Search Publications
Active Learning to Overcome Sample Selection Bias: Application to Photometric Variable Star Classification
Miller, Adam A.; Bloom, Joshua S.; Richards, Joseph W. +6 more
Despite the great promise of machine-learning algorithms to classify and predict astrophysical parameters for the vast numbers of astrophysical sources and transients observed in large-scale surveys, the peculiarities of the training data often manifest as strongly biased predictions on the data of interest. Typically, training sets are derived fr…
Carbon-rich Dust Production in Metal-poor Galaxies in the Local Group
van Loon, J. Th.; Wood, P. R.; Zijlstra, A. A. +7 more
We have observed a sample of 19 carbon stars in the Sculptor, Carina, Fornax, and Leo I dwarf spheroidal galaxies with the Infrared Spectrograph on the Spitzer Space Telescope. The spectra show significant quantities of dust around the carbon stars in Sculptor, Fornax, and Leo I, but little in Carina. Previous comparisons of carbon stars with simi…
Thermal Properties of a Solar Coronal Cavity Observed with the X-Ray Telescope on Hinode
Reeves, Katharine K.; Gibson, Sarah E.; Kucera, Therese A. +2 more
Coronal cavities are voids in coronal emission often observed above high latitude filament channels. Sometimes, these cavities have areas of bright X-ray emission in their centers. In this study, we use data from the X-ray Telescope (XRT) on the Hinode satellite to examine the thermal emission properties of a cavity observed during 2008 July that …
SN 2010ay is a Luminous and Broad-lined Type Ic Supernova within a Low-metallicity Host Galaxy
Price, P. A.; Berger, E.; Cline, T. +38 more
We report on our serendipitous pre-discovery detection and follow-up observations of the broad-lined Type Ic supernova (SN Ic) 2010ay at z = 0.067 imaged by the Pan-STARRS1 3π survey just ~4 days after explosion. The supernova (SN) had a peak luminosity, MR ≈ -20.2 mag, significantly more luminous than known GRB-SNe and one of the most …
Numerical Simulations of the Magnetic Rayleigh-Taylor Instability in the Kippenhahn-Schlüter Prominence Model. II. Reconnection-triggered Downflows
Shibata, Kazunari; Isobe, Hiroaki; Hillier, Andrew +1 more
The launch of the Hinode satellite has allowed high-resolution observations of supersonic bright downflows in quiescent prominences, known as prominence knots. We present observations in the Ca II H spectral line using the Solar Optical Telescope on board the Hinode satellite of a descending plasma knot of size ~900 km. The knot initially undergoe…
Of "Cocktail Parties" and Exoplanets
Waldmann, I. P.
The characterization of ever smaller and fainter extrasolar planets requires an intricate understanding of one's data and the analysis techniques used. Correcting the raw data at the 10-4 level of accuracy in flux is one of the central challenges. This can be difficult for instruments that do not feature a calibration plan for such high…
The Hubble Space Telescope Cluster Supernova Survey. III. Correlated Properties of Type Ia Supernovae and Their Hosts at 0.9 < Z < 1.46
Gladders, M. D.; Lidman, C.; Rubin, D. +36 more
Using the sample of Type Ia supernovae (SNe Ia) discovered by the Hubble Space Telescope (HST) Cluster Supernova Survey and augmented with HST-observed SNe Ia in the Great Observatories Origins Deep Survey (GOODS) fields, we search for correlations between the properties of SNe and their host galaxies at high redshift. We use galaxy color and quan…
The Connection between Internetwork Magnetic Elements and Supergranular Flows
Bellot Rubio, L. R.; Katsukawa, Y.; Orozco Suárez, D.
The advection of internetwork magnetic elements by supergranular convective flows is investigated using high spatial resolution, high cadence, and high signal-to-noise ratio Na I D1 magnetograms obtained with the Hinode satellite. The observations show that magnetic elements appear everywhere across the quiet Sun surface. We calculate the proper m…
Narrow Dust Jets in a Diffuse Gas Coma: A Natural Product of Small Active Regions on Comets
Combi, M. R.; Fougere, N.; Gombosi, T. I. +2 more
Comets often display narrow dust jets but more diffuse gas comae when their eccentric orbits bring them into the inner solar system and sunlight sublimates the ice on the nucleus. Comets are also understood to have one or more active areas covering only a fraction of the total surface active with sublimating volatile ices. Calculations of the gas …
X-Ray Observations of the New Unusual Magnetar Swift J1834.9-0846
Pavlov, George G.; Kargaltsev, Oleg; Griffith, Roger L. +6 more
We present X-ray observations of the new transient magnetar Swift J1834.9-0846, discovered with the Swift Burst Alert Telescope on 2011 August 7. The data were obtained with Swift, Rossi X-ray Timing Explorer (RXTE), CXO, and XMM-Newton both before and after the outburst. Timing analysis reveals single peak pulsations with a period of 2.4823 s and…