bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radiation Bursts from a Presupernova Collapsar
Authors: Kryvdyk Volodymyr 
Published: June 2019

SummaryThe radiation from the magnetic presupernova star is calculated. This radiation will generate when the magnetosphere of presupernova star compresses during collapse and its magnetic field increases considerably. The variable magnetic field will accelerate the charged particle, which generate radiation when moving in the magnetic field. The particles dynamics and their non-thermal emission in the magnetospheres of presupernova collapsing star with initial dipole magnetic fields and a certain initial energy distribution of charged particles in a magnetosphere are considered. The radiation flux depend on the distance to the star, its magnetic field, and the particle spectrum in the magnetosphere. This flux can be observed by means of modern instruments in broad band (from radio waves to gamma rays). The radiation flux grows with decreasing stellar radius and frequency and can be observed in the form of radiation bursts with duration equal to the stellar collapse time.
Deep Radio Imaging with MERLIN of the Supernova Remnants in M82
Authors: Muxlow T.W.B. , Pedlar A. , Riley J.D. , McDonald A.R. , Beswick R.J. , Wills K.A. 
Published: June 2019

SummaryAn 8 day MERLIN deep integration at 5GHz of the central region of the starburst galaxy M82 has been used to investigate the radio structure of a number of supernova remnants in unprecedented detail revealing new shells and partial shell structures for the first time. In addition, by comparing the new deep 2002 image with an astrometrically aligned image from 36 hours of data taken in 1992, it has been possible to directly measure the expansion velocities of 4 of the most compact remnants in M82. For the two most compact remnants, 41.95+575 and 43.31+592, expansion velocities of 2800 ± 300 km s-1 and 8750 ± 400kms-1have been derived. These confirm and refine the measured expansion velocities which have been derived from VLBI multi-epoch studies. For remnants 43.18+583 and 44.01+596, expansion velocities of 10500 ± 750km s-1 and 2400 ± 250 kms-1have been measured for the first time. In addition, the peak of the radio emission for SNR 45.17+612 has moved between the two epochs implying velocities around 7500km s-1. The relatively compact remnants in M82 are thus found to be expanding over a wide range of velocities which appear unrelated to their size. The new 2002 map is the most sensitive high-resolution image yet made of M82, achieving an rms noise level of 17μJy beam-1. This establishes a first epoch for subsequent deep studies of expansion velocities for many SNR within M82.
Two New Possible Mechanisms of Supernova-Like Explosions
Authors: Tikhomirov V.V. , Yuralevich S.E. 
Published: June 2019

SummaryPrimordial black holes (PBHs) of microscopical size can completely absorb neutron stars (NSs) and white dwarfs (WDs) for less than the Hubble time. NS absorption is accompanied by inverse URCA process giving rise to emission of antineutrino. However considerable part of these antineutrino fails to escape NS being drawn into the growing black hole by accreting NS matter. The final stage of dense WD absorption is accompanied by 1051 erg neutrino burst able to ignite nuclear burning giving rise to supernova-like WD explosion.
Tests for Supernova Explosion Models: from Light Curves to X-ray Emission of Supernova Remnants
Authors: Sorokina Elena , Blinnikov Sergey 
Published: June 2019

SummaryThe successful theoretical supernova explosion models should be able to explain any features of the emission from supernovae at any evolutionary stage. We check several models from two different points of view. With the multi-frequency radiation hydro code STELLA we calculate gamma-ray, bolometric and broad-band UBVI light curves. Then we use the same models to calculate the emission from young supernova remnants. Here we present new plots for gamma-ray luminosity from several SN Ia models and recomputations of bolometric and UBVRI light curves of model 13C for SN 1993J.
Nucleosynthesis in Multi-Dimensional Simulations of SNII
Authors: Travaglio C. , Kifonidis K. , Müller E. 
Published: June 2019

SummaryWe investigate explosive nuclear burning in core collapse supernovae by coupling a tracer particle method to one- and two-dimensional Eulerian hydrodynamic calculations. Adopting the most recent experimental and theoretical nuclear data, we compute the nucleosynthetic yields for 15 M⊙ stars with solar metallicity, by post-processing the temperature and density history of advected tracer particles. We compare our results to 1D calculations published in the literature.
The Infrared Supernova Rate
Authors: Mannucci F. , Cresci G. , Maiolino R. , Valle M.Della 
Published: June 2019

SummaryOptical searches can detect supernovae (SNe) only if they suffer of a limited amount of dust extinction. This is a severe limitation as most of the core-collapse SNe could explode inside dusty regions. We describe a few ongoing projects aimed at detecting dusty SNe at near-IR wavelengths both in ground-based and HST images and to study their properties.
The Rate and the Origin of Type Ia SNe in Radio Galaxies
Authors: Della Valle M. , Panagia N. , Cappellaro E. , Padovani P. , Turatto M. 
Published: June 2019

SummaryAn analysis of type Ia supernova (SNIa) events in early type galaxies from the Cappellaro et al. [6] database provides strong evidence that the rate of type Ia supernovae (SNe) in radio-loud galaxies is about 4 times higher than the rate measured in radio-quiet galaxies, i.e. SNIa-rate(radio-loud) SNe per century and per 1010 (SNU) as compared to SNIa-rate(radio-quiet)= 0.11 ± 0.03 SNU. The exact value of the enhancement is still rather uncertain, but is likely to be in the range ~ 2 – 7. We discuss the possible causes of this result and we conclude that the enhancement of the SNIa explosion rate in radio-loud galaxies has the same common origin as their being strong radio sources, but that there is no causality link between the two phenomena. We argue that repeated episodes of interaction and/or mergers of early type galaxies with dwarf companions are responsible for inducing both strong radio activity in ~14% of early type galaxies, and the ~ 1 Gyr old stellar population needed to supply an adequate number SNIa progenitors.
Supernovae in Galaxy Clusters
Authors: Gal-Yam A. , Maoz D. , Sharon K. , Prada F. , Guhathakurta P. , Filippenko A.V. 
Published: June 2019

SummaryWe present the results of several surveys for supernovae (SNe) in galaxy clusters. SNe discovered in deep, archival HST images were used to measure the cluster SN Ia rate to z = 1. A search for SNe in nearby (0.06 ≤ z ≤ 0.2) Abell galaxy clusters yielded 15 SNe, 12 of which were spectroscopically confirmed. Of these, 7 are cluster SNe Ia, which we will use to measure the SN Ia rate in nearby clusters. This search has also discovered the first convincing examples of intergalactic SNe. We conclude with a brief description of ongoing and future cluster SN surveys.
On the Central Engine of Short Gamma-ray Bursts
Authors: Rosswog Stephan , Ramírez-Ruiz Enrico 
Published: June 2019

SummaryWe assess the ability of neutron star binary coalescence to produce short gamma-ray bursts (GRBs). We find that the neutrino annihilation above the merged remnant will drive bipolar, relativistic jets along the initial binary rotation axis. This outflow can be collimated by the energetic, neutrino-driven baryonic wind that is blown off the remnant. Despite the narrow neutron star mass distribution the apparent luminosities will be spread over a broad range from ~ 1049 to ~ 1052erg s−1, typical jet opening half-angles are around 5 degrees. If the central core of the merger remnant does not collapse immediately convective dynamo action will set in and the available kinetic energy can be transformed into magnetic fields in excess of 1017 G. The corresponding spin-down time scale is ~ 0.2 s, just about the duration of a short GRB.
The Expanding and Accelerating Universe
Authors: Schmidt Brian P. 
Published: June 2019

SummaryMeasuring distances back to a significant portion of the look back time probes the make-up of the Universe, through the effects of different types of matter on the cosmological geometry and expansion. Over the past five years two teams have used type Ia supernovae to trace the expansion of the Universe to a look back time more than 70% of the age of the Universe. These observations show an accelerating Universe which is best explained by a cosmological constant, or other form of dark energy with an equation of state near w = p/ρ = −1. There are many possible lurking systematic effects. However, while difficult to completely eliminate, none of these appears large enough to challenge current results. However, as future experiments attempt to better characterize the equation of state of the matter leading to the observed acceleration, these systematic effects will ultimately limit progress.
Observing the First Stars, One Star at a Time
Authors: Loeb Abraham 
Published: June 2019

SummaryGamma-Ray Bursts (GRBs) are believed to originate in compact remnants (black holes or neutron stars) of massive stars. Their high luminosities make them detectable out to the edge of the visible universe. We describe the many advantages of GRB afterglows relative to quasars as probes of the intergalactic medium during the epoch of reionization. The Swift satellite, planned for launch by the end of 2004, will likely open a new era in observations of the high redshift universe.
A Geometric Determination of the Distance to SN 1987A and the LMC
Authors: Panagia Nino 
Published: June 2019

SummaryUsing the definitive reductions of the IUE light curves by [15] and an extensive set of HST images of SN 1987A we have repeated and improved our original analysis [8, 9] to derive a better determination of the distance to the supernova. In this way we have obtained an absolute size of the ring Rabs = (6.23 ± 0.08) × 1017 cm and an angular size R″ = 808 ± 17 mas, which give a distance to the supernova d(SN1987A) = 51.4±1.2 kpc and a distance modulus (m − M)sN1987A = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to be d(LMC) = 51.7±1.3 kpc, which corresponds to a distance modulus of (m − M)LMC = 18.56 ± 0.05.
Use of the World Wide Web in astronomy teaching
Authors: Pasachoff Jay M. 
Published: June 2019

I discuss the burgeoning World Wide Web and how it can be used to aid astronomy teaching.I supply a list of a variety of useful Web sites.The World Wide Web was invented 5 years ago at CERN, which is now translated as the European Laboratory for Particle Physics, as a way of aiding access to information from remote sites. The invention of graphic interfaces, notably Mosaic by a group at the National Supercomputer Center in Illinois and then Netscape Navigator as a private development by many of the original Mosaic people, led to an explosion in use of the Web. Millions of people around the world are now able to access information from over 100,000 Web sites.There is much astronomical information on the Web, though that information make up only a small fraction of all the information available through this medium.
Alternative frameworks amongst University of Plymouth Astronomy Students
Authors: Broughton Mike P.V. 
Published: June 2019

In recent years much research into conceptual understanding of science has been carried out. Oddly, Astronomy (one of the smallest sciences in terms of pupil numbers) is possibly one of the most widely studied subjects, with numerous papers being produced revealing the intuitive ideas of (usually) young school children. Within these papers it is generally recognised that if students cannot assimilate the fundamental concepts of a subject, then their own initial frameworks are altered accordingly, producing mis-conceptions.Much of this research into pre/mis-conceptions, alternative frameworks etc, has been concerned with the knowledge of gravity or the shape of the Earth, the Sun and other such bodies. Another area heavily researched is that of phases/eclipses, and how the young children of today perceive these phenomena.The research presented here takes the findings from earlier papers and extends it by assessing astronomy students at the University of Plymouth.
Robot Telescopes: a new era in access to astronomy
Authors: Baruch J.E.F. 
Published: June 2019

For the teaching of astronomy there can be no alternative to the hands-on experience of using instruments on a real telescope observing on a clear dark night. Such experience is not possible for millions of students who are excited by the ideas of astronomy. It is not merely one of cost. The logistics of assembling a class of students after school hoping for clear skies destroys the possibilities of real observing for the majority of students. Robot telescopes change all that.In educational terms a robot telescope can provide a range of experiences of observational astronomy. The development of CD-ROM and the Internet to support classroom learning have produced the concept of REAL(Dunlap 1996): a Rich Environment for Active Learning as an appropriate framework on which to develop the classroom response to these technologies. The Bradford Robot Telescope has demonstrated student centred experiences to generate a Rich Environment for Active Learning(REAL), for astronomy.
How to Suceed in Convincing Municipalities to build Astronomy Centres: the experience of Campinas Region
Authors: Bretones A.L.K. , Bretones P.S. 
Published: June 2019

The objective of this work is to make known the astronomical activities in the region of Campinas, the process of developing municipal cooperation and the general conclusions that reflect this process.This research has been done by means of interviews with people related to the creation of astronomical centers in the region of the city of Campinas that is located in the state of São Paulo in Brasil (Fig. 1 and 2).The conditions studied are related with this region but many ideas could be used in developing countries or others.
Astronomy as a School Subject
Authors: Fouquet J-L. 
Published: June 2019

a) From 9 to 11, a “Science and Technology” curriculum is extensively provided by primary schools :“Pupils, through some aspects of the scientific approach, are encouraged to develop their abilities to formulate questions and logical answers through a wide scope of investigative and practical observations and other scientific activities such as collecting measures, linking data, interpreting documents“ - extract from the official syllabus which includes the following chapters :1. Unity and Diversity of the Living World :•the development of living creatures,•animal reproduction,•human sexuality,•ecology,•nutrition.
A Program Incorporating Physics, Astronomy and Environment
Authors: Kononovich E.V. , Fadeeva A.A. , Kiselev D.F. , Zasov A.V. 
Published: June 2019

A cultural role of astronomical education at all levels is well known and it is needless to repeat the corresponding arguments. Nobody denies it, but nobody can propose any universal way of introducing Astronomy on a level this branch of science deserves.There is a good tradition to appreciate Astronomy in Russian schools. For more than a century part of the natural history science in school dedicated to the Universe has been considered as a separate part of the school curriculum in Russia. Before 1917 it was named Cosmography, and Astronomy thereafter. And up to now there is no decision or prescription to rule it out of the school program.
Magnetic Fields in Be Stars? (Review Paper)
Authors: Barker Paul K. 
Published: June 2019

AbstractNo mean longitudinal or toroidal magnetic fields have yet been detected on any classical Be star. Models of stellar winds and circumstellar envelopes around magnetic Be stars are not appreciably constrained by present observed upper limits on field strength. A few magnetic Be stars do exist among the helium strong stars, but these objects show spectral phenomenology which is unmistakably distinct from that shown by every other object known as a Be star.
Is HR 9070 Really Pulsating?
Authors: J.P. Sareyan , M. Alvarez , J. Chauville , J.M. Le Contel , R. Michel , D. Ballereau 
Published: June 2019

As Be stars and classical β CMa variables both have a distribution peak at B2, one can wonder if there is a connection between these two phenomena. A way to solve this problem could be to carry out a systematic survey of emission on short periodic B variables,over months and years.Another way, chosen by our grouns in Nice, Ensenada and Meudon, is to improve time resolution in photometric and spectrographic observations on the Be stars already known to have short time scale variations. Special attention is paid to longitude cooperation, essential to detect or measure longer time constants.
Some Important Results From Two Photometric Campaigns on Short Term Variability in Be Stars
Authors: Stagg C.R. 
Published: June 2019

In 1983 and 1984 a programme of UBV observations was carried out to set up a network of standard stars, identify short term variables, and analyse the variability of the 86 bright (V ≳ 6.5) southern (δ < -20°) Be stars.The timing of the observations was designed specifically to reveal short term variability. Each group of Be and comparison stars was observed at least four times. Where possible, the first two sets of observations were made on one night and the next two sets on the next night (and sometimes a fifth set of observations was also made). Eleven Be stars were identified as possible short or intermediate term variables (Stagg, in preparation). These included the Be star 28 ω CMa, whose V and B-V (but not U-B) variations were consistent with the spectroscopic period of 1.37 days found by Baade (1982).
Rotating Stellar Atmospheres (Review Paper)
Authors: Cassinelli Joseph P. 
Published: June 2019

AbstractThe effects of rapid rotation on the emergent energy distribution, line profiles, atmospheric motions and polarization are discussed. A simplified explanation of some of the effects is presented. Results of detailed radiation transfer calculations are briefly reviewed. The rotation can lead to circulation and turbulent motions in the photospheric layers which could affect the outflow from the Be stars. The rotation rates actually observed in the Be stars are sufficiently below the critical rate that many of the effects predicted by the plane parallel atmosphere calculations should be small. Nevertheless, the models are useful and necessary for estimating rotation speeds from lines that are widely separated in wavelength. The rapidly rotating photospheric models predict far too small an infrared excess, as well as too small an intrinsic polarization. The explanation of these observations requires that geometrically extended envelopes be considered. Theoretical models for the intrinsic polarization are critically discussed. It is stressed that polarization is a powerful diagnostic for determining the asymmetrical structure of the outer atmospheres of the Be stars.
Double Periodicity in Be Stars
Authors: Clarke D. , McGale P.A. 
Published: June 2019

SummaryPhotometric periodicities with two unequal maxima and minima reported for Be stars are shown to result from a fundamental and overtone associated with rotation of an atmospheric bulge. It is the form of the scattering function of the free electron that produces the double periodicity; the stellar geometry — co-latitude of the bulge and inclination of the stellar rotational pole — controls the amplitudes of the two components. The form of the light curves is consistent with the oblique rotator model.
Long-Term Polarization Changes of 88 Her
Authors: Arsenijević J. , Jankov S. , Djurašević G. 
Published: June 2019

AbstractLinear optical polarization of 88 Her has been measured in V spectral region during the period 1974–1985. The mean annual values of the intrinsic polarization parameters are presented. The polarization percentage changes from 0.15%(1976) to 0.56%(1979). Small values of the polarization percentage correspond to the period when the envelope effect is negligible. The maximum of polarization percentage has been found during the early period of strong shell phase. The polarization position angle varies between 53 and 83 degrees.
Profiles of Emission Lines From Rotating Disks
Authors: Brown D.A. 
Published: June 2019

Profiles of emission lines contain key information on the dynamics, the physical condition, and the geometry of the cool envelopes of Be stars. Despite much observational evidence, doubts persist about the rotating, equatorial ring model first proposed by Struve (1931) to explain the gross features of the profiles and later developed by Huang (1972) in the two-dimensional, transparent limit. The basic rotating model is now reconsidered and profile formation studied from a physical point of view.The excitation structure of a disk rotating around a B star in circular, Keplerian orbits is computed by means of a new, iterative approach. The approach takes full account of both stellar and diffuse radiation at line and continuum frequencies and makes no assumptions about the optical properties of the disk. It is applied to an isothermal model with parameters based on observations of the shell star 48 Librae.
HE I Lines in the BE + K Binary KX and
Authors: Štefl S. 
Published: June 2019

KX And (HD 218:193) is a peculiar interacting binary with the period of about 38.9 days. This study is a first attempt to model the system as a double-line binary. The main results of the He I - line analysis are summarized.The intensity tracings of sixty blue-violet spectra were used. All the spectra were obtained in the coudé focus of the Ondřejov 2m telescope in the period 1972 – 1981. The original dispersion was 8 or 16 A mm -l. The phases of the observations were computed according to the ephemeris derived from the radial velocities of optical shell lines (Štefl et al. in preparation). Phase zero corresponds to the velocity maximum.
On the Percentage of Be Stars in Galactic Open Clusters
Authors: Reitermann A. , Krautter J. , Wolf B. , Bashek B. 
Published: June 2019

Knowing that especially young clusters can contain a considerable high fraction of Be stars (Mermilliod 1982, Feast 1972) we made a spectroscopic study of Hα on the ratio of B/Be stars. The aim was to select normal B stars for chemical abundance analyses.It is well known that a promising way to investigate the evolutionary status of Be stars is to study their frequency and positions in the H-R diagram of open clusters. However, these studies have not yet provided satisfactory results (cf. e.g. Slettebak 1985); observations concerning the B/Be star ratio are badly needed. Therefore we present our observations although they are only a by-product from a different program.
The Infrared Period - 2.2/µm Magnitude Relation for RR Lyrae Stars
Authors: Longmore A.J. 
Published: June 2019

AbstractThe observational and theoretical basis for the log P vs. K-mag relation is reviewed. The observed gradient in all well observed globular clusters agrees well with the theoretical prediction. An indistinguishable result is found for field RR Lyrae stars whose absolute magnitudes have been determined from infrared Baade-Wesselink analyses. A full reference list is given for the source of these magnitudes. Application of the results to find the distance to globular clusters and the Galactic Centre is discussed.