Analysis of the Spectrum of the Type V Supernova SN1986J (original) (raw)
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Low Radio Frequency Observations and Spectral Modelling of the Remnant of Supernova 1987A
We present Murchison Widefield Array observations of the supernova remnant (SNR) 1987A between 72 and 230 MHz, representing the lowest frequency observations of the source to date. This large lever arm in frequency space constrains the properties of the circumstellar medium created by the progenitor of SNR 1987A when it was in its red supergiant phase. As of late-2013, the radio spectrum of SNR 1987A between 72 MHz and 8.64 GHz does not show any deviation from a non-thermal power-law with a spectral index of −0.74 ± 0.02. This spectral index is consistent with that derived at higher frequencies, beneath 100 GHz, and with a shock in its adiabatic phase. A spectral turnover due to free-free absorption by the circumstellar medium has to occur below 72 MHz, which places upper limits on the optical depth of ≤ 0.1 at a reference frequency of 72 MHz, emission measure of 13,000 cm −6 pc, and an electron density of 110 cm −3. This upper limit on the electron density is consistent with the detection of prompt radio emission and models of the X-ray emission from the supernova. The electron density upper limit implies that some hydrodynamic simulations derived a red supergiant mass loss rate that is too high, or a wind velocity that is too low. The mass loss rate of ∼ 5 × 10 −6 solar mass yr −1 and wind velocity of 10 km s −1 obtained from optical observations are consistent with our upper limits, predicting a current turnover frequency due to free-free absorption between 5 and 60 MHz.
THE FIRST MAXIMUM-LIGHT ULTRAVIOLET THROUGH NEAR-INFRARED SPECTRUM OF A TYPE Ia SUPERNOVA
The Astrophysical Journal, 2012
We present the first maximum-light ultraviolet (UV) through near-infrared (NIR) Type Ia supernova (SN Ia) spectrum. This spectrum of SN 2011iv was obtained nearly simultaneously by the Hubble Space Telescope at UV/optical wavelengths and the Magellan Baade telescope at NIR wavelengths. These data provide the opportunity to examine the entire maximum-light SN Ia spectral-energy distribution. Since the UV region of a SN Ia spectrum is extremely sensitive to the composition of the outer layers of the explosion, which are transparent at longer wavelengths, this unprecedented spectrum can provide strong constraints on the composition of the SN ejecta, and similarly the SN explosion and progenitor system. SN 2011iv is spectroscopically normal, but has a relatively fast decline (∆m 15 (B) = 1.69 ± 0.05 mag). We compare SN 2011iv to other SNe Ia with UV spectra near maximum light and examine trends between UV spectral properties, light-curve shape, and ejecta velocity. We tentatively find that SNe with similar light-curve shapes but different ejecta velocities have similar UV spectra, while those with similar ejecta velocities but different light-curve shapes have very different UV spectra. Through a comparison with explosion models, we find that both a solar-metallicity W7 and a zero-metallicity delayed-detonation model provide a reasonable fit to the spectrum of SN 2011iv from the UV to the NIR. Subject headings: supernovae: general -supernovae: individual (SN 2011iv) 1 Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-12592.
Eleven years of radio monitoring of the Type IIn supernova SN 1995N
We present radio observations of the optically bright Type IIn supernova SN 1995N. We observed the SN at radio wavelengths with the Very Large Array (VLA) for 11 years. We also observed it at low radio frequencies with the Giant Metrewave Radio Telescope (GMRT) at various epochs within 6.5−106.5-106.5−10 years since explosion. Although there are indications of an early optically thick phase, most of the data are in the optically thin regime so it is difficult to distinguish between synchrotron self absorption (SSA) and free-free absorption (FFA) mechanisms. However, the information from other wavelengths indicates that the FFA is the dominant absorption process. Model fits of radio emission with the FFA give reasonable physical parameters. Making use of X-ray and optical observations, we derive the physical conditions of the shocked ejecta and the shocked CSM.
MAPPING HIGH-VELOCITY H α AND Ly α EMISSION FROM SUPERNOVA 1987A
The Astrophysical Journal, 2015
We present new Hubble Space Telescope images of high-velocity H-α and Lyman-α emission in the outer debris of SN 1987A. The H-α images are dominated by emission from hydrogen atoms crossing the reverse shock. For the first time we observe emission from the reverse shock surface well above and below the equatorial ring, suggesting a bipolar or conical structure perpendicular to the ring plane. Using the Hα imaging, we measure the mass flux of hydrogen atoms crossing the reverse shock front, in the velocity intervals (−7,500 < V obs < −2,800 km s −1) and (1,000 < V obs < 7,500 km s −1), M H = 1.2 × 10 −3 M ⊙ yr −1. We also present the first Lyman-α imaging of the whole remnant and new Chandra X-ray observations. Comparing the spatial distribution of the Lyman-α and X-ray emission, we observe that the majority of the high-velocity Lyman-α emission originates interior to the equatorial ring. The observed Lyman-α/H-α photon ratio, R(Lα/Hα) ≈ 17, is significantly higher than the theoretically predicted ratio of ≈ 5 for neutral atoms crossing the reverse shock front. We attribute this excess to Lyman-α emission produced by X-ray heating of the outer debris. The spatial orientation of the Lyman-α and X-ray emission suggests that X-ray heating of the outer debris is the dominant Lyman-α production mechanism in SN 1987A at this phase in its evolution.
Hydrogen and helium in the spectra of Type Ia supernovae
Monthly Notices of the Royal Astronomical Society, 2013
We present predictions for hydrogen and helium emission line luminosities from circumstellar matter around Type Ia supernovae (SNe Ia) using time dependent photoionization modelling. Early high-resolution ESO/Very Large Telescope (VLT) optical echelle spectra of the SN Ia 2000cx were taken before and up to ∼70 d after maximum to probe the existence of such narrow emission lines from the supernova. We detect no such lines, and from our modelling place an upper limit on the mass-loss rate for the putative wind from the progenitor system, M 1.3 × 10 −5 M yr −1 , assuming a speed of 10 km s −1 and solar abundances for the wind. If the wind would be helium-enriched and/or faster, the upper limit onṀ could be significantly higher. In the helium-enriched case, we show that the best line to constrain the mass-loss would be He I λ10 830. In addition to confirming the details of interstellar Na I and Ca II absorption towards SN 2000cx as discussed by Patat et al., we also find evidence for 6613.56 Å diffuse interstellar band absorption in the Milky Way. We also discuss measurements of the X-ray emission from the interaction between the supernova ejecta and the wind and we re-evaluate observations of SN 1992A obtained ∼16 d after maximum by Schlegel & Petre. We find an upper limit ofṀ ∼ 1.3 × 10 −5 M yr −1 which is significantly higher than that estimated by Schlegel & Petre. These results, together with the previous observational work on the normal SNe Ia 1994D and 2001el, disfavour a symbiotic star in the upper mass-loss rate regime (so-called Mira-type systems) from being the likely progenitor scenario for these SNe. Our model calculations are general, and can also be used for the subclass of SNe Ia that do show circumstellar interaction, e.g. the recent PTF 11kx. To constrain hydrogen in late-time spectra, we present ESO/VLT and ESO/New Technology Telescope optical and infrared observations of SNe Ia 1998bu and 2000cx in the nebular phase, 251−388 d after maximum. We see no signs of hydrogen line emission in SNe 1998bu and 2000cx at these epochs, and from the absence of Hα with a width of the order of ∼10 3 km s −1 , we argue from modelling that the mass of such hydrogen-rich gas must be 0.03 M for both supernovae. Comparing similar upper limits with recent models of Pan et al., it seems that hydrogen-rich donors with a separation of 5 times the radius of the donor may be ruled out for the five SNe Ia 1998bu, 2000cx, 2001el, 2005am and 2005cf. Larger separation, helium-rich donors, or a double-degenerate origin for these supernovae seems more likely. Our models have also been used to put the limit on hydrogen-rich gas in the recent SN 2011fe, and for this supernova, a double-degenerate origin seems likely.
Mapping High-Velocity H- and Lyman- Emission from Supernova 1987A
arXiv (Cornell University), 2015
We present new Hubble Space Telescope images of high-velocity H-α and Lyman-α emission in the outer debris of SN 1987A. The H-α images are dominated by emission from hydrogen atoms crossing the reverse shock. For the first time we observe emission from the reverse shock surface well above and below the equatorial ring, suggesting a bipolar or conical structure perpendicular to the ring plane. Using the Hα imaging, we measure the mass flux of hydrogen atoms crossing the reverse shock front, in the velocity intervals (−7,500 < V obs < −2,800 km s −1) and (1,000 < V obs < 7,500 km s −1), M H = 1.2 × 10 −3 M ⊙ yr −1. We also present the first Lyman-α imaging of the whole remnant and new Chandra X-ray observations. Comparing the spatial distribution of the Lyman-α and X-ray emission, we observe that the majority of the high-velocity Lyman-α emission originates interior to the equatorial ring. The observed Lyman-α/H-α photon ratio, R(Lα/Hα) ≈ 17, is significantly higher than the theoretically predicted ratio of ≈ 5 for neutral atoms crossing the reverse shock front. We attribute this excess to Lyman-α emission produced by X-ray heating of the outer debris. The spatial orientation of the Lyman-α and X-ray emission suggests that X-ray heating of the outer debris is the dominant Lyman-α production mechanism in SN 1987A at this phase in its evolution.
The stellar-wind envelope around the supernova XRF/GRB060218/SN2006aj massive progenitor star
2008
In BTA spectra of the supernova SN 2006aj, identified with the X-ray flash (XRF) and gamma-ray burst XRF/GRB 060218/SN 2006aj, we detected details interpreted as hydrogen lines, which is a sign of stellar-wind envelope around a massive progenitor star of the gamma-ray burst. Results of modeling two early spectra obtained with the BTA in 2.55 and 3.55 days after the explosion of Type Ic supernova SN 2006aj (z=0.0331) are presented.
2016
MSH 15–56 (G326.3-1.8) is a composite supernova remnant (SNR) that consists of an SNR shell and a displaced pulsar wind nebula (PWN) in the radio. We present XMM-Newton and Chandra X-ray observations of the remnant that reveal a compact source at the tip of the radio PWN and complex structures that provide evidence for mixing of the supernova (SN) ejecta with PWN material following a reverse shock interaction. The X-ray spectra are well fitted by a non-thermal power-law model whose photon index steepens with distance from the presumed pulsar, and a thermal component with an average temperature of 0.55 keV. The enhanced abundances of silicon and sulfur in some regions, and the similar temperature and ionization timescale, suggest that much of the X-ray emission can be attributed to SN ejecta that have either been heated by the reverse shock or swept up by the PWN. We find one region with a lower temperature of 0.3 keV that appears to be in ionization equilibrium. Assuming the Sedov m...
Monthly Notices of the Royal Astronomical Society, 2008
As part of the European Supernova Collaboration we obtained extensive photometry and spectroscopy of the type Ia SN 2002dj covering epochs from 11 days before to nearly two years after maximum. Detailed optical and near-infrared observations show that this object belongs to the class of the high-velocity gradient events as indicated by Si, S and Ca lines. The light curve shape and velocity evolution of SN 2002dj appear to be nearly identical to SN 2002bo. The only significant difference is observed in the optical to near-IR colours and a reduced spectral emission beyond 6500Å. For high-velocity gradient Type Ia supernovae, we tentatively identify a faster rise to maximum, a more pronounced inflection in the V and R light curves after maximum and a brighter, slower declining late-time B light curve as common photometric properties of this class of objects. They also seem to be characterized by a different colour and colour evolution with respect to "normal" SNe Ia. The usual light curve shape parameters do not distinguish these events. Stronger, more blueshifted absorption features of intermediate-mass elements and lower temperatures are the most prominent spectroscopic features of Type Ia supernovae displaying high velocity gradients. It appears that these events burn more intermediate-mass elements in the outer layers. Possible connections to the metallicity of the progenitor star are explored.
Characterizing the V -Band Light-Curves of Hydrogen-Rich Type II Supernovae
The Astrophysical Journal, 2014
We present an analysis of the diversity of V-band light-curves of hydrogen-rich type II supernovae. Analyzing a sample of 116 supernovae, several magnitude measurements are defined, together with decline rates at different epochs, and time durations of different phases. It is found that magnitudes measured at maximum light correlate more strongly with decline rates than those measured at other epochs: brighter supernovae at maximum generally have faster declining light-curves at all epochs. We find a relation between the decline rate during the 'plateau' phase and peak magnitudes, which has a dispersion of 0.56 magnitudes, offering the prospect of using type II supernovae as purely photometric distance indicators. Our analysis suggests that the type II population spans a continuum from low-luminosity events which have flat light-curves during the 'plateau' stage, through to the brightest events which decline much faster. A large range in optically thick phase durations is observed, implying a range in progenitor envelope masses at the epoch of explosion. During the radioactive tails, we find many supernovae with faster declining light-curves than expected from full trapping of radioactive emission, implying low mass ejecta. It is suggested that the main driver of light-curve diversity is the extent of hydrogen envelopes retained before explosion. Finally, a new classification scheme is introduced where hydrogen-rich events are typed as simply 'SN II' with an 's 2 ' value giving the decline rate during the 'plateau' phase, indicating its morphological type. Subject headings: (stars:) supernovae: general * Based on observations obtained with the du-Pont and Swope telescopes at LCO, and the Steward Observatory's CTIO60, SO90 and CTIO36 telescopes.