Precise radial velocities of giant stars IX. HD 59686 Ab: a massive circumstellar planet orbiting a giant star in a ~13.6 au eccentric binary system

Context: For over 12 yr, we have carried out a precise radial velocity survey of a sample of 373 G and K giant stars using the Hamilton \'Echelle Spectrograph at Lick Observatory. There are, among others, a number of multiple planetary systems in our sample as well as several planetary candidates in stellar binaries. Aims: We aim at detecting and characterizing substellar+stellar companions to the giant star HD 59686 A (HR 2877, HIP 36616). Methods: We obtained high precision radial velocity (RV) measurements of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in the RVs, we can assess the nature of companions in the system. In order to discriminate between RV variations due to non-radial pulsation or stellar spots we used infrared RVs taken with the CRIRES spectrograph at the Very Large Telescope. Additionally, to further characterize the system, we obtain high-resolution images with LMIRCam at the Large Binocular Telescope. Results: We report the likely discovery of a giant planet with a mass of $m_{p}~\sin i=6.92_{-0.24}^{+0.18}~M_{Jup}$ orbiting at $a_{p}=1.0860_{-0.0007}^{+0.0006}$ au from the giant star HD 59686 A. Besides the planetary signal, we discover an eccentric ($e_{B}=0.729_{-0.003}^{+0.004}$) binary companion with a mass of $m_{B}~\sin i=0.5296_{-0.0008}^{+0.0011}~M_{Sun}$ orbiting at a semi-major axis of just $a_{B}=13.56_{-0.14}^{+0.18}$ au. Conclusions: The existence of the planet HD 59686 Ab in a tight eccentric binary system severely challenges standard giant planet formation theories and requires substantial improvements to such theories in tight binaries. Otherwise, alternative planet formation scenarios such as second generation planets or dynamical interactions in an early phase of the system's lifetime should be seriously considered in order to better understand the origin of this enigmatic planet.Comment: 14 pages, 11 figures, 2 tables. Accepted for publication in A&A. Updated version to match the published pape

An Unbiased Near-infrared Interferometric Survey for Hot Exozodiacal Dust

Exozodiacal dust is warm or hot dust found in the inner regions of planetary systems orbiting main sequence stars, in or around their habitable zones. The dust can be the most luminous component of extrasolar planetary systems, but predominantly emits in the near- to mid-infrared where it is outshone by the host star. Interferometry provides a unique method of separating this dusty emission from the stellar emission. The visitor instrument PIONIER at the Very Large Telescope Interferometer (VLTI) has been used to search for hot exozodiacal dust around a large sample of nearby main sequence stars. The results of this survey are summarised: 9 out of 85 stars show excess exozodiacal emission over the stellar photospheric emission.Comment: Invited review of our paper (Ertel et al., 2014) for ESO's The Messenger, issue 159. Final version as published in The Messenge

Lophelia reefs

PHASECam is the fringe tracker for the Large Binocular Telescope Interferometer (LBTI). It is a near-infrared camera that is used to measure both tip/tilt and fringe phase variations between the two adaptive optics-corrected apertures of the Large Binocular Telescope (LBT). Tip/tilt and phase sensing are currently performed in the H (1.65 mu m) and K (2.2 mu m) bands at 1 kHz, but only the K-band phase telemetry is used to send corrections to the system in order to maintain fringe coherence and visibility. However, due to the cyclic nature of the fringe phase, only the phase, modulo 360 deg, can be measured. PHASECam's phase unwrapping algorithm, which attempts to mitigate this issue, occasionally fails in cases of fast, large phase variations or low signal-to-noise ratio. This can cause a fringe jump in which case the optical path difference correction will be incorrect by a wavelength. This can currently be manually corrected by the operator. However, as the LBTI commissions further modes that require robust, active phase control and for which fringe jumps are harder to detect, including multiaxial (Fizeau) interferometry and dual-aperture nonredundant aperture masking interferometry, a more reliable and automated solution is desired. We present a multiwavelength method of fringe jump capture and correction that involves direct comparison between the K-band and H-band phase telemetry. We demonstrate the method utilizing archival PHASECam telemetry, showing it provides a robust, reliable way of detecting fringe jumps that can potentially recover a significant fraction of the data lost to them. (C) 2020 Society of Photo-Optical Instrumentation Engineers (SPIE)This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Target Selection for the LBTI Exozodi Key Science Program

The Hunt for Observable Signatures of Terrestrial planetary Systems (HOSTS) on the Large Binocular Telescope Interferometer will survey nearby stars for faint emission arising from ~300 K dust (exozodiacal dust), and aims to determine the exozodiacal dust luminosity function. HOSTS results will enable planning for future space telescopes aimed at direct spectroscopy of habitable zone terrestrial planets, as well as greater understanding of the evolution of exozodiacal disks and planetary systems. We lay out here the considerations that lead to the final HOSTS target list. Our target selection strategy maximizes the ability of the survey to constrain the exozodi luminosity function by selecting a combination of stars selected for suitability as targets of future missions and as sensitive exozodi probes. With a survey of approximately 50 stars, we show that HOSTS can enable an understanding of the statistical distribution of warm dust around various types of stars and is robust to the effects of varying levels of survey sensitivity induced by weather conditions.Comment: accepted to ApJ

Towards a Better Understanding of OPD Limitations for Higher Sensitivity and Contrast at the VLTI

Precise control of the optical path differences (OPD) in the Very Large Telescope Interferometer (VLTI) was critical for the characterization of the black hole at the center of our Galaxy - leading to the 2020 Nobel prize in physics. There is now significant effort to push these OPD limits even further, in-particular achieving 100nm OPD RMS on the 8m unit telescopes (UT's) to allow higher contrast and sensitivity at the VLTI. This work calculated the theoretical atmospheric OPD limit of the VLTI as 5nm and 15nm RMS, with current levels around 200nm and 100nm RMS for the UT and 1.8m auxillary telescopes (AT's) respectively, when using bright targets in good atmospheric conditions. We find experimental evidence for the $f^{-17/3}$ power law theoretically predicted from the effect of telescope filtering in the case of the ATs which is not currently observed for the UT's. Fitting a series of vibrating mirrors modelled as dampened harmonic oscillators, we were able to model the UT OPD PSD of the gravity fringe tracker to $<1nm/\sqrt{Hz}$ RMSE up to 100Hz, which could adequately explain a hidden $f^{-17/3}$ power law on the UTs. Vibration frequencies in the range of 60-90Hz and also 40-50Hz were found to generally dominate the closed loop OPD residuals of Gravity. Cross correlating accelerometer with Gravity data, it was found that strong contributions in the 40-50Hz range are coming from the M1-M3 mirrors, while a significant portion of power from the 60-100Hz contributions are likely coming from between the M4-M10. From the vibrating mirror model it was shown that achieving sub 100nm OPD RMS for particular baselines (that have OPD$\sim$200nm RMS) required removing nearly all vibration sources below 100Hz

The VORTEX project: first results and perspectives

(abridged) Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations. They feature a very small inner working angle, a clear 360 degree discovery space, have demonstrated very high contrast capabilities, are easy to implement on high-contrast imaging instruments, and have already been extensively tested on the sky. Since 2005, we have been designing, developing and testing an implementation of the charge-2 vector vortex phase mask based on concentric subwavelength gratings, referred to as the Annular Groove Phase Mask (AGPM). Science-grade mid-infrared AGPMs were produced in 2012 for the first time, using plasma etching on synthetic diamond substrates. They have been validated on a coronagraphic test bench, showing broadband peak rejection up to 500:1 in the L band, which translates into a raw contrast of about $6\times 10^{-5}$ at $2 \lambda/D$. Three of them have now been installed on world-leading diffraction-limited infrared cameras (VLT/NACO, VLT/VISIR and LBT/LMIRCam). During the science verification observations with our L-band AGPM on NACO, we observed the beta Pictoris system and obtained unprecedented sensitivity limits to planetary companions down to the diffraction limit ($0.1''$). More recently, we obtained new images of the HR 8799 system at L band during the AGPM first light on LMIRCam. After reviewing these first results obtained with mid-infrared AGPMs, we will discuss the short- and mid-term goals of the on-going VORTEX project, which aims to improve the performance of our vortex phase masks for future applications on second-generation high-contrast imagers and on future extremely large telescopes (ELTs).Comment: To appear in SPIE proceedings vol. 914

Asgard/NOTT: L-band nulling interferometry at the VLTI I. Simulating the expected high-contrast performance

Context: NOTT (formerly Hi-5) is a new high-contrast L' band (3.5-4.0 \textmu m) beam combiner for the VLTI with the ambitious goal to be sensitive to young giant exoplanets down to 5 mas separation around nearby stars. The performance of nulling interferometers in these wavelengths is affected both by fundamental noise from the background and by the contributions of instrumental noises. This motivates the development of end-to-end simulations to optimize these instruments. Aims: To enable the performance evaluation and inform the design of such instruments on the current and future infrastructures, taking into account the different sources of noise, and their correlation. Methods: SCIFYsim is an end-to-end simulator for single mode filtered beam combiners, with an emphasis on nulling interferometers. It is used to compute a covariance matrix of the errors. Statistical detection tests based on likelihood ratios are then used to compute compound detection limits for the instrument. Results: With the current assumptions on the performance of the wavefront correction systems, the errors are dominated by correlated instrumental errors down to stars of magnitude 6-7 in the L band, beyond which thermal background from the telescopes and relay system becomes dominant. Conclusions: SCIFYsim is suited to anticipate some of the challenges of design, tuning, operation and signal processing for integrated optics beam combiners. The detection limits found for this early version of NOTT simulation with the unit telescopes are compatible with detections at contrasts up to $10^5$ in the L band at separations of 5 to 80 mas around bright stars

Three years of harvest with the vector vortex coronagraph in the thermal infrared

For several years, we have been developing vortex phase masks based on sub-wavelength gratings, known as Annular Groove Phase Masks. Etched onto diamond substrates, these AGPMs are currently designed to be used in the thermal infrared (ranging from 3 to 13 {\mu}m). Our AGPMs were first installed on VLT/NACO and VLT/VISIR in 2012, followed by LBT/LMIRCam in 2013 and Keck/NIRC2 in 2015. In this paper, we review the development, commissioning, on-sky performance, and early scientific results of these new coronagraphic modes and report on the lessons learned. We conclude with perspectives for future developments and applications.Comment: To appear in SPIE proceedings vol. 990

Darwin -— an experimental astronomy mission to search for extrasolar planets

As a response to ESA call for mission concepts for its Cosmic Vision 2015–2025 plan, we propose a mission called Darwin. Its primary goal is the study of terrestrial extrasolar planets and the search for life on them. In this paper, we describe different characteristics of the instrument