present ultraviolet, optical and near infrared observations of five type II SNe, namely SNe 2009dd, 2007pk, 2010aj, 1995ad, and 1996W. Together with few other SNe they form a group of moderately luminous type II events. We collected photometry and spectroscopy with several telescopes in order to construct well-sampled light curves and spectral evolutions from the photospheric to the nebular phases. Both photometry and spectroscopy indicate a degree of heterogeneity in this sample. The light curves have luminous peak magnitudes ($-16.95<M_{B}<-18.70$). The ejected masses of ^56\ni for three SNe span a wide range of values ($2.8\times10^{-2}$Msun$<$M(\ni)$<1.4\times10^{-1}$Msun), while for a fourth (SN2010aj) we could determine a stringent upper limit ($7\times10^{-3}$Msun). Clues of interaction, such as the presence of high velocity (HV) features of the Balmer lines, are visible in the photospheric spectra of SNe 2009dd and 1996W. For SN2007pk we observe a spectral transition from a type IIn to a standard type II SN. Modelling the observations of SNe 2009dd, 2010aj and 1995ad with radiation hydrodynamics codes, we infer kinetic plus thermal energies of about 0.2-0.5 foe, initial radii of 2-5$\times10^{13}$ cm and ejected masses of $\sim$5.0-9.5 Msun. These values suggest moderate-mass, super-asymptotic giant branch (SAGB) or red super-giants (RSG) stars as SN precursors, in analogy with other luminous type IIP SNe 2007od and 2009bw.

astro-ph.CO↗

arXiv2013

Helium-ignited violent mergers as a unified model for normal and rapidly declining Type Ia Supernovae

The progenitors of Type Ia Supernovae (SNe Ia) are still unknown, despite significant progress during the last years in theory and observations. Violent mergers of two carbon--oxygen (CO) white dwarfs (WDs) are one candidate suggested to be responsible for at least a significant fraction of normal SNe Ia. Here, we simulate the merger of two CO WDs using a moving-mesh code that allows for the inclusion of thin helium (He) shells (0.01\,\msun) on top of the WDs, at an unprecedented numerical resolution. The accretion of He onto the primary WD leads to the formation of a detonation in its He shell. This detonation propagates around the CO WD and sends a converging shock wave into its core, known to robustly trigger a second detonation, as in the well-known double-detonation scenario for He-accreting CO WDs. However, in contrast to that scenario where a massive He shell is required to form a detonation through thermal instability, here the He detonation is ignited dynamically. Accordingly the required He-shell mass is significantly smaller, and hence its burning products are unlikely to affect the optical display of the explosion. We show that this scenario, which works for CO primary WDs with CO- as well as He-WD companions, has the potential to explain the different brightness distributions, delay times and relative rates of normal and fast declining SNe Ia. Finally, we discuss extensions to our unified merger model needed to obtain a comprehensive picture of the full observed diversity of SNe Ia.

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arXiv2013

Super Luminous Ic Supernovae: catching a magnetar by the tail

We report extensive observational data for five of the lowest redshift Super-Luminous Type Ic Supernovae (SL-SNe Ic) discovered to date, namely PTF10hgi, SN2011ke, PTF11rks, SN2011kf and SN2012il. Photometric imaging of the transients at +50 to +230 days after peak combined with host galaxy subtraction reveals a luminous tail phase for four of these SL-SNe. A high resolution, optical and near infrared spectrum from xshooter provides detection of a broad He I $λ$10830 emission line in the spectrum (+50d) of SN2012il, revealing that at least some SL-SNe Ic are not completely helium free. At first sight, the tail luminosity decline rates that we measure are consistent with the radioactive decay of \co, and would require 1-4M of \ni to produce the luminosity. These \ni masses cannot be made consistent with the short diffusion times at peak, and indeed are insufficient to power the peak luminosity. We instead favour energy deposition by newborn magnetars as the power source for these objects. A semi-analytical diffusion model with energy input from the spin-down of a magnetar reproduces the extensive lightcurve data well. The model predictions of ejecta velocities and temperatures which are required are in reasonable agreement with those determined from our observations. We derive magnetar energies of $0.4\lesssim E$($10^{51}$erg) $\lesssim6.9$ and ejecta masses of $2.3\lesssim M_{ej}$(\M) $\lesssim 8.6$. The sample of five SL-SNe Ic presented here, combined with SN 2010gx - the best sampled SL-SNe Ic so far - point toward an explosion driven by a magnetar as a viable explanation for all SL-SNe Ic.

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arXiv2013

Spectrophotometric time series of SN 2011fe from the Nearby Supernova Factory

We present 32 epochs of optical (3300-9700 Å) spectrophotometric observations of the nearby quintessential "normal" type Ia supernova (SN Ia) SN 2011fe in the galaxy M101, extending from -15 to +97 d with respect to B-band maximum, obtained by the Nearby Supernova Factory collaboration. SN 2011fe is the closest (μ= 29.04) and brightest (Bmax = 9.94 mag) SN Ia observed since the advent of modern large scale programs for the intensive periodic followup of supernovae. Both synthetic light curve measurements and spectral feature analysis attest to the normality of SN 2011fe. There is very little evidence for reddening in its host galaxy. The homogeneous calibration, intensive time sampling, and high signal-to-noise ratio of the data set make it unique. Thus it is ideal for studying the physics of SN Ia explosions in detail, and for furthering the use of SNe Ia as standardizable candles for cosmology. Several such applications are shown, from the creation of a bolometric light curve and measurement of the 56Ni mass, to the simulation of detection thresholds for unburned carbon, direct comparisons with other SNe Ia, and existing spectral templates.

astro-ph.CO↗

arXiv2013

How much H and He is "hidden" in SNe Ib/c? I. - low-mass objects

H and He features in photospheric spectra have seldom been used to infer quantitatively the properties of Type IIb, Ib and Ic supernovae (SNe IIb, Ib and Ic) and their progenitor stars. Most radiative transfer models ignored NLTE effects, which are extremely strong especially in the He-dominated zones. In this paper, a comprehensive set of model atmospheres for low-mass SNe IIb/Ib/Ic is presented. Long-standing questions such as how much He can be contained in SNe Ic, where He lines are not seen, can thus be addressed. The state of H and He is computed in full NLTE, including the effect of heating by fast electrons. The models are constructed to represent iso-energetic explosions of the same stellar core with differently massive H/He envelopes on top. The synthetic spectra suggest that 0.06 - 0.14 M_sun of He and even smaller amounts of H suffice for optical lines to be present, unless ejecta asymmetries play a major role. This strongly supports the conjecture that low-mass SNe Ic originate from binaries where progenitor mass loss can be extremely efficient.

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arXiv2013

Interacting Supernovae and Supernova Impostors. SN 2009ip, is this the end?

We report the results of a 3 year-long dedicated monitoring campaign of a restless Luminous Blue Variable (LBV) in NGC 7259. The object, named SN 2009ip, was observed photometrically and spectroscopically in the optical and near-infrared domains. We monitored a number of erupting episodes in the past few years, and increased the density of our observations during eruptive episodes. In this paper we present the full historical data set from 2009-2012 with multi-wavelength dense coverage of the two high luminosity events between August - September 2012. We construct bolometric light curves and measure the total luminosities of these eruptive or explosive events. We label them the 2012a event (lasting ~50 days) with a peak of 3x10^41 erg/s, and the 2012b event (14 day rise time, still ongoing) with a peak of 8x10^42 erg/s. The latter event reached an absolute R-band magnitude of about -18, comparable to that of a core-collapse supernova (SN). Our historical monitoring has detected high-velocity spectral features (~13000 km/s) in September 2011, one year before the current SN-like event. This implies that the detection of such high velocity outflows cannot, conclusively, point to a core-collapse SN origin. We suggest that the initial peak in the 2012a event was unlikely to be due to a faint core-collapse SN. We propose that the high intrinsic luminosity of the latest peak, the variability history of SN 2009ip, and the detection of broad spectral lines indicative of high-velocity ejecta are consistent with a pulsational pair-instability event, and that the star may have survived the last outburst. The question of the survival of the LBV progenitor star and its future fate remain open issues, only to be answered with future monitoring of this historically unique explosion.

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arXiv2012

3D deflagration simulations leaving bound remnants: a model for 2002cx-like Type Ia supernovae

2002cx-like supernovae are a sub-class of sub-luminous Type Ia supernovae. Their light curves and spectra are characterized by distinct features that indicate strong mixing of the explosion ejecta. Pure turbulent deflagrations have been shown to produce such mixed ejecta. Here, we present hydrodynamics, nucleosynthesis and radiative transfer calculations for a 3D full-star deflagration of a Chandrasekhar-mass white dwarf. Our model is able to reproduce the characteristic observational features of SN 2005hk (a proto-typical 2002cx-like supernova), not only in the optical, but also in the near-infrared. For that purpose we present, for the first time, five near-infrared spectra of SN 2005hk from -0.2 to 26.6 days with respect to B-band maximum. Since our model burns only small parts of the initial white dwarf, it fails to completely unbind the white dwarf and leaves behind a bound remnant of ~1.03 solar masses -- consisting mainly of unburned carbon and oxygen, but also enriched by some amount of intermediate-mass and iron-group elements from the explosion products that fall back on the remnant. We discuss possibilities for detecting this bound remnant and how it might influence the late-time observables of 2002cx-like SNe.

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arXiv2012

On the brightness distribution of Type Ia supernovae from violent white dwarf mergers

We investigate the brightness distribution expected for thermonuclear explosions that might result from the ignition of a detonation during the violent merger of white dwarf (WD) binaries. Determining their brightness distribution is critical for evaluating whether such an explosion model could be responsible for a significant fraction of the observed population of SNe Ia. We argue that the brightness of an explosion realized via the violent merger model is determined by the mass of nickel 56 produced in the detonation of the primary WD. We use a set of sub-Chandrasekhar mass WD detonation models to derive a relationship between primary WD mass and expected peak bolometric brightness. We use this relationship to convert the masses of merging primary WDs from binary population models to a predicted distribution of explosion brightness. We find a striking similarity between the shape of our theoretical peak-magnitude distribution and that observed for SNe Ia: our model produces a brightness distribution that roughly covers the range and matches the shape of the one observed for SNe Ia. However, this agreement hinges on a particular phase of mass accretion during binary evolution: the primary WD gains ~0.15-0.35 Msun from a slightly-evolved helium star companion. We also find that with high probability, violent WD mergers involving the most massive primaries (which should produce bright SNe) have delay times <500 Myr (Abridged).

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arXiv2012

Interpreting the near-infrared spectra of the 'golden standard' Type Ia supernova 2005cf

We present nine near-infrared (NIR) spectra of supernova (SN) 2005cf at epochs from -10 d to +42 d with respect to B-band maximum, complementing the existing excellent data sets available for this prototypical Type Ia SN at other wavelengths. The spectra show a time evolution and spectral features characteristic of normal Type Ia SNe, as illustrated by a comparison with SNe 1999ee, 2002bo and 2003du. The broad-band spectral energy distribution (SED) of SN 2005cf is studied in combined ultraviolet (UV), optical and NIR spectra at five epochs between ~ 8 d before and ~ 10 d after maximum light. We also present synthetic spectra of the hydrodynamic explosion model W7, which reproduce the key properties of SN 2005cf not only at UV-optical as previously reported, but also at NIR wavelengths. From the radiative-transfer calculations we infer that fluorescence is the driving mechanism that shapes the SED of SNe Ia. In particular, the NIR part of the spectrum is almost devoid of absorption features, and instead dominated by fluorescent emission of both iron-group material and intermediate-mass elements at pre-maximum epochs, and pure iron-group material after maximum light. A single P-Cygni feature of Mg II at early epochs and a series of relatively unblended Co II lines at late phases allow us to constrain the regions of the ejecta in which the respective elements are abundant.

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