On the nature of rapidly fading Type II supernovae Moriya, Takashi J; Pruzhinskaya, Maria V; Ergon, Mattias ...
Monthly notices of the Royal Astronomical Society,
01/2016, Letnik:
455, Številka:
1
Journal Article
Recenzirano
Odprti dostop
It has been suggested that Type II supernovae with rapidly fading light curves (a.k.a. Type IIL supernovae) are explosions of progenitors with low-mass hydrogen-rich envelopes which are of the order ...of 1 M⊙. We investigate light-curve properties of supernovae from such progenitors. We confirm that such progenitors lead to rapidly fading Type II supernovae. We find that the luminosity of supernovae from such progenitors with the canonical explosion energy of 1051 erg and 56Ni mass of 0.05 M⊙ can increase temporarily shortly before all the hydrogen in the envelope recombines. As a result, a bump appears in their light curves. The bump appears because the heating from the nuclear decay of 56Ni can keep the bottom of hydrogen-rich layers in the ejecta ionized, and thus the photosphere can stay there for a while. We find that the light-curve bump becomes less significant when we make explosion energy larger (≳2 × 1051 erg), 56Ni mass smaller (≲0.01 M⊙), 56Ni mixed in the ejecta, or the progenitor radius larger. Helium mixing in hydrogen-rich layers makes the light-curve decline rates large but does not help reducing the light-curve bump. Because the light-curve bump we found in our light-curve models has not been observed in rapidly fading Type II supernovae, they may be characterized by not only low-mass hydrogen-rich envelopes but also higher explosion energy, larger degrees of 56Ni mixing, and/or larger progenitor radii than slowly fading Type II supernovae, so that the light-curve bump does not become significant.
It is well known that massive stars (M > 8 M☉) evolve up to the collapse of the stellar core, resulting in most cases in a supernova (SN) explosion. Their heterogeneity is related mainly to different ...configurations of the progenitor star at the moment of the explosion and to their immediate environments. We present photometry and spectroscopy of SN 2010bt, which was classified as a Type IIn SN from a spectrum obtained soon after discovery and was observed extensively for about 2 months. After the seasonal interruption owing to its proximity to the Sun, the SN was below the detection threshold, indicative of a rapid luminosity decline. We can identify the likely progenitor with a very luminous star (log L/L☉ 7) through comparison of Hubble Space Telescope images of the host galaxy prior to explosion with those of the SN obtained after maximum light. Such a luminosity is not expected for a quiescent star, but rather for a massive star in an active phase. This progenitor candidate was later confirmed via images taken in 2015 (∼5 yr post-discovery), in which no bright point source was detected at the SN position. Given these results and the SN behavior, we conclude that SN 2010bt was likely a Type IIn SN and that its progenitor was a massive star that experienced an outburst shortly before the final explosion, leading to a dense H-rich circumstellar environment around the SN progenitor.
We use the new non-local-thermodynamical-equilibrium (NLTE) light curve and spectral synthesis code JEKYLL to evolve a macro-scopically mixed ejecta model of a Type IIb supernova (SN) originating ...from a star with an initial mass of 12
M
⊙
through the photospheric and nebular phase. The ejecta model is adopted from earlier work and has a mass of 1.7
M
⊙
, has a kinetic energy of 0.7 foe, and contains 0.075
M
⊙
of
56
Ni. The macroscopic mixing is simulated through a statistical representation of ejecta fragmented into small clumps but spherically symmetric on average. We compare our model with SN 2011dh and find that both the spectra and the light curves are well reproduced in both the photospheric and nebular phase, although there are also some differences. Our work further strengthens the evidence that this SN originated from a star with an initial mass of ~12
M
⊙
that had lost all but a tiny (<0.1
M
⊙
) fraction of its hydrogen envelope, strongly suggesting a binary origin. We also investigate the effects of the macroscopic mixing by comparing macroscopically and microscopically mixed models and by varying the clumping geometry. In the photospheric phase, we find strong effects on the effective opacity in the macroscopically mixed regions, which affects the model light curves. The diffusion peak is considerably narrower (rise time decreased by 11%) in the macroscopically mixed case and differs strongly (rise time decreased by 29%) if the radioactive material in the helium envelope is allowed to expand more than in our standard model. The effect is mainly geometrical and is driven by the expansion of the clumps that contain radioactive material, which tend to decrease the effective opacity. In the limit of optically thick clumps, the decrease is roughly given by the product of the (volume) expansion and filling factors for the radioactive material, and in our models values up to ~8 are explored. These findings have implications for light curve modelling of stripped-envelope SNe in general, and the effect would increase the estimated ejecta masses. In the nebular phase, we find strong effects on the collisional cooling rates in the macroscopically mixed regions, which affects lines driven by collisional cooling, in particular the Ca
ii
7291, 7323 Å and O
i
6300, 6364 Å lines. The effect is mainly related to differences in composition between macroscopically and microscopically mixed ejecta. As these lines are often used for mass determinations, this highlights the importance of how and to what extent the calcium- and oxygen-rich material is mixed. As shown in this and earlier work, both NLTE and macroscopic mixing are essential ingredients for accurately modelling the light curves and spectra of Type IIb SNe throughout their evolution.
We present observations of the Type Ic supernova (SN Ic) 2011bm spanning a period of about one year. The data establish that SN 2011bm is a spectroscopically normal SN Ic with moderately low ejecta ...velocities and with a very slow spectroscopic and photometric evolution (more than twice as slow as SN 1998bw). The Pan-STARRS1 retrospective detection shows that the rise time from explosion to peak was ~40 days in the R band. Through an analysis of the light curve and the spectral sequence, we estimate a kinetic energy of ~7-17 foe and a total ejected mass of ~7-17 M sub(middot in circle), 5-10 M sub(middot in circle) of which is oxygen and 0.6-0.7 M sub(middot in circle) is super(56)Ni. The physical parameters obtained for SN 2011bm suggest that its progenitor was a massive star of initial mass 30-50 M sub(middot in circle). The profile of the forbidden oxygen lines in the nebular spectra shows no evidence of a bi-polar geometry in the ejected material.
SN 2004et is one of the nearest and best-observed Type IIP supernovae, with a progenitor detection as well as good photometric and spectroscopic observational coverage well into the nebular phase. ...Based on nucleosynthesis from stellar evolution/explosion models we apply spectral modeling to analyze its 140−700 day evolution from ultraviolet to mid-infrared. We find a MZAMS = 15 M⊙ progenitor star (with an oxygen mass of 0.8 M⊙) to satisfactorily reproduce O i λλ6300, 6364 and other emission lines of carbon, sodium, magnesium, and silicon, while 12 M⊙ and 19 M⊙ models under- and overproduce most of these lines, respectively. This result is in fair agreement with the mass derived from the progenitor detection, but in disagreement with hydrodynamical modeling of the early-time light curve. From modeling of the mid-infrared iron-group emission lines, we determine the density of the “Ni-bubble” to ρ(t) ≃ 7 × 10-14 × (t/100 d)-3 g cm-3, corresponding to a filling factor of f = 0.15 in the metal core region (V = 1800 km s-1). We also confirm that silicate dust, CO, and SiO emission are all present in the spectra.
PTF12os and iPTF13bvn Fremling, C; Sollerman, J; Taddia, F ...
Astronomy and astrophysics (Berlin),
09/2016, Letnik:
593
Journal Article
Recenzirano
Odprti dostop
Context. We investigate two stripped-envelope supernovae (SNe) discovered in the nearby galaxy NGC 5806 by the (intermediate) Palomar Transient Factory (i)PTF. These SNe, designated PTF12os/SN 2012P ...and iPTF13bvn, exploded within ~520 days of one another at a similar distance from the host-galaxy center. We classify PTF12os as a Type IIb SN based on our spectral sequence; iPTF13bvn has previously been classified as Type Ib having a likely progenitor with zero age main sequence (ZAMS) mass below ~17 M sub(middot in circle). Because of the shared and nearby host, we are presented with a unique opportunity to compare these two SNe. Aims. Our main objective is to constrain the explosion parameters of iPTF12os and iPTF13bvn, and to put constraints on the SN progenitors. We also aim to spatially map the metallicity in the host galaxy, and to investigate the presence of hydrogen in early-time spectra of both SNe. Methods. We present comprehensive datasets collected on PTF12os and iPTF13bvn, and introduce a new automatic reference-subtraction photometry pipeline (FPipe) currently in use by the iPTF. We perform a detailed study of the light curves (LCs) and spectral evolution of the SNe. The bolometric LCs are modeled using the hydrodynamical code hyde. We analyze early spectra of both SNe to investigate the presence of hydrogen; for iPTF13bvn we also investigate the regions of the Paschen lines in infrared spectra. We perform spectral line analysis of helium and iron lines to map the ejecta structure of both SNe. We use nebular models and late-time spectroscopy to constrain the ZAMS mass of the progenitors. We also perform image registration of ground-based images of PTF12os to archival HST images of NGC 5806 to identify a potential progenitor candidate. Results. We find that our nebular spectroscopy of iPTF13bvn remains consistent with a low-mass progenitor, likely having a ZAMS mass of ~12M sub(middot in circle). Our late-time spectroscopy of PTF12os is consistent with a ZAMS mass of ~15M sub(middot in circle). We successfully identify a source in pre-explosion HST images coincident with PTF12os. The colors and absolute magnitude of this object are consistent between pre-explosion and late-time HST images, implying it is a cluster of massive stars. Our hydrodynamical modeling suggests that the progenitor of PTF12os had a compact He core with a mass of 3.25 super(+ 0.77) sub(-0.56)M sub(middot in circle) at the time of the explosion, which had a total kinetic energy of 0.54 super(+ 0.41) sub(-0.25) x 10 super(51) erg and synthesized 0.063 super(+ 0.020) sub(-0.011)M sub(middot in circle) of strongly mixed super(56) Ni. Spectral comparisons to the Type IIb SN 2011dh indicate that the progenitor of PTF12os was surrounded by a thin hydrogen envelope with a mass lower than 0.02M sub(middot in circle). We also find tentative evidence that the progenitor of iPTF13bvn could have been surrounded by a small amount of hydrogen prior to the explosion. This result is supported by possible weak signals of hydrogen in both optical and infrared spectra.
Stellar winds of cool and pulsating asymptotic giant branch (AGB) stars enrich the interstellar medium with large amounts of processed elements and various types of dust. We present the first study ...on the influence of gas-to-dust drift on ab initio simulations of stellar winds of M-type stars driven by radiation pressure on forsterite particles. Our study is based on our radiation hydrodynamic model code T-800 that includes frequency-dependent radiative transfer, dust extinction based on Mie scattering, grain growth and ablation, gas-to-dust drift using one mean grain size, a piston that simulates stellar pulsations, and an accurate high spatial resolution numerical scheme. To enable this study, we calculated new gas opacities based on the E
XO
M
OL
database, and we extended the model code to handle the formation of minerals that may form in M-type stars. We determine the effects of drift by comparing drift models to our new and extant non-drift models. Three out of four new drift models show high drift velocities, 87–310 km s
−1
. Our new drift model mass-loss rates are 1.7–13 per cent of the corresponding values of our non-drift models, but compared to the results of two extant non-drift models that use the same stellar parameters, these same values are 0.33–1.5 per cent. Meanwhile, a comparison of other properties such as the expansion velocity and grain size show similar values. Our results, which are based on single-component forsterite particles, show that the inclusion of gas-to-drift is of fundamental importance in stellar wind models driven by such transparent grains. Assuming that the drift velocity is insignificant, properties such as the mass-loss rate may be off from more realistic values by a factor of 50 or more.
We present optical and near-infrared (NIR) photometry and spectroscopy as well as modelling of the lightcurves of the Type IIb supernova (SN) 2011dh. Our extensive dataset, for which we present the ...observations obtained after day 100, spans two years, and complemented with Spitzer mid-infrared (MIR) data, we use it to build an optical-to-MIR bolometric lightcurve between days 3 and 732. To model the bolometric lightcurve before day 400 we use a grid of hydrodynamical SN models, which allows us to determine the errors in the derived quantities, and a bolometric correction determined with steady-state non-local thermodynamic equilibrium (NLTE) modelling. Using this method we find a helium core mass of 3.1+0.7-0.4 M⊙ for SN 2011dh, consistent within error bars with previous results obtained using the bolometric lightcurve before day 80. We compute bolometric and broad-band lightcurves between days 100 and 500 from spectral steady-state NLTE models, presented and discussed in a companion paper. The preferred 12 M⊙ (initial mass) model, previously found to agree well with the observed spectra, shows a good overall agreement with the observed lightcurves, although some discrepancies exist. Time-dependent NLTE modelling shows that after day ~600 a steady-state assumption is no longer valid. The radioactive energy deposition in this phase is likely dominated by the positrons emitted in the decay of 56Co, but seems insufficient to reproduce the lightcurves, and what energy source is dominating the emitted flux is unclear. We find an excess in the K and the MIR bands developing between days 100 and 250, during which an increase in the optical decline rate is also observed. A local origin of the excess is suggested by the depth of the He i 20 581 Å absorption. Steady-state NLTE models with a modest dust opacity in the core (τ = 0.44), turned on during this period, reproduce the observed behaviour, but an additional excess in the Spitzer 4.5 μm band remains. Carbon-monoxide (CO) first-overtone band emission is detected at day 206, and possibly at day 89, and assuming the additional excess to bedominated by CO fundamental band emission, we find fundamental to first-overtone band ratios considerably higher than observed in SN 1987A. The profiles of the O i 6300 Å and Mg i 4571 Å lines show a remarkable similarity, suggesting that these lines originate from a common nuclear burning zone (O/Ne/Mg), and using small scale fluctuations in the line profiles we estimate a filling factor of ≲0.07 for the emitting material. This paper concludes our extensive observational and modelling work on SN 2011dh. The results from hydrodynamical modelling, steady-state NLTE modelling, and stellar evolutionary progenitor analysis are all consistent, and suggest an initial mass of ~12 M⊙ for the progenitor.
Hubble Space Telescope and ground-based observations of the Type IIn supernova (SN) 2010jl are analyzed, including photometry and spectroscopy in the ultraviolet, optical, and near-IR bands, 26-1128 ...days after first detection. At maximum, the bolometric luminosity was similar to 3 x 10(43) erg s(-1) and even at 850 days exceeds 10(42) erg s(-1). A near-IR excess, dominating after 400 days, probably originates in dust in the circumstellar medium (CSM). The total radiated energy is greater than or similar to 6.5x10(50) erg, excluding the dust component. The spectral lines can be separated into one broad component that is due to electron scattering and one narrow with expansion velocity similar to 100 km s(-1) from the CSM. The broad component is initially symmetric around zero velocity but becomes blueshifted after similar to 50 days, while remaining symmetric about a shifted centroid velocity. Dust absorption in the ejecta is unlikely to explain the line shifts, and we attribute the shift instead to acceleration by the SN radiation. From the optical lines and the X-ray and dust properties, there is strong evidence for large-scale asymmetries in the CSM. The ultraviolet lines indicate CNO processing in the progenitor, while the optical shows a number of narrow coronal lines excited by the X-rays. The bolometric light curve is consistent with a radiative shock in an r(-2) CSM with a mass-loss rate of M similar to 0.1 M(circle dot)yr(-1). The total mass lost is greater than or similar to 3 M-circle dot. These properties are consistent with the SN expanding into a CSM characteristic of a luminous blue variable progenitor with a bipolar geometry. The apparent absence of nuclear processing is attributed to a CSM that is still opaque to electron scattering.
PDF
