Search Publications
The Secret Lives of Cepheids: Evolution, Mass-Loss, and Ultraviolet Emission of the Long-period Classical Cepheid
Guinan, Edward F.; Engle, Scott G.; Neilson, Hilding R. +2 more
The classical Cepheid l Carinae is an essential calibrator of the Cepheid Leavitt Law as a rare long-period Galactic Cepheid. Understanding the properties of this star will also constrain the physics and evolution of massive (M ≥ 8 M ⊙) Cepheids. The challenge, however, is precisely measuring the star's pulsation period and its rate of …
Flux and spectral variability of the blazar PKS 2155 -304 with XMM-Newton: Evidence of particle acceleration and synchrotron cooling
Bhagwan, Jai; Papadakis, I. E.; Wiita, Paul J. +1 more
We have analyzed XMM-Newton observations of the high energy peaked blazar, PKS 2155 -304, made on 24 May 2002 in the 0.3-10 keV X-ray band. These observations display a mini-flare, a nearly constant flux period and a strong flux increase. We performed a time-resolved spectral study of the data, by dividing the data into eight segments. We fitted t…
Hybrid simulation of Titan's interaction with the supersonic solar wind during Cassini's T96 flyby
Simon, Sven; Motschmann, Uwe; Neubauer, Fritz M. +5 more
By applying a hybrid (kinetic ions and fluid electrons) simulation code, we study the plasma environment of Saturn's largest moon Titan during Cassini's T96 flyby on 1 December 2013. The T96 encounter marks the only observed event of the entire Cassini mission where Titan was located in the supersonic solar wind in front of Saturn's bow shock. Our…
Source region and growth analysis of narrowband Z-mode emission at Saturn
Gurnett, D. A.; Coates, A. J.; Santolík, O. +5 more
Intense Z-mode emission is observed in the lower density region near the inner edge of the Enceladus torus at Saturn, where these waves may resonate with MeV electrons. The source mechanism of this emission, which is narrow-banded and most intense near 5 kHz, is not well understood. We survey the Cassini Radio and Plasma Wave Science data to isola…
Shadowing and anisotropy of solar energetic ions at Mars measured by MAVEN during the March 2015 solar storm
Lee, Christina O.; Larson, Davin; Halekas, Jasper S. +4 more
The Solar Energetic Particle (SEP) Instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft is meant to characterize the variability of SEP fluxes at Mars. SEP ion precipitation is an important source of heating, ionization, and chemical changes in the upper atmosphere of Mars and may have played a substantial role in driving at…
A Chandra Study of Temperature Distributions of the Intracluster Medium in 50 Galaxy Clusters
Hu, Dan; Xu, Haiguang; Zhu, Zhenghao +10 more
To investigate the spatial distribution of the intracluster medium temperature in galaxy clusters in a quantitative way and probe the physics behind it, we analyze the X-ray spectra from a sample of 50 clusters that were observed with the Chandra ACIS instrument over the past 15 years and measure the radial temperature profiles out to 0.45r50…
Estimating sizes of faint, distant galaxies in the submillimetre regime
Karim, A.; Hodge, J. A.; Coppin, K. +8 more
We measure the sizes of redshift ∼2 star-forming galaxies by stacking data from the Atacama Large Millimeter/submillimeter Array (ALMA). We use a uv-stacking algorithm in combination with model fitting in the uv-domain and show that this allows for robust measures of the sizes of marginally resolved sources. The analysis is primarily based on the …
GAMA/H-ATLAS: common star formation rate indicators and their dependence on galaxy physical parameters
Wang, L.; Cooray, A.; Ibar, E. +30 more
We compare common star formation rate (SFR) indicators in the local Universe in the Galaxy and Mass Assembly (GAMA) equatorial fields (∼160 deg2), using ultraviolet (UV) photometry from GALEX, far-infrared and sub-millimetre (sub-mm) photometry from Herschel Astrophysical Terahertz Large Area Survey, and Hα spectroscopy from the GAMA su…
The Binary Black Hole Model for Mrk 231 Bites the Dust
Gallagher, Sarah C.; Terndrup, Donald M.; Leighly, Karen M. +1 more
Mrk 231 is a nearby quasar with an unusually red near-UV-to-optical continuum, generally explained as heavy reddening by dust. Yan et al. proposed that Mrk 231 is a milliparsec black hole binary with little intrinsic reddening. We show that if the observed FUV continuum is intrinsic, as assumed by Yan et al., it fails by a factor of about 100 in p…
Eta Carinae's Thermal X-Ray Tail Measured with XMM-Newton and NuSTAR
Hamaguchi, Kenji; Corcoran, Michael F.; Russell, Christopher M. P. +12 more
The evolved, massive highly eccentric binary system, η Car, underwent a periastron passage in the summer of 2014. We obtained two coordinated X-ray observations with XMM-Newton and NuSTAR during the elevated X-ray flux state and just before the X-ray minimum flux state around this passage. These NuSTAR observations clearly detected X-ray emission …