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1.
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.
Najdeno v: osebi
Ključne besede: dust, extinction – galaxies: individual (Messier 82) – supernovae: individual (SN 2014J)
Objavljeno: 22.01.2018; Ogledov: 2200; Prenosov: 0 
(1 glas)
.pdf Polno besedilo (2,55 MB)

2.
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: 1828; Prenosov: 0
.pdf Polno besedilo (683,44 KB)

3.
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: 1838; Prenosov: 0
.pdf Polno besedilo (6,52 MB)

4.
iPTF16geu: A multiply imaged, gravitationally lensed type Ia supernova
Tanja Petrushevska, S.R. Kulkarni, Rahman Amanullah, Ariel Goobar, 2017, izvirni znanstveni članek

Opis: We report the discovery of a multiply-imaged gravitationally lensed Type Ia supernova, iPTF16geu, at redshift z = 0.409. This phenomenon could be iden- tified because the light from the stellar explosion was magnified more than fifty times by the curvature of space around matter in an intervening galaxy. We used high spatial resolution observations to resolve four images of the lensed supernova, approximately 0.300 from the center of the foreground galaxy. The observations probe a physical scale of ⇠1 kiloparsec, smaller than what is typical in other studies of extragalactic gravitational lensing. The large mag- nification and symmetric image configuration implies close alignment between the line-of-sight to the supernova and the lens. The relative magnifications of the four images provide evidence for sub-structures in the lensing galaxy.
Najdeno v: osebi
Ključne besede: lensed supernova, strong lensing, galaxy lens, multiply-lensed supernova
Objavljeno: 23.01.2018; Ogledov: 1812; Prenosov: 0
.pdf Polno besedilo (2,53 MB)

5.
Testing for redshift evolution of Type Ia supernovae using the strongly lensed PS1-10afx at z = 1.4
Tanja Petrushevska, Rahman Amanullah, Mattia Bulla, Markus Kromer, Raphael Ferretti, Ariel Goobar, Semeli Papadogiannakis, 2017, izvirni znanstveni članek

Opis: Context. The light from distant supernovae (SNe ) can be magnified through gravitational lensing when a foreground galaxy is located along the line of sight. This line-up allows for detailed studies of SNe at high redshift that otherwise would not be possible. Spectroscopic observations of lensed high-redshift Type Ia supernovae (SNe Ia) are of particular interest since they can be used to test for evolution of their intrinsic properties. The use of SNe Ia for probing the cosmic expansion history has proven to be an extremely powerful method for measuring cosmological parameters. However, if systematic redshift-dependent properties are found, their usefulness for future surveys could be challenged. Aims. We investigate whether the spectroscopic properties of the strongly lensed and very distant SN Ia PS1-10afx at z = 1.4, deviates from the well-studied populations of normal SNe Ia at nearby or intermediate distance. Methods. We created median spectra from nearby and intermediate-redshift spectroscopically normal SNe Ia from the literature at −5 and +1 days from light-curve maximum. We then compared these median spectra to those of PS1-10afx. Results. We do not find signs of spectral evolution in PS1-10afx. The observed deviation between PS1-10afx and the median templates are within what is found for SNe at low and intermediate redshift. There is a noticeable broad feature centred at λ ∼ 3500 Å, which is present only to a lesser extent in individual low- and intermediate-redshift SN Ia spectra. From a comparison with a recently developed explosion model, we find this feature to be dominated by iron peak elements, in particular, singly ionized cobalt and chromium.
Najdeno v: osebi
Ključne besede: supernovae: individual: PS1-10afx – gravitational lensing: strong – supernovae: general
Objavljeno: 23.01.2018; Ogledov: 1958; Prenosov: 0
.pdf Polno besedilo (1,00 MB)

6.
Probing gas and dust in the tidal tail of NGC 5221 with the type Ia supernova iPTF16abc
Raphael Ferretti, Rahman Amanullah, Ariel Goobar, Tanja Petrushevska, 2017, izvirni znanstveni članek

Opis: Context. Type Ia supernovae (SNe Ia) can be used to address numerous questions in astrophysics and cosmology. Due to their well known spectral and photometric properties, SNe Ia are well suited to study gas and dust along the lines-of-sight to the explosions. For example, narrow Na I D and Ca II H&K absorption lines can be studied easily, because of the well-defined spectral continuum of SNe Ia around these features. Aims. We aim to study the gas and dust along the line-of-sight to iPTF16abc, which occurred in an unusual location, in a tidal arm, 80 kpc from centre of the galaxy NGC 5221. Methods. Using a time-series of high-resolution spectra, we have examined narrow Na I D and Ca II H&K absorption features for variations in time, which would be indicative for circumstellar (CS) matter. Furthermore, we have taken advantage of the well known photometric properties of SNe Ia to determine reddening due to dust along the line-of-sight. Results. From the lack of variations in Na I D and Ca II H&K, we determine that none of the detected absorption features originate from the CS medium of iPTF16abc. While the Na I D and Ca II H&K absorption is found to be optically thick, a negligible amount of reddening points to a small column of interstellar dust. Conclusions. We find that the gas along the line-of-sight to iPTF16abc is typical of what might be found in the interstellar medium (ISM) within a galaxy. It suggests that we are observing gas that has been tidally stripped during an interaction of NGC 5221 with one of its neighbouring galaxies in the past ∼109 yr. In the future, the gas clouds could become the locations of star formation. On a longer time scale, the clouds might diffuse, enriching the circum-galactic medium (CGM) with metals. The gas profile along the line-of-sight should be useful for future studies of the dynamics of the galaxy group containing NGC 5221.
Najdeno v: osebi
Ključne besede: supernovae: individual: iPTF16abc – galaxies: individual: NGC 5221 – galaxies: ISM – galaxies
Objavljeno: 23.01.2018; Ogledov: 1599; Prenosov: 0
.pdf Polno besedilo (1,57 MB)

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