109 research outputs found
Metallicity at the explosion sites of interacting transients
Context. Some circumstellar-interacting (CSI) supernovae (SNe) are produced
by the explosions of massive stars that have lost mass shortly before the SN
explosion. There is evidence that the precursors of some SNe IIn were luminous
blue variable (LBV) stars. For a small number of CSI SNe, outbursts have been
observed before the SN explosion. Eruptive events of massive stars are named as
SN impostors (SN IMs) and whether they herald a forthcoming SN or not is still
unclear. The large variety of observational properties of CSI SNe suggests the
existence of other progenitors, such as red supergiant (RSG) stars with
superwinds. Furthermore, the role of metallicity in the mass loss of CSI SN
progenitors is still largely unexplored. Aims. Our goal is to gain insight on
the nature of the progenitor stars of CSI SNe by studying their environments,
in particular the metallicity at their locations. Methods. We obtain
metallicity measurements at the location of 60 transients (including SNe IIn,
SNe Ibn, and SN IMs), via emission-line diagnostic on optical spectra obtained
at the Nordic Optical Telescope and through public archives. Metallicity values
from the literature complement our sample. We compare the metallicity
distributions among the different CSI SN subtypes and to those of other
core-collapse SN types. We also search for possible correlations between
metallicity and CSI SN observational properties. Results. We find that SN IMs
tend to occur in environments with lower metallicity than those of SNe IIn.
Among SNe IIn, SN IIn-L(1998S-like) SNe show higher metallicities, similar to
those of SNe IIL/P, whereas long-lasting SNe IIn (1988Z-like) show lower
metallicities, similar to those of SN IMs. The metallicity distribution of SNe
IIn can be reproduced by combining the metallicity distributions of SN IMs
(that may be produced by major outbursts of massive stars like LBVs) and SNe
IIP (produced by RSGs). The same applies to the distributions of the Normalized
Cumulative Rank (NCR) values, which quantifies the SN association to H II
regions. For SNe IIn, we find larger mass-loss rates and higher CSM velocities
at higher metallicities. The luminosity increment in the optical bands during
SN IM outbursts tend to be larger at higher metallicity, whereas the SN IM
quiescent optical luminosities tend to be lower. Conclusions. The difference in
metallicity between SNe IIn and SN IMs suggests that LBVs are only one of the
progenitor channels for SNe IIn, with 1988Z-like and 1998S-like SNe possibly
arising from LBVs and RSGs, respectively. Finally, even though linedriven winds
likely do not primarily drive the late mass-loss of CSI SN progenitors,
metallicity has some impact on the observational properties of these
transients. Key words. supernovae: general - stars: evolution - galaxies:
abundancesComment: Submitted to Astronomy and Astrophysics on 28/02/2015; submitted to
arXiv after the 1st referee repor
The Unusually Luminous Extragalactic Nova SN 2010U
We present observations of the unusual optical transient SN 2010U, including
spectra taken 1.03 days to 15.3 days after maximum light that identify it as a
fast and luminous Fe II type nova. Our multi-band light curve traces the fast
decline (t_2 = 3.5 days) from maximum light (M_V = -10.2 mag), placing SN 2010U
in the top 0.5% of the most luminous novae ever observed. We find typical
ejecta velocities of approximately 1100 km/s and that SN 2010U shares many
spectral and photometric characteristics with two other fast and luminous Fe II
type novae, including Nova LMC 1991 and M31N-2007-11d. For the extreme
luminosity of this nova, the maximum magnitude vs. rate of decline relationship
indicates a massive white dwarf progenitor with a low pre-outburst accretion
rate. However, this prediction is in conflict with emerging theories of nova
populations, which predict that luminous novae from massive white dwarfs should
preferentially exhibit an alternate spectral type (He/N) near maximum light.Comment: 16 pages, 16 figures. Submitted to the Astrophysical Journa
The Type IIn Supernova SN 2010bt: The Explosion of a Star in Outburst
Indexación: Scopus.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. © 2018. The American Astronomical Society. All rights reserved.https://iopscience.iop.org/article/10.3847/1538-4357/aac51
iPTF15dtg: a double-peaked Type Ic supernova from a massive progenitor
Context. Type Ic supernovae (SNe Ic) arise from the core-collapse of H- (and He-) poor stars, which could either be single Wolf-Rayet (WR) stars or lower-mass stars stripped of their envelope by a companion. Their light curves are radioactively powered and usually show a fast rise to peak (~10−15 d), without any early (in the first few days) emission bumps (with the exception of broad-lined SNe Ic) as sometimes seen for other types of stripped-envelope SNe (e.g., Type IIb SN 1993J and Type Ib SN 2008D).
Aims. We have studied iPTF15dtg, a spectroscopically normal SN Ic with an early excess in the optical light curves followed by a long (~30 d) rise to the main peak. It is the first spectroscopically-normal double-peaked SN Ic to be observed. Our aim is to determine the properties of this explosion and of its progenitor star.
Methods. Optical photometry and spectroscopy of iPTF15dtg was obtained with multiple telescopes. The resulting light curves and spectral sequence are analyzed and modeled with hydrodynamical and analytical models, with particular focus on the early emission.
Results. iPTF15dtg is a slow rising SN Ic, similar to SN 2011bm. Hydrodynamical modeling of the bolometric properties reveals a large ejecta mass (~10 M_⊙) and strong ^(56)Ni mixing. The luminous early emission can be reproduced if we account for the presence of an extended (≳500 R_⊙), low-mass (≳0.045 M_⊙) envelope around the progenitor star. Alternative scenarios for the early peak, such as the interaction with a companion, a shock-breakout (SBO) cooling tail from the progenitor surface, or a magnetar-driven SBO are not favored.
Conclusions. The large ejecta mass and the presence of H- and He-free extended material around the star suggest that the progenitor of iPTF15dtg was a massive (≳35 M_⊙) WR star that experienced strong mass loss
Massive stars exploding in a He-rich circumstellar medium. IV. Transitional Type Ibn Supernovae
We present ultraviolet, optical and near-infrared data of the Type Ibn
supernovae (SNe) 2010al and 2011hw. SN 2010al reaches an absolute magnitude at
peak of M(R) = -18.86 +- 0.21. Its early light curve shows similarities with
normal SNe Ib, with a rise to maximum slower than most SNe Ibn. The spectra are
dominated by a blue continuum at early stages, with narrow P-Cygni He I lines
indicating the presence of a slow-moving, He-rich circumstellar medium. At
later epochs the spectra well match those of the prototypical SN Ibn 2006jc,
although the broader lines suggest that a significant amount of He was still
present in the stellar envelope at the time of the explosion. SN 2011hw is
somewhat different. It was discovered after the first maximum, but the light
curve shows a double-peak. The absolute magnitude at discovery is similar to
that of the second peak (M(R) = -18.59 +- 0.25), and slightly fainter than the
average of SNe Ibn. Though the spectra of SN 2011hw are similar to those of SN
2006jc, coronal lines and narrow Balmer lines are cleary detected. This
indicates substantial interaction of the SN ejecta with He-rich, but not
H-free, circumstellar material. The spectra of SN 2011hw suggest that it is a
transitional SN Ibn/IIn event similar to SN 2005la. While for SN 2010al the
spectro-photometric evolution favours a H-deprived Wolf-Rayet progenitor (of
WN-type), we agree with the conclusion of Smith et al. (2012) that the
precursor of SN 2011hw was likely in transition from a luminous blue variable
to an early Wolf-Rayet (Ofpe/WN9) stage.Comment: 23 pages, 11 figures, 6 tables. Accepted by MNRA
Long-rising Type II supernovae from Palomar Transient Factory and Caltech Core-Collapse Project
Context. Supernova (SN) 1987A was a peculiar hydrogen-rich event with a long-rising (~ 84 d) light curve, stemming from the explosion of a compact blue supergiant star. Only a few similar events have been presented in the literature in recent decades. Aims. We present new data for a sample of six long-rising Type II SNe (SNe II), three of which were discovered and observed by the Palomar Transient Factory (PTF) and three observed by the Caltech Core-Collapse Project (CCCP). Our aim is to enlarge this
small family of long-rising SNe II, characterizing their differences in terms of progenitor and explosion parameters. We also study the metallicity of their environments.
Methods. Optical light curves, spectra, and host-galaxy properties of these SNe are presented and analyzed. Detailed comparisons with known SN 1987A-like events in the literature are shown, with particular emphasis on the absolute magnitudes, colors, expansion velocities, and host-galaxy metallicities. Bolometric properties are derived from the multiband light curves. By modeling the early time emission with scaling relations derived from the SuperNova Explosion Code (SNEC) models of MESA progenitor stars, we estimate the progenitor radii of these transients. The modeling of the bolometric light curves also allows us to estimate other progenitor and explosion parameters, such as the ejected ^(56)Ni mass, the explosion energy, and the ejecta mass.
Results. We present PTF12kso, a long-rising SN II that is estimated to have the largest amount of ejected ^(56)Ni mass measured for this class. PTF09gpn and PTF12kso are found at the lowest host metallicities observed for this SN group. The variety of early light curve luminosities depends on the wide range of progenitor radii of these SNe, from a few tens of R_⊙ (SN 2005ci) up to thousands
(SN 2004ek) with some intermediate cases between 100 R_⊙ (PTF09gpn) and 300 R_⊙ (SN 2004em).
Conclusions. We confirm that long-rising SNe II with light-curve shapes closely resembling that of SN 1987A generally arise from blue supergiant (BSG) stars. However, some of them, such as SN 2004em, likely have progenitors with larger radii (~ 300 R_⊙, typical of yellow supergiants) and can thus be regarded as intermediate cases between normal SNe IIP and SN 1987A-like SNe. Some
extended red supergiant (RSG) stars such as the progenitor of SN 2004ek can also produce long-rising SNe II if they synthesized a large amount of ^(56 0Ni in the explosion. Low host metallicity is confirmed as a characteristic of the SNe arising from compact BSG stars
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 . The produced nickel-mass
is estimated to be . 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 , the ejected mass as , and the initial radius as .Comment: 23 pages, 18 figures, accepted for publication by MNRA
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