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 …
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…
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…
A MegaCam Survey of Outer Halo Satellites. I. Description of the Survey
Djorgovski, S. G.; Geha, Marla; Oyarzún, Grecco A. +5 more
We describe a deep, systematic imaging study of satellites in the outer halo of the Milky Way. Our sample consists of 58 stellar overdensities—i.e., substructures classified as either globular clusters, classical dwarf galaxies, or ultra-faint dwarf galaxies—that are located at Galactocentric distances of R GC ≥ 25 kpc (outer halo) and …
Young Accreting Compact Objects in M31: The Combined Power of NuSTAR, Chandra, and Hubble
Lehmer, B. D.; Hornschemeier, A. E.; Yukita, M. +11 more
We present 15 high-mass X-ray binary (HMXB) candidates in the disk of M31 for which we are able to infer compact object type, spectral type of the donor star, and age using multiwavelength observations from NuSTAR, Chandra, and the Hubble Space Telescope. The hard X-ray colors and luminosities from NuSTAR permit the tentative classification of acc…
Possible Phase-dependent Absorption Feature in the X-Ray Spectrum of the Middle-aged PSR J0659+1414
Pavlov, George G.; Kargaltsev, Oleg; Hare, Jeremy +2 more
We report on the energy-resolved timing and phase-resolved spectral analysis of X-ray emission from PSR J0659+1414 observed with XMM-Newton and NuSTAR. We find that the new data rule out the previously suggested model of the phase-dependent spectrum as a three-component (two blackbodies + power law) continuum, which shows large residuals between 0…
TRGB Distances to Galaxies in Front of the Virgo Cluster
Shaya, Edward J.; Tully, R. Brent; Karachentsev, Igor D. +2 more
Tip of the red giant branch distances are acquired from Hubble Space Telescope images for 16 galaxies to the foreground of the Virgo Cluster. The new distances with 5% accuracy, combined with archival measurements, tightly constrain the near-side location of the onset of infall into the Virgo Cluster to be 7.3 ± 0.3 Mpc from the cluster, reaching …
Expanding CO Shells in the Orion A Molecular Cloud
Nakamura, Fumitaka; Shimajiri, Yoshito; Kawabe, Ryohei +6 more
We present the discovery of expanding spherical shells around low- to intermediate-mass young stars in the Orion A giant molecular cloud using observations of {}12{CO}(1-0) and {}13{CO}(1-0) from the Nobeyama Radio Observatory 45 m telescope. The shells have radii from 0.05 to 0.85 pc and expand outward at 0.8-5 km s-1