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Tanja Petrushevska, 2013, objavljeni znanstveni prispevek na konferenci

Opis: We shortly present here the ongoing project by the Stockholm supernova group about the search of high-z supernovae with the ALFOSC camera at the Nordic Optical Telescope by using galaxy clusters as gravitational telescope.
Ključne besede: gravitational telescopes, Abell 1689, galaxy clusters, telescopes, lensed supernovae, strong lensing
Objavljeno: 23.01.2018; Ogledov: 19; Prenosov: 0
.pdf Polno besedilo (59,07 KB)
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Time-varying sodium absorption in the Type Ia supernova 2013gh
Raphael Ferretti, R. Amanullah, Ariel Goobar, Joel Johansson, T. Petrushevska, 2016, izvirni znanstveni članek

Opis: Context. Temporal variability of narrow absorption lines in high-resolution spectra of Type Ia supernovae (SNe Ia) is studied to search for circumstellar matter. Time series which resolve the profiles of absorption lines such as Na I D or Ca II H&K are expected to reveal variations due to photoionisation and subsequent recombination of the gases. The presence, composition, and geometry of circumstellar matter may hint at the elusive progenitor system of SNe Ia and could also affect the observed reddening law. Aims. To date, there are few known cases of time-varying Na I D absorption in SNe Ia, all of which occurred during relatively late phases of the supernova (SN) evolution. Photoionisation, however, is predicted to occur during the early phases of SNe Ia, when the supernovae peak in the ultraviolet. We attempt, therefore, to observe early-time absorption-line variations by obtaining high-resolution spectra of SNe before maximum light. Methods. We have obtained photometry and high-resolution spectroscopy of SNe Ia 2013gh and iPTF 13dge, to search for absorptionline variations. Furthermore, we study interstellar absorption features in relation to the observed photometric colours of the SNe. Results. Both SNe display deep Na I D and Ca II H&K absorption features. Furthermore, small but significant variations are detected in a feature of the Na I D profile of SN 2013gh. The variations are consistent with either geometric effects of rapidly moving or patchy gas clouds or photoionisation of Na I gas at R ≈ 1019 cm from the explosion. Conclusions. Our analysis indicates that it is necessary to focus on early phases to detect photoionisation effects of gases in the circumstellar medium of SNe Ia. Different absorbers such as Na I and Ca II can be used to probe for matter at different distances from the SNe. The nondetection of variations during early phases makes it possible to put limits on the abundance of the species at those distances.
Ključne besede: supernovae: general – supernovae: individual: SN 2013gh – dust, extinction – circumstellar matter – supernovae: individual: iPTF 13dge
Objavljeno: 23.01.2018; Ogledov: 33; Prenosov: 0
.pdf Polno besedilo (1,84 MB)

Diversity in extinction laws of Type Ia supernovae measured between 0.2 and 2 μm
Rahman Amanullah, Tanja Petrushevska, 2015, izvirni znanstveni članek

Opis: We present ultraviolet (UV) observations of six nearby Type Ia supernovae (SNe Ia) obtained with the Hubble Space Telescope, three of which were also observed in the near-IR (NIR) with Wide-Field Camera 3. UV observations with the Swift satellite, as well as ground-based optical and NIR data provide complementary information. The combined data set covers the wavelength range 0.2–2 μm. By also including archival data of SN 2014J, we analyse a sample spanning observed colour excesses up to E(B − V) = 1.4 mag. We study the wavelength-dependent extinction of each individual SN and find a diversity of reddening laws when characterized by the total-to-selective extinction RV. In particular, we note that for the two SNe with E(B − V) ≳ 1 mag, for which the colour excess is dominated by dust extinction, we find RV = 1.4 ± 0.1 and RV = 2.8 ± 0.1. Adding UV photometry reduces the uncertainty of fitted RV by ∼50 per cent allowing us to also measure RV of individual low-extinction objects which point to a similar diversity, currently not accounted for in the analyses when SNe Ia are used for studying the expansion history of the Universe.
Ključne besede: circumstellar matter, supernovae: general, supernovae: individual: SNe 2012cg, supernovae: individual: 2012cu, dust, extinction
Objavljeno: 23.01.2018; Ogledov: 26; Prenosov: 0
.pdf Polno besedilo (6,52 MB)

Supernova spectra below strong circumstellar interaction
Giorgos Leloudas, E.Y. Hsiao, Joel Johansson, Keichi Maeda, T.J. Moriya, Jakob Nordin, Tanja Petrushevska, J. M. Silverman, Jesper Sollerman, M.D. Stritzinger, Francesco Taddia, D. Xu, 2015, izvirni znanstveni članek

Opis: We construct spectra of supernovae (SNe) interacting strongly with a circumstellar medium (CSM) by adding SN templates, a blackbody continuum, and an emission-line spectrum. In a Monte Carlo simulation we vary a large number of parameters, such as the SN type, brightness and phase, the strength of the CSM interaction, the extinction, and the signal to noise ratio (S/N) of the observed spectrum. We generate more than 800 spectra, distribute them to ten different human classifiers, and study how the different simulation parameters affect the appearance of the spectra and their classification. The SNe IIn showing some structure over the continuum were characterized as “SNe IInS” to allow for a better quantification. We demonstrate that the flux ratio of the underlying SN to the continuum fV is the single most important parameter determining whether a spectrum can be classified correctly. Other parameters, such as extinction, S/N, and the width and strength of the emission lines, do not play a significant role. Thermonuclear SNe get progressively classified as Ia-CSM, IInS, and IIn as fV decreases. The transition between Ia-CSM and IInS occurs at fV ∼ 0.2−0.3. It is therefore possible to determine that SNe Ia-CSM are found at the (un-extincted) magnitude range −19.5 > M > −21.6, in very good agreement with observations, and that the faintest SN IIn that can hide a SN Ia has M = −20.1. The literature sample of SNe Ia-CSM shows an association with 91T-like SNe Ia. Our experiment does not support that this association can be attributed to a luminosity bias (91T-like being brighter than normal events). We therefore conclude that this association has real physical origins and we propose that 91T-like explosions result from single degenerate progenitors that are responsible for the CSM. Despite the spectroscopic similarities between SNe Ibc and SNe Ia, the number of misclassifications between these types was very small in our simulation and mostly at low S/N. Combined with the SN luminosity function needed to reproduce the observed SN Ia-CSM luminosities, it is unlikely that SNe Ibc constitute an important contaminant within this sample. We show how Type II spectra transition to IIn and how the Hα profiles vary with fV . SNe IIn fainter than M = −17.2 are unable to mask SNe IIP brighter than M = −15. A more advanced simulation, including radiative transfer, shows that our simplified model is a good first order approximation. The spectra obtained are in good agreement with real data.
Ključne besede: supernovae
Objavljeno: 22.01.2018; Ogledov: 30; Prenosov: 0
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Rahman Amanullah, Ariel Goobar, Joel Johansson, D.P.K. Banerjee, V. Venkataraman, V. Joshi, N.M. Ashok, Yi Cao, Mansi Kasliwal, S.R. Kulkarni, P.E. Nugent, Tanja Petrushevska, V. Stanishev, 2014, izvirni znanstveni članek

Opis: The wavelength dependence of the extinction of Type Ia SN 2014J in the nearby galaxy M82 has been measured using UV to near-IR photometry obtained with the Hubble Space Telescope, the Nordic Optical Telescope, and the Mount Abu Infrared Telescope. This is the first time that the reddening of an SN Ia is characterized over the full wavelength range of 0.2–2μm. A total-to-selective extinction, RV 3.1, is ruled out with high significance. The best fit at maximum using a Galactic type extinction law yields RV = 1.4 ± 0.1. The observed reddening of SN 2014J is also compatible with a power-law extinction, Aλ/AV = (λ/λV ) p as expected from multiple scattering of light, with p = −2.1 ± 0.1. After correcting for differences in reddening, SN 2014J appears to be very similar to SN 2011fe over the 14 broadband filter light curves used in our study.
Ključne besede: dust, extinction – galaxies: individual (Messier 82) – supernovae: individual SN2014J
Objavljeno: 22.01.2018; Ogledov: 24; Prenosov: 0
.pdf Polno besedilo (683,44 KB)

Ariel Goobar, Joel Johansson, Rahman Amanullah, Yi Cao, Mansi Kasliwal, Raphael Ferretti, Peter Nugent, Daniel Perley, Avishay Gal-Yam, Eran Ofek, S. P. Tendulkar, M. Dennefeld, Stefano Valenti, Iair Arcavi, D.P.K. Banerjee, V. Venkataraman, Brad Cenko, Tanja Petrushevska, T.J. Dupuy, M.C. Liu, 2014, izvirni znanstveni članek

Opis: We report on the discovery of SN 2014J in the nearby galaxy M82. Given its proximity, it offers the best opportunity to date to study a thermonuclear supernova (SN) over a wide range of the electromagnetic spectrum. Optical, nearIR, and mid-IR observations on the rising light curve, orchestrated by the intermediate Palomar Transient Factory, show that SN 2014J is a spectroscopically normal Type Ia supernova (SN Ia), albeit exhibiting high-velocity features in its spectrum and heavily reddened by dust in the host galaxy. Our earliest detections start just hours after the fitted time of explosion. We use high-resolution optical spectroscopy to analyze the dense intervening material and do not detect any evolution in the resolved absorption features during the light curve rise. Similar to other highly reddened SNe Ia, a low value of total-to-selective extinction, RV 2, provides the best match to our observations. We also study pre-explosion optical and near-IR images from Hubble Space Telescope with special emphasis on the sources nearest to the SN location.
Ključne besede: dust, extinction – galaxies: individual (Messier 82) – supernovae: individual (SN 2014J)
Objavljeno: 22.01.2018; Ogledov: 43; Prenosov: 0 
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.pdf Polno besedilo (2,55 MB)

Slovenska romantika (učno gradivo)
Zoran Božič, 2018, drugo učno gradivo

Opis: Didaktična predstavitev pesmi Urbana Jarnika, Jovana Vesela Koseskega, Jakoba Zupana, življenja in pesmi Franceta Prešerna (Gazele, Glosa, Hčere svet, Neiztrohnjeno srce, Nezakonska mati, Pevcu, Pismo staršem, Slovo od mladosti, Sonetje nesreče, Učenec in Zdravljica) ter slovenske romantične proze (Jela).
Ključne besede: didaktika, romantika, poezija, proza, Zvezdje, Damon na Melito, Potažba, Novice bravcam ob novem letu, Kdo je mar?, sonet, balada, romanca, lirika, pesimizem, glosa, gazela, himna, Valentin Mandelc
Objavljeno: 22.01.2018; Ogledov: 33; Prenosov: 2
.pdf Polno besedilo (653,08 KB)

Evropski realizem (učno gradivo)
Zoran Božič, 2018, drugo učno gradivo

Opis: Didaktična predstavitev romana Vojna in mir, novele Nakit in romana Beznica.
Ključne besede: didaktika, realizem, naturalizem, Lev Nikolajevič Tolstoj, Guy de Maupassant, Emile Zola, roman, novela, Napoleon, Rusija, Pariz
Objavljeno: 22.01.2018; Ogledov: 31; Prenosov: 2
.pdf Polno besedilo (459,20 KB)

Evropska romantika (učno gradivo)
Zoran Božič, 2018, drugo učno gradivo

Opis: Didaktična predstavitev značilne lirske poezije (Byron, Leopardi, Musset), pesmi Lamartina, Puškina, Lermontova in Heineja ter romantične proze E. T. A. Hoffmanna.
Ključne besede: didaktika, romantika, Romanje grofiča Harolda, Sam sebi, Žalost, sonet, Jezero, A. P. Kernovi, Čaadajevu, Jadro, Lorelei, Nemčija, zimska pravljica, Gospod Cinober
Objavljeno: 22.01.2018; Ogledov: 33; Prenosov: 1
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Slovenski realizem (učno gradivo)
Zoran Božič, 2018, drugo učno gradivo

Opis: Didaktična predstavitev besedil Obujenke, Obrazi, Ognjeplamtič, Tilka, Popotovanje iz Litije do Čateža, Telečja pečenka, Človeka nikar!, Moj črni plašč, Soči, Mejnik, Brodnik, Ponočna potnica in Zimska romanca.
Ključne besede: didaktika, Simon Jenko, Fran Levstik, Josip Jurčič, Simon Gregorčič, Anton Aškerc, realizem, cikel lirskih pesmi, satirična pesnitev, literarni program, novela, svetobolje, blada, socialna poezija
Objavljeno: 22.01.2018; Ogledov: 34; Prenosov: 1
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