Apai Group

The Apai Research Group in 2017

The Apai Exoplanet Group in 2017.

Apai Exoplanet Research Group - 2015

Apai Exoplanet Research Group – 2015: Theodora Karalidi, Jake Hanson, Ben Rackham, Daniel Apai, Kevin Wagner, Hao Yang, Yifan Zhou.

(Left to Right): Min Fang, Ben Wei Peng, Ben Rackham, Yifan Zhou, Kevin Wagner, Gijs Mulders, Daniel Apai, Theodora Karalidi, Hao Yang, Xianyu Tan

(Left to Right): Min Fang, Ben Wei Peng, Ben Rackham, Yifan Zhou, Kevin Wagner, Gijs Mulders, Daniel Apai, Theodora Karalidi, Hao Yang, Xianyu Tan

Dr Daniel Apai, Associate Professor, Astronomy and Planetary SciencesAD-large-hq-4419
Daniel’s research encompasses exoplanet and brown dwarf atmospheres, planet formation, and the search for habitable exoplanets. He is leading multiple HST and Spitzer programs to characterize the physical structure and dust properties in circumstellar disks and also uses these facilities for time-resolved observations of rotating brown dwarfs. His work also includes connecting the stages of planet formation in the Solar System to those observed in protoplanetary disks around other stars. He is leading the Extrasolar Storms, the Earths in Other Systems, and the Cloud Atlas programs.

At the EOS Meeting

Ben Rackham, Kevin Wagner, Daniel Apai, Ben Lew Peng, Yifan Zhou

Dr Elena Manjavacas, Postdoctoral Researcher

Dr. Elena Manjavacas

Projects: Cloud Atlas

Elena is an expert in spectroscopic and polarimetric observations of brown dwarf atmospheres. She holds a PhD from the Max Planck Institute for Astronomy, Heidelberg, and has worked as an instrument scientist at IAC before joining the Cloud Atlas project. Within Cloud Atlas she is leading Hubble Space Telescope time-resolved spectroscopy studies as well as a major HST spectral atlas on brown dwarfs and gas giant exoplanets. She recently led a study presenting the discovery of rotational spectroscopic brightness modulations in an L-dwarf companion to a star (LP261B).  In addition to her work in Cloud Atlas, she is also leading an XSHOOTER program to characterize the spectra and surface gravity indicators in brown dwarfs.

Dr Jon Rees, Postdoctoral Researcher

Dr. Jon Rees

Projects: Omega Centauri HST Treasury Program

Jon is an expert on photometric studies of star cluster ages and the evolution. Jon holds a PhD from Exeter University. He is member of the Omega Centauri Large Hubble Space Telescope Treasury program, where he is leading detailed comparisons of stellar atmosphere models and ultra high-precision HST multi-band photometry of the multiple main sequences in the Omega Centauri globular cluster. A particularly important aspect of his work is the exploration of the coolest stars in Omega Centauri and the search for brown dwarfs in this old and metal-poor but very rich stellar cluster.


Ben Wei Lew Peng
UA Planetary Science Ben Graduate Student
Project: Cloud Atlas

Ben is third year graduate student of Planetary Science. As member of the Cloud Atlas Large HST Treasury program Ben is studying how dust clouds impact the atmospheres of cool brown dwarfs and exoplanets. He recently discovered large-amplitude brightness modulations in one of the reddest known brown dwarfs (WISE0047). In addition to his involvement in Cloud Atlas, Ben is also leading a larger NTT photometric study focusing on unusually red brown dwarfs.

Benjamin Rackham
UA Astronomy Graduate Student, NSF Graduate Research Fellow
Projects: ACCESS, Earths In Other Systems
Benjamin Rackham
Ben studies the atmospheres of exoplanets via ground-based observations. He uses spectroscopic and photometric approaches to investigate molecular absorption and emission features of super-earths and hot jupiters, which constrain atmospheric models of these planets. These techniques can be applied to future projects characterizing the atmospheres of Earth-like planets in the habitable zones of nearby stars. His results are highlighting the important impact of stellar heterogeneities (unocculted starspots and faculae) that provide a very significant contamination to transit spectroscopy and a major challenge to detecting atmospheric biosignatures. Methods Ben are developing will be essential for enabling future transit spectroscopic detections of biosignatures.


Kevin Wagner,
UA Astronomy Graduate Student and NSF Graduate Research Fellow
Projects: Scorpion Survey, Earths in Other Systems

Kevin WagnerKevin is currently a third year graduate student at Steward Observatory supported through the National Science Foundation Graduate Research Fellowship Program. He completed his Bachelor of Science degree at University of Cincinnati in 2015 with majors in Astrophysics, Physics, and Mathematics. His research focuses on searching for and characterizing exoplanets via directly imaging and identifying signs of planet formation in structures within circumstellar disks. Kevin is leading multiple programs using extreme adaptive optics systems (VLT/SPHERE, Gemini/GPI, Magellan/MagAO).


Yifan Zhou
UA Astronomy Graduate Student
NASA Earth and Space Science Fellow, TRIF Graduate Research Fellow

Projects: Patchy Clouds on Exoplanets, Cloud Atlas

Yifan is an expert in characterizing exoplanet and brown dwarf atmospheres with high-contrast, time-resolved HST images. Among other results he was the first to discovered rotational modulations in a directly imaged exoplanet, a result suggesting that clouds in directly imaged exoplanets are similar to those in field brown dwarfs. Yifan also led the development of a solid state-physics based model for charge trapping in the HST/WFC3/IR detector, the most important systematics that is affecting HST time-resolved observations. His model successfully corrects for the charge trapping (ramp) effect in all past HST datasets and increases the efficiency of future HST/WFC3 transit spectroscopic observations by 30%.


Alex Bixel
Alex BixelUA Astronomy Graduate Student
NASA Earth and Space Science Fellow

Projects: Earths in Other Solar Systems, ACCESS

Alex is a second year graduate student at Steward Observatory. His work focuses on the characterization of exoplanets. He is leading transit spectroscopic observations of hot jupiters within the ACCESS project. He also led a study that placed rigorous, probabilistic constraints on the properties and nature of Proxima Centauri b, the closest habitable planet candidate. In his project supported by a NASA Earth and Space Science Fellowship he is extending his Proxima Cen b study to explore how can future direct imaging observations constrain the properties and habitability of planet candidates, considering all information (and their uncertainties) known about the system and in the context of the exoplanet population.

Past Group Members

Dr Hao Yang, Postdoctoral Researcher
Dr Esther Buenzli, Postdoc, became a Postdoctoral Fellow at MPIA Heidelberg
Jake Hanson, UA Undergraduate Researcher, now ASU Astronomy Graduate Student
Justin Rogers, Astronomy Graduate student, Johns Hopkins University
Quadry Chance, UA Undergraduate student
Emily Berkson, UA Undergraduate Researcher, now MS student at RIT
Davin Flateau, NSF Graduate Student Research Fellow, UA LPL MS Student
Michael Iuzzolino, UA Undergraduate Student
Dr Veselin Kostov, John Hopkins Graduate Student, now NASA Postdoctoral Fellow at GSFC
Dr. Theodora Karalidi, Postdoctoral researcher, now postdoc at UCSC
William Nolan, Summer Student
Laszlo Szucs, Summer Student at STScI; now Postdoctoral Researcher at MPE Germany