Search Publications
A Possible Detection of M31* with Chandra
Williams, Benjamin F.; Kong, Albert K. H.; Barmby, Pauline +5 more
Two independent sets of Chandra and HST images of the nuclear region of M31 allow registration of X-ray and optical images to ~0.1". This registration shows that none of the bright (~1037 ergs s-1) X-ray sources near the nucleus is coincident with the central supermassive black hole, M31*. A 50 ks Chandra HRC image shows 2.5 …
Deep Near-Infrared Imaging and Photometry of the Antennae Galaxies with WIRC
Hayward, T. L.; Houck, J. R.; Brandl, B. R. +6 more
We present deep near-infrared images of the Antennae galaxies, taken with the Palomar Wide-Field Infrared Camera (WIRC). The images cover a 4.33 arcmin ×4.33 arcmin (24.7×24.7 kpc) area around the galaxy interaction zone. We derive J- and Ks-band photometric fluxes for 172 infrared star clusters and discuss details of the two galactic n…
Effect of a Converging Flow at the Streamer Cusp on the Genesis of the Slow Solar Wind
Lapenta, Giovanni; Knoll, D. A.
The observation by the Large Angle and Spectrometric Coronagraph (LASCO) instrument on the Solar and Heliospheric Observatory of blobs of plasma generated near the cusp region of the streamer belt has sparked the hope of gaining new insight into the genesis of the slow solar wind. The observations suggest that open and closed field lines reconnect…
A Statistical Study of the Correlation between Magnetic Helicity Injection and Soft X-Ray Activity in Solar Active Regions
Kusano, K.; Sakurai, T.; Yokoyama, T. +1 more
The correlation between magnetic helicity injection across the photosphere and soft X-ray activity in the solar corona is statistically investigated for seven active regions appearing in the years 1997-2000. The magnetic helicity flux into the solar corona is analyzed by the induction equation method, using magnetograms observed by the Michelson D…
The Discovery of a High-Redshift X-Ray-Emitting QSO Very Close to the Nucleus of NGC 7319
Zibetti, Stefano; Burbidge, E. M.; Galianni, Pasquale +3 more
A strong X-ray source only 8" from the nucleus of the Seyfert 2 galaxy NGC 7319 in Stephan's Quintet has been discovered by Chandra. We have identified the optical counterpart and show that it is a QSO with ze=2.114. It is also an ultraluminous X-ray source with LX=1.5×1040 ergs s-1. From the optical spe…
Predicted and Empirical Radii of RR Lyrae Stars
Marconi, M.; Bono, G.; Caputo, F. +2 more
We present new theoretical period-radius-metallicity relations for RR Lyrae stars. Current predictions are based on a large set of nonlinear, convective models that cover a broad range of chemical abundances and input parameters. We also provide new and homogeneous estimates of angular diameters for a sample of field RR Lyrae stars using a recent …
To Be or Not to Be: Very Young Globular Clusters in M31
Matthews, Keith; Cohen, Judith G.; Cameron, P. Brian
We present observations made with the newly commissioned Keck laser guide star adaptive optics (LGSAO) system of six objects in M31 that are alleged in multiple recent studies to be young globular clusters (GCs); all are supposed to have ages <=5 Gyr. The resulting FWHM of the PSF core in our images is ~70 mas. The four youngest of these object…
A HST Study of the Stellar Populations in the Cometary Dwarf Irregular Galaxy NGC 2366
Thuan, Trinh X.; Izotov, Yuri I.
We present V and I photometry of the resolved stars in the cometary dwarf irregular galaxy NGC 2366, using Wide Field Planetary Camera 2 images obtained with the Hubble Space Telescope. The resulting color-magnitude diagram reaches down to I~26.0 mag. It reveals not only a young population of blue main-sequence stars (age <~30 Myr) but also an …
UVCS Observation of Sungrazer C/2001 C2: Possible Comet Fragmentation and Plasma-Dust Interactions
Lamy, P.; Raymond, J. C.; Biesecker, D. A. +5 more
In this paper we analyze SOHO Ultraviolet Coronagraph Spectrometer (UVCS) observations of the sungrazing comet C/2001 C2, a member of the Kreutz family, observed on 2001 February 7 at heliocentric distances of 4.98 and 3.60 Rsolar. This comet apparently went through sequential fragmentation events along its path: further indication of f…
BIMA Millimeter-Wave Observations of the Core-Jet and Molecular Gas in the FR I Radio Galaxy NGC 3801
Baum, Stefi A.; O'Dea, Christopher P.; Vogel, Stuart N. +2 more
We present BIMA 3 mm observations of the radio continuum source and the molecular gas disk in the radio-loud Fanaroff and Riley type I (FR I) galaxy NGC 3801. We have detected a continuum source in the nucleus and determined that it has a flat millimeter-wave spectrum, suggesting that the emission is nonthermal and due to an AGN; the radio core is…