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11.
iPTF16geu: A multiply imaged, gravitationally lensed type Ia supernova
Tanja Petrushevska, S.R. Kulkarni, Rahman Amanullah, Ariel Goobar, 2017, original scientific article

Abstract: 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.
Found in: osebi
Keywords: lensed supernova, strong lensing, galaxy lens, multiply-lensed supernova
Published: 23.01.2018; Views: 2331; Downloads: 0
.pdf Fulltext (2,53 MB)

12.
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, original scientific article

Abstract: 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.
Found in: osebi
Keywords: supernovae: individual: PS1-10afx – gravitational lensing: strong – supernovae: general
Published: 23.01.2018; Views: 2487; Downloads: 0
.pdf Fulltext (1,00 MB)

13.
VizieR Online Data Catalog: Measured photometry of SN 2014J from HST (Amanullah+, 2014)
R. Amanullah, Tanja Petrushevska, complete scientific database or corpus

Abstract: 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.
Found in: osebi
Keywords: Supernovae, Photometry: HST, Photometry: UBVRI, Photometry: infrared, Extinction
Published: 23.01.2018; Views: 2256; Downloads: 0
.pdf Fulltext (430,24 KB)

14.
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, original scientific article

Abstract: 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.
Found in: osebi
Keywords: supernovae: individual: iPTF16abc – galaxies: individual: NGC 5221 – galaxies: ISM – galaxies
Published: 23.01.2018; Views: 2026; Downloads: 0
.pdf Fulltext (1,57 MB)

15.
Color Me Intrigued: The Discovery of iPTF 16fnm, an SN 2002cx-like Object
A. A. Miller, Tanja Petrushevska, 2017, original scientific article

Abstract: Modern wide-field, optical time-domain surveys must solve a basic optimization problem: maximize the number of transient discoveries or minimize the follow-up needed for the new discoveries. Here, we describe the Color Me Intrigued experiment, the first from the intermediate Palomar Transient Factory (iPTF) to search for transients simultaneously in the gPTF and RPTF bands. During the course of this experiment, we discovered iPTF 16fnm, a new member of the 02cx-like subclass of Type Ia supernovae (SNe). iPTF 16fnm peaked at Mg 15.09 0.17 mag PTF =-  , making it the second-least-luminous known SN Ia. iPTF 16fnm exhibits all the hallmarks of the 02cx-like class: (i) low luminosity at peak, (ii) low ejecta velocities, and (iii) a non-nebular spectrum several months after peak. Spectroscopically, iPTF 16fnm exhibits a striking resemblance to two other low-luminosity 02cx-like SNe: SN 2007qd and SN 2010ae. iPTF 16fnm and SN 2005hk decline at nearly the same rate, despite a 3 mag difference in brightness at peak. When considering the full subclass of 02cx-like SNe, we do not find evidence for a tight correlation between peak luminosity and decline rate in either the g′ or r′ band. We measure the relative rate of 02cx-like SNe to normal SNe Ia and find rN N 02 Ia cx = 33- + 25 158%. We further examine the g′ − r′ evolution of 02cx-like SNe and find that their unique color evolution can be used to separate them from 91bg-like and normal SNe Ia. This selection function will be especially important in the spectroscopically incomplete Zwicky Transient Facility/Large Synoptic Survey Telescope (LSST) era. Finally, we close by recommending that LSST periodically evaluate, and possibly update, its observing cadence to maximize transient science.
Found in: osebi
Keywords: methods: observational – surveys – supernovae: general – supernovae: individual (SN 2002cx, SN 2005hk, iPTF 16fnm)
Published: 23.01.2018; Views: 2075; Downloads: 0
.pdf Fulltext (2,37 MB)

16.
SIFTING FOR SAPPHIRES: SYSTEMATIC SELECTION OF TIDAL DISRUPTION EVENTS IN iPTF
Tiara Hung, Suvi Gezari, Tanja Petrushevska, 2018, original scientific article

Abstract: We present results from a systematic selection of tidal disruption events (TDEs) in a wide area (4800 deg2 ) g + R band experiment by the Intermediate Palomar Transient Factory (iPTF) with a rolling cadence of 1 and 3 days. We use photometric selection criteria to down select from a total of 493 nuclear transients detected during the experiment to a sample of 26 blue (g − r < 0 mag) nuclear transients in red host galaxies. Using Swift follow-up UV and X-ray imaging, and ground-based optical spectroscopy, we classify 14 Type Ia supernovae (SNe Ia), 9 highly variable active galactic nuclei (AGNs), 2 confirmed TDEs, and 1 potential core-collapse supernova. From our study, we measure a TDE per galaxy rate of 1.7 +2.85 −1.27 ×10−4 gal−1 yr−1 (90% CL in Poisson statistics) using a galaxy number density estimated from the SDSS luminosity function. We find that it is possible to filter out AGNs by employing a more stringent transient color cut (g − r < −0.2 mag). The UV is an important discriminator for filtering out SN contamination, since in the optical, SNe Ia can appear as blue as TDEs in their early phases. However, the contamination from SN Ia drops significantly with a more stringent spatial offset cut, suggesting higher precision in astrometry is essential for separating TDEs from SNe Ia in the optical. Our most stringent optical photometric selection criteria yields a contamination rate of 4.5:1, allowing for a manageable number of TDE candidates for complete spectroscopic follow-up and real-time classification in the ZTF era.
Found in: osebi
Keywords: accretion, accretion disks – black hole physics – galaxies: nuclei – ultraviolet: general
Published: 02.03.2022; Views: 430; Downloads: 21
.pdf Fulltext (1,18 MB)

17.
Supernovae seen through gravitational telescopes
Tanja Petrushevska, 2017, doctoral dissertation

Abstract: Gravitational lenses such as galaxies and galaxy clusters, can magnify the flux of background galaxies. These galaxies at high redshift can host supernovae (SNe) which, thanks to the magnification boost due to lensing, can be observed, otherwise too faint to be detected by current telescopes. Under the right circumstances, the background galaxies may also have multiple images due to the strong lensing. Of particular interest is to detect lensed supernovae of type Ia (SNe Ia), because of their standard brightness. They could help improve lensing models and, if multiple images are observed, the Hubble constant can be measured independently. In this thesis, we use galaxy clusters as gravitational telescopes to search for lensed SNe at high redshift. We performed ground-based, near-infrared and optical search campaigns towards the massive clusters Abell 1689 and 370, which are among the most powerful gravitational telescopes known. Our search resulted in the discovery of five photometrically classified, core- collapse SNe at redshifts of 0.671 < z < 1.703 with significant magnification from the cluster. Owing to the power of the lensing cluster, we calculated the volumetric core-collapse SN rates for 0.4  z < 2.9, and find good agreement with previous estimates and predictions from cosmic star formation history. During our survey, we also discovered two SNe Ia in A1689 cluster members, which allowed us to determine the cluster Ia rate. Furthermore, we discuss the expectations of finding lensed SNe at high redshift in simulated search campaigns that can be conducted with upcoming ground- and space-based telescopes. Magnification from a galaxy lens also allows for detailed studies of the SN properties at high redshift that otherwise would not be possible. Spec- troscopic observations of lensed high-redshift SNe Ia are of particular interest since they can be used to test for evolution of the standard candle nature of these objects. However, if systematic redshift-dependent properties are found, their utility for future surveys could be challenged. We investigate whether the properties of the strongly lensed and very distant SN Ia PS1- 10afx at z = 1.4, deviates from the well-studied nearby and intermediate populations of normal SNe Ia. In other study, we report the discovery of the first resolved multiply-imaged gravitationally lensed SN Ia.
Found in: osebi
Keywords: supernovae, gravitational telescopes, galaxy clusters, lensed supernovae, strong lensing, astronomical surveys and telescopes
Published: 23.01.2018; Views: 2660; Downloads: 0
.pdf Fulltext (28,31 MB)

18.
iPTF discovery and identification of bright transients
Thomas Kupfer, Tanja Petrushevska, 2017, other component parts

Abstract: The intermediate Palomar Transient Factory (ATel #4807) reports the discovery of the following bright transients. We report as ATel alerts all objects brighter than 19 mag. Our discoveries are reported in two filters: sdss-g and Mould-I, denoted as g, and I. Both are in the AB magnitude system.
Found in: osebi
Keywords: Supernovae, Transient
Published: 23.01.2018; Views: 1947; Downloads: 0
.pdf Fulltext (338,36 KB)

19.
iPTF discovery and classification of bright transients
Nadejda Blagorodnova, Tanja Petrushevska, 2017, other component parts

Abstract: The intermediate Palomar Transient Factory (ATel #4807) reports the discovery of the following bright transients. We report as ATel alerts all objects brighter than 19 mag. Our discoveries are reported in three filters: sdss-r, Mould-R and Mould-I, denoted as g, r and i. All three are in the AB magnitude system.
Found in: osebi
Keywords: Supernovae, Transients
Published: 23.01.2018; Views: 2255; Downloads: 0
.pdf Fulltext (352,50 KB)

20.
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