The shape of the light-curve peak of radioactive-powered core-collapse ‘stripped-envelope’ supernovae constrains the ejecta mass, nickel mass and kinetic energy by the brightness and diffusion time ...for a given opacity and observed expansion velocity. Late-time light curves give constraints on the ejecta mass and energy, given the gamma-ray opacity. Previous work has shown that the principal light-curve peaks for SN IIb with small amounts of hydrogen and for hydrogen/helium-deficient SN Ib/c are often rather similar near maximum light, suggesting similar ejecta masses and kinetic energies, but that late-time light curves show a wide dispersion, suggesting a dispersion in ejecta masses and kinetic energies. It was also shown that SN IIb and SN Ib/c can have very similar late-time light curves, but different ejecta velocities demanding significantly different ejecta masses and kinetic energies. We revisit these topics by collecting and analysing well-sampled single-band and quasi-bolometric light curves from the literature. We find that the late-time light curves of stripped-envelope core-collapse supernovae are heterogeneous. We also show that the observed properties, the photospheric velocity at peak, the rise time and the late decay time, can be used to determine the mean opacity appropriate to the peak. The opacity determined in this way is considerably smaller than common estimates. We discuss how the small effective opacity may result from recombination and asymmetries in the ejecta.
Abstract
We introduce the Automatic Learning for the Rapid Classification of Events (ALeRCE) broker, an astronomical alert broker designed to provide a rapid and self-consistent classification of ...large etendue telescope alert streams, such as that provided by the Zwicky Transient Facility (ZTF) and, in the future, the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). ALeRCE is a Chilean-led broker run by an interdisciplinary team of astronomers and engineers working to become intermediaries between survey and follow-up facilities. ALeRCE uses a pipeline that includes the real-time ingestion, aggregation, cross-matching, machine-learning (ML) classification, and visualization of the ZTF alert stream. We use two classifiers: a stamp-based classifier, designed for rapid classification, and a light curve–based classifier, which uses the multiband flux evolution to achieve a more refined classification. We describe in detail our pipeline, data products, tools, and services, which are made public for the community (see
https://alerce.science
). Since we began operating our real-time ML classification of the ZTF alert stream in early 2019, we have grown a large community of active users around the globe. We describe our results to date, including the real-time processing of 1.5 × 10
8
alerts, the stamp classification of 3.4 × 10
7
objects, the light-curve classification of 1.1 × 10
6
objects, the report of 6162 supernova candidates, and different experiments using LSST-like alert streams. Finally, we discuss the challenges ahead in going from a single stream of alerts such as ZTF to a multistream ecosystem dominated by LSST.
Aims. The aim of this paper is twofold: 1) to investigate the properties of extragalactic dust and compare them to what is seen in the Galaxy; 2) to address in an independent way the problem of the ...anomalous extinction curves reported for reddened Type Ia Supernovae (SN) in connection to the environments in which they explode. Methods. The properties of the dust are derived from the wavelength dependence of the continuum polarization observed in four reddened Type Ia SN: 1986G, 2006X, 2008fp, and 2014J. The method is based on the observed fact that Type Ia SN have a negligible intrinsic continuum polarization. This and their large luminosity makes them ideal tools to probe the dust properties in extragalactic environments. Results. All four objects are characterized by exceptionally low total-to-selective absorption ratios (RV) and display an anomalous interstellar polarization law, characterized by very blue polarization peaks. In all cases the polarization position angle is well aligned with the local spiral structure. While SN 1986G is compatible with the most extreme cases of interstellar polarization known in the Galaxy, SN 2006X, 2008fp, and 2014J show unprecedented behaviours. The observed deviations do not appear to be connected to selection effects related to the relatively large amounts of reddening characterizing the objects in the sample. Conclusions. The dust responsible for the polarization of these four SN is most likely of interstellar nature. The polarization properties can be interpreted in terms of a significantly enhanced abundance of small grains. The anomalous behaviour is apparently associated with the properties of the galactic environment in which the SN explode, rather than with the progenitor system from which they originate. For the extreme case of SN 2014J, we cannot exclude the contribution of light scattered by local material; however, the observed polarization properties require an ad hoc geometrical dust distribution.
We present optical photometry and spectroscopy of the Type II supernova ASASSN-14jb, together with Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) integral field observations of ...its host galaxy and a nebular-phase spectrum. This supernova, in the nearby galaxy ESO 467-G051 (z = 0.006), was discovered and followed-up by the all-sky automated survey for supernovae (ASAS-SN). We obtained well-sampled las cumbres network (LCOGTN) BVgri and Swift w2m1w1ubv optical, near-UV/optical light curves, and several optical spectra in the early photospheric phases. The transient ASASSN-14jb exploded ∼2 kpc above the star-forming disk of ESO 467-G051, an edge-on disk galaxy. The large projected distance from the disk of the supernova position and the non-detection of any H II region in a 1.4 kpc radius in projection are in conflict with the standard environment of core-collapse supernova progenitors and suggests the possible scenario that the progenitor received a kick in a binary interaction. We present analysis of the optical light curves and spectra, from which we derived a distance of 25 ± 2 Mpc using state-of-the-art empirical methods for Type II SNe, physical properties of the SN explosion (56Ni mass, explosion energy, and ejected mass), and properties of the progenitor; namely the progenitor radius, mass, and metallicity. Our analysis yields a 56Ni mass of 0.0210 ± 0.0025 M⊙, an explosion energy of ≈0.25 × 1051 ergs, and an ejected mass of ≈6 M⊙. We also constrained the progenitor radius to be R* = 580 ± 28 R⊙ which seems to be consistent with the sub-Solar metallicity of 0.3 ± 0.1 Z⊙ derived from the supernova Fe II λ5018 line. The nebular spectrum constrains strongly the progenitor mass to be in the range 10–12 M⊙. From the Spitzer data archive we detect ASASSN-14jb ≈330 days past explosion and we derived a total dust mass of 10−4 M⊙ from the 3.6 μm and 4.5 μm photometry. Using the FUV, NUV, BVgri,Ks, 3.6 μm, and 4.5 μm total magnitudes for the host galaxy, we fit stellar population synthesis models, which give an estimate of M* ≈ 1 × 109 M⊙, an age of 3.2 Gyr, and a SFR ≈0.07 M⊙ yr−1. We also discuss the low oxygen abundance of the host galaxy derived from the MUSE data, having an average of 12 + log(O/H) = 8.27+0.16−0.20 12 + log ( O / H ) = 8 . 27 − 0.20 + 0.16 $ 12+\log\mathrm{(O/H)} = 8.27^{+0.16}_{-0.20} $ using the O3N2 diagnostic with strong line methods. We compared it with the supernova spectra, which is also consistent with a sub-Solar metallicity progenitor. Following recent observations of extraplanar H II regions in nearby edge-on galaxies, we derived the metallicity offset from the disk, being positive, but consistent with zero at 2σ, suggesting enrichment from disk outflows. We finally discuss the possible scenarios for the unusual environment for ASASSN-14jb and conclude that either the in-situ star formation or runaway scenario would imply a low-mass progenitor, agreeing with our estimate from the supernova nebular spectrum. Regardless of the true origin of ASASSN-14jb, we show that the detailed study of the environment roughly agree with the stronger constraints from the observation of the transient.
Abstract
We present a study of the continuum polarization over the 400–600 nm range of 19 SNe Ia obtained with FORS at the VLT. We separate them into those that show Na
i
D lines at the velocity of ...their hosts and those that do not. Continuum polarization of the sodium sample near maximum light displays a broad range of values, from extremely polarized cases like SN 2006X to almost unpolarized ones like SN 2011ae. The non-sodium sample shows, typically, smaller polarization values. The continuum polarization of the sodium sample in the 400–600 nm range is linear with wavelength and can be characterized by the mean polarization (
). Its values span a wide range and show a linear correlation with color, color excess, and extinction in the visual band. Larger dispersion correlations were found with the equivalent width of the Na
i
D and Ca
ii
H and K lines, and also a noisy relation between
and
R
V
, the ratio of total to selective extinction. Redder SNe show stronger continuum polarization, with larger color excesses and extinctions. We also confirm that high continuum polarization is associated with small values of
R
V
. The correlation between extinction and polarization—and polarization angles—suggest that the dominant fraction of dust polarization is imprinted in interstellar regions of the host galaxies. We show that Na
i
D lines from foreground matter in the SN host are usually associated with non-galactic ISM, challenging the typical assumptions in foreground interstellar polarization models.
Spectropolarimetry of the Type Ia supernova 2012fr Maund, J. R; Spyromilio, J; Höflich, P. A ...
Monthly notices of the Royal Astronomical Society. Letters,
07/2013, Letnik:
433, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Spectropolarimetry provides the means to probe the 3D geometries of supernovae (SNe) at early times. We report spectropolarimetric observations of the Type Ia SN 2012fr at four epochs: −11, −5, +2 ...and +24 d, with respect to B-light-curve maximum. SN 2012fr is a normal Type Ia SN, similar to SNe 1990N, 2000cx and 2005hj (that all exhibit low velocity decline rates for the principal Si ii line). The SN displays high-velocity components at −11 d that are highly polarized. The polarization of these features decreases as they become weaker from −5 d. At +2 d, the polarization angles of the low-velocity components of silicon and calcium are identical and oriented at 90° relative to the high-velocity Ca component. In addition to having very different velocities, the high- and low-velocity Ca components have orthogonal distributions in the plane of the sky. The continuum polarization for the SN at all four epochs is low, <0.1 per cent. We conclude that the low level of continuum polarization is inconsistent with the merger-induced explosion scenario. The simple axial symmetry evident from the polarization angles of the high-velocity and low-velocity Ca components, along with the presence of high-velocity components of Si and Ca, is perhaps more consistent with the pulsating delayed detonation model. We predict that, during the nebular phase, SN 2012fr will display blueshifted emission lines of Fe-group elements.
We present constraints on the dark energy equation-of-state parameter, w = P/(pc super(2)), using 60 SNe Ia from the ESSENCE supernova survey. We derive a set of constraints on the nature of the dark ...energy assuming a flat universe. By including constraints on ( Omega sub(M), w) from baryon acoustic oscillations, we obtain a value for a static equation-of-state parameter w = -1.05 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(1) sub(1) super(3) sub(2) (stat 1 sigma ) plus or minus 0.13 (sys) and Omega sub(M) = 0.274 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(0) sub(0) super(3) sub(2) super(3) sub(0) (stat 1 sigma ) with a best-fit X super(2)/dof of 0.96. These results are consistent with those reported by the Supernova Legacy Survey from the first year of a similar program measuring supernova distances and redshifts. We evaluate sources of systematic error that afflict supernova observations and present Monte Carlo simulations that explore these effects. Currently, the largest systematic with the potential to affect our measurements is the treatment of extinction due to dust in the supernova host galaxies. Combining our set of ESSENCE SNe Ia with the first-results Supernova Legacy Survey SNe Ia, we obtain a joint constraint of w = -1.07 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(0) sub(0) super(9) sub(9) (stat 1 sigma ) plus or minus 0.13 (sys), Omega sub(M) = 0.267 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(0) sub(0) super(2) sub(1) super(8) sub(8) (stat 1 sigma ) with a best-fit X super(2)/dof of 0.91. The current global SN Ia data alone rule out empty ( Omega sub(M) = 0), matter-only Omega sub(M) = 0.3, and Omega sub(M) = 1 universes at >4.5 sigma . The current SN Ia data are fully consistent with a cosmological constant.
The 3D shape of Type IIb SN 2011hs Stevance, H F; Maund, J R; Baade, D ...
Monthly notices of the Royal Astronomical Society,
05/2019, Letnik:
485, Številka:
1
Journal Article
ABSTRACT
We present optical and near-infrared data of three Type II supernovae (SNe II), SN 2008bm, SN 2009aj, and SN 2009au. These SNe display the following common characteristics: signs of early ...interaction of the ejecta with circumstellar material (CSM), blue B − V colours, weakness of metal lines, low expansion velocities, and V-band absolute magnitudes 2–3 mag brighter than those expected for normal SNe II based on their expansion velocities. Two more SNe reported in the literature (SN 1983K and LSQ13fn) share properties similar to our sample. Analysing this set of five SNe II, which are luminous for their low expansion velocities (LLEV), we find that their properties can be reproduced assuming ejecta–CSM interaction that lasts between 4 and 11 weeks post-explosion. The contribution of this interaction to the radiation field seems to be the dominant component determining the observed weakness of metal lines in the spectra rather than the progenitor metallicity. Based on hydrodynamic simulations, we find that the interaction of the ejecta with a CSM of ∼3.6 M⊙ can reproduce the light curves and expansion velocities of SN 2009aj. Using data collected by the Chilean Automatic Supernova Search, we estimate an upper limit for the LLEV SNe II fraction to be 2–4 per cent of all normal SNe II. With the current data set, it is not clear whether the LLEV events are a separated class of SNe II with a different progenitor system, or whether they are the extreme of a continuum mediated by CSM interaction with the rest of the normal SN II population.
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