Search Publications
Detection of the Stellar Intracluster Medium in Perseus (Abell 426)
Harris, William E.; Mulholland, Courtney J.
Hubble Space Telescope (HST) photometry from the ACS/WFC and WFPC2 cameras is used to detect and measure globular clusters (GCs) in the central region of the rich Perseus cluster of galaxies. A detectable population of Intragalactic GCs is found extending out to at least 500 kpc from the cluster center. These objects display luminosity and color (…
CLASP/SJ Observations of Rapid Time Variations in the Lyα Emission in a Solar Active Region
Narukage, Noriyuki; Kobayashi, Ken; Kubo, Masahito +8 more
The Chromospheric Lyα SpectroPolarimeter (CLASP) is a sounding rocket experiment launched on 2015 September 3 to investigate the solar chromosphere and transition region. The slit-jaw (SJ) optical system captured Lyα images with a high time cadence of 0.6 s. From the CLASP/SJ observations, many variations in the solar chromosphere and transition r…
Two Distinct Types of CME-flare Relationships Based on SOHO and STEREO Observations
Moon, Yong-Jae; Jang, Soojeong; Kim, Sujin +2 more
In this paper, we present two distinct types of coronal mass ejection (CME)-flare relationships according to their observing time differences using 107 events from 2010 to 2013. The observing time difference, ΔT, is defined as flare peak time minus CME first appearance time at Solar Terrestrial Relations Observatory (STEREO) COR1 field of view. Th…
On Estimating Force-freeness Based on Observed Magnetograms
Su, J. T.; Zhang, M.; Zhang, X. M.
It is a common practice in the solar physics community to test whether or not measured photospheric or chromospheric vector magnetograms are force-free, using the Maxwell stress as a measure. Some previous studies have suggested that magnetic fields of active regions in the solar chromosphere are close to being force-free whereas there is no consi…
Analysis of Low Excitation HDO Transitions toward the High-mass Star-forming Regions G34.26+0.15, W51e1/e2, and W49N
Kulczak-Jastrzębska, Magda
We present observations of the ground state 10,1-00,0 rotational transition of HDO at 464.925 GHz and the 11,0-10,1 transition at 509.292 GHz, toward three high-mass star-forming regions: G34.26+0.15, W49N, and W51e1/e2, carried out with the Caltech Submillimeter Observatory. For th…
A Universal Transition in Atmospheric Diffusion for Hot Subdwarfs Near 18,000 K
Dalessandro, E.; Salaris, M.; Bedin, L. R. +6 more
In the color-magnitude diagrams of globular clusters, when the locus of stars on the horizontal branch extends to hot temperatures, discontinuities are observed at colors corresponding to ∼12,000 and ∼18,000 K. The former is the “Grundahl jump” that is associated with the onset of radiative levitation in the atmospheres of hot subdwarfs. The latte…
The Radial Distribution of Mono-metallicity Populations in the Galactic Disk as Evidence for Two-phase Disk Formation
Domínguez-Tenreiro, R.; Obreja, A.; Brook, C. B. +2 more
Recent determinations of the radial distributions of mono-metallicity populations (MMPs, I.e., stars in narrow bins in [Fe/H] within wider [α/Fe] ranges) by the SDSS-III/APOGEE DR12 survey cast doubts on the classical thin- and thick-disk dichotomy. The analysis of these observations led to the non-[α /Fe] enhanced populations splitting into MMPs …
Constraining the Dust Opacity Law in Three Small and Isolated Molecular Clouds
Di Francesco, J.; Sadavoy, S.; Kainulainen, J. +6 more
Density profiles of isolated cores derived from thermal dust continuum emission rely on models of dust properties, such as mass opacity, that are poorly constrained. With complementary measures from near-infrared extinction maps, we can assess the reliability of commonly used dust models. In this work, we compare Herschel-derived maps of the optic…
Time Evolution of Elemental Ratios in Solar Energetic Particle Events
Dalla, S.; Cohen, C. M. S.; Mewaldt, R. A. +1 more
Heavy ion ratio abundances in solar energetic particle (SEP) events, e.g., Fe/O, often exhibit decreases over time. Using particle instruments on the Advanced Composition Explorer, Solar and Heliospheric Observatory and Solar Terrestrial Relations Observatory spacecraft, we analyzed heavy ion data from 4 SEP events taking place between 2006 Decemb…
MAXI J1957+032: An Accreting Neutron Star Possibly in a Triple System
Ravi, V.
I present an optical characterization of the Galactic X-ray transient source MAXI J1957+032. This system flares by a factor of ≳104 every few hundred days, with each flare lasting ∼5 days. I identify its quiescent counterpart to be a late-K/early-M dwarf star at a distance of 5 ± 2 kpc. This implies that the peak 0.5{--}10 {keV} luminos…