1. Tidal Disruption Events seen through the eyes of Vera C. Rubin ObservatoryKatja Bučar Bricman, 2021, doctoral dissertation Abstract: Tidal Disruption Events (TDEs) are rare transients, which are considered to be promising tools in probing supermassive black holes (SMBHs) and their environments in quiescent galaxies, accretion physics, and jet formation mechanisms. The majority of $\approx$ 60 detected TDEs has been discovered with large field of view time-domain surveys in the last two decades. Currently, about 10 TDEs are discovered per year, and we expect this number will increase largely once the Legacy Survey of Space and Time (LSST) at Vera C. Rubin Observatory begins its observations.
In this work we demonstrate and explore the capabilities of the LSST to study TDEs. To begin with, we simulate LSST observations of TDEs over $10$ years of survey duration by including realistic SED models from MOSFiT into the simulation framework of the LSST. SEDs are then converted into observed fluxes and light curves are simulated with the LSST observing strategy minion_1016. Simulated observations are used to estimate the number of TDEs the LSST is expected to observe and to assess the possibility of probing the SMBH mass distribution in the Universe with the observed TDE sample. We find that the LSST has a potential of observing ~1000 TDEs per year, the exact number depending on the SMBH mass distribution and the adopted observing strategy. In spite of this large number, we find that probing the SMBH mass distribution with LSST observed TDEs will not be straightforward, especially at the low-mass end. This is largely attributed to the fact that TDEs caused by low-mass black holes ($\le 10^6 M_\odot$) are less luminous and shorter than TDEs by heavier SMBHs ($> 10^6 M_\odot$), and the probability of observationally missing them with LSST is higher.
Second, we built a MAF TDE metric for photometric identification of TDEs based on LSST data. We use the metric to evaluate the performance of different proposed survey strategies in identifying TDEs with pre-defined identification requirements. Since TDEs are blue in color for months after peak light, which separates them well from SNe and AGN, we include u-band observations as one of the criteria for a positive identification. We find that the number of identified TDEs strongly depends of the observing strategy and the number of u-band visits to a given field in the sky. Observing strategies with a larger number of u-band observations perform significantly better. For these strategies up to 10% of LSST observed TDEs satisfy the identification requirements.
Keywords: Ground-based ultraviolet, optical and infrared telescopes
Astronomical catalogs, atlases, sky surveys, databases, retrieval systems, archives, Black holes, Galactic nuclei (including black holes), circumnuclear matter, and bulges, Infall, accretion, and accretion disks
Published in RUNG: 03.01.2022; Views: 3912; Downloads: 89
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2. Observing TDEs in the era of LSSTKatja Bricman, 2020, 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 most promising phenomena in the study of dormant supermassive black holes (SMBHs) in the Universe, and if their observed optical light curves are sampled frequently enough, TDEs can serve as indicators of SMBH mass. We present our simulations of TDE observations with the LSST, the resulting SMBH mass distributions of observed TDEs, and the efficiency of different proposed observing strategies of the LSST in finding these rare transients.
Keywords: Tidal Disruption Events, Supermassive black holes, sky surveys
Published in RUNG: 04.01.2021; Views: 3277; Downloads: 0
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4. Studying TDEs in the era of LSSTKatja 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.
Keywords: Tidal Disruption Events, sky surveys
Published in RUNG: 04.01.2021; Views: 3580; Downloads: 86
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5. Observing TDEs in the era of LSSTKatja 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.
Keywords: Tidal Disruption Events, sky surveys
Published in RUNG: 04.01.2021; Views: 3303; Downloads: 69
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6. TDEs with LSSTKatja 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.
Keywords: Tidal Disruption Events, Supermassive Black Holes, Sky Surveys
Published in RUNG: 04.01.2021; Views: 3850; Downloads: 67
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7. Fermi Large Area Telescope fourth source catalogS. Abdollahi, Fabio Acero, M. Ajello, W. B. Atwood, M. Axelsson, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, Gabrijela Zaharijas, 2020, original scientific article Keywords: astronomy, gamma rays, sky surveys
Published in RUNG: 22.05.2020; Views: 3627; Downloads: 201
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8. A Northern Sky Survey for Point-Like Sources of EeV Neutral Particles with the Telescope Array ExperimentR.U. Abbasi, Jon Paul Lundquist, 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.
Keywords: acceleration of particles, cosmic rays, surveys
Published in RUNG: 24.04.2020; Views: 4350; Downloads: 0
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9. 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 ExperimentR.U. Abbasi, Jon Paul Lundquist, 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).
Keywords: acceleration of particles, cosmic rays, large-scale structure of universe, surveys
Published in RUNG: 24.04.2020; Views: 3948; Downloads: 0
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10. Color Me Intrigued: The Discovery of iPTF 16fnm, an SN 2002cx-like ObjectA. 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.
Keywords: methods: observational – surveys – supernovae: general – supernovae: individual (SN 2002cx, SN
2005hk, iPTF 16fnm)
Published in RUNG: 23.01.2018; Views: 3958; Downloads: 0
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