EPRV Research Coordination Network
Welcome!
The EPRV Research Coordination Network (RCN), sponsored by NASA’s Exoplanet Exploration Program, aims to support increased communication and collaboration within the radial velocity community as we work towards the goal of obtaining robust mass measurements for Earth analog planets.
Membership is open to the community and we invite participants from all corners of the RV community and related fields, including but not limited to: observational efforts, instrumentation, data analysis techniques, solar studies, and stellar variability mitigation. Please see the side bar for instructions / links on how to join the RCN.
Note: All members of the EPRV RCN will be required to follow our Code of Conduct
EPRV RCN Colloquium Series
Our next RCN Colloquium will take place on Thursday, April 24th, at 8a Pacific Time and feature Dr. Ancy Anna John [University of Birmingham] who will provide an overview of an intensive HARPS-N observing campaign on the Maunder minimum K-dwarf HD166620 and what it tells us about granulation and super-granulations signals in Sun-like stars.
Title: Know Thy star: Fine-Tuning the Search for Earth 2.0
Abstract: With the EPRV spectrographs achieving unprecedented precision below 30 cm/s, the challenge of granulation mitigation in the context of exoplanet detection has intensified. Granulation-driven stellar variability limits current RV measurement precision to ~50 cm/s — far from the 10 cm/s precision required to detect long-period Earth-mass planets. Post-processing techniques have advanced, but overcoming granulation remains a pressing concern for the EPRV community. To address this challenge, we conducted dense, high-cadence observations over two nights of the Maunder minimum K-dwarf HD166620 using HARPS-N. With negligible magnetic activity, this star provides an ideal testbed to isolate granulation-driven variability. After correcting for a newly identified instrumental systematics, we evaluated the sensitivity of granulation signatures across photospheric layers by analysing RVs with different line-formation temperature information. Our analysis revealed granulation variability with a characteristic timescale of ~50 minutes and an amplitude of ~20 cm/s. We found that granulation signatures were more pronounced in upper, shallower layers rather than deeper ones where weaker lines form, in contrast with prior models based on Solar studies. This work marks a pivotal step in understanding granulation-driven variability, refining models, and advancing the precision needed to detect Earth-twins.
Background on the RCN
The 2018 National Academies’ Exoplanet Science Strategy, which provided input to the Astro 2020 Decadal Survey, acknowledged the importance of the radial velocity method “to provide essential mass, orbit, and census information to support both transiting and directly imaged exoplanet science for the foreseeable future” and recommended that “NASA and NSF should establish a strategic initiative in extremely precise radial velocities (EPRV) to develop methods and facilities for measuring the masses of temperate terrestrial planets orbiting Sun-like stars.” Subsequently, a community Extreme Precision Radial Velocity (EPRV) Working Group was chartered, which developed a roadmap for advancing the radial velocity technique to the point where EPRV detection or exclusion of Earth analogs orbiting nearby target stars of a future direct imaging mission would be feasible.
With the Astro2020 Decadal Survey recommendation for NASA to develop a large infrared/optical/ultraviolet space telescope capable of observing and spectrally characterizing potentially habitable exoplanets orbiting nearby stars, development of EPRV capabilities is critical as they will provide the only method potentially capable of discovering Earth analogs from the ground and measuring their masses. As part of its plan to “break the stellar variability barrier” and work towards enabling EPRV surveys capable of measuring the masses of Earth analogs, the EPRV WG report recommended that NASA establish an EPRV Research Coordination Network (RCN) of scientists across disciplines (solar, stellar, exoplanetary) and instruments.“ Thus, the development of this RCN, which endeavors to support the EPRV community in advancing towards the goal of detecting temperate, terrestrial, planets around Sun-like stars.