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1.
2.
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: ključnih besedah
Summary of found: ...Modern wide-field, optical time-domain surveys must solve a basic optimization problem: maximize...
Keywords: methods: observational – surveys – supernovae: general – supernovae: individual (SN 2002cx, SN 2005hk, iPTF 16fnm)
Published: 23.01.2018; Views: 1241; Downloads: 0
.pdf Fulltext (2,37 MB)

3.
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: ključnih besedah
Summary of found: ...properties are found, their utility for future surveys could be challenged. We investigate whether the...
Keywords: supernovae, gravitational telescopes, galaxy clusters, lensed supernovae, strong lensing, astronomical surveys and telescopes
Published: 23.01.2018; Views: 1705; Downloads: 0
.pdf Fulltext (28,31 MB)

4.
Indications of Intermediate-Scale Anisotropy of Cosmic Rays with Energy Greater Than 57 EeV in the Northern Sky Measured with the Surface Detector of the Telescope Array Experiment
J. P. Lundquist, R.U. Abbasi, 2014, original scientific article

Abstract: We have searched for intermediate-scale anisotropy in the arrival directions of ultrahigh-energy cosmic rays with energies above 57 EeV in the northern sky using data collected over a 5 year period by the surface detector of the Telescope Array experiment. We report on a cluster of events that we call the hotspot, found by oversampling using 20∘-radius circles. The hotspot has a Li-Ma statistical significance of 5.1σ, and is centered at R.A.=146.7∘, Dec.=43.2∘. The position of the hotspot is about 19∘ off of the supergalactic plane. The probability of a cluster of events of 5.1σ significance, appearing by chance in an isotropic cosmic-ray sky, is estimated to be 3.7×10−4 (3.4σ).
Found in: ključnih besedah
Keywords: acceleration of particles, cosmic rays, large-scale structure of universe, surveys
Published: 24.04.2020; Views: 873; Downloads: 0
.pdf Fulltext (529,81 KB)

5.
A Northern Sky Survey for Point-Like Sources of EeV Neutral Particles with the Telescope Array Experiment
J. P. Lundquist, R.U. Abbasi, 2015, original scientific article

Abstract: We report on the search for steady point-like sources of neutral particles around 1018 eV between 2008 and 2013 May with the scintillator SD of the Telescope Array experiment. We found overall no significant point-like excess above 0.5 EeV in the northern sky. Subsequently, we also searched for coincidence with the Fermi bright Galactic sources. No significant coincidence was found within the statistical uncertainty. Hence, we set an upper limit on the neutron flux that corresponds to an averaged flux of 0.07 km−2 yr−1 for E > 1EeV in the northern sky at the 95% confidence level. This is the most stringent flux upper limit in a northern sky survey assuming point-like sources. The upper limit at the 95% confidence level on the neutron flux from Cygnus X-3 is also set to 0.2 km−2 yr−1 for E > 0.5 EeV. This is an order of magnitude lower than previous flux measurements.
Found in: ključnih besedah
Keywords: acceleration of particles, cosmic rays, surveys
Published: 24.04.2020; Views: 1171; Downloads: 0
.pdf Fulltext (1,63 MB)

6.
Fermi Large Area Telescope fourth source catalog
S. Abdollahi, F. Acero, M. Ajello, W. B. Atwood, M. Axelsson, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, Gabrijela Zaharijas, 2020, original scientific article

Found in: ključnih besedah
Keywords: astronomy, gamma rays, sky surveys
Published: 22.05.2020; Views: 699; Downloads: 28
.pdf Fulltext (2,55 MB)
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7.
TDEs with LSST
Katja Bricman, 2018, published scientific conference contribution abstract

Abstract: The Large Synoptic Survey Telescope (LSST) is an upcoming ground-based survey telescope in Chile, which will produce a multi-color survey of 18000 square degrees of the Southern Sky during its 10 years of observations. Due to its large coverage of the sky and its observing strategy it will be a perfect tool in search for transient astrophysical events, including rare Tidal Disruption Events (TDEs). TDEs occur when a star passes close by a supermassive black hole (SMBH) in a center of a galaxy and gets disrupted by its tidal forces. These events emit a bright flare of light, which can be observed to cosmological distances. In the seminar I will provide an overview of the LSST and TDEs, and present the preliminary results on the estimated absolute rates of TDE detection in 10 years of LSST operations, which were obtained by simulations of TDE light curves with an end-to-end LSST simulations framework.
Found in: ključnih besedah
Keywords: Tidal Disruption Events, Supermassive Black Holes, Sky Surveys
Published: 04.01.2021; Views: 373; Downloads: 13
.pdf Fulltext (1009,99 KB)

8.
The prospects of observing Tidal Disruption Events with the Large Synoptic Survey Telescope (LSST)
Andreja Gomboc, Katja Bricman, 2018, published scientific conference contribution abstract

Found in: ključnih besedah
Keywords: Tidal disruption events, sky surveys
Published: 04.01.2021; Views: 365; Downloads: 0
.docx Fulltext (548,11 KB)

9.
Studying TDEs in the era of LSST
Katja Bricman, Andreja Gomboc, 2019, published scientific conference contribution abstract

Abstract: The observing strategy with continuous scanning and large sky coverage of the upcoming ground-based Large Synoptic Survey Telescope (LSST) will make it a perfect tool in search of rare transients, such as Tidal Disruption Events (TDEs). Bright optical flares resulting from tidal disruption of stars by their host supermassive black hole (SMBH) can provide us with important information about the mass of the SMBH involved in the disruption and thus enable the study of quiescent SMBHs, which represent a large majority of SMBHs found in centres of galaxies. These types of transients are extremely rare, with only about few tens of candidates discovered so far. It is expected that the LSST will provide a large sample of new TDE light curves. Here we present simulations of TDE observations using an end-to-end LSST simulation framework. Based on the analysis of simulated light curves we estimate the number of TDEs with good quality light curves the LSST is expected to discover in 10 years of observations. In addition, we investigate whether TDEs observed by the LSST could be used to probe the SMBH mass distribution in the universe.
Found in: ključnih besedah
Keywords: Tidal Disruption Events, sky surveys
Published: 04.01.2021; Views: 364; Downloads: 15

10.
Observing TDEs in the era of LSST
Katja Bricman, 2019, published scientific conference contribution abstract

Abstract: The upcoming Large Synoptic Survey Telescope (LSST) will observe ~18000 square degrees of the Southern sky and is expected to discover thousands of transients every night due to its large coverage of the sky and its observing strategy. Being an exceptional transient hunter, we expect the LSST to increase the current observed sample of Tidal Disruption Events (TDEs) by a factor of ~1000 in 10 years of survey duration. TDEs are one of the only probes of dormant supermassive black holes in the Universe, and if their observed optical light curves are sampled frequently enough, TDEs can serve as indicators of SMBH mass. In this talk I will present our simulations of TDE observations with LSST, the resulting SMBH mass distributions of observed TDEs, and the efficiency of different proposed observing strategies of LSST in finding these rare transients.
Found in: ključnih besedah
Keywords: Tidal Disruption Events, sky surveys
Published: 04.01.2021; Views: 347; Downloads: 14
.pdf Fulltext (15,43 MB)

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