Graduate Thesis Or Dissertation
EUV/FUV Sounding Rocket Observations of Epsilon CMa to Better Constrain the B Star Contribution to Ionization in the Universe Public Deposited
Hot star models are foundational for understanding the ionizing outputs of star forming galaxies and the contribution of stars to ionization in the Universe across cosmic time. When tested against 505-730 A EUVE observations of B star Epsilon CMa, these hot star models appear to underpredict hot star EUV flux by a factor of 10-20 X, calling into question their accuracy in predicting the strength of the B star contribution to ionizing flux in the Universe.
I have obtained the first-ever observation of a hot, massive, ionizing star (Epsilon CMa) in the critical 730-900 A bandpass in which neutral hydrogen is most sensitive to ionization. By comparing this new, highly-ionizing spectrum to stellar models generated using the range of published stellar parameters of Epsilon CMa, the goal of this work is to determine if and to what extent these models fail to correctly predict the most ionizing fluxes of massive hot stars, and whether the role of B stars as sources of large-scale ionization in the Universe needs to subsequently be revised.
I constructed, calibrated, and launched the DEUCE sounding rocket to obtain this first-ever spectrum of Epsilon CMa near the Lyman Limit and allow the predictive power of hot star models to be more comprehensively tested and appraised in the EUV. In this thesis, I discuss the motivations for this observation, the construction and calibration of the the DEUCE instrument, the DEUCE launches and the reduction of their data, and the accuracy of hot star models when compared to these data in the EUV.
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