The γ Dor variable HR 8799: results from a multisite campaign

Zerbi, F. M.; Rodríguez‐López, C.; Garrido, R.; Martín, S.; Ferro, A. Arellano; Sareyan, J. P.; Krisciunas, K.; Akan, Mustafa; Evren, S.; İbanoǧlu, C.; Keskin, V.; Pekünlü, R.; Tunca, Z.; Luedeke, K. D.; Paparó, M.; Nuspl, J.; Guerrero, G.

doi:10.1046/j.1365-8711.1999.02209.x

Cited by 65 publications

(38 citation statements)

References 7 publications

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“…Reddening is unlikely to be responsible for the brightness deficits of these two objects: reddening is negligible within 75 pc of the Sun (e.g. Leroy 1993), and HR 8799 itself has negligible reddening (Zerbi et al 1999). We conclude that both of the two strongest NOMAD candidates identified by Close & Males (2009) are probably background field stars, unassociated with HR 8799.…”

Section: On the Candidate Common Proper Motion Starsmentioning

confidence: 66%

Thermal Infrared Mmtao Observations of the Hr 8799 Planetary System

Hinz

Rodigas

Kenworthy

et al. 2010

ApJ

121

157

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We present direct imaging observations at wavelengths of 3.3, 3.8 (L ′ band), and 4.8 (M band) µm, for the planetary system surrounding HR 8799. All three planets are detected at L ′ . The c and d component are detected at 3.3 µm, and upper limits are derived from the M band observations. These observations provide useful constraints on warm giant planet atmospheres. We discuss the current age constraints on the HR 8799 system, and show that several potential co-eval objects can be excluded from being co-moving with the star. Comparison of the photometry is made to models for giant planet atmospheres. Models which include non-equilibrium chemistry provide a reasonable match to the colors of c and d. From the observed colors in the thermal infrared we estimate T eff < 960 K for b, and T eff =1300 and 1170 K for c and d, respectively. This provides an independent check on the effective temperatures and thus masses of the objects from the Marois et al. (2008) results.

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Section: On the Candidate Common Proper Motion Starsmentioning

confidence: 66%

Thermal Infrared Mmtao Observations of the Hr 8799 Planetary System

Hinz

Rodigas

Kenworthy

et al. 2010

ApJ

121

157

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“…The first two frequencies (1.9791 and 1.7368 d −1 ) found in the multisite campaign presented in Zerbi et al (1999) …”

Section: Hd 218396 = Hip 114189 = Hr 8799 = V342 Pegmentioning

confidence: 87%

Long-term photometric monitoring with the Mercator telescope

Cuypers¹,

Aerts

Cat³

et al. 2009

A&A

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Context. γ Dor stars are excellent targets for asteroseismology since the gravity modes present in these stars probe the deep stellar interiors. Mode identification will improve the knowledge of these stars considerably. Aims. A selected group of γ Dor stars and some candidates were observed with the Mercator telescope to find and/or confirm the periodicities in the light variations and to derive reliable amplitude ratios in different pass bands. Methods. A frequency analysis was performed on all new data obtained in the Geneva photometric system. In order to have more reliable and accurate frequencies, the new data were combined with similar data from the literature and with Hipparcos observations. A set of frequencies that minimized the residuals in a harmonic fit was searched for while allowing means and amplitudes to vary from one observation set to another. Results. Frequencies and amplitudes in the photometric passbands of the Geneva system are given for 21 γ Dor stars. We report the discovery of HD 74504 as a newly found γ Dor star. Conclusions. Our study provides the first extensive multicolour database for the understanding of gravity modes in F-type stars.

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“…10. A comparison of log g values derived from Geneva photometry and from other sources (photometry and spectroscopy) 6 Rodríguez & Breger (2001); Rodríguez et al (2000); ; Poretti et al (1997);Breger et al (1997); Zerbi et al (1997Zerbi et al ( , 1999; Aerts et al (1998); Kaye et al (1999b); Gray & Kaye (1999) indicates a systematic difference of about 0.4 dex for log g values above 4.35 dex as calculated from the Geneva photometry (Cuypers & Hendrix, priv. comm.).…”

Section: Characterization Of Stars That Show No Clear Periodic Variabmentioning

confidence: 99%

TheKeplercharacterization of the variability among A- and F-type stars

Uytterhoeven

Moya

Grigahcène

et al. 2011

A&A

311

316

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Context. The Kepler spacecraft is providing time series of photometric data with micromagnitude precision for hundreds of A-F type stars. Aims. We present a first general characterization of the pulsational behaviour of A-F type stars as observed in the Kepler light curves of a sample of 750 candidate A-F type stars, and observationally investigate the relation between γ Doradus (γ Dor), δ Scuti (δ Sct), and hybrid stars. Methods. We compile a database of physical parameters for the sample stars from the literature and new ground-based observations. We analyse the Kepler light curve of each star and extract the pulsational frequencies using different frequency analysis methods. We construct two new observables, "energy" and "efficiency", related to the driving energy of the pulsation mode and the convective efficiency of the outer convective zone, respectively. Results. We propose three main groups to describe the observed variety in pulsating A-F type stars: γ Dor, δ Sct, and hybrid stars. We assign 63% of our sample to one of the three groups, and identify the remaining part as rotationally modulated/active stars, binaries, stars of different spectral type, or stars that show no clear periodic variability. 23% of the stars (171 stars) are hybrid stars, which is a much higher fraction than what has been observed before. We characterize for the first time a large number of A-F type stars (475 stars) in terms of number of detected frequencies, frequency range, and typical pulsation amplitudes. The majority of hybrid stars show frequencies with all kinds of periodicities within the γ Dor and δ Sct range, also between 5 and 10 d −1 , which is a challenge for the current models. We find indications for the existence of δ Sct and γ Dor stars beyond the edges of the current observational instability strips. The hybrid stars occupy the entire region within the δ Sct and γ Dor instability strips and beyond. Non-variable stars seem to exist within the instability strips. The location of γ Dor and δ Sct classes in the (T eff , log g)-diagram has been extended. We investigate two newly constructed variables, "efficiency" and "energy", as a means to explore the relation between γ Dor and δ Sct stars. Conclusions. Our results suggest a revision of the current observational instability strips of δ Sct and γ Dor stars and imply an investigation of pulsation mechanisms to supplement the κ mechanism and convective blocking effect to drive hybrid pulsations. Accurate physical parameters for all stars are needed to confirm these findings.

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The γ Dor variable HR 8799: results from a multisite campaign

Cited by 65 publications

References 7 publications

Thermal Infrared Mmtao Observations of the Hr 8799 Planetary System

Thermal Infrared Mmtao Observations of the Hr 8799 Planetary System

Long-term photometric monitoring with the Mercator telescope

TheKeplercharacterization of the variability among A- and F-type stars

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