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1.
PASSERBY BECOME SUPERNOVA HUNTERS IN KUNGSTRÄDGÅRDEN
Tanja Petrushevska, S. Papadogiannakis, Emir Karamehmetoglu, 2015, druga izvedena dela

Opis: Fysik i Kungsträdgården is one of the major outreach events in Stockholm where scientists have the chance to show their research. This year the supernova group at the OKC invited the public to look for supernovae with us using the intermediate Palomar (Transient) Factory (iPTF) collaboration telescope in Palomar, California, U.S.A. Due to the time difference between Stockholm and California, we were able to look at live images as they were taken from the telescope, to search for new transient objects such as supernovae. The event was successful, bringing a lot of people from the park in central Stockholm to come and search with us.
Najdeno v: osebi
Ključne besede: science outreach, supernova hunting for the public
Objavljeno: 09.02.2018; Ogledov: 265; Prenosov: 0
.pdf Polno besedilo (572,84 KB)

2.
Жените во науката
Daniel Evrosimoski, Tanja Petrushevska, 2018, intervju

Najdeno v: osebi
Ključne besede: women in science, international day of women in science, interview, newspaper
Objavljeno: 12.02.2018; Ogledov: 225; Prenosov: 0 
(1 glas)
.pdf Polno besedilo (1,57 MB)

3.
THE RISE OF SN 2014J IN THE NEARBY GALAXY M82
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.
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Ključne besede: dust, extinction – galaxies: individual (Messier 82) – supernovae: individual (SN 2014J)
Objavljeno: 22.01.2018; Ogledov: 257; Prenosov: 0 
(1 glas)
.pdf Polno besedilo (2,55 MB)

4.
SEARCH FOR LENSED SUPERNOVAE BY MASSIVE GALAXY CLUSTERS WITH THE 2.5m NORDIC OPTICAL TELESCOPE
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.
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Ključne besede: gravitational telescopes, Abell 1689, galaxy clusters, telescopes, lensed supernovae, strong lensing
Objavljeno: 23.01.2018; Ogledov: 234; Prenosov: 0
.pdf Polno besedilo (59,07 KB)
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5.
THE PECULIAR EXTINCTION LAW OF SN 2014J MEASURED WITH THE HUBBLE SPACE TELESCOPE
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.
Najdeno v: osebi
Ključne besede: dust, extinction – galaxies: individual (Messier 82) – supernovae: individual SN2014J
Objavljeno: 22.01.2018; Ogledov: 220; Prenosov: 0
.pdf Polno besedilo (683,44 KB)

6.
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.
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Ključne besede: supernovae
Objavljeno: 22.01.2018; Ogledov: 219; Prenosov: 0
.pdf Polno besedilo (906,70 KB)

7.
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.
Najdeno v: osebi
Ključne besede: circumstellar matter, supernovae: general, supernovae: individual: SNe 2012cg, supernovae: individual: 2012cu, dust, extinction
Objavljeno: 23.01.2018; Ogledov: 192; Prenosov: 0
.pdf Polno besedilo (6,52 MB)

8.
VizieR Online Data Catalog: Photometry of SN 2013gh and iPTF13dge (Ferretti+, 2016)
Raphael Ferretti, Tanja Petrushevska, zaključena znanstvena zbirka podatkov ali korpus

Opis: Measured photometry of type Ia supernovae 2013gh and iPTF13dge are presented. Furthermore, the effective light-curve-width-corrected phase and the natural magnitude in specified filters have been computed. Thereby, the corresponding Galactic absorption (Ax_MW) and the filter corrections (Kx) to the corresponding rest-frame filter for SN 2011fe as described by Amanullah et al. (2015MNRAS.453.3300A) are presented. The corrected magnitude can be obtained as X-AXMW-KX. All corrections have been calculated after the SN 2011fe template has been reddened with the best-fit Fitzpatrick (1999PASP..111...63F) law, for each SN. Furthermore, the V magnitude and corrections for each phase phase are included. The V magnitude was either measured (M) or calculated (D) using the SNooPy model. The V magnitude is only shown for data points used in the colour analysis, with phases between -10 and +35-days. The corrected colour can be obtained as (X-AXMW-KX)-(V-AVMW-KV) and can be compared with the corresponding colour of SN 2011fe in order to study the reddening laws of the SNe.
Najdeno v: osebi
Ključne besede: Supernovae, Photometry: UBV, Photometry: ugriz, Photometry: ultraviolet
Objavljeno: 23.01.2018; Ogledov: 238; Prenosov: 0
.pdf Polno besedilo (439,40 KB)

9.
High-redshift supernova rates measured with the gravitational telescope A 1689
Tanja Petrushevska, R. Amanullah, Ariel Goobar, S. Fabbro, Joel Johansson, Tor Kjellsson, Chris Lidman, K. Paech, Johan Richard, H. Dahle, Raphael Ferretti, J.P. Kneib, M. Limousin, Jakob Nordin, V. Stanishev, 2016, izvirni znanstveni članek

Opis: Aims. We present a ground-based, near-infrared search for lensed supernovae behind the massive cluster Abell 1689 at z = 0.18, which is one of the most powerful gravitational telescopes that nature provides. Methods. Our survey was based on multi-epoch J-band observations with the HAWK-I instrument on VLT, with supporting optical data from the Nordic Optical Telescope. Results. Our search resulted in the discovery of five photometrically classified, core-collapse supernovae with high redshifts of 0.671 < z < 1.703 and magnifications in the range ∆m = −0.31 to −1.58 mag, as calculated from lensing models in the literature. Owing to the power of the lensing cluster, the survey had the sensitivity to detect supernovae up to very high redshifts, z ∼ 3, albeit for a limited region of space. We present a study of the core-collapse supernova rates for 0.4 ≤ z < 2.9, and find good agreement with previous estimates and predictions from star formation history. During our survey, we also discovered two Type Ia supernovae in A 1689 cluster members, which allowed us to determine the cluster Ia rate to be 0.14+0.19 −0.09 ± 0.01 SNuB h 2 (SNuB ≡ 10−12 SNe L −1 ,B yr−1 ), where the error bars indicate 1σ confidence intervals, statistical and systematic, respectively. The cluster rate normalized by the stellar mass is 0.10+0.13 −0.06 ± 0.02 in SNuM h 2 (SNuM ≡ 10−12 SNe M−1 yr−1 ). Furthermore, we explore the optimal future survey for improving the core-collapse supernova rate measurements at z & 2 using gravitational telescopes, and for detections with multiply lensed images, and we find that the planned WFIRST space mission has excellent prospects. Conclusions. Massive clusters can be used as gravitational telescopes to significantly expand the survey range of supernova searches, with important implications for the study of the high-z transient Universe.
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Ključne besede: supernovae: general – gravitational lensing: strong – galaxies: star formation – galaxies: clusters: individual: A 1689 – techniques: photometric
Objavljeno: 23.01.2018; Ogledov: 168; Prenosov: 0
.pdf Polno besedilo (2,64 MB)

10.
VizieR Online Data Catalog: A 1689 HAWK-I J-band image (Petrushevska+, 2016)
Tanja Petrushevska, zaključena znanstvena zbirka podatkov ali korpus

Opis: The NIR data were obtained with the High Acuity Wide field K-band imager mounted on the VLT (Programmes ID 082.A-0431, 0.83.A-0398, 090.A-0492, 091.A-0108, P.I. Goobar). The HAWK-I has an array of four 2048x2048 HgCdTe detectors covering a total area of 7.5'x7.5' with a sampling of 0.106"/pix per pixel. The chips are separated by a 15" gap.
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Ključne besede: Clusters: galaxy, Infrared sources
Objavljeno: 23.01.2018; Ogledov: 238; Prenosov: 0
.pdf Polno besedilo (341,31 KB)

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