Rotational Modulation of Hα Emission in RS CVN Systems

Frasca, A.; Catalano, S.; Marilli, E.

doi:10.1007/978-94-009-0315-9_103

Cited by 46 publications

(57 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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

113

View full text Add to dashboard Cite

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.

show abstract

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

113

View full text Add to dashboard Cite

show abstract

“…We estimated the chromospheric emission level with the "spectral subtraction" technique (see, e.g., Herbig 1985;Barden 1985;Frasca & Catalano 1994;Montes et al 1995), which is based on the subtraction of a reference "non-active" spectrum built up with synthetic model-atmosphere spectra or with observed spectra of slowly-rotating stars of the same spectral type with a negligible level of chromospheric activity. The net equivalent width of the Hα line, W em Hα , was measured in the spectrum obtained after subtracting the non-active template by integrating the residual Hα emission profile.…”

Section: Chromospheric Emissionmentioning

confidence: 99%

A spectroscopic survey of the youngest field stars in the solar neighbourhood

Guillout¹,

Klutsch²,

Frasca

et al. 2009

A&A

Self Cite

View full text Add to dashboard Cite

Aims. We present the first results of an ambitious ground-based observation programme conducted on 1-4 meter class telescopes. Our sample consists of 1097 active and presumably young stars, all of them being optical (Tycho Catalogue) counterparts of ROSAT All-Sky Survey X-ray sources in the northern hemisphere. In this paper, we concentrate on the optically brightest (V T 9. m 5) candidates (704 objects). We acquired high-resolution optical spectroscopy in the Hα and/or lithium spectral regions for 426 of such stars without relevant data in the literature. We describe the star sample and the observations and we start to discuss the physical properties of the investigated stars. Methods. We used a cross-correlation technique and other tools developed by us to derive accurate radial and rotational velocities and to perform an automatic spectral classification for both single stars and double-lined systems. The spectral subtraction technique was used to derive chromospheric activity levels and lithium abundances. We estimated the fraction of young single stars and multiple systems in stellar soft X-ray surveys and the contamination by more evolved systems, like RS CVn binaries. We classified stars on the basis of their lithium abundance and give a glimpse of their sky distribution.Results. The sample appears to be a mixture of quite young Pleiades-like and Hyades-like stars plus an older lithium-poor population probably born within the last 1-2 Gyr. Seven stars with a lithium abundance compatible with the age of IC 2602 (about 30 Myr) or even younger were detected as well, although two appear to be lithium-rich giants.The discovery of a large number of highly or moderately lithium-rich giants is another outcome of the present survey. Conclusions. The contamination of soft X-ray surveys by old systems in which the activity level is enhanced by tidal synchronisation is not negligible, especially for K-type stars. Five stars with lithium content close to the primordial abundance are probably associated with already known moving groups in the solar neighbourhood. Some of them are good post-T Tauri candidates according to their positions in the HR diagram.

show abstract

“…σ 1 CrB (G0V) and σ 2 CrB (F9V+G1V), but σ 2 is brighter than σ 1 by 1.1 mag in V. Nevertheless, the photometry must be corrected for the presence of the third light and this was done according to the formulae given in, e.g., Strassmeier & Bartus (2000). We remark though that this procedure relies on the assumption that σ 1 does not vary in light (as suggested from the spectrophotometric data of Frasca et al 1997) .…”

Section: Time-series Photometrymentioning

confidence: 99%

“…Whether this period is from one of the two σ 2 CrB components or from the G star in σ 1 CrB remains to be determined, e.g. with the spectrophotometric technique used by Frasca et al (1997).…”

Section: Rotation Period(s)mentioning

confidence: 99%

See 1 more Smart Citation

Doppler imaging of stellar surface structure

Strassmeier

Rice

2003

A&A

View full text Add to dashboard Cite

Abstract. We present the first Doppler image for both stellar components of the F9+G0 ZAMS binary σ 2 CrB and found evidence for the coexistence of cool and warm spots on both stars. Cool spots appear mainly at polar or high latitudes while a confined equatorial warm belt appears on the trailing hemisphere of each of the two stars with respect to the orbital motion. We also present an update of the TempMap imaging code that allows us to solve the stellar surface temperature distribution on both binary components simultaneously, including photometric input. Several test reconstructions are performed to demonstrate its reliability and robustness. Our new orbital solution results in very precise masses for both components -good to 0.4% -and confirms the spectral classifications of F9 and G0 for the primary and secondary, respectively. The visual component, σ 1 CrB, seems to be G4 rather than G0. All three components are on or very close to the ZAMS which is also confirmed by the relatively high lithium abundance of about twenty times the solar abundance. Photometric light variations are detected with a period of 1.157 ± 0.002 days that we interpret to be the rotation period of both binary components. A 0. m 04 dimming in y together with a reddening of 0. m 01 in b − y during the year 2000 suggests a long-term spot variability compatible with a period of at least 260 days.

show abstract

Rotational Modulation of Hα Emission in RS CVN Systems

Cited by 46 publications

References 1 publication

Chromospheric activity and rotation of FGK stars in the solar vicinity

Chromospheric activity and rotation of FGK stars in the solar vicinity

A spectroscopic survey of the youngest field stars in the solar neighbourhood

Doppler imaging of stellar surface structure

Contact Info

Product

Resources

About