Issue |
A&A
Volume 374, Number 2, August I 2001
|
|
---|---|---|
Page(s) | 697 - 702 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361:20010749 | |
Published online | 15 August 2001 |
Visual and CCD astrolabe observations of the solar radius
Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
Received:
13
February
2001
Accepted:
2
May
2001
Here we discuss and compare two sets of solar semidiameter measurements made
with Danjon astrolabes during the period 1997-1999. One is based on 10 522
CCD observations made at Rio de Janeiro, Brazil; the other one is based on
956 visual observations made at Santiago, Chile. Linear fits applied to both
data sets give a standard deviation of and
for each daily mean value of the solar radius for Rio de Janeiro and Santiago
respectively. During the period of this analysis, the apparent solar radius
had an annual variation of
according to the CCD
observations of Rio de Janeiro and of
according to
the visual observations of Santiago. We show here that this discrepancy could
be due to systematic effects, probably of instrumental origin, that produce
significant internal inconsistencies in the results of Rio de Janeiro. The
drift of the apparent solar radius observed with the astrolabe of Santiago
during 1997-1999 is consistent with former results obtained with this
instrument since 1990. These results show that the apparent semidiameter of
the Sun varies in phase with solar activity (Noël 1997, 2001).
Key words: astrometry / Sun: activity / Sun: fundamental parameters
© ESO, 2001
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