Search Publications
Is there really a Lutz-Kelker bias? Reconsidering calibration with trigonometric parallaxes
Smith, Haywood
In the recent literature there are indications of some confusion regarding the Lutz-Kelker bias: whether or not it exists, and if so, what it is and when it should be corrected. Here we carefully reexamine Lutz & Kelker's original work to understand what they actually did, and then look at their later papers and some other works on the subject…
Anatomy of the Herbig-Haro object HH7 bow shock
Smith, Michael D.; Davis, Christopher J.; Khanzadyan, Tigran
We perform a detailed shock diagnosis of the Herbig-Haro object HH7, a well-defined bow shock from a protostellar outflow. We first present molecular hydrogen images in the 2-1 S(1) and 1-0 S(1) K-band emission lines. We then introduce revised models for magneto-hydrodynamic bow shocks that incorporate a limited C and O chemistry and account for t…
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…
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>
The far-infrared signature of dust in high-latitude regions
del Burgo, C.; Ábrahám, P.; Laureijs, R. J. +1 more
We present ISOPHOT observations of eight interstellar regions in the 60-200 µm wavelength range. The regions belong to mostly quiescent high-latitude clouds and have optical extinction peaks from AV~1-6 mag. From the 150- and 200-µm emission, we derived colour temperatures for the classical big grain component which show a c…
Three-dimensional photoionization modelling of the planetary nebula NGC 3918
Morisset, C.; Barlow, M. J.; Liu, X. -W. +2 more
The three-dimensional Monte Carlo photoionization code MOCASSIN has been applied to construct a realistic model of the planetary nebula NGC 3918. Three different geometric models were tried, the first being the biconical density distribution already used some years ago by Clegg et al. In this model the nebula is approximated by a biconical structu…
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 …
A softer look at MCG-6-30-15 with XMM-Newton
Vaughan, S.; Fabian, A. C.; Lee, J. C. +1 more
We present the analysis and first results from the Reflection Grating Spectrometer (RGS) during the 320-ks XMM-Newton observation of the Seyfert 1 galaxy MCG-6-30-15. The spectrum is marked by a sharp drop in flux at 0.7 keV which has been interpreted by Branduardi-Raymont et al. using RGS spectra from an earlier and shorter observation as the blu…
X-ray and ultraviolet observations of the dwarf nova VW Hyi in quiescence
Pandel, Dirk; Howell, Steve B.; Córdova, France A.
We present an analysis of X-ray and ultraviolet (UV) data of the dwarf nova VW Hyi that were obtained with XMM-Newton during the quiescent state. The X-ray spectrum indicates the presence of an optically thin plasma in the boundary layer that cools as it settles on to the white dwarf. The plasma has a continuous temperature distribution that is we…
Statistical re-examination of reported emission lines in the X-ray afterglow of GRB 011211
Sako, Masao; Rutledge, Robert E.
A 0.2-12 keV spectrum obtained with the XMM-Newton EPIC/pn instrument of GRB 011211, taken in the first 5 ks of a 27-ks observation, was found by Reeves et al. in 2002 to contain emission lines that were interpreted to be from MgXI, SiXIV, SXVI, ArXVIII and CaXX, at a lower redshift (zobs= 1.88) than that of the host galaxy (zhost<…