1,721,198 research outputs found
Galactic and extragalactic novae - A Review
Full text linkThe outbursts of classical novae are among the strongest explosions in the Universe. The multifrequency observations are contributing to understanding the process of explosions and of the long term evolution. In this review, I discuss the observations of novae over the electromagnetic spectrum, focusing on the morphology of the decline light curves, the spectroscopic investigations, the long term evolution, the recurrent novae, the gamma ray emission in novae, extragalactic novae and the gravitational emission of novae
An analysis of early spectroscopic observations and the light curve of the nova V1663 Aql (Nova Aql 2005)
No full textI report the results of a spectroscopic follow-up of the nova V1663 Aql performed at the Loiano telescope. The emission lines in the spectra have been identified to study the early evolution. The spectra measured some weeks after the maximum show Balmer lines, several Fe multiplets and low ionization lines. The presence of Fe multiplets confirms the original classification of V1663 Aql as a Fe II nova. I have built the light curve using the observations of IAU circulars, VSNET, AFOEV, ASAS databases to estimate the parameters of the nova: time and magnitude of maximum, and the decline rates by two or three magnitudes. The parameters have been used to deduce a distance of V1663 Aql in the range 7.3 divided by 11.3 kpc. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
The new world discovered with the detection of Gravitational Waves: the era of public alerts
No full textDuring the first three observing runs of LIGO/Virgo/KAGRA Collaboration a total of 90 candidate
gravitational wave events from the mergers of black hole and neutron stars have been detected. Since
then, the O4a run took place and the O4b run is presently ongoing, contributing with the detection
of additional mergers. During the runs, all disseminated gravitational events have been the target
of multi-messenger follow-up observations, and at the same time, there has been searches of
gravitational wave emission from electromagnetic events. The present paper reviews the results
of LIGO-Virgo runs with a focus on the runs in the public alert era
Concept of high speed astronomical instrumentation based on visible light photon counters
No full textThe domain of high speed optical astrophysics is still quite unexplored. The availability of 10 meter diameter telescopes offers the unique possibility to investigate variability of faint objects at submillisecond time scales. In this paper I describe the concepts of a photometer and a spectrometer for high speed astronomical observations. The instruments are based on a photon counting detector developed for high energy physics, the Visible Light Photon Counter (VLPC). The detector has a quantum efficiency in the visible as high as 88% and performs photon counting with sub microsecond time resolution. The photometer is built using VLPC arrays. Adding a grating a VLPC array can be used in a time resolved spectrograph with medium resolution. This paper develops, starting from experimental data, the concept of the two VLPC based instruments and their application to time resolved photometry and spectroscopy of compact objects (pulsars, cataclysmic variables, low mass X-ray binary systems etc) and optical counterparts of Gamma Ray Bursts. The high speed optical observations are the ideal complement to X/gamma rays and gravitational wave studies. The application of the instruments to the optical photometry of pulsars, the spectrophotometry of the prompt optical flash from Gamma Ray Bursts and the study of binary systems are discussed in detail: in the last two applications the instruments offer better opportunities than existing instruments
The spectroscopic evolution of V2362 Cyg (Nova Cygni 2006) in the first 15 months after the outburst
No full textWe present the optical spectral evolution of the nova V2362 Cyg during the first 15 months after the outburst, from 2006 April to 2007 July. The spectroscopy, performed at the Loiano telescope, Italy, covers the evolution from the early decline to the nebular stage. V2362 Cyg exhibited an unusual secondary outburst during the decline. We have used the optical spectroscopy and photometry to investigate the physical properties of the ejecta and to constrain the nova distance. V2362 Cyg is a fast nova, with decline rates by two or three magnitudes of 4.3 and 15.8 days, respectively. The derived magnitude at maximum is M(v) = -9.0. The distance is in the range 7.2-15.8 kpc. Our observations during the first decline showed strong emission lines, typical of a Fe II nova; during the secondary outburst the spectrum reverted to features typical of early decline. After the secondary outburst V2362 Cyg entered the nebular phase. The spectroscopic evolution resembles the history of nova V1493 Aql. (C) 2008 Elsevier B.V. All rights reserved
A multifrequency review of Galactic and Extragalactic Novae
No full textNovae show emission over the whole electromagnetic spectrum and have been suggested as possible neutrino sources. The present paper is an update to the previous review about the multifrequency observations of novae presented at The Golden Age of Cataclysmic Variables and Related Objects V workshop
Estimating Hubble Constant with Gravitational Observations: A Concise Review
No full textThe Hubble constant is of paramount importance in astrophysics and cosmology. A large number of methods have been developed with different electromagnetic probes to estimate its value. The most recent results show a tension between values obtained from Cosmic Microwave Background observations and supernovae. The simultaneous detection of gravitational waves and electromagnetic radiation from GW170817 provided a direct estimation of the Hubble constant that did not depend on the astronomical distance ladder. This concise review will present the methods to estimate the Hubble constant with the gravitational observations of compact binary mergers, discussing both bright and dark sirens and reporting the state of the art of the results
High Energy Astrophysical Techniques
No full textThis textbook presents ultraviolet and X-ray astronomy, gamma-ray astronomy, cosmic ray astronomy, neutrino astronomy, and gravitational wave astronomy as distinct research areas, focusing on the astrophysics targets and the requirements with respect to instrumentation and observation methods.
The purpose of the book is to bridge the gap between the reference books and the specialized literature. For each type of astronomy, the discussion proceeds from the orders of magnitude for observable quantities. The physical principles of photon and particle detectors are then addressed, and the specific telescopes and combinations of detectors, presented.
Finally the instruments and their limits are discussed with a view to assisting readers in the planning and execution of observations.
Astronomical observations with high-energy photons and particles represent the newest additions to multimessenger astronomy and this book will be of value to all with an interest in the field
A POSSIBLE GRAVITY MEASUREMENT WITH ANTIHYDROGEN
No full textA neutral probe such as antihydrogen offers appealing experimental advantages, compared to a charged probe such as antiproton, for a measurement of the gravitational behaviour of antimatter. The feasibility of this approach is preliminarily investigated. A direct extension of the sextupolar ring technique used by Paul is not feasible but the use of a straight sextupole seems to be promising
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