Stars and stellar explosions are responsible for creating most of the elements in the periodic table. However, the specific cosmic events that synthesize elements and the details of their nucleosynthetic output (which elements and how much of each) remains an active area of study. Understanding the nucleosynthetic output of stars and their explosions is critical for developing representative, physically-motivated models of Galactic chemical evolution.

Asymptotic giant branch (AGB) stars play an important role in the synthesis of elements. The end life stage of stars above ~0.8 solar masses, AGB stars produce half of the Galactic reservoir of elements heavier than iron via the slow (s-) neutron-capture process. Much of my work focuses on AGB stars and their chemical output. The following works used stars and nebulae as cosmic probes of AGB star nucleosynthesis. Most recently, I have been interested in constraining the potential occurrence and chemical output of the intermediate neutron-capture process (i-process) in solar-metallicity AGB stars.

→ Manea C., McKenzie M., Sinha A., et al., in prep: “Signatures of i-process Nucleosynthesis in Metal-rich Barium Stars with GHOST”

→ Levine J., Manea C., et al. 2026: “Barium Stars Across the Milky Way: Probing Their Origins via the GALAH Survey”

→ Manea C., et al. 2022b: “Chemical Abundances of Eight Highly-extincted Milky Way Planetary Nebulae”

Stars serve as chemical time capsules that preserve the composition of their birth environment. By studying the compositions of stars with different ages, we can trace the chemical evolution of our Milky Way over time. I am constructing a high precision chemical abundance catalog of a few thousand stars in the Solar neighborhood. What sets this catalog apart from most is that I am determining abundances differentially, which is a technique that enables exceptionally high precisions and accuracies that are impossible using standard techniques. Once completed, this will be the largest differential abundance catalog to date and enable unprecedented high precision constraints of our Solar neighborhood’s chemical history.

→ Manea C., Bedell M., Zasowski G., et. al, 2026, in prep. “High precision constraints on the chemical evolution of the solar neighborhood using differential abundances of twin stars”

I am also extremely interested in the behavior of neutron-capture elements among Galactic disk stars. I have several works that highlight the distinguishing power of neutron-capture elements among Milky Way stars, illustrating their distinct nucleosynthetic origins and evolution.

→ Manea C., et al. 2025: “Optical Spectroscopy Reveals Hidden Neutron-capture Elemental Abundance Differences among APOGEE-identified Chemical Doppelgängers”

→ Manea C., et al. 2024: “Chemical Doppelgangers in GALAH DR3: The Distinguishing Power of Neutron-capture Elements among Milky Way Disk Stars”

→ Manea C., et al. 2022a: “A GALAH view of the chemical homogeneity and ages of stellar strings identified in Gaia”

Historically, chemically characterizing brown dwarfs and exoplanets has been impossible as we did not have the data or tools to do it. Thanks to advancements in instrumentation (e.g., JWST) and chemical characterization techniques (e.g., atmospheric retrievals), we are well-posed to begin studying exoplanet and brown dwarf compositions. However, chemical characterization of these systems is still difficult. For brown dwarfs and exoplanets with associated main sequence star hosts, we can use the chemical composition of the host star to anchor and calibrate the bulk compositions of these lower mass companions. Furthermore, differences between the composition of a host star and its lower mass companion can trace formation pathways. I have been collaborating with brown dwarf and exoplanet experts across the US to chemically characterize the FGK hosts to these lower mass objects.

→ Phillips C. L., Bedell M., Manea C., et al., 2026, ApJ, 1008, 67. “Benchmark Brown Dwarf Systems. I.Chemical Abundance Analysis of FGK Stars with Wide-separation Brown Dwarf Companions Using PEPSI”
→ Rothermich A., Faherty J., Burningham B., Manea C., et al., 2026, Accepted to AASJournals. “Sinking Silicates I: Characterizing the benchmark system containing the T0 brown dwarf CWISE J210640.16+250729.0 using JWST”
→ Zhang Z., Molliere P., Hawkins K., Manea C., et. al, 2023 “ELemental abundances of Planets and brown dwarfs Imaged around Stars (ELPIS). I.”