solar and stellar chromospheric activity
DESCRIPTION
Solar and stellar chromospheric activity. Katarzyna Mikuła Astronomical Institute , University of Wrocław March 28 th , 2014. 1 st SOLARNET Spring School March 24 th – April 4 th , 2014, Wrocław , Poland. Outline. Observations in Ca II H & K lines HK Project - PowerPoint PPT PresentationTRANSCRIPT
Solar and stellar chromospheric activity
Katarzyna MikułaAstronomical Institute, University of Wrocław
March 28th, 2014
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
1. Observations in Ca II H & K lines2. HK Project3. Stellar chromospheric activity4. Main results5. Summary
Outline
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
Chromosphere and activity
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)
What is the chromosphere?
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
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
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
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.
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
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.
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
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)
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
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 activityExamples of HK Project observations (Hall et al. 2007b).
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
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.
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
Observations of Ca II H & K
The distribution of activity in 815 southern Sun-like stars (Henry et al. 1996).
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
Grand minima
The Maunder Minimum: 1645 – 1715.
Baliunas & Jastrow (1990) - studyof magnetic activity for 70 solar-type stars.
Two different populations:I. SMWO ~ 0.17II. SMWO ~ 0.15
SMWO for the Sun: ~0.17 – 0.18 - active Sun ~0.14 - zero magnetic activity
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
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).
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
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
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
Bibliography
1. Hall, J.C., 2008, Living Reviews in Solar Physics, 5, 22. Wilson, P., 1994, Solar and Stellar Activity Cycles, CAS3. Fares, R., 2013, IAU Symp. 3024. Fletcher , L., 2012, ASP Conference Series, 448, 15. Bruevich, E.A. & Rozgacheva, I.K., 2012 eprint arXiv:1204.57056. Wilson, O., 1978, ApJ, 226, 3797. Donahue, R.A. & Baliunas, S., 1992, ApJ, 393, 638. Baliunas S. et al., 1995, ApJ, 438, 269
Katarzyna Mikuła, Astronomical Institute, University of Wrocław
Solar and stellar chromospheric activity
1st SOLARNET Spring SchoolMarch 24th – April 4th, 2014,
Wrocław, Poland
Thank you for your attention!