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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. ABSTRACT The Chandra Source Catalog (CSC) is a general purpose virtual X-ray(More)
The U.S. Virtual Astronomical Observatory (VAO) is a product-driven organization that provides new scientific research capabilities to the astronomical community. Software development for the VAO follows a lightweight framework that guides development of science applications and infrastructure. Challenges to be overcome include distributed development(More)
Systematic instrumental uncertainties in astronomical analyses have been generally ignored due to the lack of robust principled method, though the importance of incorporating instrumental calibration uncertainty is widely realized by users and instrument builders. Ignoring calibration uncertainty can cause bias in the estimate of source model parameters and(More)
Typical X-ray spectra have low counts and should be modeled using the Poisson distribution. However, χ 2 statistic is often applied as an alternative and the data are assumed to follow the Gaussian distribution. A variety of weights to the statistic or a binning of the data is performed to overcome the low counts issues. However, such modifications(More)
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