First light results from PARAS: the PRL Echelle Spectrograph

Chakraborty, Abhijit; Mahadevan, Suvrath; Roy, Arpita; Pathan, F. M.; Shah, Vishal M.; Richardson, E. H.; Ubale, G. P.; Shah, Rajesh

doi:10.1117/12.856555

Cited by 6 publications

(5 citation statements)

References 3 publications

(3 reference statements)

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“…PARAS (PRL Advanced Radial-velocity Abu-sky Search) is currently India's only exoplanet search and characterization program 59 and started science observations in 2012 (Chakraborty et al 2010(Chakraborty et al , 2014. PARAS obtains a single-shot spectral coverage of 3800-9500 Å at a resolution of 67,000 with 4 pixel sampling.…”

Section: Parasmentioning

confidence: 99%

State of the Field: Extreme Precision Radial Velocities

Fischer

Anglada‐Escudé

Arriagada³

et al. 2016

PASP

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322

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The Second Workshop on Extreme Precision Radial Velocities defined circa 2015 the state of the art Doppler precision and identified the critical path challenges for reaching 10 cm s −1 measurement precision. The presentations and discussion of key issues for instrumentation and data analysis and the workshop recommendations for achieving this bold precision are summarized here.Beginning with the HARPS spectrograph, technological advances for precision radial velocity measurements have focused on building extremely stable instruments. To reach still higher precision, future spectrometers will need to improve upon the state of the art, producing even higher fidelity spectra. This should be possible with improved environmental control, greater stability in the illumination of the spectrometer optics, better detectors, more precise wavelength calibration, and broader bandwidth spectra. Key data analysis challenges for the precision radial velocity community include distinguishing center of mass Keplerian motion from photospheric velocities (time correlated noise) and the proper treatment of telluric contamination. Success here is coupled to the instrument design, but also requires the implementation of robust statistical and modeling techniques. Center of mass velocities produce Doppler shifts that affect every line identically, while photospheric velocities produce line profile asymmetries with wavelength and temporal dependencies that are different from Keplerian signals.Exoplanets are an important subfield of astronomy and there has been an impressive rate of discovery over the past two decades. However, higher precision radial velocity measurements are required to serve as a discovery technique for potentially habitable worlds, to confirm and characterize detections from transit missions, and to provide mass measurements for other space-based missions. The future of exoplanet science has very different trajectories depending on the precision that can ultimately be achieved with Doppler measurements.

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Section: Parasmentioning

confidence: 99%

State of the Field: Extreme Precision Radial Velocities

Fischer

Anglada‐Escudé

Arriagada³

et al. 2016

PASP

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322

254

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“…It was designed based on the precision velocimetry lessons learned from its predecessors, particularly HARPS, and is a stabilized fiber-fed high-resolution (R∼67,000) spectrograph with broad wavelength coverage of 3800 -9600Å, and simultaneous ThAr calibration. 2,3 The primary goal was to target exoplanets around bright G and K dwarfs (V mag < 7) with long-term RV precisions of 1-2 m s −1 , degrading up to 5-10 m s −1 on fainter targets. PARAS is already successfully performing at this level ( Fig.…”

Section: Current Performancementioning

confidence: 99%

Precision velocimetry planet hunting with PARAS: current performance and lessons to inform future extreme precision radial velocity instruments

et al. 2016

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The PRL Advanced Radial-velocity Abu-sky Search (PARAS) instrument is a fiber-fed stabilized high-resolution cross-dispersed echelle spectrograph, located on the 1.2 m telescope in Mt. Abu India. Designed for exoplanet detection, PARAS is capable of single-shot spectral coverage of 3800 -9600Å, and currently achieving radial velocity (RV) precisions approaching ∼ 1 m s −1 over several months using simultaneous ThAr calibration. As such, it is one of the few dedicated stabilized fiber-fed spectrographs on small (1-2 m) telescopes that are able to fill an important niche in RV follow-up and stellar characterization. The success of ground-based RV surveys is motivating the push into extreme precisions, with goals of ∼ 10 cm s −1 in the optical and <1 m s −1 in the near-infrared (NIR). Lessons from existing instruments like PARAS are invaluable in informing hardware design, providing pipeline prototypes, and guiding scientific surveys. Here we present our current precision estimates of PARAS based on observations of bright RV standard stars, and describe the evolution of the data reduction and RV analysis pipeline as instrument characterization progresses and we gather longer baselines of data. Secondly, we discuss how our experience with PARAS is a critical component in the development of future cutting edge instruments like (1) the Habitable Zone Planet Finder (HPF), a near-infrared spectrograph optimized to look for planets around M dwarfs, scheduled to be commissioned on the Hobby Eberly Telescope in 2017, and (2) the NEID optical spectrograph, designed in response to the NN-EXPLORE call for an extreme precision Doppler spectrometer (EPDS) for the WIYN telescope. In anticipation of instruments like TESS and GAIA, the groundbased RV support system is being reinforced. We emphasize that instruments like PARAS will play an intrinsic role in providing both complementary follow-up and battlefront experience for these next generation of precision velocimeters.

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“…Aditya High Vacuum, Ahmedabad, India manufactured the vacuum chamber. Details of the analysis performed with ANSYS are mentioned in Chakraborty et al (2010).…”

Section: Vacuum Vessel Stability and Performancementioning

confidence: 99%

“…The region beyond 7000 Å is populated by very bright Argon lines, as well as a large number of atmospheric absorption features, making it less valuable when observing FGK stars using a Thorium-Argon simultaneous wavelength calibration source. The optical design concept and the initial engineering test results can be found in Chakraborty et al (2010) and Chakraborty et al (2008). Here we describe the spectrograph, including key elements of the optical design, and report the stability of the instrument, along with new RV results on σ Dra and HD 9407.…”

Section: Introductionmentioning

confidence: 99%

The PRL Stabilized High-Resolution Echelle Fiber-fed Spectrograph: Instrument Description and First Radial Velocity Results

Chakraborty¹,

Mahadevan²,

Roy³

et al. 2014

Publications of the Astronomical Society of the Pacific

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ABSTRACT. We present spectrograph design details and initial radial velocity results from the PRL optical fiberfed 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 À1 over a period of several months on bright RV standard stars. For observations of σ Dra, we report 1:7 m s À1 precision for a period of 7 months, and for HD 9407, we report 2:1 m s À1 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 AE 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.

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First light results from PARAS: the PRL Echelle Spectrograph

Cited by 6 publications

References 3 publications

State of the Field: Extreme Precision Radial Velocities

State of the Field: Extreme Precision Radial Velocities

Precision velocimetry planet hunting with PARAS: current performance and lessons to inform future extreme precision radial velocity instruments

The PRL Stabilized High-Resolution Echelle Fiber-fed Spectrograph: Instrument Description and First Radial Velocity Results

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