STELLAR ATMOSPHERE MODELING AND SUBSYSTEM DEVELOPMENT FOR THE ACCESS PROGRAM

[摘要] The goal of the ACCESS program (Absolute Color Calibration Experiment for Standard Stars) is to enable greater discrimination between theoretical astrophysical models and observations, where the comparison is limited by systematic errors associated with the relative flux calibration of the targets. To achieve these goals, ACCESS has been designed as a sub-orbital rocket borne payload and ground calibration program, to establish absolute flux calibration of stellar targets at <1 % precision, with a resolving power of 500 across the 0.35 to 1.7 micron (μm) bandpass. In order to obtain higher resolution spectroscopy in the optical and near-infrared range than either the ACCESS payload or CALSPEC observations provide, the ACCESS team has conducted a multi-instrument observing program at Apache Point Observatory. Using these calibrated high resolution spectra in addition to the HST/CALSPEC data, I have generated stellar atmosphere models for ACCESS flight candidates, as well as a selection of A and G stars from the CALSPEC database. I developed a system of iterative, chi-squared minimization, model fitting for these targets in this population. Using ATLAS9 and ATLAS12 Kurucz stellar atmosphere code result in models, converging to within 20 K effective temperature, 0.05 log(g), and 0.02 log[M/H] for the majority of targets. Key components of my contribution to the experiment are control software I wrote for the detector controller for flight and ground operations, and also for the ACCESS data reduction pipeline. We have been able to perform characterization tests with a modified ground cryogenic dewar system, yielding comparable dark currents to Goddard’s Detector Characterization Lab. Additionally, I performed characterization tests on the ruggedized detector controller and added a heat sink interface, enabling vacuum operations beyond the duration of our rocket flight.

[发布机构] Johns Hopkins University

[效力级别] stellar atmosphere

[关键词] astronomy;stellar atmosphere;calibration;Physics