Rubin-LSST

Abstract:

A limit on the mass of the tau neutrino mντ is derived from 4.5 × 106 tau pairs produced in an integrated luminosity of 5.0 fb-1 of e+e- → γ * → τ+τ- reactions at center of mass energies ≈ 10.6 GeV. The measurement technique involves a two-dimensional extended likelihood analysis, including the dependence of the end-point population on mντ, and allows for the first time an explicit background contribution. We use the the decays τ → 5πντ and τ → 3π2π0ντ to obtain an upper limit of 30 MeV/c2 at 95% C.L. © 1998 Elsevier Science B.V. All rights reserved.

Abstract:

We present JHK photometry and spectroscopy of RX J0019.8+2156. The spectrum appears to be dominated by the accretion disc to at least 2.4 μm, over any other source of emission. We find Paschen, Brackett and He II lines strongly in emission, but no He I. There are satellite lines approximately 850km s^-1 either side of the strongest, unblended hydrogen lines. These satellite lines may be the spectral signature of jets from the accretion disc.

Abstract:

As part of a programme to investigate spatial variations in the Galactic chemical composition, we have been searching for normal B-type stars and A-type supergiants near the Galactic center. During this search we have found eleven peculiar stars, and in some cases performed detailed abundance analyses of them which suggest that they may be at a post-AGB evolutionary stage. The A-type post-AGB candidates show [Fe/H]=-1.0 to -2.0, and [O/Fe]∼+1.4, typical of the post-AGB abundance patterns discussed in the literature. One star, LS 3591 (=SAO 243756), has also been examined recently by Oudmaijer (1996); its spectrum appears to be changing very rapidly, which may indicate erratic mass loss or the incipient formation of a planetary nebula. A B-type post-AGB candidate, LS 4950, has a similar spectrum to a well studied post-AGB star, LSIV -12 111. However, an examination of the line strengths and elemental abundances of LS 4950 show that it is peculiar for both a Population II, post-AGB, B-type star and for a normal, Population I, B-type supergiant. Two other B-type stars, LS 4825 and LS 5112, are either post-AGB stars near the Galactic center or normal B-type supergiants lying well beyond the Galactic center. In addition, several Be-type stars have been newly (or more clearly) identified from our spectra.