L. Jetsu
YOU?
Author Swipe
View article: Do the planets cause the sunspot cycles?
Do the planets cause the sunspot cycles? Open
The mainstream dynamo models predict that the sunspot cycle is non-stationary and stochastic. The official Solar Cycle Prediction Panel forecasts only the ongoing sunspot cycle because any forecast beyond one cycle is considered impossible…
View article: Topological changes in the magnetic field of LQ Hya during an activity minimum
Topological changes in the magnetic field of LQ Hya during an activity minimum Open
Aims. Previous studies have related surface temperature maps, obtained with the Doppler imaging (DI) technique, of LQ Hya with long-term photometry. Here, we compare surface magnetic field maps, obtained with the Zeeman Doppler imaging (ZD…
View article: Say Hello to Algol's New Companion Candidates
Say Hello to Algol's New Companion Candidates Open
Constant orbital period ephemerides of eclipsing binaries give the computed eclipse epochs ( C ). These ephemerides based on the old data cannot accurately predict the observed future eclipse epochs ( O ). Predictability can be improved by…
View article: Say hello to Algol's new companion candidates
Say hello to Algol's new companion candidates Open
Constant orbital period ephemerides of eclipsing binaries give the computed eclipse epochs (C). These ephemerides based on the old data can not accurately predict the observed future eclipse epochs (O). Predictability can be improved by re…
View article: About ten stars orbit eclipsing binary XZ And
About ten stars orbit eclipsing binary XZ And Open
A third body in an eclipsing binary system causes regular periodic changes in the observed (O) minus the computed (C) eclipse epochs. Fourth bodies are rarely detected from the O-C data. We apply the new Discrete Chi-square method (DCM) to…
View article: Say hello to Algol D and Algol E
Say hello to Algol D and Algol E Open
Regular changes in the observed (O) and the computed (C) epochs of binary eclipses may reveal the presence of a third or a fourth body. One recent study showed that the probability for detecting a fourth body from the O-C data is only 0.00…
View article: Say hello to Algol D, Algol E, Algol F, Algol G and Algol H candidates
Say hello to Algol D, Algol E, Algol F, Algol G and Algol H candidates Open
Regular periodic changes in the observed (O) minus the computed (C) epochs of binary eclipses may reveal the presence of a third or a fourth body. Recently, Hajdu et al. (2019) estimated that the probability for detecting a fourth body fro…
View article: Discrete Chi-square Method for Detecting Many Signals
Discrete Chi-square Method for Detecting Many Signals Open
Unambiguous detection of signals superimposed on unknown trends is difficult for unevenly spaced data. Here, we formulate the Discrete Chi-square Method (DCM) that can determine the best model for many signals superimposed on arbitrary pol…
View article: Long-term spot monitoring of the young solar analogue V889 Herculis
Long-term spot monitoring of the young solar analogue V889 Herculis Open
Context . Starspots are important manifestations of stellar magnetic activity. By studying their behaviour in young solar analogues, we can unravel the properties of their magnetic cycles. This gives crucial information of the underlying d…
View article: Algol as Horus in the Cairo Calendar: the possible means and the motives\n of the observations
Algol as Horus in the Cairo Calendar: the possible means and the motives\n of the observations Open
An ancient Egyptian Calendar of Lucky and Unlucky Days, the Cairo Calendar\n(CC), assigns luck with the period of 2.850 days. Previous astronomical,\nastrophysical and statistical analyses of CC support the idea that this was the\nperiod o…
View article: Algol as Horus in the Cairo Calendar: The Possible Means and the Motives of the Observations
Algol as Horus in the Cairo Calendar: The Possible Means and the Motives of the Observations Open
An ancient Egyptian Calendar of Lucky and Unlucky Days, the Cairo Calendar (CC), assigns luck with the period of 2.850 days. Previous astronomical, astrophysical and statistical analyses of CC support the idea that this was the period of t…
View article: Real light curves of FK Comae Berenices: Farewell flip-flop
Real light curves of FK Comae Berenices: Farewell flip-flop Open
For seven decades, the widely held view has been that the formation, the migration and the decay of short-lived starspots explain the constantly changing light curves of chromospherically active stars. Our hypothesis is that these deceptiv…
View article: General Model for Light Curves of Chromospherically Active Binary Stars<sup>∗</sup>
General Model for Light Curves of Chromospherically Active Binary Stars<sup>∗</sup> Open
The starspots on the surface of many chromospherically active binary stars concentrate on long-lived active longitudes separated by 180°. Shifts in activity between these two longitudes, the “flip-flop” events, have been observed in single…
View article: Real light curves of FK Comae Berenices: Dead end
Real light curves of FK Comae Berenices: Dead end Open
Recently, we presented a general model for the light curves of chromospherically active stars, where the observed light curve is interference of two real constant period light curves of long-lived starspots. In this first paper, we make si…
View article: Rotation And Spot Activity Of Young Solar-Type Stars From Long-Term Photometric Monitoring
Rotation And Spot Activity Of Young Solar-Type Stars From Long-Term Photometric Monitoring Open
We present results from a recent multidecade study of the spot activity of young solar-like stars, based on photometry gathered at the Fairborn observatory since 1987. Results from the time series analysis of this photometry reveal systema…
View article: Rotation And Spot Activity Of Young Solar-Type Stars
Rotation And Spot Activity Of Young Solar-Type Stars Open
We report on our study of rotation and spot activity in 21 young solar-type stars, based on period analysis of extended photometric records. Our results reveal activity cycles in nearly all of the stars and active longitudes on the more ac…
View article: Activity trends in young solar-type stars
Activity trends in young solar-type stars Open
\n Aims. We study a sample of 21 young and active solar-type stars with spectral types ranging from late F to mid K and characterize the behaviour of their activity.\n Methods. We apply the continuous period search (CPS) time series analys…
View article: Shifting Milestones of Natural Sciences: The Ancient Egyptian Discovery of Algol’s Period Confirmed
Shifting Milestones of Natural Sciences: The Ancient Egyptian Discovery of Algol’s Period Confirmed Open
The Ancient Egyptians wrote Calendars of Lucky and Unlucky Days that assigned astronomically influenced prognoses for each day of the year. The best preserved of these calendars is the Cairo Calendar (hereafter CC) dated to 1244-1163 B.C. …
View article: Periodicity in some light curves of the solar analogue V352 Canis Majoris
Periodicity in some light curves of the solar analogue V352 Canis Majoris Open
\n Aims. We applied the Continuous Period Search (CPS) method to 14 yr of V-band photometry of the active G6.5 solar analog V352 CMa. Our aim was to show that CPS can successfully model the presence or absence of periodicity in low-amplitu…