As an introduction

Twelve years ago, when I was working at Serra da Piedade Observatory (operated by Universidade Federal de Minas Gerais, Brazil), we begun with the automated data acquisition from a telescope (photometric information). We also used teleprocessing of information at a very distant computer, located at the University building - 28 miles away.

Our experience at that time was very useful for the development of a system composed by the following set of tasks

1 - To construct and program the microprocessors for the data acquisition from the stellar photoelectric photometer. This task includes hardware and software development.

2 - To program the interfaces between the analog photometer output and the digital signal transfer between the observatory site and the university building. This task deals with digital electronics, microprocessors and software developing.

3 - To program the communication software for enabling the data transferring, both at the microprocessor and at the minicomputer.

4 - To program the software for real time data analysis and the generation of adequate mandatory instructions for the system at the telescope. These instructions were only messages for the operator, as there was no automatic operation system at the Piedade's telescope.

The system saw the light in 1981. During one year of continuous observations, it was devoted to a couple of works: dwarf cepheids (the d Sct and SX Phe types of variable stars as we known at present) and eclipsing binaries (specially the close binary systems and RS CVn type). The system worked very well until my return, in 1982, to the Instituto Copérnico. Unfortunately, as far as I know, the project did not continue.

By this time, Mr. Russell Genet and I became in contact, because the IAPPP was founded and I was invited to be a Charter Member of this pioneer institution.

A few years ago, we became interested in the installation of an observatory for automated photoelectric photometry, and we tasted the possibility of joining the APT Service.

From that time, we were working on a project that I will intent to explain you during the next few minutes, if you are patient enough.

Latin American southern regional projects

Two years ago, in a Regional Encounter (Brazil, Argentina, Uruguay and Paraguay) of educators, amateur astronomers and a few professional astronomers, we idealized the possibility of building a regional observatory, devoted to scientific, educational and popularization works. During the earliest discussions, we choose the Campinas Observatory (near Campinas city, Sâo Paulo, Brazil) operated under a contract between three Brazilian Universities (UNICAMP, PUCAMP and Federal University of Rio de Janeiro), the municipal government of Campinas, the Federal Ministry of Education and Culture, and the amateur institution Observatório do Capricórnio.

We plan to begin with the installation of a photoelectric photometer at the Campinas 0.6 m reflector, but the economic troubles of Brazil and Argentina made it impossible until now. Another problem was that some of the astronomers present at the regional meeting, spent some days at Campinas and did not agree that the local weather conditions where good enough to justify the choice of Campinas as the better site.

The observing conditions at Campinas are quite good in terms of image stability, transparency, humidity, altitude (over 1000 meters), etc. Nevertheless, the total number of clear nights per year are very tiny, about 120.

Recently, the Uruguayan National Committee of Astronomy devoted new resources for the installation of an observatory near the city of Montevideo. This event opens new perspectives for the materialization of the projected regional observatory. During some talks between the Directors of both, the Department of Astronomy of the University of the Republica (Uruguay) and the Instituto Copérnico (Argentina), the possibility of mounting a Robotic Observatory at this site becomes feasible.

The observing conditions at this site are quite different than those at Campinas. The total number of clear nights oscillates between 150 and 170, but the wind during these nights is variable in strength and direction. Also, the transparency and altitude (about 100 meters) are not as good as at Campinas. The image stability is comparatively good at both places. However, the economical possibilities make it a viable prospect.

Finally, besides the regional observatory, another possible project is to place a robotic observatory at the best site in Argentina, El Leoncito, San Juan, where two observatories are actually under operation. The Felix Aguilar Observatory operates an astrographic telescope (installed by Yale-Columbia Universities) and a 70 cm reflector. On the other hand, the CASLEO operates a 2.15 m reflector. The site is very interesting because of the nice atmospheric conditions, and its general characteristics. The problem is the extremely hard economical and financial situation for the science in Argentina, however it seems to be a very interesting project for the Argentine astronomical community, and also for the Uruguayan.

Stellar seismology

During the last decade helioseismology, the study of the interior structure of the sun by the analysis of its surface oscillations, has blossomed. Their spectacular successes impulsed the desire to apply the theory developed for the sun to other stars.

A conspicuous group of nondegenerate pulsating stars is the d Scuti type of variable stars in the galaxy. They are population I, A and F main sequence and giant stars which show light variations with amplitudes ranged from a few millimagnitudes up to many tenths of a magnitude, over periods ranging 28 minutes up to many hours. Some of these stars are singly or doubly periodic radial pulsators, but there is a group of multipleperiodic ones that pulsate in a mixture of radial and non-radial modes.

Many reviews of this stars have been written during the last two decades. The most extensive are those of Fitch (1976), Breger (1979), Eggen (1979) and Wolf (1983). Shorter reviews are those of Kurtz (1986) and Shibahashi (1987). Lists and catalogues for these stars can be found in Breger (1979), Eggen (1979), Halprin and Moon (1983) and García et al. (1988).

The asteroseismologist should see the d Scuti stars as a gold mine: many of them are naked-eye stars and very easy to observe, they are common, many pulsate in non-radial modes and some pulsate in many non-radial modes simultaneously. The latter characteristic is most important since it is the variety of spherical-harmonic modes which gives us the ability to resolve the interior structure of a pulsating star, as emphasize Kurtz (1988), in a recent paper about this matter.

The complete set of characteristics of these stars imply an adequate observational program for monitoring:

i) the star magnitude that varies during the photometric integrations. This implies that shorter integration is the best.

ii) the star colors, which also vary during the photometric integrations. This implies: no standard colors but differential photometry under the best chosen filter.

iii) the smaller known amplitude. This implies: the most careful measurement of the sky background.

iv) the variation of periods from cycle to cycle. This implies: the longer time of continuous observation, the better period determination.

Therefore, the continuous monitoring of these stars is a good challenge for a network of observatories around the world. But the best choice is a network of robotic ones, because the global monitoring task is coordinated by a rigorous computer program instead of the arbitrary time assignment done by the observatory staff committee.

The increasing accuracy of the observational methods by means of the robotic observatories, let us to encourage the application of these techniques to the observation of the d Scuti stars. By now, precisions of the order of 1 millimag are achieved in differential photometry, as demonstrated in a recent paper due to Young et al. (1990a & b). This is enough precision for stellar seismology.

Conclusions

We think that d Scuti stars in the southern hemisphere are not adequately monitored due to the lack of observatories as well as astronomers devoted to this field of the astrophysical knowledge.

We also believe that the study and the continuous monitoring of these stars may enlighten something about the internal constitution and the structure of the stars.

Perhaps, these tasks would be very difficult a decade ago. But at the present time, it is impossible to achieve a good result without the collaboration of the inhabitants of the whole hemisphere, prevailing the good agree with the foundations of the network of observatories all around the world.

References

Breger, M.: 1979, Pub. A.S.P., 91, 5

Eggen, O.J.: 1979, Ap. J. Suppl., 41, 413

Fitch, W.S.: 1976, in Multiple Periodic Variable Stars, ed. W.S.

Fitch, IAU Coll. 29, D. Riedel Pub. Co., Dordrecht, p. 167

García, J.R.; Cebral, R.; DiGiorgio, F.; Romano P.; Scoccimarro, E.R., Wahnon, P.; Zimmermann, M.: 1988, Bull. Inform. CDS nr. 34, 67

Halprin, L.; Moon, T.T.: 1983, Astrophys. Space Sci., 91, 43

Kurtz, D.W.: 1986, in Highlights in Astronomy, ed. J.P.Swings, IAU, D. Riedel Pub. Co., Dordrecht, p. 237

Kurtz, D.W.: 1988, in Multimode Stellar Pulsations, ed. G. Kovács et al., Konkoly Obs. - Kultura , Budapest, p. 95

Shibahashi, H.: 1987, Lecture Notes in Physics, 274, 112

Wolf, S.C.: 1983, The A-type Stars, publ. NASA, Washington, p. 93

Young, A.T.; Genet, R.M.; Boyd, L.J.; Espand, D.H.; Lockwood, G.W.; Smith, D.P.; Donahue, R.: 1990, Pub. Ast. Soc. Pac., in preparation (preprint)

Young, A.T.; Boyd, L.J.; Genet, R.M.; Espand, D.H.; Lockwood, G.W.; Baliunas, S.L.; Smith, D.P.; Donahue, R.: 1990, IAPPP Communications, in preparation (preprint)

Instituto Copérnico, Casilla de Correos 51 Suc. 48B, 1448 Buenos Aires, Argentina

^[1] Invited talk to the Symposium on Robotic Observatories (organized by Harvard-Smithsonian Center for Astrophysics and the Astronomical Society of the Pacific), Boston University, Boston, July 13-15, 1990

Last version: Harvard, July 1990.