The PRL stabilized high-resolution echelle fiber-fed spectrograph: Instrument description and first radial velocity results

Abhijit Chakraborty, Suvrath Mahadevan, Arpita Roy, Vaibhav Dixit, Eric Harvey Richardson, Varun Dongre, F. M. Pathan, Priyanka Chaturvedi, Vishal Shah, Girish P. Ubale, B. G. Anandarao

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30 Scopus citations


We present spectrograph design details and initial radial velocity results from the PRL optical fiber-fed high-resolution cross-dispersed echelle spectrograph (PARAS), which has recently been commissioned at the Mount Abu 1.2 m telescope in India. Data obtained as part of the postcommissioning tests with PARAS show velocity precision better than 2 m s-1 over a period of several months on bright RV standard stars. For observations of σ Dra, we report 1.7 m s-1 precision for a period of 7 months, and for HD 9407, we report 2.1 m s-1 over a period of 2 months. PARAS is capable of single-shot spectral coverage of 3800-9500 Å at a resolution of ~67,000. The RV results were obtained between 3800 and 6900 Å using simultaneous wavelength calibration with a thorium-argon (ThAr) hollow cathode lamp. The spectrograph is maintained under stable conditions of temperature with a precision of 0.01-0.02° C (rms) at 25.55° C and is enclosed in a vacuum vessel at pressure of 0.1 ± 0.03 mbar. The blaze peak efficiency of the spectrograph between 5000 and 6500 Å, including the detector, is ~30%; it is ~25% with the fiber transmission. The total efficiency, including spectrograph, fiber transmission, focal ratio degradation (FRD), and telescope (with 81% reflectivity) is ~7% in the same wavelength region on a clear night with good seeing conditions. The stable point-spread function (PSF), environmental control, existence of a simultaneous calibration fiber, and availability of observing time make PARAS attractive for a variety of exoplanetary and stellar astrophysics projects. Future plans include testing of octagonal fibers for further scrambling of light and extensive calibration over the entire wavelength range up to 9500 Å using thorium-neon (ThNe) or uranium-neon (UNe) spectral lamps. Thus, we demonstrate how such highly stabilized instruments, even on small aperture telescopes, can contribute significantly to the ongoing radial velocity searches for low-mass planets around bright stars.

Original languageEnglish (US)
Pages (from-to)133-147
Number of pages15
JournalPublications of the Astronomical Society of the Pacific
Issue number936
StatePublished - Feb 2014

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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