Search Publications
Galactic structure studies with BATC star counts
Zhou, Xu; Ma, Jun; Jiang, Zhaoji +6 more
We report the first results of star counts carried out with the National Astronomical Observatories (NAOC) 60/90 cm Schmidt Telescope in 15 intermediate-band filters from 3000 to 10 000 Å in the BATC survey. We analyze a sample of over 1400 main sequence stars (14<=Vle21 ), which lie in the field with central coordinates RA=09h53
Temporal Variation of Angular Momentum in the Solar Convection Zone
Howe, R.; Komm, R.; Hill, F. +1 more
We derive the angular momentum as a function of radius and time with the help of the rotation rates resulting from inversions of helioseismic data obtained from the Global Oscillation Network Group (GONG) and the Michelson Doppler Imager (MDI) and the density distribution from a model of the Sun. The base of the convection zone can be identified a…
Temperature variations from Hubble Space Telescope spectroscopy of the Orion Nebula
Martin, P. G.; Blagrave, K. P. M.; Dufour, R. J. +5 more
We present Hubble Space Telescope (HST)/STIS long-slit spectroscopy of NGC 1976. Our goal is to measure the intrinsic line ratio [OIII] 4364/5008 and thereby evaluate the electron temperature (Te) and the fractional mean-square Te variation (t2A)across the nebula. We also measure the intrinsic line ratio…
The Luminosity Function of the Large Magellanic Cloud Globular Cluster NGC 1866
Walker, A. R.; Castellani, V.; Brocato, E. +2 more
We present Hubble Space Telescope VI photometry of the central region of the Large Magellanic Cloud cluster NGC 1866, reaching magnitudes as faint as V=27. We find evidence that the cluster luminosity function shows a strong dependence on the distance from the cluster center, with a clear deficiency of low-luminosity stars in the inner region. We …
Chandra Observations of Expanding Shells in the Dwarf Starburst Galaxy NGC 3077
Martin, Crystal L.; Ott, Jürgen; Walter, Fabian
Deep Chandra observations (53 ks, ACIS-S3) of NGC 3077, a starburst dwarf galaxy in the M81 triplet, resolve the X-ray emission from several supershells. The emission is brightest in the cavities defined by expanding shells detected previously in Hα emission. Thermal emission models fitted to the data imply temperatures ranging from ~1.3 to 4.9×10…
The Long-Term Evolution of AR 7978: The Scalings of the Coronal Plasma Parameters with the Mean Photospheric Magnetic Field
Klimchuk, J. A.; Mandrini, C. H.; van Driel-Gesztelyi, L. +2 more
We analyze the evolution of the fluxes observed in X-rays and correlate them with the magnetic flux density in active region (AR) NOAA 7978 from its birth throughout its decay, for five solar rotations. We use Solar and Heliospheric Observatory Michelson Doppler Imager (MDI) data, together with Yohkoh Soft X-Ray Telescope (SXT) and Yohkoh Bragg Cr…
The eclipsing millisecond pulsar PSR J1740-5340 and its red straggler companion
van Kerkwijk, M. H.; Orosz, J. A.
We present a high-resolution echelle spectrum taken with the Very Large Telescope and analyse archival Hubble Space Telescope photometry of the recently identified companion of the eclipsing millisecond radio pulsar
Improved Astrometry and Photometry for the Luyten Catalog. I. Bright Stars
Gould, Andrew; Salim, Samir
We outline the construction of a refined version of the New Luyten Two-Tenths (NLTT) catalog of high proper motion stars, which will contain improved astrometry and photometry for the vast majority of the ~59,000 stars in NLTT. The bright end is constructed by matching NLTT stars to Hipparcos, Tycho-2, and Starnet; the faint end by matching to USN…
Models of the Morphology, Kinematics, and Star Formation History of the Prototypical Collisional Starburst System NGC 7714/7715 = ARP 284
Struck, Curtis; Smith, Beverly J.
We present new N-body, hydrodynamical simulations of the interaction between the starburst galaxy NGC 7714 and its poststarburst companion NGC 7715, focusing on the formation of the collisional features, including (1) the gas-rich star-forming bridge, (2) the large gaseous loop (and stellar tails) to the west of the system, (3) the very extended H…
Host galaxies and black hole masses of low- and high-luminosity radio-loud active nuclei
Treves, Aldo; Falomo, Renato; Carangelo, Nicoletta
We investigate the host galaxy luminosities of BL Lac objects (BLLs) and radio-loud quasars (RLQs) at z < 0.5, imaged with the Hubble Space Telescope (HST). From a homogeneous treatment of the data, we construct the host-galaxy luminosity functions (HGLFs) and find that RLQ hosts are ~0.5 mag brighter than those of BLLs: <MR>