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31.
Ќе откриваме експлозии на небото како никогаш порано
Tanja Petrushevska, 2019, interview

Keywords: supernova, discoveries, Universe
Published in RUNG: 14.01.2019; Views: 2492; Downloads: 0
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32.
Prospects for Strongly Lensed Supernovae Behind Hubble FrontierFields Galaxy Clusters with the James Webb Space Telescope
Tanja Petrushevska, 2018, original scientific article

Abstract: Measuring time delays from strongly lensed supernovae (SNe) is emerging as a novel andindependent tool for estimating the Hubble constant (H0). This is very important given the recent discordin the value of H0) from two methods that probe different distance ranges. The success of this techniquewill rely of our ability to discover strongly lensed SNe with measurable time delays. Here, we present themagnifications and the time delay s for the multiply-imaged galaxies behind the Hubble Frontier Fields(HFF) galaxy clusters, by using recently published lensing models. Continuing on our previous work donefor Abell 1689 (A1689) and Abell 370, we also show the prospects of observing strongly lensed SNe behindthe HFF clusters with the upcoming James Webb Space Telescope (JWST). With four 1-hour visits inone year, the summed expectations of all six HFF clusters are ∼0 .5 core-collapse (CC) SNe and 0.06Type Ia SNe (SNe Ia) in F115W band, while with F150W the expectations are higher, ∼0.9 CC SNeand ∼0.06 SNe Ia. These estimates match those expected by only surveying A1689, proving that theperformance of A1689 as gravitational telescope is superior. In the five HFF clusters presented here, wefind that F150W will be able to detect SNe Ia (SNe IIP) exploding in 93 (80) pairs multiply-imaged galaxieswith time delays of less than 5 years.
Keywords: supernovae, JWST, Hubble constant, strong lensing
Published in RUNG: 03.01.2019; Views: 2774; Downloads: 0
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33.
Exploring the Universe with supernovae
Tanja Petrushevska, published scientific conference contribution abstract (invited lecture)

Abstract: Supernovae have proven to be exquisite tools for a variety of astrophysics and cosmology topics. In this lecture, I will highlight a selection of dedicated tele- scopic surveys for detecting supernovae and I will report some of our interesting discoveries during the past few years. I will dedicate special attention to strongly lensed supernovae by galaxies and galaxy clusters. Under the right circumstances, multiple images of the lensed supernovae can be observed, and due to the variable nature of the objects, the difference between the arrival times of the images can be measured. Since the images have taken different paths through space before reaching us, the time-differences are sensitive to the expansion rate of the universe. Therefore, measuring time delays from strongly lensed supernovae is emerging as a novel and independent tool for estimating the Hubble constant (H0). This is very important given the recent discord in the value of H0 from two methods that probe different distance ranges: the ESA mission Planck value corresponds to 67.74 ± 0.46 km s−1 Mpc−1; [1], while a reanalysis of the local distance scale gives 73.24 ± 1.74 km s−1 Mpc−1; [2, 3], these measurements thus being inconsistent at the ≈ 3.5σ level. Therefore, the results of additional independent and high- precision techniques, which rely on different physics, are of key importance. In this context, I will report our discovery of the first resolved multiply-imaged gra- vitationally lensed supernova Type Ia [4]. Moving forward, I will discuss some of the prospects of upcoming facilities such as the Large Synoptic Survey Telescope and James Webb Space Telescope [5, 6].
Keywords: supernovae, strong lensing, neutron stars
Published in RUNG: 29.11.2018; Views: 2957; Downloads: 0
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34.
Zvezde eksplodirajo tudi ob nedeljah
Tanja Petrushevska, 2018, popular article

Abstract: Prvič opažena ultraslečena supernova, pri kateri je nastala tesna dvojna nevtronska zvezda
Keywords: supernova, nevtronska zvezda
Published in RUNG: 22.10.2018; Views: 2646; Downloads: 133
.pdf Full text (2,70 MB)

35.
A hot and fast ultra-stripped supernova that likely formed a compact neutron star binary
Tanja Petrushevska, 2018, original scientific article

Abstract: Compact neutron star binary systems are produced from binary massive stars through stellar evolution involving up to two supernova explosions. The final stages in the formation of these systems have not been directly observed. We report the discovery of iPTF 14gqr (SN 2014ft), a type Ic supernova with a fast-evolving light curve indicating an extremely low ejecta mass (≈0.2 solar masses) and low kinetic energy (≈2 × 1050 ergs). Early photometry and spectroscopy reveal evidence of shock cooling of an extended helium-rich envelope, likely ejected in an intense pre-explosion mass-loss episode of the progenitor. Taken together, we interpret iPTF 14gqr as evidence for ultra-stripped supernovae that form neutron stars in compact binary systems.
Keywords: supernova, neutron stars, gravitational waves
Published in RUNG: 12.10.2018; Views: 3252; Downloads: 0
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36.
Sifting for Sapphires: Systematic Selection of Tidal Disruption Events in iPTF
Tanja Petrushevska, 2018, original scientific article

Keywords: tidal disruption events
Published in RUNG: 02.10.2018; Views: 3028; Downloads: 0
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37.
Prospects for observing lensed supernovae behind galaxy clusters with JWST
Tanja Petrushevska, 2018, unpublished conference contribution

Abstract: Contributed talk at the international conference "The Universe as a telescope: probing the cosmos at all scales with strong lensing" in Milan 3-7 September 2018
Keywords: strong lensing, supernovae, JWST, LSST
Published in RUNG: 12.09.2018; Views: 2736; Downloads: 0
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38.
FIRST EFFORT TO FIGHT LIGHT POLLUTION IN MACEDONIA
Tanja Petrushevska, 2018, professional article

Abstract: Light pollution is a serious problem in majority of European countries, with negative effects on the environment, animal life and human health. Not only light pollution is causing unnecessary electricity consumption, it also prevents the citizens to enjoy the dark night sky. Following the experience in Slovenia and Friuli Venezia Giulia, Italy with approaching this problem, we proposed a joined effort to perform field measurements of the light pollution, increase the awareness of this issue to the public and the policy makers in Macedonia. Light pollution is a very interdisciplinary field that necessitates the collaboration of policy makers, environmentalist, amateur and professional astronomers. The proposal was submitted to proESOF initiative in Trieste, Italy. This initiative consists of the organisation of collaborative events in North East Italy and the Balkan countries where the objective is to spread science for the benefit to the citizens. ProESOF events will happen before 2020, after which the main event “Trieste – European City of Science” will follow. Our proposal has been positively judged by the proESOF evaluators, and currently we are waiting for their decision regarding the financial support they will provide. The first step will to train a group of people to perform field measurements of light pollution. The second step is to share these results, so the target is the general public in Macedonia. To successfully fight light pollution, anti-light pollution laws have to be made and enforced, so relevant politicians and law makers in Macedonia will be included. We will use the local team who has experience and contacts with the media, so that this event gets covered well. This will be a first meeting of this kind in Skopje, Macedonia which will join experts of the region and offer new ideas to fight light pollution in Macedonia and the Balkans. Macedonia is one of the few countries that is lacking any initiative when it comes to light pollution. It is very important to act timely, also because in Macedonia there are still some regions with dark sky that can be saved. Italy and Slovenia have collaborated previously on several occasion regarding light pollution: the purpose of the project Public Lighting of the Future that was running from 2011 to 2014 was to create a common methodology and database. After our proposed workshop and measurement, the aim will be to include Macedonia in this common effort to fight light light pollution.
Keywords: light pollution
Published in RUNG: 11.09.2018; Views: 2943; Downloads: 0
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39.
Prospects for lensed supernovae behind galaxy clusters with the James Webb Space Telescope
Tanja Petrushevska, 2018, published scientific conference contribution abstract

Abstract: Galaxies, and clusters of galaxies, can act as gravitational lenses and magnify the light of objects behind them. The effect enables observations of very distant supernovae, that otherwise would be too faint to be detected by existing telescopes, and allows studies of the frequency and properties of these rare phenomena when the universe was young. Under the right circumstances, multiple images of the lensed supernovae can be observed, and due to the variable nature of the objects, the difference between the arrival times of the images can be measured. Since the images have taken different paths through space before reaching us, the time-differences are sensitive to the expansion rate of the universe. One class of supernovae, Type Ia, are of particular interest to detect. Their well known brightness can be used to determine the magnification, which can be used to understand the lensing systems. I will also report our discovery of the first resolved multiply-imaged gravitationally lensed supernova Type Ia. I will also show the expectations of search campaigns that can be conducted with future facilities, such as the James Webb Space Telescope (JWST) or the Wide-Field Infrared Survey Telescope (WFIRST).
Keywords: Strong lensing, Hubble constant, measuring expansion history with time delays, lensed supernovae
Published in RUNG: 09.07.2018; Views: 3479; Downloads: 139
.pdf Full text (4,14 MB)

40.
Searching for supernovae in the multiply-imaged galaxies behind the gravitational telescope A370
Tanja Petrushevska, Ariel Goobar, D. J. Lagattuta, R. Amanullah, Laura Hangard, S. Fabbro, C. Lindman, K. Paech, J. Richard, J.P. Kneib, 2017, original scientific article

Abstract: Aims. Strong lensing by massive galaxy clusters can provide magnification of the flux and even multiple images of the galaxies that lie behind them. This phenomenon facilitates observations of high-redshift supernovae (SNe) that would otherwise remain undetected. Type Ia supernovae (SNe Ia) detections are of particular interest because of their standard brightness, since they can be used to improve either cluster lensing models or cosmological parameter measurements. Methods. We present a ground-based, near-infrared search for lensed SNe behind the galaxy cluster Abell 370. Our survey was based on 15 epochs of J-band observations with the HAWK-I instrument on the Very Large Telescope (VLT). We use Hubble Space Telescope (HST) photometry to infer the global properties of the multiply-imaged galaxies. Using a recently published lensing model of Abell 370, we also present the predicted magnifications and time delays between the images. Results. In our survey, we did not discover any live SNe from the 13 lensed galaxies with 47 multiple images behind Abell 370. This is consistent with the expectation of 0.09 ± 0.02 SNe calculated based on the measured star formation rate. We compare the expectations of discovering strongly lensed SNe in our survey and that performed with HST during the Hubble Frontier Fields (HFF) programme. We also show the expectations of search campaigns that can be conducted with future facilities, such as the James Webb Space Telescope (JWST) or the Wide-Field Infrared Survey Telescope (WFIRST). We show that the NIRCam instrument aboard the JWST will be sensitive to most SN multiple images in the strongly lensed galaxies and thus will be able to measure their time delays if observations are scheduled accordingly.
Keywords: gravitational lensing: strong / supernovae: general / galaxies: clusters: individual: A 370
Published in RUNG: 28.06.2018; Views: 3488; Downloads: 139
.pdf Full text (4,14 MB)

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