JD8 assembled for half-day sessions on August 22 & 23, 1997 in a satisfactory meeting hall. Between 350 and 400 delegates - about 50% larger than anticipated - attended most of the sessions.

The theme of the meeting developed from initial conversations between R. H. Koch and Y. Kondo and was extended by E. F. Guinan. Opinions from the officers of Commissions 27 and 42 were favorable to seeking IAU approval and eventually the co-sponsoring Commissions came on board.

In essence, all the organizing workers recognized that there did not exist a broad recognition that we really do know specific stars whose evolution we have actually perceived and that there are also statistical interpretations (not the conventional isochrones in an HRD or CMD) for ensembles of stars which lead to the same conclusion.

The presentation compiled here is really a distillation of short offerings from the JD participants provided against a deadline which was regrettably close at hand. A full presentation of the meeting Proceedings will appear in The New Astronomy series of Elsevier. E. R. Jewell prepared the final files.

This Part of the report contains the summaries of the most affirmative conclusions about recognized evidences for stellar evolution. We would certainly prefer to know that we have actually discovered this or that piece of evidence but it can be equally valuable to know that the present state of knowledge forbids a conclusion of the sort which we wish. Not surprisingly, there are instances for which we are lucky to be able to make only a limiting statement about the matter. So affirmative here really means that a conclusion - positive or negative - has actually been attained. To the layman in stellar evolutionary studies it may be surprising that there exists such a diversity of evolutionary criteria - radiometric, spectrometric, orbital dynamical, spin dynamical - all with a defined time base available at the present day. It may be hoped that some of the conclusions summarized here will make their way routinely into undergraduate texts in the for seeable future and that tools such as the HRD or CMD will not appear as only static snapshots.

The variable post-AGB star FG Sge has provided an unique opportunity to study phenomenon which may be characteristic of the post-PN stage of stellar evolution. FG Sge is the central star in the 36-arcsec PN He 1-5 that over the last 50 yrs has been undergoing rapid evolutionary changes. Most notable are changes in temperature, luminosity, chemical composition and pulsation period. Starting in mid-1992, the star has undergone several large dimming events from which it has yet to recover. These events closely resemble the dimming events commonly observed in R CrB stars which result from dust formation in ejected envelopes. From all the evidence, it now appears that FG Sge has evolved into a R CrB star.

In this paper we first summarize the recent photometric history of the FG Sge from UBVRI photometry obtained during 1990-1997. We then combine these data with earlier photometry to define the star’s light bevavior over the last 100 yrs. The photometry is also combined with available spectroscopic polarimetric, and IR observations. Particlar attention is given to comparing FG Sge’s post-dimming behavior with contemporaneous observations of R CrB itself, also done on the same photometric system.

The peculiar T Tauri type star V1331 Cyg = LkH 120, located in the dark cloud Lynds 984, is a FU Orionis pre-outburst candidate (McMuldroch et al., 1993). This star embedded in circumstellar bright nebulosity is also surrounded by a helix-shaped nebula originated from the star. We obtained a series of speckle images of V1331 Cyg on the standard VBR system on July 18-20, 1994 using the Zeiss 1000 1.0 m telescope of the High Altitude Maydanak Observatory in Uzbekistan. We also used the results of Johnson’s system photometry of V1331 Cyg, made simultaneously at Maydanak Observatory with a 0.6 m reflector. Images were computer processed. Surface photometry of the star and surrounding nebula was made and isophotes were constructed. Fourier analysis of light curves for V1331 Cyg has shown 36.2 day periodic process (Melnikov, priv. comm.) which could be due to the presence of a circumstellar disk. Morphologic analysis revealed a complex fine structure of nebula, consisting of many bright knots and obviously show a jet-like outflow. According to spectral observations (Chavarria K. 1981; Penston & Keavey 1977) the line profiles of V1331 Cyg are P Cyg type only; there are no detections of anti-P Cyg profiles during the last 25 years observations. This indicates a stable mass loss (on average, 10−7 M ⊙/yr) with mean velocities about −410 km/s.

Visual magnitude data in Ptolemy’s Almagest are analysed by comparing them with modern photoelectric magnitudes on the Pogson scale, after taking extinction into account. This result is used to transform Almagest magnitudes to the Pogson scale.

A study is made of changes in the vusual magnitudes of supergiant stars in the Almagest between classical and modern times (an interval of nearly 19 centuries). No evidence is found for any secular changes in the mean brightness of these stars, contrary to the conclusion of Mayer (Observatory 104, 77, 1984). However, it is shown that the Almagest magnitudes for stars in the Milky Way are on average 0.34 Pogson magnitudes too faint and about the Almagest supergiants are affected by this. Finally, some evidence is cited for the visual atmospheric extinction in classical times being significantly less than today. If this is the case, and is not taken into account, it would mimic an apparent supergiant brightening of about 0.1 magnitudes over this time interval.

The light curves of luminous stars often show spectacular secular changes which can be connected to stellar evolution. Such events are, e.g. the outbursts of P Cygni in the 17th century and 77 Carinae in the last century. Both stars belong to the Luminous Blue Variables, but these changes are not restricted to blue stars. The light curve of HR 8752 (V509 Cassiopeiae) shows a certain similarity to that of the former two stars. When it was first catalogued in the middle of the 19th century, it had been a 6m star. During 100 years the star showed a secular brightening of lm. A similar yellow hypergiant, p Cassiopeiae produced at least two outbursts this century, though both have smaller amplitudes than it is in the case of the LBVs. Moreover, these yellow variables also have an apparently secular colour change: the B − V colour of HR 8752 is decreasing while that of ρ Cassiopeiae is increasing. In both cases evolutionary changes are possible but one cannot exclude other causes.

Besides these well studied stars there are several other yellow hypergiants with promising light curves. One of the most interesting cases seems to be R Puppis, which was discovered to be variable in the last century, but then did not show any appreciable change in the following 70-80 years. In the late 1970s, however, it began to vary once more.

We first consider all β Cephei stars for which long-term behavior of their pulsation periods is known from observations. As it turns out, these objects fall into two categories: one consisting of stars with complex period variations, and the other, with a constant and non-negative rate of period change, Ṗ = const ≥ 0. The problem is that stars with Ṗ close to that predicted for the hydrogen-shell burning phases of evolution are over-represented. We then compare the five β Cephei stars which exhibit long-term variations of the pulsation amplitudes and note that in each case the cause may be individual. In one star, 16 (EN) Lac, two different effects are responsible for the observed variation of the amplitudes.

An IAU travel grant is gratefully acknowledged. This work was supported by KBN grant 2P03D01611.

Using all available data, we investigate long-term variations of the amplitudes of the three strongest pulsation modes of 16 (EN) Lac and the period of the strongest mode of ν Eri. We show that in case of 16 (EN) Lac there are feasible explanations of the observed variations. The explanations involve non-linear interaction between pulsation modes (the first two observed modes) and beating between two non-interacting modes (the third observed mode). In case of ν Eri, however, we can only indicate the difficulty of accounting for the long-term period variation.

MJ gratefully acknowledges an IAU travel grant. This work was supported by KBN grant 2P03D01611.

Reported mode changes in δ Scuti stars cna usually be explained by insufficient data to obtain multiperiodic solutions and by the effect of time-variable amplitudes. The extensive data on 4 CVn obtained by the Delta Scuti network are used to illustrate that the large changes in the appearance of the power spectra in the years from 1966 to 1996 can be ascribed to amplitude variability.

The period changes of δ Scuti stars have been collected or redetermined from the available observations and are compared with values computed from evolutionary models. For the radial pulsators of Pop.I, the observations indicate (l/P)dP/dt values around 10−7 year−1 with equal distribution between period increases and decreases. The evolutionary models, on the other hand, predict that the vast majority should show increasing periods a factor of about 10 smaller than observed. Arguments are given why the rate of evolution for these relatively unevolved stars cannot yet be deduced from the observed period changes.

VW Cep is one of the brightest and longest observed short-period (P = 6.67 hours) W UMa type binaries. It consists of a G5V and K0V components in contact with their Roche surfaces. We investigated complex period changes based upon eclipse timings from the past 70 years. In addition to the well-known 30 year light time effect due to the presence of a third star in the system, we find evidence for a long term decrease in the orbital period of dP/dt = −0.02 sec/yr. This decrease in period could arise from angular momentum loss from the binary or mass exchange between components. From these timings we have refined the properties of the tertiary component and redetermined its mass and orbital parameters. After correcting the O-C’s for the third body and the steady decrease in Keplerian period, we uncovered small systematic deviations in the residual O-C’s. We are studying these second order period variations, possibly arising from mass loss in winds and/or mass flow between components, to determine if they correlate with known cycles of spot and surface activity.

An attempt at the first direct test of the theory of large-scale mass transfer between the components of a binary system is discussed. It is argued that β Lyr is the only binary in the sky for which such a test is conceivable.

R CMa is one of the best observed low mass Algol-type systems, believed to be a semidetached system composed of a nearly spherical FOV primary and a less massive highly distorted K3 IV-V star. Most of the published light curves have asymmetries of one kind or another. Analysis of the individual light curves, dating back to over 75 years, yielded somewhat different orbital solutions depending on the epoch. These inconsistencies are caused by obvious differences in the shape of the light curves obtained at different epochs and by the different models used to find solutions.

A series of light curves of R CMa (obtained at different epochs) have been analyzed by a new version of the Wilson-Devinney computing program to find a homogeneous solution. All parameters were adjusted to fit a light curve of each epoch. Then we found the weighted mean value of each parameter. These mean values were used as initial parameters and the potential and radius of each component were re-adjusted for each epoch to see the variation of radii for over 30 years. Several radial velocity curves were used to find spectroscopic parameters. The photometric parameters were combined with the corresponding spectroscopic parameters to calculate an absolute dimension of R CMa.

Finally, we examined the IUE spectra of R CMa for existence of circumstellar gas in the system and evidence of magnetic activity on the cooler component. We also discuss the evolution of the system and possible observable real time evolutionary processes.

The orbital periods of binaries are known to great accuracy, their changes produce an easily detectable cumulative effect and many systems have been observed for more than a century. In tidually locked late-type binaries the orbital period changes are often related to structural or evolutionary changes. The study of the orbital period secular evolution can therefore provide information on phenomena taking place on timescales very short when compared to the typical stellar evolutionary scales, but still much longer thant the human lifetime. This paper focuses on the dynamical evolution due to magnetic braking in late-type close binaries and on the detectability of angular momentum transfer among the stellar layers.

Close binaries with late-type components generally present rotational velocities synchronized with their orbital period. This is a well known effect of tidal evolution in binary systems which is particularly efficient in stars with convective envelopes. Nevertheless, some cases are known where the angular velocities of the componenent stars are clearly different from each other or even from that of the orbit. Good examples are the evolved systems TZ For and a Aur.

We have made a detailed study of the tidal evolution history of these binaries through integration of the relevant differential equations using the formalisms by Zahn as well as Tassoul. Our results show that a satisfactory explanation of the synchronization status of the component stars can be achieved when the influence of the rapid expansion phases, suffered by the stars after leaving the main sequence and starting core He combustion, in the actual rotational velocities is taken into account.

We briefly discuss the methods of observing stellar evolution in real time, and of interpreting these observations. Then we discuss recent results on RR Lyrae stars, Population I and II Cepheids, RV Tauri stars, and related objects.

After briefly reviewing our understanding of Miras and their evolutionary status, three aspects of real-time evolution in these and related stars are examined:

1. 1. Chemical changes (O-rich to C-rich) due to third dredge-up,

2. 2. Period changes due to the effects of the helium shell-flash,

3. 3. The existence of ‘fossil’ dust and gas shells.

Studies of resolved gas and dust shells are highlighted as particularly interesting. They will enable us to examine the mass-loss histories of many late-type stars over the last ten thousand years or so. Such observations have only recently become technically feasible and they are expected to provide important new insight into the late stages of stellar evolution.

A review of our investigations of CH Cygni in its inactive state during the period 1987-1989 has been given. Optical spectra reveal the development of physical conditions in the photosphere of the cool component as well as changes in the accretion complex around the hot component. The apparently quiescent star was actually evolving in trainsition between adjacent outbursts.

SAO 244567 (Henl357) (IRAS 17119-5926) is a high galactic latitude (1 = 331°, b = −12°) early type star, originally classified as a B or A type H-alpha emission line star by Henize (1976). It is an IRAS source with far infrared colours similar to planetary nebulae. The IUE ultraviolet spectra obtained during the last eight years show that the central star is rapidly evolving. It is found that the central star of this young PN has faded by a factor of 3 within the last seven eight years. The terminal velocity of the stellar wind has decreased from −3500 km/sec in 1988 to almost zero in 1994. In 1988 the C IV (1550A) line which was a P-Cygni profile with strong absorption component had almost vanished by 1994. The CIII] 1909A emission strength increased markedly within 4 years from 1988 to 1992. The optical spectra obtained since 1990 shows very clearly only the nebular spectrum which is very similar to that of low excitation planetary nebula. The optical spectrum of SAO 244567 obtained in 1971 shows that it was a post-AGB B 1 or B2 supergiant at that time. This result shows that SAO 244567 has turned into a planetary nebula within the last 20 years. Recently Bobrowsky (1994) obtained narrowband optically resolved images in both H-beta and [OIII] 5007A with the HST planetary camera which revealed a well resolved nebula of size 2 seconds of arc. In this paper we discuss the recent new results.