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The Supernova Working Group was re-established at the IAU XXV General Assembly in Sydney, 21 July 2003, sponsored by Commissions 28 (Galaxies) and 47 (Cosmology). Here we report on some of its activities since 2005.
We observed a sample of zero proper-motion stars (μ < 0.″50 cent−1) from a field previously studied by Suntzeff et al. (1986). This field is 2°.5 NW (2.6 kpc) of the center of the SMC. We obtained spectra for ~ 40 stars in the region of the Ca II infrared triplet using the CTIO Argus fiber-fed spectrograph. We also obtained Argus echelle spectra of a single order at 6300Å with R = 18000 in one run. The low-dispersion spectra were reduced to metallicities based on the Ca II equivalent widths using the Da Costa & Armandroff (1995) technique and the metallicity scale from Zinn & West (1984). The typical abundance error is 0.12 dex. For half the sample, we have echelle velocities which are accurate to 1.5 km s−1. For the rest of the sample, the low-dispersion data yield single-observation velocities accurate to about 5 km s−1 based on repeat observations.
The quality of observational data on Type la supernovae has improved remarkably in the last few years, due mainly to monitoring programs with CCD-equipped detectors on small aperture telescopes at observatories across the world, and at the space observatories. I will review the recent observational characteristics of Type la supernovae, focusing the discussion on our observations of SN1992A in the SO galaxy NGC 1380 in the Fornax cluster as a reference to other Type la events. We now have strong evidence that Type la events are not a homogeneous class, but vary in both color and brightness at maximum light, vary in rise time and decline from maximum, and have spectral characteristics at maximum light that are correlated with these photometric parameters. Insofar as the SBF, PNLF, and infrared Tully-Fisher distance scales are correct, the observed (uvoir) bolometric light curves also indicate that these supernovae are less luminous than expected from the models of the explosion of a C-0 white dwarf at the Chandrasekhar mass.
The RR Lyrae and globular cluster populations are used to study the Pop II in the Galaxy and the LMC. The metallicity gradient in the Galaxy changes abruptly at the position of the solar circle. The statistics of field RR Lyraes imply that the Pop II field population is older towards the Galactic center. The density of RR Lyraes in the solar neighborhood implies a luminous mass density of 6.4 ± 1.8 × 10–5M⊙ pc–3 for the Galactic halo. The total luminosities (MV) for the Galactic and LMC halos are −18.4 and −15.1, and the ratio of globular cluster to luminous Pop II mass is 0.02 in both cases. The agreement of this ratio in two systems with very different tidal fields argues against the formation of the field population as the disruption of many smaller systems.
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