scholarly journals Detecting activity cycles of late-type dwarfs in Kepler data

2013 ◽  
Vol 9 (S302) ◽  
pp. 224-227
Author(s):  
Krisztián Vida ◽  
Katalin Oláh
Keyword(s):  
Active Region ◽  
Frequency Analysis ◽  
Rotation Period ◽  
Light Curves ◽  
Late Type ◽  
Dwarf Stars ◽  
Time Frequency ◽  
Activity Cycles ◽  
Using Data ◽  
Fast Rotating

AbstractUsing data of fast-rotating active dwarf stars in the Kepler database, we perform time-frequency analysis of the light curves in order to search for signs of activity cycles. We use the phenomenon that the active region latitudes vary with the cycle (like the solar butterfly diagram), which causes the observed rotation period to change as a consequence of differential rotation. We find cycles in 8 cases of the 39 promising targets with periods between of 300–900 days.

scholarly journals Photospheric stellar activity cycles

2006 ◽  
Vol 2 (14) ◽  
pp. 283-284
Author(s):  
Katalin Oláh
Keyword(s):  
Frequency Analysis ◽  
Time Interval ◽  
Mean Values ◽  
Time Frequency ◽  
Data Archives ◽  
Cycle Lengths ◽  
Activity Cycles ◽  
Photometric Monitoring ◽  
Light Variability

AbstractCycle lengths of active stars are derived from long-term photometric monitoring of their secular light variability. With the help of photographic data archives the lengths of the datasets are extended for HK Lac and V833 Tau. Using time-frequency analysis it is shown that the cycles are continuously changing in time. Thus, the reported cycle lengths derived by simple Fourier analysis are mean values that are valid only for a given time interval.

scholarly journals Mapping Cool Gas in the ISM with ROSAT

1997 ◽  
Vol 166 ◽  
pp. 283-286
Author(s):  
I.B. Hutchinson ◽  
R.S. Warwick ◽  
R. Willingale
Keyword(s):  
Column Density ◽  
Line Of Sight ◽  
Local Interstellar Medium ◽  
Late Type ◽  
Dwarf Stars ◽  
General Direction ◽  
X Ray ◽  
White Dwarf Stars ◽  
Cool Gas ◽  
Using Data

AbstractWe have investigated the distribution of cool gas within the local interstellar medium (<150 pc) using data derived from both the ROSAT X-ray and EUV all-sky surveys. The EUV/X-ray spectra for a sample of 89 white dwarf stars and 200 active late-type stars have been analysed to give an estimate of the gas column density along each object’s line of sight. In order to extend the sky coverage we have also included in the analysis 190 late-type stars detected only in the X-ray band. The derived NHI measurements confirm the size of the local low density bubble as typically 50-100 pc and also show that in the general direction of Loop I there is a substantial excess of absorption at a range of distances from 10-150 pc.

Time-Frequency Analysis of Partial Discharge Phenomena in SF6 gas using Wavelet Transform

1997 ◽  
Vol 117 (3) ◽  
pp. 338-345 ◽  
Author(s):  
Masatake Kawada ◽  
Masakazu Wada ◽  
Zen-Ichiro Kawasaki ◽  
Kenji Matsu-ura ◽  
Makoto Kawasaki
Keyword(s):  
Wavelet Transform ◽  
Frequency Analysis ◽  
Partial Discharge ◽  
Time Frequency Analysis ◽  
Time Frequency
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