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Title:
Rotational Velocities for M Dwarfs
Authors:
Jenkins, J. S.; Ramsey, L. W.; Jones, H. R. A.; Pavlenko, Y.; Gallardo, J.; Barnes, J. R.; Pinfield, D. J.
Affiliation:
AA(Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802, USA; Department of Astronomy, Universidad de Chile, Casilla Postal 36D, Santiago, Chile ), AB(Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802, USA), AC(Center for Astrophysics, University of Hertfordshire, College Lane Campus, Hatfield, Hertfordshire AL10 9AB, UK), AD(Center for Astrophysics, University of Hertfordshire, College Lane Campus, Hatfield, Hertfordshire AL10 9AB, UK), AE(Department of Astronomy, Universidad de Chile, Casilla Postal 36D, Santiago, Chile), AF(Center for Astrophysics, University of Hertfordshire, College Lane Campus, Hatfield, Hertfordshire AL10 9AB, UK), AG(Center for Astrophysics, University of Hertfordshire, College Lane Campus, Hatfield, Hertfordshire AL10 9AB, UK)
Publication:
The Astrophysical Journal, Volume 704, Issue 2, pp. 975-988 (2009). (ApJ Homepage)
Publication Date:
10/2009
Origin:
IOP
Astronomy Keywords:
planetary systems, stars: fundamental parameters, stars: low-mass, brown dwarfs, stars: rotation
DOI:
10.1088/0004-637X/704/2/975
Bibliographic Code:
2009ApJ...704..975J

Abstract

We present spectroscopic rotation velocities (v sin i) for 56 M dwarf stars using high-resolution Hobby-Eberly Telescope High Resolution Spectrograph red spectroscopy. In addition, we have also determined photometric effective temperatures, masses, and metallicities ([Fe/H]) for some stars observed here and in the literature where we could acquire accurate parallax measurements and relevant photometry. We have increased the number of known v sin i values for mid M stars by around 80% and can confirm a weakly increasing rotation velocity with decreasing effective temperature. Our sample of v sin is peak at low velocities (~3 km s-1). We find a change in the rotational velocity distribution between early M and late M stars, which is likely due to the changing field topology between partially and fully convective stars. There is also a possible further change in the rotational distribution toward the late M dwarfs where dust begins to play a role in the stellar atmospheres. We also link v sin i to age and show how it can be used to provide mid-M star age limits. When all literature velocities for M dwarfs are added to our sample, there are 198 with v sin i <= 10 km s-1 and 124 in the mid-to-late M star regime (M3.0-M9.5) where measuring precision optical radial velocities is difficult. In addition, we also search the spectra for any significant Halpha emission or absorption. Forty three percent were found to exhibit such emission and could represent young, active objects with high levels of radial-velocity noise. We acquired two epochs of spectra for the star GJ1253 spread by almost one month and the Halpha profile changed from showing no clear signs of emission, to exhibiting a clear emission peak. Four stars in our sample appear to be low-mass binaries (GJ1080, GJ3129, Gl802, and LHS3080), with both GJ3129 and Gl802 exhibiting double Halpha emission features. The tables presented here will aid any future M star planet search target selection to extract stars with low v sin i.

Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.

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