Photometry of 50 suspected variable stars

Hooten, James T.; Hall, D. S.

doi:10.1086/191497

Cited by 51 publications

(58 citation statements)

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“…This period is quite different from the orbital period of 13.048 days determined by Balona (1987). For HD 181809 Hooten & Hall (1990) analyzed five groups of photometry ranging over about 11 years. They determined a ''best'' period of 60.23 days and found that, during the time covered by their observations, HD 181809 had a maximum V magnitude amplitude of 0.3 mag.…”

Section: Photometric Analysismentioning

confidence: 99%

Chromospherically Active Stars. XXIV. The Giant, Single-lined Binaries HD 37824, HD 181809, and HD 217188

Fekel

Henry

2005

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We have obtained spectroscopy and photometry of three chromospherically active, single-lined spectroscopic binaries, HD 37824 (V1149 Ori), HD 181809 (V4138 Sgr), and HD 217188 (AZ Psc). HD 37824 has a circular orbit with a period of 53.57 days. Its primary is a K0 III star, while the secondary is likely a G or K dwarf. HD 181809 has an orbit with a period of 13.04667 days and a low eccentricity of 0.040. The primary has a spectral type of K0 III-IV, and its secondary is probably an M dwarf. The orbit of HD 217188 has a period of 47.1209 days and a moderately high eccentricity of 0.470. The spectral type of the primary is K0 III, while the secondary is likely an M dwarf. All three systems are estimated to have near solar iron abundances. Photometric observations spanning 15-16 years for all three stars yield mean photometric periods of 53.12, 59.85, and 90.89 days for HD 37824, HD 181809, and HD 217188, respectively. Thus, HD 37824 is rotating synchronously with the orbital period, while HD 181809 and HD 217188 are both rotating considerably slower than synchronously. All three stars show longterm variations in mean brightness and photometric amplitude, but no correlations are observed between the seasonal mean brightness, photometric amplitude, and seasonal photometric period in any of the stars. No clear evidence for long-term periodic variations in any of these parameters is present. The circular orbit of HD 37824 and the synchronous rotation of its K giant argue that the star is in the core helium-burning phase of its evolution. The giant components of HD 181809 and HD 217188 are asynchronous rotators, and both systems have eccentric orbits. Thus, those two stars are likely first-ascent giants.

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Section: Photometric Analysismentioning

confidence: 99%

Chromospherically Active Stars. XXIV. The Giant, Single-lined Binaries HD 37824, HD 181809, and HD 217188

Fekel

Henry

2005

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“…The presence of an extremely active chromosphere on XX Tri was confirmed by Strassmeier et al (1990), showing that the Ca ii H&K emission intensity was two to three times that of the local continuum. The first published photometric observations dated back to 1986-87 and showed a fairly scattered light curve (Hooten & Hall 1990). Three years later, a remarkably high V amplitude of 0. m 6 was observed by Nolthenius (1991).…”

Section: Introductionmentioning

confidence: 99%

Spot evolution on the red giant star XX Triangulum

Künstler

Carroll

Strassmeier

2015

A&A

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Context. Solar spots appear to decay linearly proportional to their size. The decay rate of solar spots is directly related to magnetic diffusivity, which itself is a key quantity for the length of a magnetic-activity cycle. Is a linear spot decay also seen on other stars, and is this in agreement with the large range of solar and stellar activity cycle lengths? Aims. We investigate the evolution of starspots on the rapidly-rotating (P rot ≈ 24 d) K0 giant XX Tri, using consecutive time-series Doppler images. Our aim is to obtain a well-sampled movie of the stellar surface over many years, and thereby detect and quantify a starspot decay law for further comparison with the Sun. Methods. We obtained continuous high-resolution and phase-resolved spectroscopy with the 1.2-m robotic STELLA telescope on Tenerife over six years, and these observations are ongoing. For each observing season, we obtained between 5 to 7 independent Doppler images, one per stellar rotation, making up a total of 36 maps. All images were reconstructed with our line-profile inversion code iMap. A wavelet analysis was implemented for denoising the line profiles. To quantify starspot area decay and growth, we match the observed images with simplified spot models based on a Monte Carlo approach. Results. It is shown that the surface of XX Tri is covered with large high-latitude and even polar spots and with occasional small equatorial spots. Just over the course of six years, we see a systematically changing spot distribution with various timescales and morphology, such as spot fragmentation and spot merging as well as spot decay and formation. An average linear decay of D = −0.022 ± 0.002 SH/day is inferred. We found evidence of an active longitude in phase toward the (unseen) companion star. Furthermore, we detect a weak solar-like differential rotation with a surface shear of α = 0.016 ± 0.003. From the decay rate, we determine a turbulent diffusivity of η T = (6.3 ± 0.5) × 10 14 cm 2 /s and predict a magnetic activity cycle of ≈26 ± 6 yr. Finally, we present a short movie of the spatially resolved surface of XX Tri.

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“…Such a result implies that the lowlatitude spots seem to have shorter lifetimes than the intermediate to high-latitude spots, like most of other magnetic active stars. Hooten & Hall (1990) obtained four groups of photometric data, and found the second dataset spanned more than 5 months gave a large scatter when searching the period although it contains the largest number of data points, whereas the fourth dataset spanned less than one month gave a small scatter for the period obtained. This suggests that the spot pattern is stable for short duration, and changes for long time interval.…”

Section: Discussionmentioning

confidence: 99%

“…It is a young pre-main-sequence K2V dwarf with a large rotation velocity vsini=22-24km/s (Lopez-Santiago et al 2003, Strassmeier & Rice 2006. Previous results show that PW And is an active star with starspots and chromospheric emission (Bidelman 1985, Hooten & Hall 1990, Montes et al 2001a, Lopez-Santiago et al 2003, Strassmeier & Rice 2006.…”

Section: Introductionmentioning

confidence: 91%

Doppler imaging of the active star PW And

Cameron

Kim

2009

Proc. IAU

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Abstract. We present spot activity of the K2V pre-main-sequence star PW And based on the high-resolution spectroscopic data obtained at Xinglong station and BOAO in 2005 November and December. Using the Least-Squares Deconvolution method, we have derived time series of composite profiles of PW And with high signal to noise ratio. These have been used to reconstruct its starspot pattern via the Doppler imaging method. The result shows that intermediate to highlatitude spots are the dominant features and weak low-latitude spots also appear. Comparing Doppler images from two data subsets, it can be found that almost no difference between two images exists except the small position evolution of weak low-latitude spots, which suggests that the intermediate to high-latitude spots have longer lifetimes than one month, and the low-latitude spots have shorter lifetimes.

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Photometry of 50 suspected variable stars

Cited by 51 publications

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Chromospherically Active Stars. XXIV. The Giant, Single-lined Binaries HD 37824, HD 181809, and HD 217188

Chromospherically Active Stars. XXIV. The Giant, Single-lined Binaries HD 37824, HD 181809, and HD 217188

Spot evolution on the red giant star XX Triangulum

Doppler imaging of the active star PW And

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