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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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.

Placing a pupil mask with a gaussian aperture into the optical train of current telescopes represents a way to attain high contrast imaging that potentially improves contrast by orders of magnitude compared to current techniques. We present here the first observations ever using a gaussian aperture pupil mask (GAPM) on the Penn State near-IR Imager and Spectrograph (PIRIS) at the Mt. Wilson 100 ′′ telescope. Two nearby stars were observed, ǫ Eridani and µ Her A. A faint companion was detected around µ Her A, confirming it as a proper motion companion. Furthermore, the observed H and K magnitudes of the companion were used to constrain its nature. No companions or faint structure were observed for ǫ Eridani. We found that our observations with the GAPM achieved contrast levels similar to our coronographic images, without blocking light from the central star. The mask's performance also nearly reached sensitivities reported for other ground based adaptive optics coronographs and deep HST images, but did not reach theoretically predicted contrast levels. We outline ways that could improve the performance of the GAPM by an order of magnitude or more.

Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.22 • , ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations may be caused by reflected light from the planet's atmosphere and the dramatic change in star-planet separation surrounding the periastron passage.

We present new results on the circumstellar nebulosity around SU Aurigae, a T Tauri star of about 2 M and 5 Myr old at 152 pc in the J, H, and K bands using high-resolution adaptive optics imaging (0B30) with the Penn State Near-IR Imager and Spectrograph at the 100 inch (2.5 m) Mount Wilson telescope. A comparison with Hubble Space Telescope STIS optical (0.2-1.1 m) images shows that the orientation of the circumstellar nebulosity in the near-IR extends from position angle 210 to 270 in the H and K bands and up to 300 in the J band. We call the circumstellar nebulosity seen between 210 and 270 an ''IR nebulosity.'' We find that the IR nebulosity (which extends up to 3B5 in the J band and 2B5 in the K band) is due to scattered light from the central star. The IR nebulosity is either a cavity formed by the stellar outflows or part of the circumstellar disk. We present a schematic three-dimensional geometric model of the disk and jet of SU Aur based on STIS and our near-IR observations. According to this model, the IR nebulosity is part of the circumstellar disk seen at high inclination angles. The extension of the IR nebulosity is consistent with estimates of the disk diameter of 50-400 AU in radius, from earlier millimeter K-band interferometric observations and SED fittings.

We report the detection of a very low mass star (VLMS) companion to the primary star 1SWASPJ234318.41+295556.5A (J2343+29A), using radial velocity (RV) measurements from the PARAS (PRL Advanced Radial-velocity Abu-sky Search) high resolution echelle spectrograph. The periodicity of the single-lined eclipsing binary (SB 1 ) system, as determined from 20 sets of RV observations from PARAS and 6 supporting sets of observations from SOPHIE data, is found to be 16.953 d as against the 4.24 d period reported from Su-perWasp photometry. It is likely that inadequate phase coverage of the transit with SuperWasp photometry led to the incorrect determination of the period for this system. We derive the spectral properties of the primary star from the observed stellar spectra: T eff = 5125 ± 67 K, [F e/H] = 0.1 ± 0.14 and log g = 4.6 ± 0.14, indicating a K1V primary. Applying the Torres relation to the derived stellar parameters, we estimate a primary mass 0.864 +0.097 −0.098 M ⊙ and a radius of 0.854 +0.050 −0.060 R ⊙ . We combine RV data with SuperWASP photometry to estimate the mass of the secondary, M B = 0.098 ± 0.007M ⊙ , and its radius, R B = 0.127 ± 0.007 R ⊙ , with an accuracy of ∼7%. Although the observed radius is found to be consistent with the Baraffe's theoretical models, the uncertainties on the mass and radius of the secondary reported here are model dependent and should be used with discretion. Here, we establish this system as a potential benchmark for the study of VLMS objects, worthy 2 Chaturvedi et al.of both photometric follow-up and the investment of time on high-resolution spectrographs paired with large-aperture telescopes.

Eclipsing Binaries (EBs) with one of the companions as very low mass stars (VLMS or M dwarfs) are testbeds to substantiate stellar models and evolutionary theories. Here, we present four EB candidates with F type primaries, namely, SAO 106989, HD 24465, EPIC 211682657 and HD 205403, identified from different photometry missions, SuperWasp, KELT, Kepler 2 (K2) and STEREO. Using the highresolution spectrograph, PARAS, at the 1.2 m telescope at Mount Abu, Rajasthan, India, we hereby report the detection of four VLMS as companions to the four EBs. We performed spectroscopic analysis and found the companion masses to be 0.256 ± 0.005, 0.233 ± 0.002, 0.599 ± 0.017, and 0.406 ± 0.005 M for SAO 106989, HD 24465, EPIC 211682657 and HD 205403 respectively. We determined orbital periods of 4.39790 ± 0.00001, 7.19635 ± 0.00002, 3.142023 ± 0.000003 and 2.444949 ± 0.000001 d and eccentricities of 0.248 ± 0.005, 0.208 ± 0.002, 0.0097 ± 0.0008 and 0.002 ± 0.002 for EBs SAO 106989, HD 24465, EPIC 211682657 and HD 205403 respectively. The radius derived by modeling the photometry data are 0.326 ± 0.012 R for SAO 106989, 0.244 ± 0.001 R for HD 24465, 0.566 ± 0.005 R for EPIC 211682657, and 0.444 ± 0.014 R for HD 205403. The radii of HD 24465B and EPIC 211682657B have been measured by precise KEPLER photometry and are consistent with theory within error bars. However, the radii of SAO 106989B and HD 205403B, measured by KELT and STEREO photometry, are 17 − 20% higher than those predicted by theory. A brief comparison of the results of the current work is made with the M dwarfs already studied in literature.