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…

Two populations of the solar magnetic field

Obridko, V. N.; Sokoloff, D. D.; Livshits, I. M.

Dynamo theory suggests that there are two types of solar dynamo, namely the conventional mean-field dynamo, which produces large- and small-scale magnetic fields involved in the activity cycle, and also the small-scale dynamo, which produces a cycle independent small-scale magnetic field. The relative contribution of the two mechanisms to solar ma…

Evolutionary status of the Of?p star HD 148937 and of its surrounding nebula NGC 6164/5

Lebouteiller, V.; Nazé, Y.; Mahy, L. +3 more

Aims: The magnetic star HD 148937 is the only Galactic Of?p star surrounded by a nebula. The structure of this nebula is particularly complex and is composed, from the center out outwards, of a close bipolar ejecta nebula (NGC 6164/5), an ellipsoidal wind-blown shell, and a spherically symmetric Strömgren sphere. The exact formation process o…

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 1_0,1-0_0,0 rotational transition of HDO at 464.925 GHz and the 1_1,0-1_0,1 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…

Observations of multiharmonic ion cyclotron waves due to inverse ion cyclotron damping in the northern magnetospheric cusp

Gunell, H.; Slapak, R.; Hamrin, M.

We present a case study of inverse ion cyclotron damping taking place in the northern terrestrial magnetospheric cusp, exciting waves at the ion cyclotron frequency and its harmonics. The ion cyclotron waves are primarily seen as peaks in the magnetic-field spectral densities. The corresponding peaks in the electric-field spectral densities are no…

Least Squares Image Estimation for Large Data in the Presence of Noise and Irregular Sampling

Piazzo, Lorenzo