Search Publications
Contribution of Field Strength Gradients to the Net Vertical Current of Active Regions
Vemareddy, P.
We examined the contribution of field strength gradients for the degree of net vertical current (NVC) neutralization in active regions (ARs). We used photospheric vector magnetic field observations of AR 11158 obtained by Helioseismic and Magnetic Imager on board SDO and Hinode. The vertical component of the electric current is decomposed into twi…
A Differential Abundance Analysis of Very Metal-poor Stars
McWilliam, Andrew; Chaboyer, Brian; O'Malley, Erin M. +1 more
We have performed a differential line-by-line chemical abundance analysis, ultimately relative to the Sun, of nine very metal-poor main-sequence (MS) halo stars, near [Fe/H] = -2 dex. Our abundances range from -2.66≤slant [{Fe}/{{H}}]≤slant -1.40 dex with conservative uncertainties of 0.07 dex. We find an average [α/Fe] = 0.34 ± 0.09 dex, typical …
Chandra Observations of the Field Containing HESS J1616-508
Pavlov, George G.; Kargaltsev, Oleg; Hare, Jeremy +2 more
We report the results of three Chandra observations covering most of the extent of the TeV γ-ray source HESS J1616-508 and a search for a lower-energy counterpart to this source. We detect 56 X-ray sources, 37 of which have counterparts at lower frequencies, including a young massive star cluster, but none of them appear to be a particularly promi…
Search for Exoplanets around Northern Circumpolar Stars. II. The Detection of Radial Velocity Variations in M Giant Stars HD 36384, HD 52030, and HD 208742
Lee, Byeong-Cheol; Park, Myeong-Gu; Han, Inwoo +8 more
We present the detection of long-period RV variations in HD 36384, HD 52030, and HD 208742 by using the high-resolution, fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) for the precise radial velocity (RV) survey of about 200 northern circumpolar stars. Analyses of RV data, chromospheric activity indicators, and bisector variations spa…
Analysis of the Amplitude of the Sunyaev-Zel’dovich Effect out to Redshift z = 0.8
López-Corredoira, M.; Génova-Santos, R. T.; Gutiérrez, C. M.
The interaction of the cosmic microwave background (CMB) with the hot gas in clusters of galaxies, the so-called Sunyaev-Zel’dovich (SZ) effect, is a very useful tool that allows us to determine the physical conditions in such clusters and fundamental parameters of the cosmological models. In this work, we determine the dependence of the SZ surfac…
Are All Flare Ribbons Simply Connected to the Corona?
Judge, Philip G.; Paraschiv, Alin; Lacatus, Daniela +2 more
We consider the observational basis for the belief that flare ribbons in the chromosphere result from energy transport from the overlying corona. We study ribbons of small flares using magnetic and intensity data from the Hinode, Solar Dynamics Observatory, and IRIS missions. While most ribbons appear connected to the corona and overlie regions of…
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…