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GAIA Parallax Zero Point from RR Lyrae Stars
Kollmeier, Juna A.; Gould, Andrew
Like Hipparcos, Gaia is designed to give absolute parallaxes, independent of any astrophysical reference system. And indeed, Gaia's internal zero-point error for parallaxes is likely to be smaller than any individual parallax error. Nevertheless, due in part to mechanical issues of unknown origin, there are many astrophysical questions for which t…
XMM-Newton view of X-ray overdensities from nearby galaxy clusters: the environmental dependencies
Hudaverdi, Murat; Caglar, Turgay
In this work, we studied 10 nearby (z ≤ 0.038) galaxy clusters to understand possible interactions between hot plasma and member galaxies. A multi-band source detection was applied to detect point-like structures within the intra-cluster medium. We examined the spectral properties of a total of 391 X-ray point sources within each cluster's potenti…
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…
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…