μ Herculis: Analysis of EW time series of a solar-type pulsator

Time series spectra of the F5IV star Procyon (α CMi) were obtained at the Kitt Peak National Observatory during a 35-night observing run in January-February 1997. The observations were obtained as part of an international collaboration to detect and study acoustic p-mode oscillations in solar-type stars. Spectra covered the wavelength range from 4000 to 5300 Å, with a resolving power of approximately 3500 (1.3 Å resolution). The sampling rate was one observation per minute, and the typical S/N ratio per pixel after averaging along columns is in excess of 1000. We obtained 12,888 spectra. A sample spectrum is shown in Figure 1

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Surface differential rotation of IL Hya from time-series Doppler images

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314002543 ◽

2013 ◽

Vol 9 (S302) ◽

pp. 379-380 ◽

Cited By ~ 1

Author(s):

Zsolt Kővári ◽

Levente Kriskovics ◽

Katalin Oláh ◽

Krisztián Vida ◽

János Bartus ◽

...

Keyword(s):

Time Series ◽

Differential Rotation ◽

Cross Correlation ◽

Meridional Circulation ◽

Imaging Study ◽

Doppler Imaging ◽

Surface Pattern ◽

Cross Correlation Analysis ◽

Solar Type

AbstractWe present a time-series Doppler imaging study of the K-subgiant component in the RS CVn-type binary system IL Hya (Porb=12.905 d). From re-processing the unique long-term spectroscopic dataset of 70 days taken in 1996/97, we perform a thorough cross-correlation analysis to derive surface differential rotation. As a result we get solar-type differential rotation with a shear value α of 0.05, in agreement with preliminary suggestions from previous attempts. A possible surface pattern of meridional circulation is also detected.

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Activity time series of old stars from late F to early K

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038710 ◽

2020 ◽

Vol 644 ◽

pp. A77

Author(s):

N. Meunier ◽

A.-M. Lagrange ◽

S. Borgniet

Keyword(s):

Time Series ◽

Radial Velocity ◽

High Precision ◽

False Positive ◽

Main Sequence ◽

Habitable Zone ◽

Stellar Activity ◽

Detection Rates ◽

Solar Type ◽

Synthetic Time Series

Context. Stellar activity strongly affects and may prevent the detection of Earth-mass planets in the habitable zone of solar-type stars with radial velocity technics. Astrometry is in principle less sensitive to stellar activity because the situation is more favourable: the stellar astrometric signal is expected to be fainter than the planetary astrometric signal compared to radial velocities. Aims. We quantify the effect of stellar activity on high-precision astrometry when Earth-mass planets are searched for in the habitable zone around old main-sequence solar-type stars. Methods. We used a very large set of magnetic activity synthetic time series to characterise the properties of the stellar astrometric signal. We then studied the detectability of exoplanets based on different approaches: first based on the theoretical level of false positives derived from the synthetic time series, and then with blind tests for old main-sequence F6-K4 stars. Results. The amplitude of the signal can be up to a few times the solar value depending on the assumptions made for activity level, spectral type, and spot contrast. The detection rates for 1 MEarth planets are very good, however, with extremely low false-positive rates in the habitable zone for stars in the F6-K4 range at 10 pc. The standard false-alarm probability using classical bootstrapping on the time series strongly overestimates the false-positive level. This affects the detection rates. Conclusions. We conclude that if technological challenges can be overcome and very high precision is reached, astrometry is much more suitable for detecting Earth-mass planets in the habitable zone around nearby solar-type stars than radial velocity, and detection rates are much higher for this range of planetary masses and periods when astrometric techniques are used than with radial velocity techniques.

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Long, accurate time series measurements of radial velocities of solar-type stars

Astrophysics and Space Science ◽

10.1007/bf00984531 ◽

1994 ◽

Vol 212 (1-2) ◽

pp. 271-280 ◽

Cited By ~ 18

Author(s):

R. S. Mcmillan ◽

T. L. Moore ◽

M. L. Perry ◽

P. H. Smith

Keyword(s):

Time Series ◽

Radial Velocities ◽

Solar Type

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The LDE-Type Flare Occurrence (1969-1993)

International Astronomical Union Colloquium ◽

10.1017/s0252921100025458 ◽

1994 ◽

Vol 144 ◽

pp. 279-282

Author(s):

A. Antalová

Keyword(s):

Time Series ◽

Fourier Analysis ◽

Sunspot Cycle ◽

List Type ◽

Type Number ◽

Solar Cycles ◽

Type Iv ◽

Long Duration ◽

Cycle Maximum ◽

Flare Index

AbstractThe occurrence of LDE-type flares in the last three cycles has been investigated. The Fourier analysis spectrum was calculated for the time series of the LDE-type flare occurrence during the 20-th, the 21-st and the rising part of the 22-nd cycle. LDE-type flares (Long Duration Events in SXR) are associated with the interplanetary protons (SEP and STIP as well), energized coronal archs and radio type IV emission. Generally, in all the cycles considered, LDE-type flares mainly originated during a 6-year interval of the respective cycle (2 years before and 4 years after the sunspot cycle maximum). The following significant periodicities were found:• in the 20-th cycle: 1.4, 2.1, 2.9, 4.0, 10.7 and 54.2 of month,• in the 21-st cycle: 1.2, 1.6, 2.8, 4.9, 7.8 and 44.5 of month,• in the 22-nd cycle, till March 1992: 1.4, 1.8, 2.4, 7.2, 8.7, 11.8 and 29.1 of month,• in all interval (1969-1992):a)the longer periodicities: 232.1, 121.1 (the dominant at 10.1 of year), 80.7, 61.9 and 25.6 of month,b)the shorter periodicities: 4.7, 5.0, 6.8, 7.9, 9.1, 15.8 and 20.4 of month.Fourier analysis of the LDE-type flare index (FI) yields significant peaks at 2.3 - 2.9 months and 4.2 - 4.9 months. These short periodicities correspond remarkably in the all three last solar cycles. The larger periodicities are different in respective cycles.

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A Search for Dyson Spheres around Late-Type Stars in the Solar Neighborhood II

International Astronomical Union Colloquium ◽

10.1017/s0252921100015281 ◽

1997 ◽

Vol 161 ◽

pp. 707-709 ◽

Cited By ~ 1

Author(s):

Jun Jugaku ◽

Shiro Nishimura

Keyword(s):

Solar Neighborhood ◽

The Sun ◽

Late Type ◽

Solar Type

AbstractWe continued our search for partial (incomplete) Dyson spheres associated with 50 solar-type stars (spectral classes F, G, and K) within 25 pc of the Sun. No candidate objects were found.

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The Infancy of Solar-Type Stars and its Relevance for the Origin of Life

International Astronomical Union Colloquium ◽

10.1017/s0252921100014780 ◽

1997 ◽

Vol 161 ◽

pp. 267-282 ◽

Cited By ~ 1

Author(s):

Thierry Montmerle

Keyword(s):

Main Sequence ◽

Solar Nebula ◽

Circumstellar Disks ◽

T Tauri Stars ◽

Necessary Condition ◽

Sequence Evolution ◽

T Tauri ◽

Solar Type ◽

Optical Domain ◽

The Origin Of Life

AbstractFor life to develop, planets are a necessary condition. Likewise, for planets to form, stars must be surrounded by circumstellar disks, at least some time during their pre-main sequence evolution. Much progress has been made recently in the study of young solar-like stars. In the optical domain, these stars are known as «T Tauri stars». A significant number show IR excess, and other phenomena indirectly suggesting the presence of circumstellar disks. The current wisdom is that there is an evolutionary sequence from protostars to T Tauri stars. This sequence is characterized by the initial presence of disks, with lifetimes ~ 1-10 Myr after the intial collapse of a dense envelope having given birth to a star. While they are present, about 30% of the disks have masses larger than the minimum solar nebula. Their disappearance may correspond to the growth of dust grains, followed by planetesimal and planet formation, but this is not yet demonstrated.

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