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A Revised Calibration of the MV-W(O I 7774) Relationship using Hipparcos Data: Its Application to Cepheids and Evolved Stars
Arellano Ferro, A.; Giridhar, S.; Rojo Arellano, E.
A new calibration of the MV-W(O I 7774) relationship has been calculated using better reddening and distance estimates for a sample of 27 calibrator stars of spectral types A to G, based on accurate parallaxes and proper motions from the Hipparcos and Tycho catalogues. The present calibration predicts absolute magnitude with accuracies …
Evidence for Grain Growth in the Protostellar Disks of Orion
Bally, John; Throop, Henry; Shuping, R. Y. +1 more
We present a Brα (λ=4.05 µm) image of the largest silhouette proplyd in Orion (114-426) using the facility near-IR spectrometer NIRSPEC at the Keck Observatory. This is the longest wavelength observation of a silhouette disk to date. The diameter of the disk at 4 µm is only marginally smaller than that observed in the optical with the …
Latitudinal structure and north-south asymmetry of the solar wind from Lyman-alpha remote sensing by SWAN
Bzowski, M.; Quémerais, E.; Summanen, T. +2 more
Based on SWAN/SOHO observations carried out during 1996-2002, we analyze latitudinal profiles of the heliospheric backscatter Lyman-alpha radiation. We use these results to investigate the ionization field of neutral hydrogen in the inner heliosphere and the latitudinal distribution of the solar wind mass flux. The the depth and latitudinal range …
X-ray rotational modulation of a supersaturated star in IC 2391
Micela, G.; Peres, G.; Sciortino, S. +1 more
We present evidence of X-ray rotational modulation on VXR45, a young fast rotator star, member of IC 2391. It is a dG9 spectral type star whose rotational period and X-ray luminosity make it a supersaturated star. Our X-ray observation, made with EPIC/PN on XMM-Newton, covers about two photometric rotational periods. The detection of X-ray rotatio…
A Multiwavelength Approach to the Star Formation Rate Estimation in Galaxies at Intermediate Redshifts
Elbaz, D.; Koo, D. C.; Willmer, C. N. A. +4 more
We use a sample of seven starburst galaxies at intermediate redshifts (z~0.4 and 0.8) with observations ranging from the observed ultraviolet to 1.4 GHz, to compare the star formation rate (SFR) estimators that are used in the different wavelength regimes. We find that extinction-corrected Hα underestimates the SFR, and the degree of this underest…
The Variability of the Solar Coronal Helium Abundance: Polar Coronal Holes Compared to the Quiet Sun
Laming, J. Martin; Feldman, Uri
We report on measurements of the abundance ratio He/H in solar polar coronal holes and neighboring quiet coronal regions, using the SUMER spectrometer on board SOHO. In coronal holes we find He abundances smaller than or equal to the value found in the fast solar wind, 5% by number relative to H, suggesting that the flow speed of He up into the wi…
XMM-Newton Observations of Two Broad Absorption Line QSOs: Q1246-057 and SBS 1542+541
Elvis, M.; Grupe, D.; Mathur, S.
We report on the results of XMM-Newton observations of two broad absorption line quasars (BAL QSOs), Q1246-057 and SBS 1542+541. The unprecedented sensitivity of XMM-Newton allows spectral analysis of these X-ray-weak sources. The X-ray spectral data of these sources can be fitted by a power law with αX=1.0-1.2 and either a partially co…
Molecular gas in the central regions of the latest-type spiral galaxies
Schinnerer, E.; Böker, T.; Lisenfeld, U.
Using the IRAM 30 >m telescope, we have surveyed an unbiased sample of 47 nearby spiral galaxies of very late (Scd-Sm) Hubble-type for emission in the 12CO(1-0) and (2-1) lines. The sensitivity of our data (a few mK) allows detection of about 60% of our sample in at least one of the CO lines. The median detected H2 mass is…
Temporal variability of Mrk 421 from XMM-Newton observations
Haberl, F.; Papadakis, I. E.; Brinkmann, W. +1 more
We present the results of a detailed spectral and temporal analysis of the currently available XMM-Newton observations of the bright BL Lac object Mrk 421 using mainly the EPIC-PN data. The source was found in various intensity states differing by up to a factor of five in count rates. In general, the source is more variable and shows a harder spe…
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…