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Keywords: 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. The participation at this conference is supported by the Action CA16104 Gravitational waves, black holes and fundamental physics (GWverse), supported by COST (European Cooperation in Science and Technology).
Published in RUNG: 04.01.2021; Views: 2588; Downloads: 0

Abstract: The Pierre Auger Collaboration (Auger) recently reported a correlation between the arrival directions of cosmic rays with energies above 39 EeV and the flux pattern of 23 nearby starburst galaxies (SBGs). In this Letter, we tested the same hypothesis using cosmic rays detected by the Telescope Array experiment (TA) in the 9-year period from May 2008 to May 2017. Unlike the Auger analysis, we did not optimize the parameter values but kept them fixed to the best-fit values found by Auger, namely 9.7% for the anisotropic fraction of cosmic rays assumed to originate from the SBGs in the list and 12.9◦ for the angular scale of the correlations. The energy threshold we adopted is 43 EeV, corresponding to 39 EeV in Auger when taking into account the energy-scale difference between two experiments. We find that the TA data is compatible with isotropy to within 1.1σ and with the Auger result to within 1.4σ, meaning that it is not capable to discriminate between these two hypotheses.
Keywords: astroparticle physics, cosmic rays, galaxies: starburst, methods: data analysis
Published in RUNG: 27.04.2020; Views: 2856; Downloads: 124
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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: 3539; Downloads: 139
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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.
Keywords: supernovae: individual: iPTF16abc – galaxies: individual: NGC 5221 – galaxies: ISM – galaxies
Published in RUNG: 23.01.2018; Views: 3012; Downloads: 0
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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.
Keywords: dust, extinction – galaxies: individual (Messier 82) – supernovae: individual SN2014J
Published in RUNG: 22.01.2018; Views: 3377; Downloads: 0
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