1. THE RISE OF SN 2014J IN THE NEARBY GALAXY M82Ariel 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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Povzetek najdenega: ...SNe Ia, a low value of total-to-selective extinction, RV 2, provides the best match...
Ključne besede: dust, extinction – galaxies: individual (Messier 82) – supernovae: individual (SN 2014J)
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2. THE PECULIAR EXTINCTION LAW OF SN 2014J MEASURED WITH THE HUBBLE SPACE TELESCOPERahman 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.
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Ključne besede: dust, extinction – galaxies: individual (Messier 82) – supernovae: individual SN2014J
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3. Diversity in extinction laws of Type Ia supernovae measured between 0.2 and 2 μmRahman 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.
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Ključne besede: circumstellar matter, supernovae: general, supernovae: individual: SNe 2012cg, supernovae: individual: 2012cu, dust, extinction
Objavljeno: 23.01.2018; Ogledov: 2846; Prenosov: 0
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4. Time-varying sodium absorption in the Type Ia supernova 2013ghRaphael 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.
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Povzetek najdenega: ...– supernovae: individual: SN 2013gh – dust, extinction – circumstellar matter –
supernovae: individual: iPTF 13dge...
Ključne besede: supernovae: general – supernovae: individual: SN 2013gh – dust, extinction – circumstellar matter –
supernovae: individual: iPTF 13dge
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5. VizieR Online Data Catalog: Measured photometry of SN 2014J from HST (Amanullah+, 2014)R. Amanullah, Tanja Petrushevska, zaključena znanstvena zbirka podatkov ali korpus Opis: We obtained observations (Program DD-13621; PI: Goobar) of SN 2014J with HST in the four UV broadband filters F218W, F225W, F275W, and F336W for seven epochs using a total of seven HST orbits during Cycle 21. In addition to this we also obtained optical broad-, medium-, and narrowband photometry in filters F467M, F631N, and F845M for visits (1, 3) and optical broadband photometry using F438W, F555W, and F814W for the remaining five visits. All observations were obtained with the Wide-Field Camera-3 (WFC3) using the UVIS aperture UVIS2-C512C-SUB.
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Ključne besede: Supernovae, Photometry: HST, Photometry: UBVRI, Photometry: infrared, Extinction
Objavljeno: 23.01.2018; Ogledov: 2654; Prenosov: 0
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6. Near-infrared supernova Ia distancesTanja Petrushevska, A. M. Watson, U. C. Fremling, N. Butler, W. H. Lee, Ariel Goobar, V. Stanishev, J. Johansson, S. B. Cenko, S. Dhawan, O. D. Fox, 2021, izvirni znanstveni članek Najdeno v: ključnih besedah
Ključne besede: supernova, cosmology, extinction
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