ALBERT

Description: We present and discuss new visual wavelength-range observations of the inner regions of the supernova remnant SNR 0540–69.3 that is located in the Large Magellanic Cloud (LMC). These observations provide us with more spatial and spectral information than were previously available for this object. We use these data to create a detailed three-dimensional model of the remnant, assuming linear expansion of the ejecta. With the observations and the model, we study the general three-dimensional structure of the remnant, and the influence of an active region in the remnant – a ‘blob’ – that we address in previous papers. We used the fibre-fed integral-field Visual Multi-Object Spectrograph at the Very Large Telescope of the European Southern Observatory. The observations provide us with three-dimensional data in [O iii ] 5007 and [S ii ] 6717, 6731 at a 0.33 arcsec x 0.33 arcsec spatial sampling and a velocity resolution of about 35 km s – 1 . We decomposed the two, partially overlapping, sulphur lines and used them to calculate electron densities across the remnant at a high signal-to-noise ratio. In our study, we recover results of previous studies, but we are more importantly able to obtain more detailed information than before. Our analysis reveals a structure that stretches from the position of the ‘blob’, and into the plane of the sky at a position angle of PA ~= 60°. Assuming a remnant age of 1000 yr and the usual LMC distance, the structure has an inclination angle of about 65° to the line of sight. The position angle is close to the symmetry axis with present and past activity in the visual and the X-ray wavelength ranges. We speculate that the pulsar is positioned along this activity axis, where it has a velocity along the line of sight of a few hundred km s – 1 . The ‘blob’ is most likely a region of shock activity, as it is mainly bright in [S ii ]; future observations of [O ii ] 3726, 3729 would be useful to test whether the S/O abundance ratio is higher than average for that location in the remnant. The striking resemblance in X-rays between the pulsar wind nebula (PWN) of SNR 0540–69.3 and the Crab, in combination with our findings in this paper, suggests that the symmetry axis is part of a torus in the PWN. This is in agreement with the original suggestion by Gotthelf & Wang.

Description: We report far-infrared and submillimeter observations of supernova 1987A, the star whose explosion was observed on 23 February 1987 in the Large Magellanic Cloud, a galaxy located 160,000 light years away. The observations reveal the presence of a population of cold dust grains radiating with a temperature of about 17 to 23 kelvin at a rate of about 220 times the luminosity of the Sun. The intensity and spectral energy distribution of the emission suggest a dust mass of about 0.4 to 0.7 times the mass of the Sun. The radiation must originate from the supernova ejecta and requires the efficient precipitation of all refractory material into dust. Our observations imply that supernovae can produce the large dust masses detected in young galaxies at very high redshifts.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Matsuura, M -- Dwek, E -- Meixner, M -- Otsuka, M -- Babler, B -- Barlow, M J -- Roman-Duval, J -- Engelbracht, C -- Sandstrom, K -- Lakicevic, M -- van Loon, J Th -- Sonneborn, G -- Clayton, G C -- Long, K S -- Lundqvist, P -- Nozawa, T -- Gordon, K D -- Hony, S -- Panuzzo, P -- Okumura, K -- Misselt, K A -- Montiel, E -- Sauvage, M -- New York, N.Y. -- Science. 2011 Sep 2;333(6047):1258-61. doi: 10.1126/science.1205983. Epub 2011 Jul 7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astrophysics Group, Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK. mikako@star.ucl.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21737700" target="_blank"〉PubMed〈/a〉

Description: When a massive star explodes as a supernova, substantial amounts of radioactive elements--primarily (56)Ni, (57)Ni and (44)Ti--are produced. After the initial flash of light from shock heating, the fading light emitted by the supernova is due to the decay of these elements. However, after decades, the energy powering a supernova remnant comes from the shock interaction between the ejecta and the surrounding medium. The transition to this phase has hitherto not been observed: supernovae occur too infrequently in the Milky Way to provide a young example, and extragalactic supernovae are generally too faint and too small. Here we report observations that show this transition in the supernova SN 1987A in the Large Magellanic Cloud. From 1994 to 2001, the ejecta faded owing to radioactive decay of (44)Ti as predicted. Then the flux started to increase, more than doubling by the end of 2009. We show that this increase is the result of heat deposited by X-rays produced as the ejecta interacts with the surrounding material. In time, the X-rays will penetrate farther into the ejecta, enabling us to analyse the structure and chemistry of the vanished star.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Larsson, J -- Fransson, C -- Ostlin, G -- Groningsson, P -- Jerkstrand, A -- Kozma, C -- Sollerman, J -- Challis, P -- Kirshner, R P -- Chevalier, R A -- Heng, K -- McCray, R -- Suntzeff, N B -- Bouchet, P -- Crotts, A -- Danziger, J -- Dwek, E -- France, K -- Garnavich, P M -- Lawrence, S S -- Leibundgut, B -- Lundqvist, P -- Panagia, N -- Pun, C S J -- Smith, N -- Sonneborn, G -- Wang, L -- Wheeler, J C -- England -- Nature. 2011 Jun 8;474(7352):484-6. doi: 10.1038/nature10090.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, The Oskar Klein Centre, Stockholm University, 106 91 Stockholm, Sweden. josefin.larsson@astro.su.se〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21654749" target="_blank"〉PubMed〈/a〉

Description: Observations with the Hubble Space Telescope (HST), conducted since 1990, now offer an unprecedented glimpse into fast astrophysical shocks in the young remnant of supernova 1987A. Comparing observations taken in 2010 with the use of the refurbished instruments on HST with data taken in 2004, just before the Space Telescope Imaging Spectrograph failed, we find that the Lyalpha and Halpha lines from shock emission continue to brighten, whereas their maximum velocities continue to decrease. We observe broad, blueshifted Lyalpha, which we attribute to resonant scattering of photons emitted from hot spots on the equatorial ring. We also detect N v lambdalambda1239, 1243 angstrom line emission, but only to the red of Lyalpha. The profiles of the N v lines differ markedly from that of Halpha, suggesting that the N4+ ions are scattered and accelerated by turbulent electromagnetic fields that isotropize the ions in the collisionless shock.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉France, Kevin -- McCray, Richard -- Heng, Kevin -- Kirshner, Robert P -- Challis, Peter -- Bouchet, Patrice -- Crotts, Arlin -- Dwek, Eli -- Fransson, Claes -- Garnavich, Peter M -- Larsson, Josefin -- Lawrence, Stephen S -- Lundqvist, Peter -- Panagia, Nino -- Pun, Chun S J -- Smith, Nathan -- Sollerman, Jesper -- Sonneborn, George -- Stocke, John T -- Wang, Lifan -- Wheeler, J Craig -- New York, N.Y. -- Science. 2010 Sep 24;329(5999):1624-7. doi: 10.1126/science.1192134. Epub 2010 Sep 2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309-0389, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20813921" target="_blank"〉PubMed〈/a〉

Description: 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, $\skew4\dot{M}\lesssim 1.3\times 10^{-5} \,{\rm M}_{\odot }\,{\rm yr}^{-1}$ , 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 on $\skew4\dot{M}$ could be significantly higher. In the helium-enriched case, we show that the best line to constrain the mass-loss would be He i 10 830. 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 of $\skew4\dot{M}\sim 1.3\times 10^{-5} \,{\rm M}_{\odot }\,{\rm yr}^{-1}$ 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.

Description: We present photometric and spectroscopic observations of SN 2013fc, a bright type II supernova (SN) in a circumnuclear star-forming ring in the luminous infrared galaxy ESO 154-G010, observed as part of the Public ESO Spectroscopic Survey of Transient Objects. SN 2013fc is both photometrically and spectroscopically similar to the well-studied type IIn SN 1998S and to the bright type II-L SN 1979C. It exhibits an initial linear decline, followed by a short plateau phase and a tail phase with a decline too fast for 56 Co decay with full -ray trapping. Initially, the spectrum was blue and featureless. Later on, a strong broad (~8000 km s –1 ) H α emission profile became prominent. We apply a starlight stellar population model fit to the SN location (observed when the SN had faded) to estimate a high extinction of A V = 2.9 ± 0.2 mag and an age of $10_{-2}^{+3}$  Myr for the underlying cluster. We compare the SN to SNe 1998S and 1979C and discuss its possible progenitor star considering the similarities to these events. With a peak brightness of B = –20.46 ± 0.21 mag, SN 2013fc is 0.9 mag brighter than SN 1998S and of comparable brightness to SN 1979C. We suggest that SN 2013fc was consistent with a massive red supergiant (RSG) progenitor. Recent mass loss probably due to a strong RSG wind created the circumstellar matter illuminated through its interaction with the SN ejecta. We also observe a near-infrared excess, possibly due to newly condensed dust.