Search Publications
North-South Asymmetry of the Rotation of the Solar Magnetic Field
Qu, Zhining; Xie, Jinglan; Shi, Xiangjun
Using the rotation rates of the solar magnetic field during solar cycles 21 to 23 obtained by Chu et al. by analyzing the synoptic magnetic maps produced by the NSO/Kitt Peak and SOHO/MDI during the years 1975 to 2008, the temporal variation of the equatorial rotation rate (A) and the latitude gradient of rotation (B) in the northern and southern …
Incision of Licus Vallis, Mars, From Multiple Lake Overflow Floods
Goudge, Timothy A.; Fassett, Caleb I.
Licus Vallis is a large valley (>350 km long, >2 km wide, and >150 m deep) that heads at the outlet breach of an 30 km diameter impact crater. We present observations of the geomorphology and topography of this paleolake outlet valley and associated tributary valleys to constrain the history of incision of the Licus Vallis system. Licus V…
Spots, Flares, Accretion, and Obscuration in the Pre-main-sequence Binary DQ Tau
Pál, A.; Ábrahám, P.; Kóspál, Á. +4 more
DQ Tau is a young low-mass spectroscopic binary, consisting of two almost equal-mass stars on a 15.8 day period surrounded by a circumbinary disk. Here, we analyze DQ Tau’s light curves obtained by Kepler K2, the Spitzer Space Telescope, and ground-based facilities. We observed variability phenomena, including rotational modulation by stellar spot…
Bridging the Gap: Capturing the Lyα Counterpart of a Type-II Spicule and Its Heating Evolution with VAULT2.0 and IRIS Observations
Vourlidas, Angelos; Martínez-Sykora, Juan; De Pontieu, Bart +3 more
We present results from an observing campaign in support of the VAULT2.0 sounding rocket launch on 2014 September 30. VAULT2.0 is a Lyα (1216 Å) spectroheliograph capable of providing spectroheliograms at high cadence. Lyα observations are highly complementary to the IRIS observations of the upper chromosphere and the low transition region (TR) bu…
The Evolution of the Warm Absorber Reveals a Shocked Outflow in the Narrow Line Seyfert 1 Galaxy IRAS 17020+4544
Guainazzi, Matteo; Krongold, Yair; Panessa, Francesca +2 more
We present the analysis of grating spectra of the Narrow Line Seyfert 1 Galaxy IRAS 17020+4544 observed by XMM-Newton in 2004 and 2014. In a previous work on these data, we reported the discovery of a multicomponent ultra-fast outflow that is capable of producing feedback in the host galaxy. We also reported the presence of a slow, multiphase warm…
Transition Probabilities of Co II Weak Lines to the Ground and Low Metastable Levels
Sneden, C.; Lawler, J. E.; Cowan, J. J. +2 more
New branching fraction (BF) measurements based primarily on data from a cross-dispersed echelle spectrometer are reported for 84 lines of Co II. The BFs for 82 lines are converted to absolute atomic transition probabilities using radiative lifetimes from laser-induced fluorescence (LIF) measurements on 19 upper levels of the lines. A lifetime of 3…
Triggering the formation of the supergiant H II region NGC 604 in M 33
Tachihara, Kengo; Fukui, Yasuo; Sano, Hidetoshi +4 more
Formation mechanism of a supergiant H II region NGC 604 is discussed in terms of collision of H I clouds in M 33. An analysis of the archival H I data obtained with the Very Large Array (VLA) reveals complex velocity distributions around NGC 604. The H I clouds are composed of two velocity components separated by ∼20 km s-1 for an exten…
On the identification of wide binaries in the Kepler field
Godoy-Rivera, Diego; Chanamé, Julio
We perform a search for wide binaries in the Kepler field with the prospect of providing new constraints for gyrochronology. First, we construct our base catalogue by compiling astrometry for the stars observed by Kepler, and supplement it with parallaxes, radial velocities (RVs), and metallicities. We then mine our base catalogue for wide binary …
Solar-cycle Variations of Meridional Flows in the Solar Convection Zone Using Helioseismic Methods
Chou, Dean-Yi; Lin, Chia-Hsien
The solar meridional flow is an axisymmetric flow in solar meridional planes, extending through the convection zone. Here we study its solar-cycle variations in the convection zone using SOHO/MDI helioseismic data from 1996 to 2010, including two solar minima and one maximum. The travel-time difference between northward and southward acoustic wave…
URAT South Parallax Results
Jao, Wei-Chun; Finch, Charlie T.; Zacharias, Norbert
We present 916 trigonometric parallaxes and proper motions of newly discovered nearby stars from the United States Naval Observatory Robotic Astrometric Telescope (URAT). Observations were taken at the Cerro Tololo Interamerican Observatory over a 2-year period from 2015 to 2017 October covering the entire sky south of about +25° decl. SPM4 and UC…