Search Publications
A Luminous Recurrent Supersoft X-Ray Source in NGC 300
Kong, A. K. H.; Di Stefano, R.
We report the results of XMM-Newton observations for an especially luminous supersoft X-ray source (SSS) with a bolometric luminosity of 1039 ergs s-1 in the spiral galaxy NGC 300. The source was detected as an SSS in 1992 and disappeared in subsequent X-ray observations. The source was active again during recent XMM-Newton o…
More nitrogen rich B-type stars in the SMC cluster, NGC 330
Dufton, P. L.; Lennon, D. J.; Crowley, C.
High resolution spectra of seven early B-type giant/supergiant stars in the SMC cluster NGC 330 are analysed to obtain their chemical compositions relative to SMC field and Galactic B-type stars. It is found that all seven stars are nitrogen rich with an abundance approximately 1.3 dex higher than an SMC main-sequence field B-type star, AV304. The…
The Compact Nucleus of the Deep Silicate Absorption Galaxy NGC 4418
Scoville, N. Z.; Matthews, K.; Soifer, B. T. +6 more
High-resolution Hubble Space Telescope (HST) near-infrared and Keck mid-infrared images of the heavily extinguished infrared-luminous galaxy NGC 4418 are presented. These data make it possible to observe the imbedded near-infrared structure on scales of 10-20 pc and to constrain the size of the mid-infrared-emitting region. The 1.1-2.2 µm da…
The First Detection of Spatially Resolved Mid-Infrared Scattered Light from a Protoplanetary Disk
Duchêne, G.; Ghez, A. M.; McCabe, C.
We report spatially resolved 11.8 µm images, obtained at the W. M. Keck 10 m telescope, of the protoplanetary disk around the pre-main-sequence star HK Tau B. The mid-infrared morphology and astrometry of HK Tau B with respect to HK Tau A indicate that the flux observed in the mid-infrared from HK Tau B has been scattered off the upper surfa…
The origin of the iron lines in NGC 7213
Perola, G. C.; Bianchi, S.; Balestra, I. +1 more
The analysis of a simultaneous XMM-Newton/BeppoSAX plus three previous BeppoSAX observations revealed that NGC 7213 is a rather peculiar Seyfert 1. No significant Compton reflection component was observed, while an iron line complex, best explained in terms of three narrow lines, is clearly apparent in the data. Due to the absence of the reflectio…
Far-Ultraviolet Emission from Elliptical Galaxies at z = 0.33
Ferguson, Henry C.; Brown, Thomas M.; Rich, R. Michael +4 more
We present far-UV images of the rich galaxy cluster ZwCl 1358.1+6245, taken with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope (HST). When combined with archival HST observations, our data provide a measurement of the UV-to-optical flux ratio in eight early-type galaxies at z=0.33. Because the UV flux originates in a…
A Far-Ultraviolet Survey of 47 Tucanae. II. The Long-Period Cataclysmic Variable AKO 9
Zurek, David R.; Gilliland, Ronald L.; Shara, Michael M. +2 more
We present time-resolved far-ultraviolet (FUV) spectroscopy and photometry of the 1.1 day eclipsing binary system AKO 9 in the globular cluster 47 Tucanae. The FUV spectrum of AKO 9 is blue and exhibits prominent C IV and H II emission lines. The spectrum broadly resembles that of long-period cataclysmic variables (CVs) in the Galactic field. Comb…
Cyclical period changes in the dwarf novae V2051 Oph and V4140 Sgr
Baptista, R.; Steiner, J. E.; Bond, H. E. +3 more
We report on the identification of cyclical changes in the orbital period of the eclipsing dwarf novae V2051 Ophiuchi and V4140 Sagittarii. We used sets of white dwarf mid-eclipse timings to construct observed-minus-calculated diagrams covering, respectively, 25 and 16 yr of observations. The V2051 Oph data present cyclical variations that can be …
Hubble Space Telescope Observations of Novae in M49
Jordán, Andrés; Côté, Patrick; Ferrarese, Laura
A search for novae in M49 (NGC 4472) has been undertaken with the Hubble Space Telescope. A 55 day observing campaign in F555W (19 epochs) and F814W (five epochs) has led to the discovery of nine novae. We find that M49 may be underabundant in slow, faint novae relative to the Milky Way and M31. Instead, the decline rates of the M49 novae are rema…
Erosion Model for the Sungrazing Comets Observed with the Solar and Heliospheric Observatory
Sekanina, Zdenek
The objectives of this study are to model and interpret quantitatively the brightness variations of 27 Solar and Heliospheric Observatory (SOHO) sungrazers. The light curves, published by Uzzo et al. and by Biesecker et al., are shown to provide information on a proposed erosion process, which consists of continuous, progressive bulk fragmentation…