Aims. Long-duration gamma-ray bursts (GRBs) and broad-line, type Ic supernovae (SNe) are strongly connected. We aim at characterizing SN 2013dx, which is associated with GRB 130702A, through a ...sensitive and extensive ground-based observational campaign in the optical-IR band. Methods. We monitored the field of the Swift GRB 130702A (redshift z = 0.145) using the 8.2 m VLT, the 3.6 m TNG and the 0.6 m REM telescopes during the time interval between 4 and 40 days after the burst. Photometric and spectroscopic observations revealed the associated type Ic SN 2013dx. Our multiband photometry allowed constructing a bolometric light curve. Results. The bolometric light curve of SN 2013dx resembles that of 2003dh (associated with GRB 030329), but is ~10% faster and ~25% dimmer. From this we infer a synthesized 56Ni mass of ~0.2 M⊙. The multi-epoch optical spectroscopy shows that the SN 2013dx behavior is best matched by SN 1998bw, among the other well-known low-redshift SNe associated with GRBs and XRFs, and by SN 2010ah, an energetic type Ic SN not associated with any GRB. The photospheric velocity of the ejected material declines from ~2.7 × 104 km s-1 at 8 rest frame days from the explosion, to ~3.5 × 103 km s-1 at 40 days. These values are extremely close to those of SN1998bw and 2010ah. We deduce for SN 2013dx a kinetic energy of ~35 × 1051 erg and an ejected mass of ~7 M⊙. This suggests that the progenitor of SN2013dx had a mass of ~25–30 M⊙, which is 15–20% less massive than that of SN 1998bw. Finally, we studied the SN 2013dx environment through spectroscopy of the closeby galaxies: 9 out of the 14 inspected galaxies lie within 0.03 in redshift from z = 0.145, indicating that the host of GRB 130702A/SN 2013dx belongs to a group of galaxies, an unprecedented finding for a GRB-associated SN and, to our knowledge, for long GRBs in general.
Moderately luminous Type II supernovae Inserra, C.; Pastorello, A.; Turatto, M. ...
Astronomy and astrophysics (Berlin),
07/2013, Letnik:
555
Journal Article
Recenzirano
Odprti dostop
Context. Core-collapse Supernovae (CC-SNe) descend from progenitors more massive than about 8 M⊙. 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. Aims. 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 investigate the photometric similarities and differences among these bright objects. We also attempt to characterise them by analysing the spectral evolutions, in order to find some traces of CSM-ejecta interaction. Methods. 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. Modelling the data of SNe 2009dd, 2010aj and 1995ad allows us to constrain the explosion parameters and the properties of the progenitor stars. Results. The light curves have luminous peak magnitudes (−16.95 < MB < −18.70). The ejected masses of 56Ni for three SNe span a wide range of values (2.8 × 10-2 M⊙ < M(56Ni)< 1.4 × 10-1 M⊙), while for a fourth (SN 2010aj) we could determine a stringent upper limit (7 × 10-3 M⊙). 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 SN 2007pk 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 × 1013 cm and ejected masses of ~5.0–9.5 M⊙. Conclusions. 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.
ABSTRACT
Supernova remnants (SNRs) represent a powerful laboratory to study the cosmic ray acceleration processes at shocks, and their relation to the properties of the circumstellar medium. With the ...aim of studying the high-frequency radio emission and investigating the energy distribution of accelerated electrons and the magnetic field conditions, we performed single-dish observations of the large and complex Cygnus Loop SNR from 7.0–24.8 GHz with the Medicina and Sardinia Radio Telescopes, focusing on the northern filament (NGC 6992) and the southern shell. Both regions show a spectrum well fitted by a power-law function (S ∝ ν−α), with spectral index α = 0.45 ± 0.05 for NGC 6992 and α = 0.49 ± 0.01 for the southern shell and without any indication of a spectral break. The spectra are significantly flatter than the whole Cygnus Loop spectrum (α = 0.54 ± 0.01), suggesting a departure from the plain shock acceleration mechanisms, which for NGC 6992 could be related to the ongoing transition towards a radiative shock. We model the integrated spectrum of the whole SNR considering the evolution of the maximum energy and magnetic field amplification. Through the radio spectral parameters, we infer a magnetic field at the shock of 10 μG. This value is compatible with purely adiabatic compression of the interstellar magnetic field, suggesting that the amplification process is currently inefficient.
We present an analysis of a new sample of type II core-collapse supernovae (SNe II) occurring within low-luminosity galaxies, comparing these with a sample of events in brighter hosts. Our analysis ...is performed comparing SN II spectral and photometric parameters and estimating the influence of metallicity (inferred from host luminosity differences) on SN II transient properties. We measure the SN absolute magnitude at maximum, the light-curve plateau duration, the optically thick duration, and the plateau decline rate in the V band, together with expansion velocities and pseudo-equivalent-widths (pEWs) of several absorption lines in the SN spectra. For the SN host galaxies, we estimate the absolute magnitude and the stellar mass, a proxy for the metallicity of the host galaxy. SNe II exploding in low-luminosity galaxies display weaker pEWs of $$\rm{Fe\,\small{II}}$$ λ5018, confirming the theoretical prediction that metal lines in SN II spectra should correlate with metallicity. We also find that SNe II in low-luminosity hosts have generally slower declining light curves and display weaker absorption lines. We find no relationship between the plateau duration or the expansion velocities with SN environment, suggesting that the hydrogen envelope mass and the explosion energy are not correlated with the metallicity of the host galaxy. This result supports recent predictions that mass-loss for red supergiants is independent of metallicity.
Abstract
We present ALMA band 6 observations of the luminous blue variable
η
Car obtained within the ALMAGAL program. We report SiO
J
= 5 → 4, SiS
J
= 12 → 11, and SiN
N
= 5 → 4 emission in the ...equatorial region of the Homunculus nebula, constituting the first detection of silicon- and sulfur-bearing molecules in the outskirts of a highly evolved, early-type massive star. The SiO, SiS, and SiN trace a clumpy equatorial ring that surrounds the central binary at a projected distance of ∼2″, delineating the inner rims of the butterfly-shaped dusty region. The formation of silicon-bearing compounds is presumably related to the continuous recycling of dust due to the variable wind regime of
η
Car, which destroys grains and releases silicon back to the gas phase. We discuss possible formation routes for the observed species, contextualizing them within the current molecular inventory of
η
Car. We find that the SiO and SiS fractional abundances in localized clumps of the ring, 6.7 × 10
−9
and 1.2 × 10
−8
, respectively, are exceptionally lower than those measured in C- and O-rich AGB stars and cool supergiants, while the higher SiN abundance, 3.6 × 10
−8
, evidences the nitrogen-rich chemistry of the ejecta. These abundances must be regarded as strict upper limits, since the distribution of H
2
in the Homunculus is unknown. In any case, these findings shed new light on the peculiar molecular ecosystem of
η
Car and establish its surroundings as a new laboratory to investigate the life cycle of silicate dust in extreme astrophysical conditions.
ABSTRACT
Low- and intermediate-mass stars end their life dispersing their outer layers into the circumstellar medium, during the asymptotic and post-asymptotic giant branch phases. OH masers at 18 cm ...offer an effective way to probe their circumstellar environment. In this work, we present the discovery of seven OH maser sources likely associated with such evolved stars from the visual inspection of Australian SKA Pathfinder (ASKAP) continuum images. These seven sources do not emit real continuum emission, but the high sensitivity of our images allows us to detect their maser emission, resembling continuum sources. To confirm their nature, we carried out spectral-line observations with ATCA. All the sources showed the double-peaked spectra at 1612 MHz, typical of evolved stars. The detection of maser emission in continuum images can be a complementary and easy-to-use method to discover new maser sources with the large-area deep surveys conducted with the Square Kilometre Array (SKA) precursors. The implication for radio stars studies are remarkable since pure OH maser sources (i.e. with no continuum associated) represent, at a sensitivity of $100\,\mu \mathrm{Jy\,beam}^{-1}$, about 4 per cent of all Galactic sources and by far the most numerous stellar population.
Abstract
We present an optical and near-infrared photometric and spectroscopic study of supernova (SN) 2009kn spanning ∼1.5 yr from the discovery. The optical spectra are dominated by the narrow ...(full width at half-maximum ∼1000 km s−1) Balmer lines distinctive of a Type IIn SN with P Cygni profiles. Contrarily, the photometric evolution resembles more that of a Type IIP SN with a large drop in luminosity at the end of the plateau phase. These characteristics are similar to those of SN 1994W, whose nature has been explained with two different models with different approaches. The well-sampled data set on SN 2009kn offers the possibility to test these models, in the case of both SN 2009kn and SN 1994W. We associate the narrow P Cygni lines with a swept-up shell composed of circumstellar matter and SN ejecta. The broad emission line wings, seen during the plateau phase, arise from internal electron scattering in this shell. The slope of the light curve after the post-plateau drop is fairly consistent with that expected from the radioactive decay of 56Co, suggesting an SN origin for SN 2009kn. Assuming radioactivity to be the main source powering the light curve of SN 2009kn in the tail phase, we infer an upper limit for 56Ni mass of 0.023 M⊙. This is significantly higher than that estimated for SN 1994W, which also showed a much steeper decline of the light curve after the post-plateau drop. We also observe late-time near-infrared emission which most likely arises from newly formed dust produced by SN 2009kn. As with SN 1994W, no broad lines are observed in the spectra of SN 2009kn, not even in the late-time tail phase.
We present photometry and spectroscopy of the Type IIP supernova (SN IIP) 2009bw in UGC 2890 from a few days after the outburst to 241 d. The light curve of SN 2009bw during the photospheric phase is ...similar to that of normal SNe IIP but with a brighter peak and plateau (
mag,
mag). The luminosity drop from the photospheric to the nebular phase is one of the fastest ever observed, ∼2.2 mag in about 13 d. The radioactive tail of the bolometric light curve indicates that the amount of ejected 56Ni is ≈0.022 M⊙. The photospheric spectra reveal high-velocity lines of Hα and Hβ until about 105 d after the shock breakout, suggesting a possible early interaction between the SN ejecta and pre-existent circumstellar material, and the presence of CNO elements. By modelling the bolometric light curve, ejecta expansion velocity and photospheric temperature, we estimate a total ejected mass of ∼8-12 M⊙, a kinetic energy of ∼0.3 foe and an initial radius of ∼3.6-7 × 1013 cm.
We present an extensive optical and near-infrared photometric and spectroscopic campaign of the Type IIP supernova SN 2012aw. The data set densely covers the evolution of SN 2012aw shortly after the ...explosion through the end of the photospheric phase, with two additional photometric observations collected during the nebular phase, to fit the radioactive tail and estimate the super(56)Ni mass. Also included in our analysis is the previously published Swift UV data, therefore providing a complete view of the ultraviolet-optical-infrared evolution of the photospheric phase. On the basis of our data set, we estimate all the relevant physical parameters of SN 2012aw with our radiation-hydrodynamics code: envelope mass M sub(env) ~ 20 M sub(middot in circle), progenitor radius R ~ 3 x 10 super(13) cm (~430 R sub(middot in circle)), explosion energy E ~ 1.5 foe, and initial super(56)Ni mass ~0.06M sub(middot in circle). These mass and radius values are reasonably well supported by independent evolutionary models of the progenitor, and may suggest a progenitor mass higher than the observational limit of 16.5 + or - 1.5M sub(middot in circle) of the Type IIP events.
We present optical and near-infrared photometry and spectroscopy of SN 2009ib, a Type II-P supernova in NGC 1559. This object has moderate brightness, similar to those of the intermediate-luminosity ...SNe 2008in and 2009N. Its plateau phase is unusually long, lasting for about 130 d after explosion. The spectra are similar to those of the subluminous SN 2002gd, with moderate expansion velocities. We estimate the 56Ni mass produced as 0.046 ± 0.015 M⊙. We determine the distance to SN 2009ib using both the expanding photosphere method (EPM) and the standard candle method. We also apply EPM to SN 1986L, a Type II-P SN that exploded in the same galaxy. Combining the results of different methods, we conclude the distance to NGC 1559 as D = 19.8 ± 3.0 Mpc. We examine archival, pre-explosion images of the field taken with the Hubble Space Telescope, and find a faint source at the position of the SN, which has a yellow colour (V − I)0 = 0.85 mag. Assuming it is a single star, we estimate its initial mass as M
ZAMS = 20 M⊙. We also examine the possibility, that instead of the yellow source the progenitor of SN 2009ib is a red supergiant star too faint to be detected. In this case, we estimate the upper limit for the initial zero-age main sequence (ZAMS) mass of the progenitor to be ∼14–17 M⊙. In addition, we infer the physical properties of the progenitor at the explosion via hydrodynamical modelling of the observables, and estimate the total energy as ∼0.55 × 1051 erg, the pre-explosion radius as ∼400 R⊙, and the ejected envelope mass as ∼15 M⊙, which implies that the mass of the progenitor before explosion was ∼16.5–17 M⊙.
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