Issue |
A&A
Volume 384, Number 2, MarchIII 2002
|
|
---|---|---|
Page(s) | 650 - 653 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361:20020065 | |
Published online | 15 March 2002 |
CCD astrolabe solar diameter measurements in 1999–2000
1
Observatório Nacional, MCT, R. Gal. José Cristino 77, Rio de Janeiro, Brasil
2
Laboratório Nacional de Computação Científica, MCT, Brasil
3
Pulkovo Observatory, St. Peterburg, Russia
Corresponding author: J. L. Penna, jucira@on.br
Received:
15
October
2001
Accepted:
4
December
2001
Solar diameter observations are presented covering a period
close to the maximum of the solar activity cycle 23, from July 1999
to December 2000, at the Observatório Nacional, Rio de Janeiro.
The observations were made at 5635 Å,
with a CCD Solar Astrolabe, thus timing the limb crossing
through a fixed zenith distance. The formal precision of a single
measurement is typically 0
18. The results represent daily means
from 4625 independent measurements. The series obtained has 225
homogeneously distributed points with a mean precision of 0
12.
The average value obtained for the solar
semi-diameter within the analyzed period is 959
01 ±
0
02.
The average of the observations, made under a wide range of different
geometric, instrumental and environmental conditions, aims to provide
results representing global variations of the solar radius. From
this data, variations with amplitude equal to or larger than 0
02 can be
investigated. No statistically significant linear trend is obtained
for the examined series. There is, however, some
indication of an increasing trend for 1999 followed by a stabilization
during 2000.
Periodic variations are obtained with amplitudes
between 0
02 and 0
07. Periods related to the solar
rotation and the sunspot characteristic lifetime can be recognized.
Key words: Sun: activity / Sun: fundamental parameters
© ESO, 2002
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