Search Publications
Evidence of Solar-cycle-related Structural Changes in the Solar Convection Zone
Basu, Sarbani
While it has been relatively easy to determine solar-cycle related changes in solar dynamics, determining changes in structure in the deeper layers of the Sun has proved to be difficult. By using helioseismic data obtained over two solar cycles, and sacrificing resolution in favor of lower uncertainties, we show that there are significant changes …
Automated Photometry of γ Cassiopeiae: The Last Roundup
Smith, M. A.; Henry, G. W.
γ Cassiopeiae (B0.5IVe) is the noted prototype of a subgroup of classical Be stars exhibiting hard thermal X-ray emission. This paper reports results from a 23 yr optical campaign on this star with an automated photometric telescope (APT). A series of unstable long cycles of length 56-91 days has nearly ceased over the last decade. Also, we revise…
The First Radio Spectrum of a Rapidly Rotating A-type Star
De la Luz, V.; Moór, A.; Fehér, O. +9 more
The radio spectra of main-sequence stars remain largely unconstrained due to the lack of observational data to inform stellar atmosphere models. As such, the dominant emission mechanisms at long wavelengths, how they vary with spectral type, and how much they contribute to the expected brightness at a given radio wavelength are still relatively un…
Evidence for Cold Plasma in Planetary Nebulae From Radio Observations With the LOw Frequency ARray (LOFAR)
White, Glenn J.; Haverkorn, Marijke; Shimwell, Timothy +6 more
We present observations of planetary nebulae with the LOw Frequency ARray (LOFAR) between 120 and 168 MHz. The images show thermal free-free emission from the nebular shells. We have determined the electron temperatures for spatially resolved, optically thick nebulae. These temperatures are 20%-60% lower than those estimated from collisionally exc…
Mapping Milky Way Halo Substructure Using Stars in the Extended Blue Tail of the Horizontal Branch
Newberg, Heidi Jo; Gryncewicz, Robert; Martin, Charles +2 more
Although blue horizontal branch (BHB) stars are commonly used to trace halo substructure, the stars bluer than (g - r) < -0.3 are ignored owing to the difficulty in determining their absolute magnitudes. The blue extension of the horizontal branch (HBX) includes BHB tail stars and extreme horizontal branch (EHB) stars. We present a method for i…
Radio Proper Motions of the Energetic Pulsar PSR J1813-1749
Rodríguez, Luis F.; Dzib, Sergio A.
PSR J1813-1749 has peculiarities that make it a very interesting object of study. It is one of the most energetic and the most scattered pulsars known. It is associated with HESS J1813-178, one of the brightest and most compact TeV sources in the sky. Recently, Ho et al. used archival X-ray Chandra observations separated by more than 10 yr and det…
The Robustness of Synthetic Observations in Producing Observed Core Properties: Predictions for the TolTEC Clouds to Cores Legacy Survey
Wilson, G.; Gutermuth, R.; Pokhrel, R. +3 more
We use hydrodynamical simulations of star-forming gas with stellar feedback and sink particles-proxies for young stellar objects (YSOs)-to produce and analyze synthetic 1.1 mm continuum observations at different distances (150-1000 pc) and ages (0.49-1.27 Myr). We characterize how the inferred core properties, including mass, size, and clustering …
Mass Segregation as a New Indicator of Binary, IMBH, and Stellar-mass Black Hole Systems in Globular Clusters
Zhao, Gang; Wu, Wenbo
This study presents the mass segregation of 35 Galactic globular clusters (GCs) through the radial profile of the mean mass of main-sequence stars. Most of them are found to be mass segregated due to two-body relaxation effects. The GCs with a larger core to half-mass-radius ratio tend to be less mass segregated. Recent simulations show that energ…
VZ Sex: X-Ray Confirmation of Its Intermediate Polar Nature
Nucita, A. A.; De Paolis, F.; Ingrosso, G. +3 more
Intermediate polars are members of the cataclysmic variable binary stars. They are characterized by a moderately magnetized white dwarf accreting matter from a cool main-sequence companion star. In many cases, this accretion gives rise to a detectable X-ray emission. VZ Sex is an interesting X-ray source whose nature needs a robust confirmation. H…
V488 Per Revisited: No Strong Mid-infrared Emission Features and No Evidence for Stellar/substellar Companions
Howard, Andrew W.; Zuckerman, B.; Song, Inseok +4 more
We present characterization of the planetary system architecture for V488 Per, the dustiest main-sequence star known with a fractional infrared luminosity of ≈16%. Far-infrared imaging photometry confirms the existence of an outer planetary system dust population with a blackbody-fit temperature of ≈130 K. Mid-infrared spectroscopy probing the pre…