ABSTRACT
We present observations and analysis of 18 stripped-envelope supernovae observed during 2013–2018. This sample consists of five H/He-rich SNe, six H-poor/He-rich SNe, three narrow lined SNe ...Ic, and four broad lined SNe Ic. The peak luminosity and characteristic time-scales of the bolometric light curves are calculated, and the light curves modelled to derive 56Ni and ejecta masses (MNi and Mej). Additionally, the temperature evolution and spectral line velocity curves of each SN are examined. Analysis of the O i line in the nebular phase of eight SNe suggests their progenitors had initial masses <20 M⊙. The bolometric light curve properties are examined in combination with those of other SE events from the literature. The resulting data set gives the Mej distribution for 80 SE–SNe, the largest such sample in the literature to date, and shows that SNe Ib have the lowest median Mej, followed by narrow-lined SNe Ic, H/He-rich SNe, broad-lined SNe Ic, and finally gamma-ray burst SNe. SNe Ic-6/7 show the largest spread of Mej ranging from ∼1.2–11 M⊙, considerably greater than any other subtype. For all SE–SNe = 2.8 ± 1.5 M⊙ which further strengthens the evidence that SE–SNe arise from low-mass progenitors which are typically <5 M⊙ at the time of explosion, again suggesting MZAMS <25 M⊙. The low and lack of clear bimodality in the distribution implies <30 M⊙ progenitors and that envelope stripping via binary interaction is the dominant evolutionary pathway of these SNe.
Abstract
We present observations of two new hydrogen-poor superluminous supernovae (SLSN-I), iPTF15esb and iPTF16bad, showing late-time H
α
emission with line luminosities of
erg s
−1
and velocity ...widths of (4000–6000) km s
−1
. Including the previously published iPTF13ehe, this makes up a total of three such events to date. iPTF13ehe is one of the most luminous and the slowest evolving SLSNe-I, whereas the other two are less luminous and fast decliners. We interpret this as a result of the ejecta running into a neutral H-shell located at a radius of ∼10
16
cm. This implies that violent mass loss must have occurred several decades before the supernova explosion. Such a short time interval suggests that eruptive mass loss could be common shortly before core collapse, and more importantly helium is unlikely to be completely stripped off the progenitor and could be present in the ejecta. It is a mystery why helium features are not detected, even though nonthermal energy sources, capable of ionizing He, may exist as suggested by the O
ii
absorption series in the early-time spectra. Our late-time spectra (+240 days) appear to have intrinsically lower O
i
6300 Å luminosities than that of SN2015bn and SN2007bi, which is possibly an indication of less oxygen (<10
M
⊙
). The blueshifted H
α
emission relative to the hosts for all three events may be in tension with the binary model proposed for iPTF13ehe. Finally, iPTF15esb has a peculiar light curve (LC) with three peaks separated from one another by ∼22 days. The LC undulation is stronger in bluer bands. One possible explanation is ejecta-circumstellar medium interaction.
Type Ia supernovae are key tools for measuring distances on a cosmic scale. They are generally thought to be the thermonuclear explosion of an accreting white dwarf in a close binary system. The ...nature of the mass donor is still uncertain. In the single-degenerate model it is a main-sequence star or an evolved star, whereas in the double-degenerate model it is another white dwarf. We show that the velocity structure of absorbing material along the line of sight to 35 type Ia supernovae tends to be blueshifted. These structures are likely signatures of gas outflows from the supernova progenitor systems. Thus, many type Ia supernovae in nearby spiral galaxies may originate in single-degenerate systems.
We present new spectroscopic and photometric data of the Type Ibn supernovae 2006jc, 2000er and 2002ao. We discuss the general properties of this recently proposed supernova family, which also ...includes SN 1999cq. The early-time monitoring of SN 2000er traces the evolution of this class of objects during the first few days after the shock breakout. An overall similarity in the photometric and spectroscopic evolution is found among the members of this group, which would be unexpected if the energy in these core-collapse events was dominated by the interaction between supernova ejecta and circumstellar medium. Type Ibn supernovae appear to be rather normal Type Ib/c supernova explosions which occur within a He-rich circumstellar environment. SNe Ibn are therefore likely produced by the explosion of Wolf–Rayet progenitors still embedded in the He-rich material lost by the star in recent mass-loss episodes, which resemble known luminous blue variable eruptions. The evolved Wolf–Rayet star could either result from the evolution of a very massive star or be the more evolved member of a massive binary system. We also suggest that there are a number of arguments in favour of a Type Ibn classification for the historical SN 1885A (S-Andromedae), previously considered as an anomalous Type Ia event with some resemblance to SN 1991bg.
Abstract
We present an analysis of the Hubble diagram for 12 normal Type Ia supernovae (SNe Ia) observed in the near-infrared (NIR) J and H bands. We select SNe exclusively from the redshift range ...0.03 < z < 0.09 to reduce uncertainties coming from peculiar velocities while remaining in a cosmologically well-understood region. All of the SNe in our sample exhibit no spectral or B-band light-curve peculiarities and lie in the B-band stretch range of 0.8-1.15. Our results suggest that SNe Ia observed in the NIR are the best known standard candles. We fit previously determined NIR light-curve templates to new high-precision data to derive peak magnitudes and to determine the scatter about the Hubble line. Photometry of the 12 SNe is presented in the natural system. Using a standard cosmology of (H
0, Ωm, ΩΛ) = (70, 0.27, 0.73), we find a median J-band absolute magnitude of M
J
= −18.39 with a scatter of σ
J
= 0.116 and a median H-band absolute magnitude of M
H
= −18.36 with a scatter of σ
H
= 0.085. The scatter in the H band is the smallest yet measured. We search for correlations between residuals in the J- and H-band Hubble diagrams and SN properties, such as SN colour, B-band stretch and the projected distance from the centre of the host galaxy. The only significant correlation is between the J-band Hubble residual and the J − H pseudo-colour. We also examine how the scatter changes when fewer points in the NIR are used to constrain the light curve. With a single point in the H band taken anywhere from 10 d before to 15 d after B-band maximum light and a prior on the date of H-band maximum set from the date of B-band maximum, we find that we can measure distances to an accuracy of 6 per cent. The precision of SNe Ia in the NIR provides new opportunities for precision measurements of both the expansion history of the universe and peculiar velocities of nearby galaxies.
ABSTRACT The progenitors of some supernovae (SNe) exhibit outbursts with super-Eddington luminosities prior to their final explosions. This behavior is common among SNe IIn, but the driving ...mechanisms of these precursors are not yet well-understood. SNHunt 275 was announced as a possible new SN during 2015 May. Here we report on pre-explosion observations of the location of this event by the Palomar Transient Factory (PTF) and report the detection of a precursor about 500 days prior to the 2015 May activity (PTF 13efv). The observed velocities in the 2015 transient and its 2013 precursor absorption spectra are low (1000-2000 km s−1), so it is not clear yet if the recent activity indeed marks the final disruption of the progenitor. Regardless of the nature of this event, we use the PTF photometric and spectral observations, as well as Swift-UVOT observations, to constrain the efficiency of the radiated energy relative to the total kinetic energy of the precursor. We find that, using an order-of-magnitude estimate and under the assumption of spherical symmetry, the ratio of the radiated energy to the kinetic energy is in the range of 4 × 10−2 to 3.4 × 103.
ABSTRACT Long duration γ-ray bursts are a rare subclass of stripped-envelope core-collapse supernovae (SNe) that launch collimated relativistic outflows (jets). All γ-ray-burst-associated SNe are ...spectroscopically Type Ic, with broad-lines, but the fraction of broad-lined SNe Ic harboring low-luminosity γ-ray bursts remains largely unconstrained. Some SNe should be accompanied by off-axis γ-ray burst jets that initially remain invisible, but then emerge as strong radio sources (as the jets decelerate). However, this critical prediction of the jet model for γ-ray bursts has yet to be verified observationally. Here, we present K. G. Jansky Very Large Array observations of 15 broad-lined SNe of Type Ic discovered by the Palomar Transient Factory in an untargeted manner. Most of the SNe in our sample exclude radio emission observationally similar to that of the radio-loud, relativistic SN 1998bw. We constrain the fraction of 1998bw-like broad-lined SNe Ic to be (99.865% confidence). Most of the events in our sample also exclude off-axis jets similar to GRB 031203 and GRB 030329, but we cannot rule out off-axis γ-ray bursts expanding in a low-density wind environment. Three SNe in our sample are detected in the radio. PTF11qcj and PTF14dby show late-time radio emission with average ejecta speeds of 0.3-0.4 c, on the dividing line between relativistic and "ordinary" SNe. The speed of PTF11cmh radio ejecta is poorly constrained. We estimate that (99.865% confidence) of the broad-lined SNe Ic in our sample may harbor off-axis γ-ray bursts expanding in media with densities in the range probed by this study.
The type IIb SN 2008ax: the nature of the progenitor Crockett, R. M.; Eldridge, J. J.; Smartt, S. J. ...
Monthly notices of the Royal Astronomical Society. Letters,
November 2008, Letnik:
391, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A source coincident with the position of the type IIb supernova (SN) 2008ax is identified in pre-explosion Hubble Space Telescope (HST) Wide Field Planetary Camera 2 observations in three optical ...filters. We identify and constrain two possible progenitor systems: (i) a single massive star that lost most of its hydrogen envelope through radiatively driven mass-loss processes, prior to exploding as a helium-rich Wolf–Rayet star with a residual hydrogen envelope, and (ii) an interacting binary in a low-mass cluster producing a stripped progenitor. Late time, high-esolution observations along with detailed modelling of the SN will be required to reveal the true nature of this progenitor star.
We present an investigation of the optical spectra of 264 low-redshift (z < 0.2) Type Ia supernovae (SNe Ia) discovered by the Palomar Transient Factory, an untargeted transient survey. We focus on ...velocity and pseudo-equivalent width measurements of the Si ii 4130, 5972, and 6355 Å lines, as well those of the Ca ii near-infrared (NIR) triplet, up to +5 days relative to the SN B-band maximum light. We find that a high-velocity component of the Ca ii NIR triplet is needed to explain the spectrum in ∼95 per cent of SNe Ia observed before −5 days, decreasing to ∼80 per cent at maximum. The average velocity of the Ca ii high-velocity component is ∼8500 km s−1 higher than the photospheric component. We confirm previous results that SNe Ia around maximum light with a larger contribution from the high-velocity component relative to the photospheric component in their Ca ii NIR feature have, on average, broader light curves and lower Ca ii NIR photospheric velocities. We find that these relations are driven by both a stronger high-velocity component and a weaker contribution from the photospheric Ca ii NIR component in broader light curve SNe Ia. We identify the presence of C ii in very-early-time SN Ia spectra (before −10 days), finding that >40 per cent of SNe Ia observed at these phases show signs of unburnt material in their spectra, and that C ii features are more likely to be found in SNe Ia having narrower light curves.
Abstract
We present our analysis of the Type II supernova DLT16am (SN 2016ija). The object was discovered during the ongoing
(DLT40) one-day cadence supernova search at
in the “edge-on” nearby (
) ...galaxy NGC 1532. The subsequent prompt and high-cadenced spectroscopic and photometric follow-up revealed a highly extinguished transient, with
, consistent with a standard extinction law with
R
V
= 3.1 and a bright (
) absolute peak magnitude. A comparison of the photometric features with those of large samples of SNe II reveals a fast rise for the derived luminosity and a relatively short plateau phase, with a slope of
, consistent with the photometric properties typical of those of fast-declining SNe II. Despite the large uncertainties on the distance and the extinction in the direction of DLT16am, the measured photospheric expansion velocity and the derived absolute
V
-band magnitude at
after the explosion match the existing luminosity–velocity relation for SNe II.
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