Granulation in K-type Dwarf Stars. I. Spectroscopic observations

Details Granulation in K-type Dwarf Stars. I. Spectroscopic observations Granulation in K-type Dwarf Stars. I. Spectroscopic observations

2008-10-29

arxiv.org/abs/0810.5247v1

Astronomy and Astrophysics

Astrophysics

A&A, in press

Scientific paper

10.1051/0004-6361:200810901

Very high resolution (R~160,000-210,000), high signal-to-noise ratio (S/N>300) spectra of nine bright K-dwarfs were obtained with the 2dcoude spectrograph on the 2.7m Telescope at McDonald Observatory to determine wavelength shifts and asymmetries of Fe I lines. The observed shapes and positions of Fe I lines reveal asymmetries and wavelength shifts that indicate the presence of granulation. In particular, line bisectors show characteristic C-shapes while line core wavelengths are blueshifted by an amount that increases with decreasing equivalent width (EW). On average, Fe I line bisectors have a span that ranges from nearly 0 for the weakest lines (residual core flux > 0.7) to about 75 m/s for the strongest lines (residual core flux ~ 0.3) while wavelength shifts range from about -150 m/s in the weakest (EW ~ 10 mA) lines to 0 in the strongest (EW > 100 mA) features. A more detailed inspection of the bisectors and wavelength shifts reveals star-to-star differences that are likely associated with differences in stellar parameters, projected rotational velocity, and stellar activity. For the inactive, slow projected rotational velocity stars, we detect, unequivocally, a plateau in the line-shifts at large EW values (EW > 100 mA), a behavior that had been identified before only in the solar spectrum. The detection of this plateau allows us to determine the zero point of the convective blueshifts, which is useful to determine absolute radial velocities. Thus, we are able to measure such velocities with a mean uncertainty of about 60 m/s.

Affiliated with

Also associated with

No associations

Rating

Granulation in K-type Dwarf Stars. I. Spectroscopic observations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Granulation in K-type Dwarf Stars. I. Spectroscopic observations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Granulation in K-type Dwarf Stars. I. Spectroscopic observations will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-72150