Search Publications
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 …
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…
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 …
The Most Ancient Spiral Galaxy: A 2.6-Gyr-old Disk with a Tranquil Velocity Field
Kewley, Lisa J.; Richard, Johan; Gupta, Anshu +7 more
We report an integral-field spectroscopic (IFS) observation of a gravitationally lensed spiral galaxy A1689B11 at redshift z = 2.54. It is the most ancient spiral galaxy discovered to date and the second kinematically confirmed spiral at z≳ 2. Thanks to gravitational lensing, this is also by far the deepest IFS observation with the highest spatial…
Plasma Beta Stratification in the Solar Atmosphere: A Possible Explanation for the Penumbra Formation
Bourdin, Ph. -A.
Plasma beta is an important and fundamental physical quantity in order to understand plasma dynamics, particularly in the context of magnetically active stars, because it tells about the domination of magnetic versus thermodynamic processes on the plasma motion. We estimate the value ranges of plasma beta in different regions within the solar atmo…
Interstellar-medium Mapping in M82 through Light Echoes around Supernova 2014J
Baade, Dietrich; Sparks, William B.; Wang, Lifan +10 more
We present multiple-epoch measurements of the size and surface brightness of the light echoes from supernova (SN) 2014J in the nearby starburst galaxy M82. Hubble Space Telescope (HST) ACS/WFC images were taken ∼277 and ∼416 days after B-band maximum in the filters F475W, F606W, and F775W. Observations with HST WFC3/UVIS images at epochs ∼216 and …
New Evidence for the Dynamical Decay of a Multiple System in the Orion Kleinmann-Low Nebula
Luhman, K. L.; Robberto, M.; Manara, C. F. +5 more
We have measured astrometry for members of the Orion Nebula Cluster with images obtained in 2015 with the Wide Field Camera 3 on board the Hubble Space Telescope. By comparing those data to previous measurements with the Near-Infrared Camera and Multi-Object Spectrometer on Hubble in 1998, we have discovered that a star in the Kleinmann-Low Nebula…
Multiwavelength Stellar Polarimetry of the Filamentary Cloud IC5146. I. Dust Properties
Wang, Jia-Wei; Lai, Shih-Ping; Eswaraiah, Chakali +3 more
We present optical and near-infrared stellar polarization observations toward the dark filamentary clouds associated with IC5146. The data allow us to investigate the dust properties (this paper) and the magnetic field structure (Paper II). A total of 2022 background stars were detected in the R c , I\prime , H, and/or K ban…
Charge States and FIP Bias of the Solar Wind from Coronal Holes, Active Regions, and Quiet Sun
Fu, Hui; Madjarska, Maria S.; Li, Bo +3 more
Connecting in situ measured solar-wind plasma properties with typical regions on the Sun can provide an effective constraint and test to various solar wind models. We examine the statistical characteristics of the solar wind with an origin in different types of source regions. We find that the speed distribution of coronal-hole (CH) wind is bimoda…