J/A+A/393/225 Starspot cycles of six young solar analogues (Messina+, 2002)
Magnetic activity of six young solar analogues.
I. Starspot cycles from long-term photometry.
Messina S., Guinan E.F.
<Astron. Astrophys. 393, 225 (2002)>
=2002A&A...393..225M 2002A&A...393..225M
ADC_Keywords: Stars, late-type ; Stars, G-type ; Stars, K-type ; Magnetic fields
Keywords: stars: activity - stars: individual: BE Cet, κ1 Cet,
π1 UMa, EK Dra, HN Peg, DX Leo - stars: late-type -
stars: magnetic fields - stars: starspots
Abstract:
A long-term photometric monitoring of a selected sample of solar
analogues has been carried out since early nineties as part of
"The Sun in tim" project, which is aimed at a multiwavelength study of
stars with solar-like global properties, but with different ages and
thus at different stages of their evolution. The extended time
sequence of ground-based observations collected over more than a
decade as part of this program has revealed the existence of starspot
cycles. Also from these data it is possible to investigate surface
differential rotation of the stars. In this paper we present the
photometry collected to date and report on cycles search for a
selected subsample of five young single G0-G5V stars with ages between
∼130Myr and 700Myr: EK Dra, π1 UMa, HN Peg, κ1 Cet, BE
Cet. Also we include in this study the Pleiades-age (∼130Myr) K0V star
DX Leo (HD 82443). All the cited stars show activity cycles whose
period is, furthermore, the first determined from photometric data.
They are compared to those activity cycles derived from CaII H&K
emission fluxes and differences are discussed. All the cycle periods,
except for EK Dra, fit well the empirical relations with global
stellar parameters derived from larger stellar samples.
The following results are also inferred from the present study: i) the
fastest rotating stars tend to have longer cycles; ii) the range in
the observed cycle lengths seems to converge with stellar age from a
maximum dispersion around the Pleiades' age towards the solar cycle
value at the Sun's age; iii) the overall short- and long-term
photometric variability increases with inverse Rossby number with very
high correlation degree, indicating that the level of magnetic
activity at least in photosphere is still controlled by the stellar
rotation even on the longest time scales; iiii) the increase with
inverse Rossby number of the long-term overall photometric variability
seems to level off at the highest rotation rate, which may be
interpreted as due to a saturation in the level of photospheric
magnetic activity around the activity maximum.
Description:
The following tables contain the photometric data used to determine
the starspot cycles and longer-term trends for a sample of six young
solar analogues. The following data are listed: Mean epoch, first and
last observing HJD, number of observing nights, mean magnitude
(Vmax+Vmin)/2 and sources of photometry.
Objects:
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RA (2000) DE Designation(s) (File)
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00 22 51.8 -12 12 34 BE Cet = HD 1835 (table3.dat)
03 19 21.7 +03 22 13 kap1 Cet = HD 20630 (table4.dat)
08 39 11.7 +65 01 15 pi.1 UMa = HD 72905 (table5.dat)
21 44 31.2 +14 46 44 HN Peg = HD 206860 (table6.dat)
14 39 00.2 +64 17 30 EK Dra = HD 129333 (table7.dat)
09 32 43.8 +26 59 19 DX Leo = HD 82443 (table8.dat)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 50 24 BE Cet light curve
table4.dat 55 18 κ1 Cet light curve
table5.dat 54 35 π1 UMa light curve
table6.dat 49 12 HN Peg light curve
table7.dat 56 91 EK Dra light curve
table8.dat 54 53 DX Leo light curve
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See also:
J/A+AS/125/11 : 23 active stars UBV + V(RI)c photometry (Strassmeier+, 1997)
J/A+AS/140/29 : 47 late-type stars photometric monitoring (Strassmeier+, 1999)
Byte-by-byte Description of file: table[3-8].dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 yr Epoch Mean epoch of observation
9- 18 F10.2 d FirstJD First observing HJD
20- 29 F10.2 d LastJD Last observing HJD
33- 34 I2 --- Nights Number of observing nights
37- 41 F5.3 mag mag Mean magnitude (Vmax+Vmin)/2
44- 51 A8 --- Source [a-l, ] Sources of photometry (1)
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Note (1): Source of photometry:
a: Stepien & Geyer, 1996A&AS..117...83S 1996A&AS..117...83S
b: Cutispoto, 1991A&AS...89..435C 1991A&AS...89..435C
c: Cutispoto, 1992A&AS...95..397C 1992A&AS...95..397C
d: Cutispoto, 1995A&AS..111..507C 1995A&AS..111..507C
e: Hipparcos, Cat. I/239
f: Villanova photometry
g: Gaidos et al., 2000AJ....120.1006G 2000AJ....120.1006G
h: Frasca et al., 2000A&A...364..179F 2000A&A...364..179F
i: Lockwood et al., 1997ApJ...485..789L 1997ApJ...485..789L
j: Messina et al., 1999A&A...347..249M 1999A&A...347..249M
k: Strassmeier et al., 1997A&AS..125...11S 1997A&AS..125...11S, Cat. J/A+AS/125/11
l: Strassmeier et al., 1999A&AS..140...29S 1999A&AS..140...29S, Cat. J/A+AS/140/29
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Acknowledgements: Sergio Messina
(End) Patricia Bauer [CDS] 08-Aug-2002