Search Publications
Distribution of Supergranular Sizes
Singh, Jagdev; Raju, K. P.; Srikanth, R.
A gradient-based method of tessellation was applied to SOHO Dopplergrams and to Ca II K filtergrams in order to study the cellular pattern of the solar surface, in specific the geometric relationship between the tessellation and the chromospheric network/supergranulation. We found that for zero spatial smoothing and low temporal averaging the abov…
Detection of Planetary Transits of the Star HD 209458 in the Hipparcos Data Set
Jenkins, J.; Doyle, L.; Trilling, D. E. +2 more
A search of the Hipparcos satellite photometry data for the star HD 209458 reveals evidence for a planetary transit signature consistent with the planetary properties reported by Henry et al. and Charbonneau et al. and allows further refinement of the planet's orbital period. The long time baseline (about 2926 days or 830 periods) from the best Hi…
The Absolute Abundance of Iron in the Solar Corona
Kundu, M. R.; White, S. M.; Thomas, R. J. +1 more
We present a measurement of the abundance of Fe relative to H in the solar corona using a technique that differs from previous spectroscopic and solar wind measurements. Our method combines EUV line data from the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory with thermal bremsstrahlung radio data from the VLA. The…
Young Red Spheroidal Galaxies in the Hubble Deep Fields: Evidence for a Truncated Initial Mass Function at ~2 Msolar and a Constant Space Density to Z ~ 2
Broadhurst, Tom; Bouwens, Rychard J.
The optical-IR images of the northern and southern Hubble Deep Fields are used to measure the spectral and density evolution of early-type galaxies. The mean spectral energy distribution is found to evolve passively toward a mid-F star-dominated spectrum by z~2, becoming more sharply peaked around the 4000 Å break. We demonstrate with realistic si…
The Role of Velocity Redistribution in Enhancing the Intensity of the HE II 304 Å Line in the Quiet-Sun Spectrum
Andretta, Vincenzo; Brosius, Jeffrey W.; Thompson, William T. +5 more
We present observational evidence of the effect of small-scale (``microturbulent'') velocities in enhancing the intensity of the He II λ304 line with respect to other transition region emission lines, a process we call ``velocity redistribution,''. We first show results from the 1991 and 1993 flights of SERTS (Solar EUV Rocket Telescope and Spectr…
Dust Emission Features in NGC 7023 between 0.35 and 2.5 Microns: Extended Red Emission (0.7 Microns) and Two New Emission Features (1.15 and 1.5 Microns)
Gordon, Karl D.; Clayton, Geoffrey C.; Misselt, K. A. +6 more
We present 0.35-2.5 µm spectra of the south and northwest filaments in the reflection nebula NGC 7023. These spectra were used to test the theory of Seahra & Duley that carbon nanoparticles are responsible for extended red emission (ERE). Our spectra fail to show their predicted second emission band at 1.0 µm even though both filam…
The Balmer Wavelength Range of BP Tauri
Ardila, David R.; Basri, Gibor
We have analyzed all the observations of BP Tauri taken by the International Ultraviolet Explorer (IUE) in the low-resolution (Δλ~6 Å), long-wavelength (λ=1850-3350 Å) range. This data set contains 61 spectra. We observe variability in the ultraviolet continuum of Δmcont.~1 mag and variability in the Mg II line flux of ΔmMgII…
Pinpointing the Position of the Post-Asymptotic Giant Branch Star at the Core of RAFGL 2688 Using Polarimetric Imaging with NICMOS
Hines, Dean C.; Kastner, Joel H.; Sahai, Raghvendra +1 more
We have used infrared polarimetric imaging with NICMOS to determine precisely the position of the star that illuminates (and presumably generated) the bipolar, preplanetary reflection nebula RAFGL 2688 (the Egg Nebula). The polarimetric data pinpoint the illuminating star, which is not detected directly at wavelengths <=2 µm, at a positio…
ISO Long Wavelength Spectrograph Observations of Cold Dust in Galaxies
Madore, Barry F.; Bianchi, Simone; Trewhella, Matthew +2 more
We describe observations of five nearby galaxies obtained using the Long Wavelength Spectrograph (LWS) on the Infrared Space Observatory (ISO). We observed five galaxies, using spectrograph apertures positioned at the galactic center and in the outskirts of the disk, to compare the spectral energy distribution of the emitting dust at different pos…
On the Transition Region Explosive Events
Tarbell, T. D.; Ryutova, M. P.
We describe the properties of high-velocity and explosive events in the solar transition region determined from time series of data taken by the Transition Region and Coronal Explorer and the SUMER instrument on the Solar and Heliospheric Observatory (SOHO) simultaneously in several chromospheric and transition region lines co-aligned with high-re…