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Ph.D., Columbia University
B.A., Cornell University
My research focuses on observational high energy astrophysics and experimental particle astrophysics.
In high energy astrophysics my group is heavily involved in the Nuclear Spectroscopic Telescope Array (NuSTAR) mission. NuSTAR is a NASA mission that has flown the first true, focusing telescopes in the hard X-ray band. NuSTAR’s telescopes have sub-arcminute angular resolution and operate in the 3-79 keV band. The NuSTAR optics were assembled and tested at Columbia. My group is part of the NuSTAR Galactic Plane Survey working group, which I chair. Our research focuses on the Galactic Center and its immediate environs. We are studying the time history of violent emissions from the supermassive black hole (SMBH) at the Galactic Center through the flares the SMBH emits today, and the reflected X-rays from molecular clouds, which serve as a marker of the past flaring history of the SMBH. We are also investigating a new, diffuse hard X-ray emission NuSTAR discovered in the immediate vicinity of the SMBH, and whose origins are unclear. NuSTAR has also discovered a number of hard X-ray emitting, non-thermal radio filaments in the Galactic Center, and we are investigating the origin of their emission. For instance, we have found one filament emitting due to a supernova remnant-molecular cloud interaction, and another emitting because cosmic-ray electrons have become trapped in magnetic flux tubes. We are also investigating the nature and origin of X-ray emission from the ~ 6 dozen hard X-ray point sources NuSTAR has discovered in the Galactic Center region. These are likely neutron star and black hole binaries and cataclysmic variables, a type of white dwarf binary. Of particular notes was our discovery of a magnetar – a neutron star with an intense magnetic field – in the immediate vicinity of the SMBH. The magnetar has important implications for our ability to probe many characteristics of the SMBH and its environment. We also conduct research on pulsar wind nebulae, using the hard X-ray emission to better understand how these objects are able accelerate particles to the enormous energies (~ 100 TeV+) that are required to produce energetic X-ray emission.
I am also the principal investigator of a balloon-borne experiment to hunt for dark matter - The General Antiparticle Spectrometer Experiment (GAPS) - will search for cosmic antideuterons. Many beyond-the Standard-Model theories postulate weakly interacting massive particles (WIMPS) that can annihilate in WIMP-WIMP interactions in the galactic halo. The antideuterons are produced as a rare byproduct of these annihilations, and potentially offer a smoking gun signature of dark matter. In many beyond-the-Standard-Model theories, antideuteron searches offer the most sensitive means to detect dark matter. GAPS uses a novel scheme to detect antimatter through identification of atomic deexcitation X-rays and particles produced when antimatter is captured in an atom and subsequently annihilates in the nucleus. GAPS requires the development of a novel pixellated Si(Li) detector, and this development is currently underway in my group at Columbia. A prototype experiment was successfully flow from Hokkaido, Japan in June 2012. The full science experiment, which involves about a dozen US and international partners, will fly from Antarctica in late 2020.
Another experiment I am engaged with is the International Axion X-ray Observatory. IAXO will seek to image the sun in solar axions by converting them to X-rays in a large magnet, and detecting the X-rays with the same type of telescope used for NuSTAR. Axions are a potential dark matter candidate. A proposal to NSF for this project will be submitted in 2017.
C.J. Hailey et. al., "Evidence for Intermediate Polars as the Origin of the Galactic Center X-ray Emission," Astrophysical Journal, 826, 160, 2016.
T. Aramaki et. al., "Antideuteron Sensitivity of the GAPS Experiment," Astroparticle Physics, 74, 6, 2016.
F. Aznar et.al., "A Micromegas-based Low-Background X-ray Detector Coupled to a Slumped-Glass Telescope for Axion Research," Journal of Cosmology and Astroparticle Physics, vol. 2015, 2015.
K. Perez et. al., "Extended Hard X-ray Emission in the Inner Few Parsecs of the Galaxy," Nature, 520, 646, 2015.
T. Aramaki et.al, “Potential for Precision Measurement of Low-Energy Antiprotons with GAPS for Dark Matter and Primordial Black Hole Physics,” Astroparticle Physics 59, 12, 2014.
P. von Doetinchem et. al., “The Flight of the GAPS Prototype Experiment,” Astroparticle Physics, 54, 93, 2014.
M. Nynka et. al., “NuSTAR Study of Hard X-ray Morphology and Spectroscopy of PWN G21.5-0.9,” Astrophysical Journal, 789, 72, 2014.
S. Zhang et. al., “High-Energy X-ray Detection of G359.89-0.08 (Sgr A-E): Magnetic Flux Tube Emission Powered by Cosmic-rays?” Astrophysical Journal, 784, 6, 2014
K. Mori et. al., “NuSTAR Discovery of a 3.76-second transient magnetar near Sagittarius A*,” Astrophysical Journal, 770, L23, 2013.
C.J. Hailey, “An Indirect Search for Dark Matter Using Antideuterons: the GAPS Experiment,” New Journal of Physics, vol. 11, 105022, 2009.