bluuebunny/crossref_metadata_2025 huggingface dataset:
The Planetoid-Impact Hypothesis of CP F, A, and B Star Formation: Possibilities and Perspectives
Authors: Drobyshevski E.M.
Published: July 2016

A possibility is analyzed of explaining the chemical anomalies of chemically peculiar (CP) F-A-B stars basing on the assumption of the formation of a large number of moonlike planetoids both in the course of separation of the components and in late stages of close binary evolution.

Primitive igneous differentiation of such planetoids results in their crust becoming deficient in Mg, Ca, Sc and enriched in Pe, Sr, Ba, and the Rare Earths. Infall of such planetoids or crust fragments ejected in their collisions with one another onto an A star makes it Am-type. The deficiency of some elements relative to normal abundance can be accounted for if one assumes that these elements present in the matter streaming from one binary component to another condense with subsequent rain-out into a component or formation of the planetoids.

The more diverse and complex anomalies (including the separation of isotopes) can be explained in the same context of the close binary evolution by invoking the ideas of magnetic cosmochemistry which considers the consequences of extremely nonequilibrium processes associated with the flow of magnetic-field generated electrical currents through a rarefied matter in space.
The Historical Contribution of Amateurs to the Study of Double Stars
Authors: Couteau P.
Published: July 2016

Double stars are favourite objects for amateurs, who can see them with modest instruments and easily observe their eventual motion. Moreover, it is possible to calculate their orbits, and even masses, with no other equipment than a pencil, a piece of thread and two pins to draw the ellipses that these systems have been following for centuries.

Binary stars are part of those classes of objects whose geometrical structure remains the same at different scales, they are internally homothetic and represent a field to which fractal geometry may be applied. All this explains the popularity of these objects with amateurs: anyone is able to see some of them, whatever the power of their instruments.
Amateur Astronomy in Poland: Past and Present
Authors: Turaj Katarzyna
Published: July 2016

Amateur astronomy in Poland has its own history dating from the 17th century to the present day. Before the 17th century, the term “amateur astronomer” loses its meaning. Otherwise we might pose the rather paradoxical question: “Was Copernicus an amateur?” and probably have to give the answer: “Yes, he was an amateur, being first a priest, a physician and a lawyer.” Let us leave him in peace and instead turn to more undoubted amateurs. The history can be divided into two general periods: before and after the creation of the Polish Amateur Astronomical Society, PA AS (Polskie Towarzystwo Milosników Astronomii – PTMA). Here we present 16 Polish amateur astronomers who contributed to astronomy from the 17th to the 20th centuries, except Jan Heweliusz – the greatest – who is discussed elsewhere (1). All are selected from a much larger group, the selection being made in accordance with the rules described in the very useful and practical “Criteria for identifying an astronomer as an amateur”, formulated by Tom Williams a few years ago and presented here (2). There is also a short history and current information about the PAAS. Finally, we summarize successes and failures of amateur astronomy in Poland and put some general questions about its future.
Amateur Astronomers and the Hubble Space Telescope
Authors: Edberg Stephen J.
Published: July 2016

In December 1985 the leaders of major amateur astronomy organizations in the U.S. met with the director and staff of the Space Telescope Science Institute (STScI) at their invitation to discuss the possibility of organizing a program for U.S. citizens who don’t work professionally in astronomy to make use of the Hubble Space Telescope. Director Riccardo Giaconni’s previous successful experience in cooperating with the American Association of Variable Star Observers (AAVSO) on studies of various objects with the orbiting High Energy Astronomy Observatory prompted him to bring together representative of the AAVSO, Association of Lunar and Planetary Observers (ALPO), Astronomical League (AL), International Amateur-Professional Photoelectric Photometry (IAPPP), Independent Space Research Group (ISRG), International Occultation Timing Association (IOTA), and Western Amateur Astronomers (WAA) to work out an approach to making HST observing time available to amateur astronomers, educators, and anyone else who might have a good research idea. Dr Giaconni offered to make some of his director’s discretionary time available to qualified non-professional astronomers if the representatives present would design and carry out a program to find the good research ideas and have them ready for his selection. They would then be inserted in the HST observing program once the first six months of Guaranteed Time Observations had been carried out and the regular General Observing program had begun. With this as its charge, the representatives organized themselves into the Amateur Astronomers Working Group and have prepared a procedure for the selection of non-professional researchers to use the Hubble Space Telescope.
Achievements in Astronomical Video Data Collection
Authors: Maley Paul D.
Published: July 2016

Observation by amateurs has been traditionally viewed with some suspicion by the professional astronomical community, especially in the case of transient events(1). For example, data from variable star monitoring where information from many observers can be integrated over long intervals, have a higher weight than visual observations of an asteroid occultation. Serious amateurs who choose to contribute to the science face a continuing challenge to maintain the highest standards.

In an effort to upgrade the quality of information transmitted to professional institutions, we have experimented since 1984 with a baseline design of mobile video equipment which can be coupled to objective lenses ranging from 28mm to 625mm aperture (2).
Video Grazing Occultations
Authors: Dunham David W.
Published: July 2016

Grazing occultations are always visible at the projections onto the surface of the Earth of the lines tangent to the lunar limb that are created by the motion of the Moon relative to the star being occulted.

Most information about the lunar profile continues to be provided by visual observers using simple equipment. Everyone is to be encouraged to join expeditions to observe grazes, because the accuracy of the observed profile is proportional to the number of stations. The use of grazes improves knowledge of the lunar profile (needed for the analysis of solar eclipse timings), data about close binaries, and galactic rotation from stellar reference-frame determination. Contact timings made near the edges of a solar eclipse track, for example, enable the diameter of the Sun to be derived relative to the lunar diameter, the latter being determined from occultations.
Asteroid and Cometary Occultations
Authors: Dunham David W.
Published: July 2016

Occultations of stars by minor planets and comets can be used to determine the diameter of the occulting body. With photoelectric equipment, it might also be possible to measure the diameter of the occulted star or to resolve close binary systems at the same time.

On 1983 May 29, (2) Pallas occulted the 4.7-mag. star 1 Vulpeculae. A star this bright is occulted by one of the four largest asteroids only once every 60 years. Timings were sent by 130 observers in Florida, Louisiana, Texas, Arizona, Sonora, and Baja California, making it the best-observed asteroidal occultation to date. Asteroidal grazing phenomena were confirmed for the first time. The star is a spectroscopic binary. Several observers timed contacts of the 6th-mag. companion, determining the separation to ± 0.0004 arcsec. An elliptical fit to the timings projected onto the plane of the sky has been made. Unfortunately, clouds prevented timings from near the southern limit, so about 100° of Pallas’ circumference was not observed.
Video Recordings of Asteroidal Occultations
Authors: Boninsegna Roland , Lecacheux Jean
Published: July 2016

Video recordings of two occultations were shown, the first concerning the star AGK3+29 0398 and (93) Minerva on 1982 November 22, 03:31 UT, using the 1-m telescope at Pic du Midi. The occultation was also observed in Spain and in the U.S.A. The second event involved AGK3+17 1309 and (146) Lucina on 1982 April 18, 20:23 UT, using the 1-m telescope at Meudon. A short secondary occultation (0.6 sec) was observed, not caused by the minor planet. A possible interpretation is a small satellite (5.7 km minimum diameter) near Lucina.
Scientific Goals for a Collaboration Between Amateur and Professional Astronomers in the Study of Variable Stars
Authors: Poretti Ennio
Published: July 2016

Variable stars are a field where the contribution of amateur astronomers is of great importance. This contribution can be separated in to complementary parts:

1)

collaboration with professional institutes that well-equipped amateurs can easily undertake in the field of photoelectric observation;

2)

visual observation of variable stars, which in many cases can be a preliminary approach to photoelectric photometry.
Professional/Amateur Cooperation in the Study of Variable Stars as Illustrated by the Fourth Edition of the GCVS
Authors: Frolov M.S.
Published: July 2016

Let us divide variable stars into two main groups: the first “classical” group, includes objects known for a long time, such as Cepheids, RR-Lyrae stars, Miras, cataclysmic variables, eclipsing binaries, etc. The second group includes micropulsating variables of δ Scuti and β Cephei types, magnetic variables, rotating variables of BY Draconis type, etc.

Historically, the contribution of amateurs in investigating the first group was very significant, and it continues to increase. On the other hand, involvement in studying the second group of stars was practically equal to zero some years ago, but today one can see the beginnings of an expansion of amateur work on this second group of variables – among brighter objects, of course. One reason is the beginning of cooperation between amateurs and professional astronomers having powerful instruments.
Amateurs and the Search for Supernovae
Authors: Lucas Stephen H.
Published: July 2016

The role of amateur astronomers in the search of extragalactic supernovae is emerging. Visual discoveries by John Bennett in 1968 and Gus Johnson in 1979 were isolated and surprising encounters, but are indicative of the possibilities. Between 1980 and the present, these possibilities have been well-tested by the Rev. Robert O. Evans, who has discovered 15 SN’s and shares credit for a 16th. Rev. Evans’ record was achieved through an organized approach to observation and assisted by the development of a unique observing regimen. Detection of SN is a formidable challenge, but the obvious conclusion is that amateurs may expect to attain more than marginal success. We approach this subject from the standpoint of visual observation, but are obliged to acknowledge the contemporaneous and successful application of photography as a search tool.
Comet Halley: A Media Event
Authors: Heudier Jean-Louis
Published: July 2016

Comet P/Halley’s life as a “media event” started long ago, because the first use of communication (in the modern sense of the term) goes back to Rabelais, who published in Patagrueline Prognostication pour l’an 1532:

“And whyth the comete sene laste yeare and the retrograte of Saturne a greate skoundrell shalle die, all weazynge and courd in scabbes, in the hospitall, and at his death there will be horrible warre between cattes and rattes, dogges and hares, faulcons and duckes, monkes and egges.”

Since then ways of spreading ideas have progressed enormously, but comets have remained “fashionable” and each of the last six apparitions of P/Halley has been the occasion of outbursts that are far removed from the scientific view.
Teaching Astronomy in Schools
Authors: Iwaniszewska Cecylia
Published: July 2016

This contribution summarized the ways in which astronomical teaching was evolving and some of the teaching aids that could be employed. The work of GIREP (Groupe International de Recherche sur l’Enseignment de la Physique) – which holds conferences on the teaching of physics, including astronomy, every two years – was described together with some material reported at the 1986 conference which was devoted to astronomy.
The Planetarium at the Palais de la Découverte
Authors: Oudenot Gérard
Published: July 2016

This large planetarium has about 250000 visitors every year. It seats 201 persons and has a modern Carl-Zeiss Jena projector. Two or five showings from a series of about ten different programmes are given daily to the general public. Special programmes at a much higher level are presented in conjunction with navigation, astronomy and other academic courses.
The Planetarium at a School in Nice
Authors: Chappelet Jeanine
Published: July 2016

An observatory, laboratory and planetarium were set up by pupils at a school in Nice with assistance from the Club des Pleiades. Various presentations were given, for children and adults, and some with the assistance of astronomers from the Observatory at Nice for teacher-training.
Astronomy in the Big Apple
Authors: Pazmino John
Published: July 2016

New York is probably unique in metropolitan cities worldwide in that it has no “official” or “public” astronomical institution. The Amateur Astronomers’ Association, an amateur body, fulfils that role and answers many queries from the general public and various organisations. Founded in 1927, it has around 500 members. Apart from providing all the usual services to its members, it also organizes regular observing sessions in parks and open spaces away from the worst of the light-pollution. It staged very successful public Halley watches in which over 10000 visitors participated.
A Decade of Organized Work in Venezuela
Authors: Sanchez Domingo
Published: July 2016

In 1978 Venezuelan amateur astronomers decided to meet yearly to provide a forum for the exchange of ideas and discussion of observing programmes. The contribution summarized the ten years of work and the papers that had been presented to the meetings.
The Triel Observatory
Authors: Trachier Jean-Paul
Published: July 2016

Although with limited equipment, this small observatory mounts a permanent exhibition and conducts various astronomical courses. It is primarily concerned with astronomical education and is visited by 5000–6000 pupils every year.
Observed Lithium Abundances as a Test of Stellar Internal Structure
Authors: Vauclair Sylvie
Published: July 2016

The “lithium gap” observed in the Hyades and other galactic clusters by Ann Boesgaard and her collaborators (Boesgaard and Tripicco 1986, Boesgaard 1987, Boesgaard, Budge and Burck 1987) gives a challenge to theoreticians. Indeed a good fit between the theoretical results and the observations will give a clue for our understanding of the stellar internal structure and evolution.

A theoretical explanation of the “lithium gap” by gravitational and radiative diffusion has been proposed by Michaud 1986. In G type stars, the convection zone is too deep for gravitational settling to take place: the density at the bottom of the convection zone is so large that the diffusion time scale exceeds the age of the star. Increasing the effective temperature leads to a decrease of the convection zone, and consequently to a decrease of the diffusion time scale. In F stars it becomes smaller than the stellar age, leading qualitatively to a lithium abundance decrease as observed. When the convection zone is shallow enough, the radiative acceleration on lithium becomes important as lithium is in the hydrogenic form of li III (while it is a bare nucleus, li IV, deeper in the star). This radiative acceleration may prevent lithium settling for hotter F stars. This is a very attractive explanation, which leads to a minimum of the lithium abundance nearly at the place where it is observed in effective temperature. However it suffers from some difficulties: the theory predicts an increase of the lithium abundance larger than normal in the hottest F stars, which is not observed, and the predicted minimum lithium abundance is one or two orders of magnitude higher than the minimum observed in the Hyades. The former may be overcome if mass loss occurs in these stars (Michaud 86). Let us focus on the latter.
Abundances in Cool Evolved Stars
Authors: Pilachowski Catherine A.
Published: July 2016

Nature has filled the upper right quadrant of the Hertzsprung-Russell diagram with more varieties of peculiar stars and odd chemical compositions than even our most speculative observers and theorists could dream up. To bring some structure to this vast subject I will categorize the phenomena we observe according to our model of stellar evolution, dividing the stars among the first ascent of the giant branch and the core-helium burning phase, the asymptotic giant branch (double shell-burning) phase, and the post-AGB and pre-planetary nebula stars. The types of stars found in these three groups are summarized below.
Abundances in Hot Evolved Stars
Authors: Husfeld D.
Published: July 2016

In the upper left corner of the HR-diagram various stars have been found that are clearly not members of the hydrogen main sequence. The majority of them lie to the left and below the main sequence, indicating that they are highly evolved stars close to the extinction of their thermonuclear power source and hence to rapid cooling towards the white dwarf domain. The implication is that a “short” time ago they were red giants and as such experienced phenomena like mixing, dredge-up and heavy mass loss. Therefore, one expects the hot evolved stars to display the consequences of the afore mentioned processes that are up to now not satisfactorily understood.
Stellar mass loss and atmospheric Instability
Authors: de Jager Cornelis , Nieuwenhuijzen Hans
Published: July 2016

A review is given of rate of mass-loss values in the upper part of the Hertzsprung-Russell diagram. Near the luminosity limit of stellar existance = −10−4 M⊙ yr−1. Episodical mass loss in bright variable super- and hypergiants does not significantly increase this value. For Wolf-Rayet stars the rate of mass loss is larger by a factor 140 than for non-evolved stars with the same Teff and L; for C stars this factor is ten. This can be explained qualitatively. Rotation appears hardly to influence the rate of mass loss except for vrot-values close to the break-up velocity. This is in accordance with theory. We suggest the existence of a Red Supergiant Branch; along that branch mass loss is virtually independent of luminosity. Stellar winds along the upper limit of stellar existence are mainly due: to radiation pressure for hot supergiants (≳ 10 000 K); to turbulent pressure for cool supergiants (3000-10 000 K), and to dust-driven and pulsation-driven winds for cooler stars. The turbulent pressure may originate in largescale stochastic motions as observed in Alpha Cyg. Episodical mass loss, as observed in P Cyg, HR 8752 and other Very Luminous Variables may be due to occasional violent stochastic motions, resulting in a shock-driven episodical mass-loss component.
A New Driving Mechanism of the Episodic Mass-Loss in Be Stars
Authors: Ando Hiroyasu
Published: July 2016

Be stars are well known to be rapid rotator and to show intermittent emission-line activity. Such an activity is now interpreted as an abrupt mass-ejection and formation of a cool disk in the equatorial region and then its gradual disappearance mass-loss is called as episodic mass-loss.

Rapid rotation and mass-loss connection in Be stars was suggested for the first time by struve(1931), which necessarily leads to the requirement of break-up velocity in Be stars. However, Vsin i statistics suggests almost all Be stars are well below the break-up velocity. The additional forces have been searched for so far; i.e., stellar wind, magnetic field, mass accretion, and so on. At the moment, none of them can succeed in explaining the episodic mass-loss in Be stars.
Molecular Spectroscopy as Diagnostics of Outer Atmosphere of Cool Luminous Stars: Quasi-Static Turbulent Molecular Formation Zone and Stellar Mass-Loss
Authors: Tsuji Takashi
Published: July 2016

The origin of mass-loss in cool luminous stars is still obscure; several known mechanisms such as thermally driven wind, radiation-driven wind(via dust), wave-driven wind etc all have serious difficulties, if examined in the light of recent observations. At the same time, recent observations in the infrared and radio spectral domains revealed that outer envelope of red (super)giant stars has highly complicated spatial and velocity structures, while inner envelope may have new component that had not been recognized before. For example, recent high resolution infrared spectroscopy revealed a possible presence of a quasi-static turbulent molecular dissociation zone somewhere in the outer atmosphere. This new component may represent a transition zone between the warm chromosphere and the huge expanding molecular envelope, and may be a cool component of chromospheric inhomogeneity or a moleclar condensation in a cool corona extended by turbulent pressure. Such a result can be regarded as observational evidence in support of a recent theory of autocatalytic molecular formation by thermal instability due to molecular cooling. Thus, observation and theory consistently show the presence of a new component - quasi-static turbulent molecular formation zone - in outer atmosphere of cool luminous stars, and a possibility of a unified understanding of outer atmospheric structure and mass-loss, in which turbulence may play important role, can be proposed.
A Model Oscillator of Irregular Stellar Variability
Authors: Takeuti Mine , Tanaka Yasuo
Published: July 2016

Stellar pulsation is one of the condidates for strong mass loss from red giant stars. Recent investigations have shown sporadic outbursts of the pulsation can eject a considerable mass from the stars. Such a sporadic increase of the amplitudes seems to have a connection with the irregularity found in the pulsations. Recently the iregular propreties in stellar pulsation are investigated in the relation to nonlinear dynamics (see for instance Perdang, 1985). Unfortunately no single model oscillator of a star of which the equilibrium state is dynamically stable had been found. In the present paper, we shall discuss a simple oscillator which shows period-doubling and chaotic, that is, irregular oscillations.
Mass and Energy Transfer in Semi-Detached Binary Systems
Authors: Unno Wasaburo , Kiguchi Masayoshi , Kitamura Masatoshi
Published: July 2016

Recently, Kitamura and Nakamura have found that the anomalous gravity darkening occurs in semi-detached binary systems. The exponent of gravity darkening for the secondary components, which is defined by where F is the radiative flux and g is the gravitational accerelation, is significantly greater than the unity as shown in Table 1. We interpret this in terms of the energy transport by the mass outflow from the secondary component filling the Roche-lobe.

Table 1.

Empirical αc-values and physical quantities of five semi-detached binary systems.

From the analysis based on this interpretation, we show that 1) the mass out-flow carries energy if ∇ < ∇ad and 2) the anomalous gravity darkening requires that the flow must originate from deep interior. The mass loss rate can be estimated from the anomalous gravity darkening. Thus, the anomalous gravity darkening can be used not only to estimate the mass transfer rate but also to probe the interior structure and the evolution of the secondary star of the semi-detached binary. This model links Morton’s instability[2] of the secondary with the accretion disk of the primary.
Numerical Modelling of the Classical Nova Outburst
Authors: Kutter G. Siegfried , Sparks Warren M.
Published: July 2016

We describe a mechanism that promises to explain how classical nova outbursts take place on white dwarfs of 1 M⊙ or less and for accretion rates of 4 × 10−10 M⊙ yr−1 or greater.
Superoutbursts and Superhumps of SU UMa Stars
Authors: Osaki Yoji , Hirose Masahito
Published: July 2016

SU UMa stars are one of subclasses of dwarf novae. Dwarf novae are semi-detached close binary systems in which a Roche-lobe filling red dwarf secondary loses matter and the white dwarf primary accretes it through the accretion disk. The main characteristics of SU UMa subclass is that they show two kinds of outbursts: normal outbursts and superoutbursts. In addition to the more frequent narrow outbursts of normal dwarf nova, SU UMa stars exhibit “superoutbursts”, in which stars reach about 1 magnitude brighter and stay longer than in normal outburst. Careful photometric studies during superoutburst have almost always revealed the “superhumps”: periodic humps in light curves with a period very close to the orbital period of the system. However, the most curious of all is that this superhump period is not exactly equal to the orbital period, but it is always longer by a few percent than the orbital period.
SN 1987A: Ultraviolet Observations and Mass Loss
Authors: Kirshner Robert P.
Published: July 2016

Mass loss from the B3 Ia progenitor star for SN 1987A is revealed by the recent emergence of narrow ultraviolet emission lines. The emitting gas is nitrogen-rich, has low velocity, and may be located a light-year from the supernova. This gives every sign of having been ejected from the SK −69 202 progenitor when it was a red supergiant, prior to its brief and ultimately violent life as a blue supergiant. Changes in the hydrogen line profiles during the early evolution provide a way to estimate the density distribution in the supernova atmosphere, and the mass of hydrogen it contains. A preliminary estimate is that the power-law index of density in the envelope goes as V−11 and the mass that lies above a velocity of 6, 000 km s−1 is between 1 and 6 solar masses.
Enrichment of s-Process Elements in the Progenitor of SN 1987A
Authors: Williams R.E.
Published: July 2016

Existing calculations of s-process nucleosynthesis in massive stars such as Sk −69° 202 show enhancements in the He-burning shells which, when mixed to the surface, lead to Sc, Sr, and Ba enrichments of factors of 2 to 15. Abundances derived from the supernova absorption lines using a simple scattering model yield enhancements of this magnitude. Thus, the observed and predicted s-process abundances are roughly in accord, although the Ba/Sr ratio derived for the supernova may be higher than the s-process can account for.
On the Origin of Supernovae of Type Ib
Authors: Branch David
Published: July 2016

The issue I want to discuss is this: supernovae observed during their photospheric phases display three distinct kinds of spectra - but there are four distinct chemical compositions that should be considered for the outer layers of exploding stars. What is the correspondence between the observed supernova type and the chemical composition?

The three kinds of observed spectra are Type II, which by definition shows optical hydrogen lines, Type Ia, which has neither hydrogen nor helium lines, and Type Ib, which has helium but not hydrogen.

The compositions to be considered are hydrogen-rich, or, speaking loosely, “solar”; helium-rich, or, loosely, “Wolf-Rayet”; deflagration - initially a mixture of heavy elements from carbon to radioactive nickel, which decays through cobalt to iron; and detonation - initially a mixture of just helium and radioactive nickel.
Spectroscopic Diagnosis of SN1987A and Lesser Lights
Authors: Wheeler J. Craig , Harkness Robert P. , Barkat Zalman
Published: July 2016

SN 1987A gives a unique chance to study both the precursor star and the subsequent dynamical evolution of the explosion. Comparison of the light curves shows that either H0 ∼ 100 km/s/Mpc, or SN 1987A ejected significantly less 56Ni than ordinary Type II supernovae. Investigation of the stellar structure pertinent to SK -69 202 reveals multiple solutions. For given luminosity, effective temperature, core mass and core radius, there are two families of envelope mass, one with large envelope mass and one with small envelope mass. The small envelope mass solutions can be ruled out by considerations of kinematics and the light curve. Envelopes of moderate mass may avoid each of these problems, but must be helium rich to be structurally self-consistent.

The spectrum in both the optical and the ultraviolet at about two days is fairly well represented by a hydrogen envelope with a power law density profile (ρ∝r-11 ) of one-quarter solar metallicity in LTE. Theoretical spectra at this early epoch tend to favor luminosities on the high side of observational estimates in order to ionize Ca II and prevent excessively strong lines at H and K and the infrared triplet, with some ramifications for distance estimates.

The spectra of SN1987A present an interesting contrast to other SN II events. A McDonald Observatory spectrum of SN 1985H in NGC 3359 of uncertain epoch shows a very close resemblance to that of SN 1987A at about two month’s age, including the strong line at 607 nm attributed by Williams to Barium. SN 1985H may have been of the same class of event as SN 1987A.
X-rays and γ-rays from Supernova 1987a
Authors: Sutherland P. , Xu Y. , McCray R. , Ross R.
Published: July 2016

The observation of X-rays and γ-rays from SN 1987a can provide important constraints on parameters for models of this unique event. We present the results of detailed Monte Carlo calculations of the fluxes to be expected in several X-ray bands and for the strong line at 847 keV associated with the decay of 56Co. Our calculations use Model 10H of Woosley, Pinto, and Ensman(1988), with 0.075M⊙ of radioactive material. If it is assumed that there is no mixing of this material with the layers above, then the X-ray fluxes do not become detectable as early as the observations made by the Ginga team in August, 1987. If these observations correspond to X-rays arising from γ-rays Compton scattered down in energy in the supernova ejecta, rather than the interaction of the ejecta with circumstellar matter, then they can only be explained by mixing outward of radioactive material or an envelope with some combination of less mass or greater kinetic energy per unit mass.
X-Ray Observation of SN1987A from Ginga
Authors: Tanaka Y.
Published: July 2016

An unusual hard X-ray source was discovered in an error box of 0.2° × 0.3° including SN1987A from the X-ray astronomy satellite Ginga. The energy spectrum is quite unusual for any known classes of X-ray source, and apparently consists of two separate components, a soft component and a very hard component. This source is considered to be identified with SN1987A. The X-ray emergence occurred in July, 1987, or possibly even earlier. The soft component is significantly time-variable and also showed a flare-like increase in January, 1988, while the intensity of the hard component has remained relatively unchanged for more than 200 days.
The Evolution of the Precursor of SN 1987 A
Authors: Maeder André
Published: July 2016

Ideally, the evolutionary models for the precursor of SN 1987 A should account for both the SN properties and the observational constraints for massive stars with relevant mass and composition.

Mass loss is an essential property of massive star evolution. Recent parametrisations of mass loss rates for galactic stars cover the whole HR diagram. There are indications that for given L and Teff values, is lower at lower metallicity and therefore is lower in the LMC than in the Galaxy, thus we take with f < 1. Various models of an intitial 20 M⊙ star with f=0.2, 0.4, 0.6 and 1.0 are constructed (cf. Fig. 1) with a metallicity Z=0.006 and a moderate overshooting dover=0.3 Hp. From these models, we suggest an initial mass on the zero age sequence of 17 to 18 M⊙. The pre-SN location in the HR diagram very much depends on the remaining stellar mass, or more precisely on the mass of the remaining H-rich envelope. A final location at log Teff ≃ 4.2 is obtained for a final mass of about 9.0 M⊙ (cf. Fig.1). Scaled to an initial value of 17 M⊙, this corresponds to a final mass of about 8 M⊙ and a remaining H-rich envelope of a few tenths of a solar mass at most. The stellar surface exhibits CNO equilibrium values with C/N ≃ 0.01 and O/N ≃ 0.1 in mass fraction, and an hydrogen content X (surf) = 0.39. The blue progenitor is obtained for f=0.4, i.e. for -values in the LMC equal to 40% of the galactic values.
Evolution of the Precursor of SN1987A
Authors: Wood P.R. , Faulkner D.J.
Published: July 2016

The evolution of a 17.5 M⊙ star, chosen to be similar to the precursor of SN1987A, has been studied using the input physics described in Wood and Faulkner (1987). The calculations: use opacities from the Astrophysical Opacity Library of Huebner et al (1977) with H, He, C, N, O and other metals in LMC ratios; treat semi-convection in the manner of Lamb, Iben and Howard (1976); and assume the mass loss rate to be the minimum of (a) α times the rate give in Waldron (1985) (this rate applied in the blue part of the HR diagram), and (b) L/(cv) (this rate applied in the red), where v is the stellar wind expansion velocity which was taken to be 12 km s−1.

Typical evolutionary tracks resulting from these calculations are shown in Figure 1. The track shown as a continuous line is the one shown in Wood and Faulkner (1987) and corresponds to α = 2.5, while the track shown as a dotted line results from a slightly different treatment of semi-convection on the main-sequence and to α = 1.
The Effect of General Relativity and Equation of State on the Adiabatic Collapse and Explosion of a Stellar Core
Authors: Sack N. , Lichtenstadt I.
Published: July 2016

The collapse of the iron core of massive stars ( M ≥ 8 MO) is initiated by photodissociation and electron capture. The collapse of the inner core proceeds homologously until it is stopped by the stiffness of the equation of state (hereafter EOS) at nuclear density and it stops or rebounds. A shock forms at the edge of homology. The initial strength of the shock increases with the velocity difference between the inner and outer cores, i.e. it increases with a larger rebound of the inner core. The uniterrupted propagation of this prompt shock through the remainder of the core to the stellar mantle, where it can deliver enough energy to blow off the loosely bound outer layers, has long been proposed as the mechanism of type II supernovae explosions. However most authors did not get an explosion as a result of the prompt mechanism. Recently Baron et al. (1985) reported that the combination of General Relativity (GR) with a relatively soft EOS at nuclear densities leads to a much greater blow off than they got with Newtonian hydrodynamics. In order to see where purely hydrodynamical effects are important, namely for what EOS the GR outburst is greater than the Newtonian, we did a set of pure hydrodynamical adiabatic calculations (complete neutrino trapping) with different EOS above nuclear densities, turning the GR terms on and off. Neutrino leakage, which we do not incorporate, usually leads to harmful energy losses.
Analysis of Neutrinos from Supernova 1987A
Authors: Chiu H. Y. , Chan K. L. , Kondo Y.
Published: July 2016

W ehave developed a time-energy correlation method1 to bring forth the mass signature from Supernova 1987a neutrino observations, if the neutrino has any mass at all. This method is particularly effective in analyzing data sets with a small number of events, such as the Kamiokande II2 and the IMB3 observations of neutrino bursts from Supernova 1987A. The time dispersion Δt12 between two simultaneously emitted neutrinos of energies E1, E2 (E1 < E2 ) and a neutrino mass energy mv is given by:

where L is the distance of the source and c is the velocity of light. Conversely, Eq.(1) can also be used to establish time relationships of detected neutrinos and the existence of a mass. Applying Eq.(1) to all pairs for which real values of mv (called the correlation mass) are obtained from the observed Δt12, E1, E2, the existence of a cluster of pairs with essentially the same mass mv will indicate (a) many pairs of neutrinos were emitted within a narrow time window, and (b) the existence of a mass at mv. If a group of neutrinos were emitted within a narrow window, these groups will show a strong time correlation. Thus, this method of analysis does not impose a condition for the emission mechanism - rather, if the result of this analysis indicates the existence of a mass, there must exist a time correlation among the neutrinos.
Analysis of Neutrino Burst from the Supernova in the Large Magellanic Cloud
Authors: Suzuki Hideyuki , Sato Katsuhiko
Published: July 2016

A massive star has been believed to end his life with the collapsed driven supernova explosion and the formation of the compact object such as a neutron star or a black hole. When the compact object is formed, a large amount of energy corresponding to the binding energy of the object must be released. It has been considered that most of the energy is emitted by neutrinos because of their adequate coupling with the matter. The observation of the neutrino burst from SN1987A by Kamiokande and IMB offered us the first chance to test these scenarios of the collapse driven supernova explosion directly. We began to analyze the data just after their publication and got many important results which are presented below. In our analysis the distance of SN1987A is assumed to be 50kpc.
SN1987A and Constraint on the Mass and Lifetime of Tau Neutrinos
Authors: Takahara Mariko , Sato Katsuhiko
Published: July 2016

Recently it has been suggested that neutrinos have nonvanishing mass from both experimental and theoretical investigations. Accelerator experiments and cosmology, however, impose the constraints on mass mv and lifetime τv of vτ (see Fig. 1). As we showed in the previous paper [1], supernova explosion also imposes the stringent constraint on them. The purpose of this paper is to investigate the constraint imposed on mv and τv of vτ from SN1987A.

Tau neutrinos are emitted from the central part of the iron core together with the electron neutrinos because they are also in thermal equilibrium with matter there.
Collapse of the Neutron Star Induced by Phase Transitions and Neutrino Emission from SN1987A
Authors: Takahara Mariko , Sato Katsuhiko
Published: July 2016

The neutrino burst from SN1987A were detected by KAMIOKANDE and also IMB in February this year. The neutrino events detected by KAMIOKANDE were clustered into three bunches; event number 1-5, 7-9, 10-12. The first two bunches of the neutrino events can be understood by the standard scenario of supernova explosions.

However, it is very difficult to explain the last bunch of the neutrino events by the standard scenario, especially the total energy of the neutrinos and the radius of the neutrino sphere; it is necessary at least several times of 1052 ergs to explain the total energy of the last three events. In order to explain this energy, we must consider the non-standard mechanism of the neutrino emission.
The Statistical analysis of Supernovae
Authors: Li Zongwei
Published: July 2016

Due to the growing interest in the SN(supernovae) phenomenon in recent years, and to large amount of data which has been accumulating lately, there is now a need for a new publication in which to find all the essential data on SNe and their parentgalaxies. A revised 568 supernova catalogue has published by Barbon et al (1984).

The paper supplements 65 SNe, discovered since 1984 up to update, and some statistical studies were completed.

The first two comprehensive lists of SNe were published by Zwicky(1958, 1965) and included the 54 and 111 objects respectively reported up to 1956 and 1962. A more complete list was issued by Zwicky(1964), 154 SNe is inclused.
Radio Patrol Camera for Supernovae Search
Authors: Daishido T. , Asuma K. , Inoue S. , Nishibori K. , Ohara H. , Komatsu S. , Nagane K.
Published: July 2016

Zwicky started extragalactic supernovae patrol using 10 inch Schmidt camera about fifty years ago. After that the research of supernovae was accelerated, because the wide view of the Schmidt camera made it possible to watch large field of the sky. The key technology of the Schmidt camera was its sophisticated optical system.

Anticipated next supernova in our Galaxy may be undetectable by the optical instrument due to the Galactic extinction. However, supernovae are now known to be intense radio sources after a year or so of the explosion. Even if the positions are beyond the Galactic center, the radio supernova could be observed using middle size radio telescope.
The dependence of mass loss on the basic stellar parameters
Authors: Lamers Henny J.G.L.M.
Published: July 2016

We determined the dependence of mass loss on the stellar parameters for O and B stars of various luminosities. We used four homogenous sets of mass loss rates derived by different authors from the radioflux, the infrared excess, the UV lines and Hα emission. As the rates derived from the radio flux are the least dependent on model assumptions for the stellar wind, these will be adopted as our standards. The others sets of mass loss rates will be corrected for the differences in the adopted wind model, especially in the velocity law, by scaling the rates to those derived from radio data, using the stars which the different sets have in common.
The velocity characteristics of WR stellar winds
Authors: Willis Allan J.
Published: July 2016

The stellar winds of hot early-type stars are characterised spectroscopically by the presence of P-Cygni profiles, which are most marked for resonance transitions of common ions and generally occur in the UV, and typical resonance lines of SiIV, CIV, NV and OVI are well known P-Cygni signatures of stellar winds in luminous OB stars. Analyses of these profiles can lead to important information concerning the velocity, density and temperature structure of such winds. The WR stars have more developed stellar winds than OB stars, supporting higher particle densities at larger distances from the stellar “photosphere”. Recently Barlow, Smith & Willis, hereinafter BSW, (1980), have derived reliable mass loss rates for 21 WR stars. The mean value is 4x10-5 M0 /y and the rates are considerably larger than can be accomodated by soley radiative models. The, as yet unidentified, mechanism initiating the WR mass loss may also be important for Of stars ( Lamers 1980 ).
Wind characteristics of the 07 n star HD 217086 in the Cep OB 3 association
Authors: Perinotto Mario , Panagia Nino
Published: July 2016

The 07 n star HD 217086 which provides the ionization of the H II region S 155 A and is the brightest member of the Cep OB 3 association, has been observed in the ultraviolet with IUE. From an analysis of the UV spectra we determine a terminal velocity of 3560 ± 100 km s-1 and a mass loss rate of . A comparison is made with the stars of similar spectral type.
Mass loss rates of OB stars derived from infrared observations
Authors: Tanzi E.G. , Tarenghi M. , Panagia N.
Published: July 2016

In this paper we report briefly on a study of the mass loss of early type stars in the infrared. Up to now near infrared (1.25 - 4.8 μ ) broad band photometry of 70 southern OB stars of various luminosity class has been secured. Program stars have been selected, among those bright enough in the infrared to give a suitable photometric accuracy, in order to cover a wide range of spectral types (Fig. 1).

37 stars are found to exhibit emission in excess over a blackbody photospheric continuum, which is interpreted in terms of gas ejected in the form of an accelerated wind. By means of model calculations the corresponding mass loss rates are derived. The obtained values compare well with those determined indipendently by various Authors for stars in common. Our data show that mass loss rates increase with luminosity and are a decreasing function of surface gravity.
Radio observations and the mass flow rate of α Cyg (A2Ia)
Authors: Wolf B. , Stahl O. , Altenhoff W.J.
Published: July 2016

From the free-free excess at 10μ. Barlow and Cohen (1977) (hereafter referred to as BC) derived a mass loss rate of 6.9 10-7 M⊙ yr-1 for α Cyg. They predicted a 10 GHz radio flux of 2.2 mJy. On the other hand Praderie et al. (1980) derived a considerable lower mass loss rate of 1.1 10 -8 ≤Ṁ ≤ 7 10-8 M ⊙ yr-1 from a curve of growth analysis of the envelope ultraviolet Fell-lines of α Cyg. Radio observations are desirable to make a decision about these discrepant results. Therefore we observed α Cyg at 15 GHz with the 100 m telescope of the MPIfR at Effelsberg. The observations are discussed together with recent VLA data of Abbott et al. (1980).
On the stellar gravity and effective temperature dependence of the ratio of
terminal to escape velocities in stellar winds
Authors: Carrasco Luis
Published: July 2016

Contrary to the results of some investigators, the ratio of terminal to escape velocities (V∞/Vesc) observed for the winds in early-type stars is found to be linearly correlated with log Γ - Γ being the ratio of stellar to Eddington's luminosities.

Although the determination of terminal velocities for O-type main sequence stars from edge velocity information may be somewhat questionable (Lamers, 1980). The determined values for the β and γ fitting parameters for the observed profiles by Conti and Garmany (1980) are tipically on the order of one for these stars. Hence, from the grid of profiles by Castor and Lamers (1979), we estimate that at most a 10% error is introduced by adopting the edge velocities as representative values of the terminal velocities of main sequence O-type stars.
Observational evidences of stellar wind
Authors: Tarafdar S.P.
Published: July 2016

Observations mainly from the IUE Spectra of HD 152236 (Blla) have been used to provide support to the various aspects of the theory of stellar wind (SW) and its interaction with the interstellar medium (ISM). Lines arising from excited levels connected radiatively to the ground level tend to be more frequent and/or strong compared to those arising from radiatively forbidden levels of similar excitation as expected from radiatively driven wind. The outward velocity from shifts of Si III lines from different excited levels increases steeply with decreasing excitation energy in agreement with theories. Absorption lines (P-Cygni like) of C II, Al II, Si II and Mg II shifted shortward by about 300 km s-1 suggest an expanding shell around the star. As this velocity is smaller than the terminal velocity (880 km s-1) the circumstellar shell may have been formed as a result of interaction of SW with ISM.
The radial velocity variations in IC 418
Authors: Méndez Roberto H. , Verga Alberto D.
Published: July 2016

The present observations are part of a search for spectral and radial velocity variations among central stars of planetary nebulae (Méndez 1980). The spectrograms were taken with the image-tube spectrographs of the 1-m and 4-m telescopes at the Cerro Tololo Inter-American Observatory (CTIO). The emulsion was always IIIa-J baked in “forming gas” (N2+H2). The “blue” spectrograms extend from 3600 to 5000 Å at 45 Å mm-1; the “red” ones extend from 5000 to 7000 Å, at 45 Å mm-1 (4-m plates) and 90 Å mm-1 (1-m plates). All plates were calibrated with a spot sensitometer. Seven “blue” and seven “red” spectrograms, all obtained with the 4-m telescope, were traced with the PDS microphotometer of the David Dunlap Observatory. The intensities from each plate were stored in computer memory and were later added together, in order to improve the signal-to-noise ratio. The resulting intensity tracings reveal more details than had previously been observed (Swings and Struve 1941, Aller and Wilson 1954, Andrillat 1957, Aller and Kaler 1964).