Multiwavelength optical observations of chromospherically active binary systems

Gálvez, M. C.; Montes, D.; Fernández-Figueroa, M. J.; Castro, E. de; Cornide, M.

doi:10.1051/0004-6361:20067015

Cited by 15 publications

(21 citation statements)

References 36 publications

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“…However, we accumulated enough observations for all systems to allow for orbital solutions just using our own data for a certain epoch. This was motivated not only by consistency arguments but also by detections of orbital-period variations in active binaries and particularly in one of our targets (FF UMa; Gálvez et al 2007) 2 . Orbital-period variations of magnetically active binaries are known for a long time (e.g.…”

Section: Binary Orbitsmentioning

confidence: 90%

Rotation, activity, and lithium abundance in cool binary stars

et al. 2012

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We have used two robotic telescopes to obtain time-series high-resolution optical echelle spectroscopy and VI and/or by photometry for a sample of 60 active stars, mostly binaries. Orbital solutions are presented for 26 double-lined systems and for 19 single-lined systems, seven of them for the first time but all of them with unprecedented phase coverage and accuracy. Eighteen systems turned out to be single stars. The total of 6609 R = 55 000échelle spectra are also used to systematically determine effective temperatures, gravities, metallicities, rotational velocities, lithium abundances and absolute Hα-core fluxes as a function of time. The photometry is used to infer unspotted brightness, V − I and/or b − y colors, spot-induced brightness amplitudes and precise rotation periods. An extra 22 radial-velocity standard stars were monitored throughout the science observations and yield a new barycentric zero point for our STELLA/SES robotic system. Our data are complemented by literature data and are used to determine rotation-temperature-activity relations for active binary components. We also relate lithium abundance to rotation and surface temperature. We find that 74 % of all known rapidly-rotating active binary stars are synchronized and in circular orbits but 26 % (61 systems) are rotating asynchronously of which half have Prot > P orb and e > 0. Because rotational synchronization is predicted to occur before orbital circularization active binaries should undergo an extra spin-down besides tidal dissipation. We suspect this to be due to a magnetically channeled wind with its subsequent braking torque. We find a steep increase of rotation period with decreasing effective temperature for active stars, Prot ∝ T −7 eff , for both single and binaries, main sequence and evolved. For inactive, single giants with Prot > 100 d, the relation is much weaker, Prot ∝ T −1.12 eff . Our data also indicate a period-activity relation for Hα of the form RHα ∝ P −0.24 rot for binaries and RHα ∝ P −0.14 rot for singles. Its power-law difference is possibly significant. Lithium abundances in our (field-star) sample generally increase with effective temperature and are paralleled with an increase of the dispersion. The dispersion for binaries can be 1-2 orders of magnitude larger than for singles, peaking at an absolute spread of 3 orders of magnitude near T eff ≈ 5000 K. On average, binaries of comparable effective temperature appear to exhibit 0.25 dex less surface lithium than singles, as expected if the depletion mechanism is rotation dependent. We also find a trend of increased Li abundance with rotational period of form log n(Li) ∝ −0.6 log Prot but again with a dispersion of as large as 3-4 orders of magnitude.

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Section: Binary Orbitsmentioning

confidence: 90%

Rotation, activity, and lithium abundance in cool binary stars

et al. 2012

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“…We have determined the heliocentric RVs by making use of cross‐correlation technique (see e.g. Gálvez et al 2007). The spectra of the target were cross‐correlated order by order, using the routine fxcor in iraf , against spectra of RV standards with similar spectral type taken from Beavers et al (1979).…”

Section: Stellar Parametersmentioning

confidence: 99%

“…However, this behaviour may be caused by the difference in rotational velocity ( v sin i ) between the target and standard star (see e.g. Gálvez et al 2007) when the standard is a much slower rotator than the target. The CCF is essentially the broadening function that would be applied to the template spectrum.…”

Section: Stellar Parametersmentioning

confidence: 99%

FR Cnc revisited: photometry, polarimetry and spectroscopy★

Golovin

Galvez-Ortiz

Hernán‐Obispo

et al. 2012

Monthly Notices of the Royal Astronomical Society

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This paper is part of a multiwavelength study aimed at using complementary photometric, polarimetric and spectroscopic data to achieve an understanding of the activity process in late‐type stars. Here, we present the study of FR Cnc, a young, active and spotted star. We performed analysis of All Sky Automated Survey 3 (ASAS‐3) data for the years 2002–08 and amended the value of the rotational period to be 0.826518 d. The amplitude of photometric variations decreased abruptly in the year 2005, while the mean brightness remained the same, which was interpreted as a quick redistribution of spots. BVRC and IC broad‐band photometric calibration was performed for 166 stars in FR Cnc vicinity. The photometry at Terskol Observatory shows two brightening episodes, one of which occurred at the same phase as the flare of 2006 November 23. Polarimetric BVR observations indicate the probable presence of a supplementary source of polarization. We monitored FR Cnc spectroscopically during the years 2004–08. We concluded that the radial velocity changes cannot be explained by the binary nature of FR Cnc. We determined the spectral type of FR Cnc as K7V. Calculated galactic space‐velocity components (U, V, W) indicate that FR Cnc belongs to the young disc population and might also belong to the IC 2391 moving group. Based on Li iλ6707.8 measurement, we estimated the age of FR Cnc to be between 10 and 120 Myr. Doppler tomography was applied to create a starspot image of FR Cnc. We optimized the goodness of fit to the deconvolved profiles for axial inclination, equivalent width and v sin i, finding v sin i=46.2 km s−1 and i= 55°. We also generated a synthetic V‐band light curve based on Doppler imaging that makes simultaneous use of spectroscopic and photometric data. This synthetic light curve displays the same morphology and amplitude as the observed one. The starspot distribution of FR Cnc is also of interest since it is one of the latest spectral types to have been imaged. No polar spot was detected on FR Cnc.

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“…This technique has been extensively used before because it permits the detecion of weak emission features in the cores of chromospheric lines. In addition, it is the most effective means of identifying other chromospheric activity indicators such as the Balmer lines or the Ca ii IRT, where no calibrations of the photospheric minimum flux exists (Barden 1985;Huenemoerder et al 1989;Hall & Ramcey 1992;Frasca & Catalano 1994;Gunn & Doyle 1997;Lázaro & Arévalo 1997;Montes et al 1995aMontes et al , 1996bMontes et al , 1997Montes et al , 2000Montes et al , 2001Gálvez et al 2002Gálvez et al , 2007Gálvez et al , 2009López-Santiago et al 2003. Inactive, slowly rotating stars, observed in the same observing run as the active stars, were used as reference to construct a morphed spectrum for each active star, using the program jstarmod.…”

Section: Equivalent Widths and Fluxesmentioning

confidence: 99%

Chromospheric activity and rotation of FGK stars in the solar vicinity

Martínez-Arnáiz¹,

Maldonado

Montes³

et al. 2010

A&A

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113

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Context. Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These spots clearly affect the spectral line profiles, and their perturbations alter the line centroids creating a radial velocity jitter that might "contaminate" the variations induced by a planet. Precise chromospheric activity measurements are needed to estimate the activity-induced noise that should be expected for a given star. Aims. We obtain precise chromospheric activity measurements and projected rotational velocities for nearby (d ≤ 25 pc) cool (spectral types F to K) stars, to estimate their expected activity-related jitter. As a complementary objective, we attempt to obtain relationships between fluxes in different activity indicator lines, that permit a transformation of traditional activity indicators, i.e., Ca ii H & K lines, to others that hold noteworthy advantages.Methods. We used high resolution (∼50 000) echelle optical spectra. Standard data reduction was performed using the IRAF echelle package. To determine the chromospheric emission of the stars in the sample, we used the spectral subtraction technique. We measured the equivalent widths of the chromospheric emission lines in the subtracted spectrum and transformed them into fluxes by applying empirical equivalent width and flux relationships. Rotational velocities were determined using the cross-correlation technique. To infer activity-related radial velocity (RV) jitter, we used empirical relationships between this jitter and the R HK index. Results. We measured chromospheric activity, as given by different indicators throughout the optical spectra, and projected rotational velocities for 371 nearby cool stars. We have built empirical relationships among the most important chromospheric emission lines. Finally, we used the measured chromospheric activity to estimate the expected RV jitter for the active stars in the sample.

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Multiwavelength optical observations of chromospherically active binary systems

Cited by 15 publications

References 36 publications

Rotation, activity, and lithium abundance in cool binary stars

Rotation, activity, and lithium abundance in cool binary stars

FR Cnc revisited: photometry, polarimetry and spectroscopy★

Chromospheric activity and rotation of FGK stars in the solar vicinity

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