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High-redshift supernova rates measured with the gravitational telescope A1689
Tanja Petrushevska, 2016, published scientific conference contribution abstract

Abstract: 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 ± 0.01 SNuB h2 (SNuB ≡ −0.09 10−12 SNe L−1 yr−1 ), where the error bars indicate 1σ confidence intervals, statistical and systematic, respectively. The cluster rate ⊙,B normalized by the stellar mass is 0.10+0.13 ± 0.02 in SNuM h2 (SNuM ≡ 10−12 SNe M−1 yr−1). Furthermore, we explore the optimal −0.06 ⊙ 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.
Keywords: supernova, gravitational telescope, galaxy clusters, Abell 1689, strong lensing
Published in RUNG: 26.01.2018; Views: 3370; Downloads: 0
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134.
GRB 160227A: NOT redshift
Dong Xu, Tanja Petrushevska, 2016, final research report

Keywords: Gamma Ray Burst classification, GRB, Nordic Optic Telescope
Published in RUNG: 24.01.2018; Views: 3457; Downloads: 0
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135.
High-Energy Astroparticle Detection
Lili Yang, invited lecture at foreign university

Abstract: Astroparticle Physics has evolved as a new interdisciplinary field at the intersection of particle physics, astronomy and cosmology, addressing some of the most fundamental questions of contemporary physics. Neutrinos, cosmic rays, gamma rays and also gravitational waves as the cosmic messengers, take the information from the universe to tell us more about those energetic astro phenomena. Physicists have been developing experiments to detect and study these messengers. I would like to talk about the basic ideas and searching results from the dedicate cosmic ray detector Pierre Auger Observatory and also the future performance of Cherenkov Telescope Array (CTA), the next-generation ground based telescope array. CTA will play an very important role in detecting GeV-TeV gamma rays and represents the era of precision gamma ray astronomy. The multi-messenger and multi-wavelength study with various messengers are the main field in astrophysics.
Keywords: Cherenkov Telescope Array
Published in RUNG: 17.01.2018; Views: 3727; Downloads: 0
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136.
Simulations of Tidal Disruption Events Observations with the LSST
Katja Bricman, 2017, master's thesis

Abstract: The Large Synoptic Survey Telescope (LSST) will produce a multi-colour survey of 25000 square deg of the Southern sky during its 10 years of operations. It will observe over 20 billion galaxies and a similar number of stars, map the Solar System and the Milky Way, and probe dark matter and dark energy. In addition, it will discover thousands of transients every night, including new classes of objects, which have not yet been observed. Due to its large coverage of the sky it will be a perfect tool for the search of rare Tidal Disruption Events (TDEs), which occur when a star passes close by a supermassive black hole and gets disrupted by its tidal force. Afterwards the stellar debris fall back to the black hole, initially at a rate exceeding the Eddington rate, producing an outflow, which releases a flare of energy. When the fallback rate subsides below the Eddington rate, the gas accretes onto the black hole via accretion disk. The LSST simulation framework enables us to simulate observations of different types of objects with the LSST. In this work, we include TDEs in the LSST simulation framework, estimate the number of detected TDEs, and simulate their light curves using a theoretical model, which predicts a t^(-2.6) light curve decline with time in the outflow phase and a t^{-0.4} decline in the disk phase. We also take a closer look at the distribution of the detected TDEs over cosmological redshift and black hole mass.
Keywords: Astronomical observations, Large Synoptic Survey Telescope, Tidal Disruption Events, Black Holes, simulations
Published in RUNG: 17.10.2017; Views: 4322; Downloads: 0
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