Solar and stellar chromospheric activity

Report
Solar and stellar
chromospheric activity
Katarzyna Mikuła
Astronomical Institute, University of Wrocław
March 28th, 2014
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Outline
1.
2.
3.
4.
5.
Observations in Ca II H & K lines
HK Project
Stellar chromospheric activity
Main results
Summary
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
Chromosphere and activity
What is the chromosphere?
Indicators of chromospheric activity:
 UV lines: Ly α, O I (1304 Å), C I (1557 Å, 1561 Å), Si II (1808 Å, 1817 Å), Mg II h & k
(2796 Å, 2803 Å)
 VIS lines: Ca II H & K (3968 Å, 3934 Å)
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
Observations in Ca II H & K
 Eberhard & Schwarzschild (1913) – discovered emission in Ca II
H & K lines in Arcturus and other stars spectra
 Wilson (1963) and Wilson & Skumanich (1964) – from
observations (Mount Wilson Observatory) they discovered that
chromospheric activity of main-sequence stars decreases with
age
 Result of the observations was confirmed by Skumanich (1972):
t -1/2
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
Long-term observations in Ca II H & K
Linear relation between the absolute magnitude and the logarithm
of the K line emission widths (Wilson - Bappu effect):
MV = 27.59 – 14.94 log W0(K)
Similar relationships were found for other resonance lines, such as
Mg II k and Ly α.
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
HK Project
Systematic program of Ca II H & K observations of main-sequnece
stars.
 First phase: 1966 – 1977
Does the chromospheric activity of main-sequence stars vary
with time, and if so, how?
~Olin Wilson
Wilson, O., 1978, Chromospheric Variations in Main-sequence Stars.
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
HK Project
 HK Project continued under the direction of S. Baliunas
(1977 – 2003)
Mount Wilson Observatory S index:
SMWO = α[(H+K)/(R+V)]
Another observations:
 O. Wilson – observed the Moon as a solar proxy
 National Solar Observatory (1974)
 Sacramento Peak (1976)
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
Observations of Ca II H & K
From HK Project
observations (to 1991):
 60 % of stars exhibited
periodic, cyclic variations
 25 % - irregular or
periodic variability
 15 % - flat activity
Examples of HK Project observations (Hall et al. 2007b).
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
HD 114710
MWO series can be used:
 Identify rotation periods
 Diferrential rotation via drifts
Donahue & Baliunas (1992) – reported detection of a drift in the apparent
rotation period in β Com = HD 114710.
Solar cycle: 1. activity is low, ARs appear at high latitudes 2. the mean latitude of
ARs moves toward the equator (shortest rotation period).
HD 114710 cycle: rotation period increase from cycle maximum through cycle
minimum.
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
Observations of Ca II H & K
The distribution of activity in 815 southern Sun-like stars (Henry et al. 1996).
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
Grand minima
The Maunder Minimum:
1645 – 1715.
Baliunas & Jastrow (1990) - study
of magnetic activity for 70 solar-type stars.
Two different populations:
I.
SMWO ~ 0.17
II.
SMWO ~ 0.15
SMWO for the Sun:
~0.17 – 0.18 - active Sun
~0.14 - zero magnetic activity
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
Grand minima
HK flux variations for two stars (HD 10476
and HD 3651) with similar mass and
rotation.
Left: HD14538 appears to have made a transition from a at activity state to short cycle
in 2000 (Hall et al. 2007b). Right: HD 3651 shows evidence of having entered a at activity state
around 1980 (Baliunas et al. 1995).
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
Summary
 Long-term observations of stellar chromospheric activity – over
60 years of observations in Ca II H & K lines
 The most of stars reveal activity cycles similar to solar activity
cycle
 The samples of stars are not large – we cannot understand
chromospheric activity to the end
 Studying of solar/stellar dynamo
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
Bibliography
1. Hall, J.C., 2008, Living Reviews in Solar Physics, 5, 2
2. Wilson, P., 1994, Solar and Stellar Activity Cycles, CAS
3. Fares, R., 2013, IAU Symp. 302
4. Fletcher , L., 2012, ASP Conference Series, 448, 1
5. Bruevich, E.A. & Rozgacheva, I.K., 2012 eprint arXiv:1204.5705
6. Wilson, O., 1978, ApJ, 226, 379
7. Donahue, R.A. & Baliunas, S., 1992, ApJ, 393, 63
8. Baliunas S. et al., 1995, ApJ, 438, 269
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
Thank you for your attention!
1st SOLARNET Spring School
March 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity

similar documents