3 research outputs found
The CARMENES search for exoplanets around M dwarfs High-resolution optical and near-infrared spectroscopy of 324 survey stars
The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets. In this paper, we present the survey sample by publishing one CARMENES spectrum for each M dwarf. These spectra cover the wavelength range 520–1710 nm at a resolution of at least R >80 000, and we measure its RV, Hα emission, and projected rotation velocity. We present an atlas of high-resolution M-dwarf spectra and compare the spectra to atmospheric models. To quantify the RV precision that can be achieved in low-mass stars over the CARMENES wavelength range, we analyze our empirical information on the RV precision from more than 6500 observations. We compare our high-resolution M-dwarf spectra to atmospheric models where we determine the spectroscopic RV information content, Q, and signal-to-noise ratio. We find that for all M-type dwarfs, the highest RV precision can be reached in the wavelength range 700–900 nm. Observations at longer wavelengths are equally precise only at the very latest spectral types (M8 and M9). We demonstrate that in this spectroscopic range, the large amount of absorption features compensates for the intrinsic faintness of an M7 star. To reach an RV precision of 1 m s−1 in very low mass M dwarfs at longer wavelengths likely requires the use of a 10 m class telescope. For spectral types M6 and earlier, the combination of a red visual and a near-infrared spectrograph is ideal to search for low-mass planets and to distinguish between planets and stellar variability. At a 4 m class telescope, an instrument like CARMENES has the potential to push the RV precision well below the typical jitter level of 3–4 m s−1
CARMENES: high-resolution spectra and precise radial velocities in the red and infrared
SPIE Astronomical Telescopes + Instrumentation (2018, Austin, Texas, United States
A differential least-squares deconvolution method for high precision spectroscopy of stars and exoplanets - I. Application to obliquity measurements of HARPS observations of HD189733b
High precision measurements of stellar spectroscopic line profiles and their
changes over time contain very valuable information about the physics of the
stellar photosphere (stellar activity) and can be used to characterize
extrasolar planets via the Rossiter-McLaughlin effect or from reflected light
from the planet.
In this paper we present a new method for measuring small changes in the mean
line profile of a spectrum by performing what we call differential Least
Squares Deconvolution (dLSD). The method consists in finding the convolution
function (or kernel) required to transform a high signal-to-noise ratio
template of the star into each observed spectrum. Compared to similar
techniques, the method presented here does not require any assumptions on the
template spectrum (eg. no line-list or cross-correlation mask required).
We show that our implementation of dLSD is able to perform -at least- as good
as other techniques by applying it to star-planet obliquity measurements of
exoplanet HD183799 during its transit. Among other things, the method should
enable model independent detection of light reflected by an exoplanet.Comment: 8 page