Probing Exoplanet Atmospheric Properties from Phase Variations and Polarization
Laura Mayorga, NMSU
The study of exoplanets is evolving past simple transit and Doppler method discovery and characterization. One of the many goals of the upcoming mission WFIRST-AFTA is to directly image giant exoplanets with a coronagraph. We undertake a study to determine the types of exoplanets that missions such as WFIRST will encounter and what instruments these missions require to best characterize giant planet atmospheres. We will first complete a benchmark study of how Jupiter reflects and scatters light as a function of phase angle. We will use Cassini flyby data from late 2000 to measure Jupiter’s phase curve, spherical albedo, and degree of polarization. Using Jupiter as a comparison, we will then study a sample of exoplanet atmosphere models generated to explore the atmospheric parameter space of giant planets and estimate what WFIRST might observe. Our study will provide valuable refinements to Jupiter-like models of planet evolution and atmospheric composition. We will also help inform future missions of what instruments are needed to characterize similar planets and what science goals will further our knowledge of giant worlds in our universe.
On the Edge: Exoplanets with Orbital Periods Shorter Than a Peter Jackson Movie
Brian Jackson, Boise State Univeristy
From wispy gas giants to tiny rocky bodies, exoplanets with orbital periods of several days and less challenge theories of planet formation and evolution. Recent searches have found small rocky planets with orbits reaching almost down to their host stars’ surfaces, including an iron-rich Mars-sized body with an orbital period of only four hours. So close to their host stars that some of them are actively disintegrating, these objects’ origins remain unclear, and even formation models that allow significant migration have trouble accounting for their very short periods. Some are members of multi-planet system and may have been driven inward via secular excitation and tidal damping by their sibling planets. Others may be the fossil cores of former gas giants whose atmospheres were stripped by tides.
In this presentation, I’ll discuss the work of our Short-Period Planets Group (SuPerPiG), focused on finding and understanding this surprising new class of exoplanets. We are sifting data from the reincarnated Kepler Mission, K2, to search for additional short-period planets and have found several new candidates. We are also modeling the tidal decay and disruption of close-in gaseous planets to determine how we could identify their remnants, and preliminary results suggest the cores have a distinctive mass-period relationship that may be apparent in the observed population. Whatever their origins, short-period planets are particularly amenable to discovery and detailed follow-up by ongoing and future surveys, including the TESS mission.
Our Current Understanding of Classical Be Stars
Dr. Thomas Rivinius, Chile, ESO Paranal
I will introduce Be stars as B-type stars with gaseous disks in Keplerian rotation. These disks form by mass ejection from the star itself and their evolution is then governed by viscosity. The observables and their formation in the disk will be discussed, as well as what we know about the central stars: they are the most rapidly rotating non-degenerate stars, they are non-radial pulsators, and they do not show magnetic fields. The pulsation is clearly (phenomenologically) linked to the mass ejection, but the physical mechanism responsible for the ejection and disk formation is not known. Finally, I will discuss several open questions of broader interest, including the (possibly absent) chemical mixing of very rapid rotators and the unexpectedly large viscosity of Be star disks.
Characterizing the oscillatory response of the chromosphere during solar flares
Laurel Farris; NMSU Astronomy Department
Quasi-periodic pulsations (QPPs) are observed in the emission of solar flares over a wide range of wavelengths,
particularly in the radio and hard x-ray regimes where non-thermal emission dominates. These pulsations are
considered to be an intrinsic feature of flares, yet the exact mechanism that triggers them remains unclear.
There have been reports of an increase in the oscillatory power at 3-minute periods (the local acoustic
cutoff frequency) in the solar chromosphere associated with flaring events. I propose to investigate the
chromospheric response to flares by inspecting the spatial and temporal onset and evolution of the 3-minute
oscillatory power, along with any QPP patterns that may appear in chromospheric emission. The analysis
will be extended to multiple flares, and will include time before, during, and after the main event. To test
initial methods, the target of interest was the well-studied 2011 February 15 X-class flare. Data from two
instruments on board the Solar Dynamics Observatory (SDO) were used in the preliminary study, including
continuum images from the Helioseismic and Magnetic Imager (HMI) and UV images at 1600 and 1700
Angstroms from the Atmospheric Imaging Assembly (AIA). Later, spectroscopic data from the Interface
Region Imaging Spectrometer (IRIS) will be used to examine velocity patterns in addition to intensity.