Search Publications
A Rogues’ Gallery of Andromeda's Dwarf Galaxies. I. A Predominance of Red Horizontal Branches
Lewis, Geraint F.; Dolphin, Andrew E.; Skillman, Evan D. +11 more
We present homogeneous, sub-horizontal branch photometry of 20 dwarf spheroidal satellite galaxies of M31 observed with the Hubble Space Telescope. Combining our new data for 16 systems with archival data in the same filters for another four, we show that Andromeda dwarf spheroidal galaxies favor strikingly red horizontal branches or red clumps do…
Relationship between turbulence energy and density variance in the solar neighbourhood molecular clouds
Federrath, C.; Kainulainen, J.
The relationship between turbulence energy and gas density variance is a fundamental prediction for turbulence-dominated media and is commonly used in analytic models of star formation. We determine this relationship for 15 molecular clouds in the solar neighbourhood. We use the line widths of the CO molecule as the probe of the turbulence energy …
The Small Magellanic Cloud Investigation of Dust and Gas Evolution (SMIDGE): The Dust Extinction Curve from Red Clump Stars
Dolphin, Andrew E.; Yanchulova Merica-Jones, Petia; Williams, Benjamin F. +6 more
We use Hubble Space Telescope (HST) observations of red clump stars taken as part of the Small Magellanic Cloud Investigation of Dust and Gas Evolution (SMIDGE) program to measure the average dust extinction curve in a ∼200 pc × 100 pc region in the southwest bar of the Small Magellanic Cloud (SMC). The rich information provided by our eight-band …
New outburst of the symbiotic nova AG Pegasi after 165 yr
Wolf, M.; Boyd, D.; Skopal, A. +13 more
Context. AG Peg is known as the slowest symbiotic nova, which experienced its nova-like outburst around 1850. After 165 yr, during June of 2015, it erupted again showing characteristics of the Z And-type outburst.
Aims: The primary objective is to determine basic characteristics, the nature and type of the 2015 outburst of AG Peg.
Method…
The Carbon and Nitrogen Abundance Ratio in the Broad Line Region of Tidal Disruption Events
Ferland, Gary J.; Zhou, Hongyan; Jiang, Ning +4 more
The rest-frame UV spectra of three recent tidal disruption events (TDEs), ASASSN-14li, PTF15af, and iPTF16fnl, display strong nitrogen emission lines but weak or undetectable carbon lines. In these three objects, the upper limits of the C III] λ 1908/N III] λ 1750 ratio are about two orders of magnitude lower than those of quasars, suggesting a hi…
The Secret Lives of Cepheids: δ Cep—The Prototype of a New Class of Pulsating X-Ray Variable Stars
Harper, Graham M.; Guinan, Edward F.; Engle, Scott G. +4 more
From our Secret Lives of Cepheids program, the prototype Classical Cepheid, δ Cep, is found to be an X-ray source with periodic pulsation-modulated X-ray variations. This finding complements our earlier reported phase-dependent FUV-UV emissions of the star that increase ∼10-20 times with highest fluxes at ∼ 0.90{--}0.95φ , just prior to maximum br…
Jupiter's auroral-related stratospheric heating and chemistry I: Analysis of Voyager-IRIS and Cassini-CIRS spectra
Fletcher, L. N.; Irwin, P. G. J.; Orton, G. S. +4 more
Auroral processes are evident in Jupiter's polar atmosphere over a large range in wavelength (X-ray to radio). In particular, previous observations in the mid-infrared (5-15 µm) have shown enhanced emission from CH4, C2H2 and C2H4 and further stratospheric hydrocarbon species in spatial …
Analysis and modeling of remote observations of the martian hydrogen exosphere
Bertaux, J. -L.; Chaufray, J. -Y.; Clarke, J. T. +2 more
Past observations of the martian exosphere have given a wide range of values for the mean temperature and number density of the hydrogen population that occupies this uppermost layer. More recently, observations by HST and MEX have found large variations over short timescales exhibited by this layer, which have been attributed to seasonal effects.…
Alfvén Wave Turbulence as a Coronal Heating Mechanism: Simultaneously Predicting the Heating Rate and the Wave-induced Emission Line Broadening
Gombosi, T. I.; Landi, E.; Sokolov, I. V. +2 more
We test the predictions of the Alfvén Wave Solar Model (AWSoM), a global wave-driven magnetohydrodynamic (MHD) model of the solar atmosphere, against high-resolution spectra emitted by the quiescent off-disk solar corona. AWSoM incorporates Alfvén wave propagation and dissipation in both closed and open magnetic field lines; turbulent dissipation …
A combined HST and XMM-Newton campaign for the magnetic O9.7 V star HD 54879. Constraining the weak-wind problem of massive stars
Ilyin, I.; Hamann, W. -R.; Hubrig, S. +7 more
Context.
Aims: To gain insights into the interplay between atmospheres, winds, and magnetic fields of massive s…