Daniel J. Stevens

Daniel J. Stevens
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Daniel J. Stevens
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Earth and Planetary Astrophysics (9)
 
Solar and Stellar Astrophysics (6)
 
Astrophysics of Galaxies (2)
 
Physics - Data Analysis; Statistics and Probability (1)
 
Instrumentation and Methods for Astrophysics (1)
 
Cosmology and Nongalactic Astrophysics (1)

Publications Authored By Daniel J. Stevens

We present the first results from an optical reverberation mapping campaign executed in 2014, targeting the active galactic nuclei (AGN) MCG+08-11-011, NGC 2617, NGC 4051, 3C 382, and Mrk 374. Our targets have diverse and interesting observational properties, including a "changing look" AGN and a broad-line radio galaxy. Based on continuum-H$\beta$ lags, we measure black hole masses for all five targets. Read More

Be stars have generally been characterized by the emission lines in their spectra, and especially the time variability of those spectroscopic features. They are known to also exhibit photometric variability at multiple timescales, but have not been broadly compared and analyzed by that behavior. We have taken advantage of the advent of wide-field, long-baseline, and high-cadence photometric surveys that search for transiting exoplanets to perform a comprehensive analysis of brightness variations among a large number of known Be stars. Read More

We report the discovery of KELT-12b, a highly inflated Jupiter-mass planet transiting a mildly evolved host star. We identified the initial transit signal in the KELT-North survey data and established the planetary nature of the companion through precise follow-up photometry, high-resolution spectroscopy, precise radial velocity measurements, and high-resolution adaptive optics imaging. Our preferred best-fit model indicates that the $V = 10. Read More

SPHEREx is a proposed SMEX mission selected for Phase A. SPHEREx will carry out the first all-sky spectral survey and provide for every 6.2" pixel a spectra between 0. Read More

We present photometric observations of RW Aurigae, a Classical T Tauri system, that reveal two remarkable dimming events. These events are similar to that which we observed in 2010-2011, which was the first such deep dimming observed in RW Aur in a century's worth of photometric monitoring. We suggested the 2010-2011 dimming was the result of an occultation of the star by its tidally disrupted circumstellar disk. Read More

Typically, when estimating the prior transit probability, one assumes a uniform distribution for the cosine of the inclination angle i of the companion's orbit, which yields the familiar estimate of ~R_*/a. However, the posterior transit probability depends not only on the prior probability distribution of i but also on the prior probability distribution of the companion mass M_c. In general, the posterior can be larger or smaller than the prior transit probability. Read More

Selection among alternative theoretical models given an observed data set is an important challenge in many areas of physics and astronomy. Reversible-jump Markov chain Monte Carlo (RJMCMC) is an extremely powerful technique for performing Bayesian model selection, but it suffers from a fundamental difficulty: it requires jumps between model parameter spaces, but cannot efficiently explore both parameter spaces at once. Thus, a naive jump between parameter spaces is unlikely to be accepted in the MCMC algorithm and convergence is correspondingly slow. Read More