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1.
2.
New limits on Quantum Gravity energy scale with PKS 2155-304 H.E.S.S. data using a likelihood fit
Serguei Vorobiov, J. Bolmont, 2010, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ...y-ray telescopes, H.E.S.S. system, Cherenkov telescopes, active galaxies, quantum gravity, Lorentz invariance breaking, ...
Keywords: ground based y-ray telescopes, H.E.S.S. system, Cherenkov telescopes, active galaxies, quantum gravity, Lorentz invariance breaking
Published: 25.04.2014; Views: 3419; Downloads: 21
URL Fulltext (0,00 KB)

3.
Searching for Pair Halos
Serguei Vorobiov, Lisa Fallon, 2010, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ...y-ray telescopes, H.E.S.S. system, Cherenkov telescopes, active galaxies, extragalactic background light, electromagnetic cascades, pair halos,...
Keywords: ground based y-ray telescopes, H.E.S.S. system, Cherenkov telescopes, active galaxies, extragalactic background light, electromagnetic cascades, pair halos
Published: 25.04.2014; Views: 4064; Downloads: 17
URL Fulltext (0,00 KB)

4.
THE RISE OF SN 2014J IN THE NEARBY GALAXY M82
Ariel 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, original scientific article

Abstract: 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.
Found in: ključnih besedah
Summary of found: ...dust, extinction – galaxies: individual (Messier 82) – supernovae: individual (SN...
Keywords: dust, extinction – galaxies: individual (Messier 82) – supernovae: individual (SN 2014J)
Published: 22.01.2018; Views: 2760; Downloads: 0 
(1 vote)
.pdf Fulltext (2,55 MB)

5.
THE PECULIAR EXTINCTION LAW OF SN 2014J MEASURED WITH THE HUBBLE SPACE TELESCOPE
Rahman 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, original scientific article

Abstract: 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.
Found in: ključnih besedah
Summary of found: ...dust, extinction – galaxies: individual (Messier 82) – supernovae: individual SN2014J...
Keywords: dust, extinction – galaxies: individual (Messier 82) – supernovae: individual SN2014J
Published: 22.01.2018; Views: 2373; Downloads: 0
.pdf Fulltext (683,44 KB)

6.
High-redshift supernova rates measured with the gravitational telescope A 1689
Tanja Petrushevska, R. Amanullah, Ariel Goobar, S. Fabbro, Joel Johansson, Tor Kjellsson, Chris Lidman, K. Paech, Johan Richard, H. Dahle, Raphael Ferretti, J.P. Kneib, M. Limousin, Jakob Nordin, V. Stanishev, 2016, original scientific article

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 −0.09 ± 0.01 SNuB h 2 (SNuB ≡ 10−12 SNe L −1 ,B yr−1), where the error bars indicate 1σ confidence intervals, statistical and systematic, respectively. The cluster rate normalized by the stellar mass is 0.10+0.13 −0.06 ± 0.02 in SNuM h 2 (SNuM ≡ 10−12 SNe M−1 yr−1). Furthermore, we explore the optimal 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.
Found in: ključnih besedah
Summary of found: ...supernovae: general – gravitational lensing: strong – galaxies: star formation – galaxies: clusters: individual: A...
Keywords: supernovae: general – gravitational lensing: strong – galaxies: star formation – galaxies: clusters: individual: A 1689 – techniques: photometric
Published: 23.01.2018; Views: 2535; Downloads: 0
.pdf Fulltext (2,64 MB)

7.
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: ključnih besedah
Summary of found: ...of NGC 5221 with one of its neighbouring galaxies in the past ∼109 yr. In the...
Keywords: supernovae: individual: iPTF16abc – galaxies: individual: NGC 5221 – galaxies: ISM – galaxies
Published: 23.01.2018; Views: 2045; Downloads: 0
.pdf Fulltext (1,57 MB)

8.
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: ključnih besedah
Summary of found: ...< 0 mag) nuclear transients in red host galaxies. Using Swift follow-up UV and X-ray imaging,...
Keywords: accretion, accretion disks – black hole physics – galaxies: nuclei – ultraviolet: general
Published: 02.03.2022; Views: 454; Downloads: 21
.pdf Fulltext (1,18 MB)

9.
An Indication of Anisotropy in Arrival Directions of Ultra-high-energy Cosmic Rays through Comparison to the Flux Pattern of Extragalactic Gamma-Ray Sources
Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Darko Veberič, Marta Trini, Samo Stanič, Ahmed Saleh, Gašper Kukec Mezek, Andrej Filipčič, A. Aab, 2018, original scientific article

Found in: ključnih besedah
Summary of found: ...astroparticle physics, cosmic rays, active galaxies, starburst galaxies, data analysis methods...
Keywords: astroparticle physics, cosmic rays, active galaxies, starburst galaxies, data analysis methods
Published: 14.02.2018; Views: 2419; Downloads: 0
.pdf Fulltext (2,83 MB)

10.
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.
Found in: ključnih besedah
Keywords: gravitational lensing: strong / supernovae: general / galaxies: clusters: individual: A 370
Published: 28.06.2018; Views: 2420; Downloads: 116
.pdf Fulltext (4,14 MB)

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