BDNYC Team Member Graduating and Moving to California

The BDNYC team is pleased to announce that Rocio Kiman will be defending her PhD dissertation on July 16, 2021, and has accepted postdoc positions at the Kavli Institute for Theoretical Physics in Santa Barbara and the California Institute of Technology.

Rocio Kiman

Rocio Kiman

Rocio Kiman is an Argentinian PhD student at the City University of New York (CUNY). Rocio completed her undergraduate studies in physics at the University of Buenos Aires. She then moved to the U.S. to pursue her PhD at CUNY, working with Dr. Kelle Cruz and Dr. Jackie Faherty as advisors. Over the course of her PhD program, Rocio has also collaborated with mentors Dr. Ruth Angus and Dr. Sarah Schmidt. The main goal of Rocio’s PhD work is to estimate the ages of M dwarfs, the lowest mass stars in the Galaxy. As the most common star in the Galaxy, M dwarfs are also the most likely to host Earth-like exoplanets, making them key to our understanding of the evolution and habitability of exoplanets.

Rocio recently published a first-author paper titled “Calibration of the Halpha Age-Activity relation for M dwarfs,” which examines the relation between Halpha equivalent width (line strength) and age for M dwarfs. Rocio and her collaborators compiled a calibration sample of 892 M dwarfs with Halpha measurements from the literature, and identified that they were either co-moving with a white dwarf or in a known young association to obtain their ages. They found that the Halpha decreases with increasing age, and they classified the age-calibrators as active and inactive according to Halpha equivalent width and their Gaia red color (smaller color, higher mass star). Rocio and her collaborators found that the active fraction changes with mass and with age (Figure), noting that the evolution of the active fraction with time changes according to the color. They also fit the age-activity relation with a broken power-law, but did not have enough stars to precisely constrain the breaking point or the slope of the decrease after 1 Gyr.

Figure 1

Rocio’s paper, “Calibration of the Halpha Age-Activity relation for M dwarfs,” is important to estimating M dwarf ages, which are notoriously hard to estimate. Stellar ages in general are difficult to obtain; for higher mass stars there are methods that work, but none of those methods are useful for M dwarfs.

Rocio’s current research combines the relation with age found in the paper for the active fraction with 3D kinematics (which is another age indicator for stars) to estimate M dwarf ages in a Bayesian framework. By combining different age indicators, the precision of the age improves. Rocio then uses the estimated ages to study the evolution of rotation period with age for M dwarfs, which is currently not understood.

Rocio notes that although writing her thesis has been an intense experience, she feels fortunate that her husband Javier Roulet is sharing the process with her. Having met at the University of Buenos Aires, the couple completed their undergraduate studies together before moving to the U.S., and are now finishing their respective PhDs together as well. Once both PhDs are successfully obtained, Rocio and Javier will move to California, where Rocio will work one year at the Kavli Institute for Theoretical Physics in Santa Barbara as a postdoc, and then move on to a three-year postdoc position at the California Institute of Technology. At both institutes, Rocio plans to continue her research on M dwarf ages, and additionally begin new research on brown dwarfs using data from the James Webb Space Telescope. Rocio is thrilled to be moving on to these postdoc positions and is very excited about her future research.

You can read more about Rocio Kiman’s work and follow her journey on her website and Twitter account. The entire BDNYC team is looking forward to celebrating her achievements after her thesis defense on July 16, and wishes her the very best with all of her future research!

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