Search Publications

Determination of Hyperfine-Induced Transition Rates from Observations of a Planetary Nebula

Judge, Philip G.; Proffitt, Charles R.; Brage, Tomas

Observations of the planetary nebula NGC3918 made with the STIS instrument on the Hubble Space Telescope reveal the first unambiguous detection of a hyperfine-induced transition 2s2p

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Non-LTE Calculation of the Ni I 676.8 Nanometer Line in a Flaring Atmosphere

Qiu, Jiong; Wang, Haimin; Ding, M. D.

The Ni I 676.8 nm line is used by the Solar and Heliospheric Observatory Michelson Doppler Imager to measure the magnetic field and velocity field in the solar atmosphere. We make non-LTE calculations of this line in an atmosphere that is bombarded by an energetic electron beam. This case is associated with the occurrence of solar flares. The elec…

The time variation in infrared water-vapour bands in Mira variables

Onaka, T.; Murakami, H.; Yamamura, I. +2 more

The time variation in the water-vapour bands in oxygen-rich Mira variables has been investigated using multi-epoch ISO/SWS spectra of four Mira variables in the 2.5-4.0 mu m region. All four stars show H₂O bands in absorption around minimum in the visual light curve. At maximum, H₂O emission features appear in the ~ 3.5-4.0 m…

Velocity-resolved [Fe II] Line Spectroscopy of L1551 IRS 5: A Partially Ionized Wind under Collimation around an Ionized Fast Jet

Kobayashi, Naoto; Tokunaga, Alan T.; Terada, Hiroshi +5 more

We present a new [Fe II] λ1.644 µm emission-line image of the L1551 IRS 5 jets and a velocity-resolved spectrum obtained with the Subaru Telescope. In the [Fe II] line image showing two separate jetlike features, a strong and spatially wide [Fe II] emission feature was found elongated along the northern jet at its base. The echelle spectrum …

The HST survey of the B2 sample of radio-galaxies: Optical nuclei and the FR I/BL Lac unified scheme

Capetti, A.; Morganti, R.; Chiaberge, M. +4 more

We examine the optical properties of the nuclei of low luminosity radio-galaxies using snapshot HST images of the B2 sample. In agreement with the results obtained from the analysis of the brighter 3C/FR I sample, we find a correlation between fluxes (and luminosities) of the optical and radio cores. This provides further support for the interpret…

NGC 4314. IV. Photometry of Star Clusters with the Hubble Space Telescope: History of Star Formation in the Vicinity of a Nuclear Ring

Smith, Beverly J.; Jørgensen, Inger; Kenney, Jeffrey D. P. +2 more

Using Hubble Space Telescope (HST) WFPC2 images, we have obtained U, B, V, I, and Hα photometry for 76 star clusters in the nuclear star-forming ring of the barred spiral galaxy NGC 4314. These clusters are likely associated with an inner inner Lindblad resonance (IILR). The blue colors and Hα emission for most of these clusters imply very young a…

Structural Parameters and Dynamical Masses for Globular Clusters in M33

Brodie, Jean P.; Huchra, John P.; Sarajedini, Ata +1 more

Using high-dispersion spectra from the HIRES echelle spectrograph on the Keck I telescope, we measure velocity dispersions for four globular clusters (GCs) in M33. Combining the velocity dispersions with integrated photometry and structural parameters derived from King-Michie model fits to Wide Field Planetary Camera 2 images, we obtain mass-to-li…

X-Ray and Optical Variations in the Classical Be Star γ Cassiopeia: The Discovery of a Possible Magnetic Dynamo

Smith, Myron A.; Henry, Gregory W.; Robinson, Richard D.

The classical B0.5e star γ Cassiopeia is known to be a unique X-ray source by virtue of its moderate L_X (10³³ ergs s^-1), hard X-ray spectrum, and light curve punctuated by ubiquitous flares and slow undulations. The peculiarities of this star have led to a controversy concerning the origin of these emissions: wheth…

SPICES II: Optical and Near-Infrared Identifications of Faint X-Ray Sources from Deep Chandra Observations of Lynx

Dey, Arjun; Rosati, Piero; Stanford, S. A. +10 more

We present our first results on field X-ray sources detected in a deep, 184.7 ks observation with the Advanced CCD Imaging Spectrometer (ACIS-I) on the Chandra X-Ray Observatory. The observations target the Lynx field (α=08^h48^m, δ=+44°54') of SPICES, the Spectroscopic Photometric Infrared-Chosen Extragalactic Survey, which co…

An X-Ray Investigation of the NGC 346 Field in the Small Magellanic Cloud I. The Luminous Blue Variable HD 5980 and the NGC 346 Cluster

Koenigsberger, G.; Corcoran, M. F.; Nazé, Y. +5 more

We present results from a Chandra observation of the NGC 346 cluster. This cluster contains numerous massive stars and is responsible for the ionization of N66, the most luminous H II region and the largest star formation region in the SMC. In this first paper we will focus on the characteristics of the main objects of the field. The NGC 346 clust…