Radial velocities with CRIRES

Abstract

With the advent of high-resolution infrared spectrographs, radial relocity (RV) searches enter into a new domain. As of today, the most important technical question to address is which wavelength reference is the most suitable for high-precision RV measurements. In this work we use atmospheric absorption features as wavelength reference on CRIRES data obtained on two programs and three different targets. We analyzed the data from the TW Hya campaign again, reaching a dispersion of about 6 m/s on the RV standard on a time scale of roughly 1 week. We confirm that there is a low-amplitude RV signal on TW Hya itself, with an amplitude roughly 3 times smaller than the one reported at visible wavelengths. We present RV measurements of Gl 86 as well, showing that our approach is capable of detecting the signal induced by a planet and correctly quantifying it. Our data show that CRIRES is capable of reaching an RV precision of less than 10 m/s on a time scale of one week. The limitations of this particular approach are discussed, along with the limiting factors on RV precision in the IR in a general way. The implications of this work on the design of future dedicated IR spectrographs are addressed as well.

Evidence of a substellar companion around a very young T Tauri star

“…Spectra were collected using the 4096 × 512 pixel Aladdin III detectors and a 0.2" slit which delivered a R∼100000 around 1598.0 nm (CRIRES setup 36). This particular setting was chosen because we could benefit from the CO 2 telluric atmospheric lines as simultaneous wavelength calibrators (Huélamo et al 2008;Figueira et al 2010c) to derive precise RVs. Previous studies have indeed shown that telluric lines are steady RV zero-point tracers (Figueira et al 2010b) that display a long-term stability and, for this reason, can deliver RVs with a precision down to 5-10 ms −1 .…”

“…Wavelength calibration was performed using telluric absorption lines (see e.g., Figueira et al 2010c;Bailey et al 2012). Laboratory wavelength zero-points of each telluric spectral line were collected from the HITRAN database (Rothman & Gordon 2009).…”

“…Laboratory wavelength zero-points of each telluric spectral line were collected from the HITRAN database (Rothman & Gordon 2009). The RVs in this study were derived using the Figueira et al (2010c) pipeline and its adapted version to young stars developed by Viana Almeida et al (2012). Both versions of the pipeline are based on a two-dimensional (2D) cross-correlation function (CCF) inspired by TODCOR (Mazeh & Zucker 1992).…”

Detecting planets around very cool dwarfs at near infrared wavelengths with the radial velocity technique

“…In the observations, the telluric lines are superimposed on the stellar spectra, and Seifahrt et al (2008) showed that these atmospheric lines are stable in terms of velocity in the order of 10 m s −1 . Figueira et al (2010) adopted telluric lines as a stable wavelength reference, and showed that these lines allow us to reach RV precisions that are even better than 10 m s −1 when accounting for the changing weather conditions at the observatory during the observations. Special lamps that produce a dense forest of emission lines are used with most of the high-precision and stabilized spectrographs in the optical.…”

“…Bean et al (2010) conducted high-resolution data of 31 M-dwarfs (spectral types M4-M9), and report an RV precision of better than 5 m s −1 . Figueira et al (2010) took observations of the planetary candidate TW Hya and achieved a RV precision better than 10 m s −1 by adopting telluric lines as a stable reference. However, the exploration of the RVs in the IR is in its infancy, and a revolution is expected in the forthcoming years with the arrival of the new generation of high-resolution nearinfrared spectrographs.…”