We describe the technique that will be used to develop a set of on-orbit calibrators for IRAC and demonstrate the validity of the method for stars with spectral types either K0-M0III or A0-A5V. For application to SIRTF, the approach is intended to operate with all available optical, near-infrared (NIR), and mid-infrared (MIR) photometry, and to yield complete absolute spectra from UV to MIR. One set of stars is picked from Landolt's extensive network of optical (UBV RI) calibrators; the other from the Carter-Meadows set of faint infrared standards. Traceability to the "Cohen-Walker-Witteborn" framework of absolute photometry and stellar spectra is assured (Cohen, Walker, & Witteborn 1992a).The method is based on the use of either "supertemplates", that represent the intrinsic shapes of the spectra of K0-M0III stars from far-ultraviolet (1150Å) to MIR (35 µm) wavelengths, or Kurucz synthetic spectra for A0-5V stars. Each supertemplate or Kurucz model is reddened according to the individual star's extinction and is normalized using available characterized optical photometry. This paper tests our capability to predict NIR (JHK) magnitudes using supertemplates or models constrained by Hipparcos/Tycho or precision ground-based optical data. We provide absolutely calibrated 0.275-35.00 µm spectra of thirty three Landolt or Carter-Meadows optical standard stars to demonstrate the viability of this technique, and to offer a set of IR calibrators 100-1000 times fainter than those we have previously published. As an indication of what we can expect for actual IRAC calibration stars, we have calculated the absolute uncertainties associated with predicting the IRAC magnitudes for the faintest cool giant and hot dwarf in this new set of calibration stars.

We present a total of 12,436 photometric measures of 371 Ðeld stars of 26 quasars in the visible (UBV RI) and 22,276 photometric measures of 122 Ðeld stars of 13 quasars in the near-infrared (JHK), giving a total of 34,712 measures. Of these, 115 stars in 12 Ðelds are calibrated in both ranges. One further Ðeld, Mrk 421, was calibrated, but on close examination all sources were found to be probably nonstellar ; thus these results are not included here. The stars observed cover the range from V \ 11 to V \ 20 and from K \ 9 to K \ 17 and are well distributed around the sky north of declination [30¡. This represents the initial sample of an extensive catalog of calibrated Ðelds that will cover the northern sky down to declination [30¡ and that will cover a wide range of Galactic latitudes. These Ðelds will be useful both for photometry of AGNs in the range from B to K and also as faint calibration standards for large telescopes. The median absolute total error on the photometry, including all known error sources, ranges from 0.008 mag in J to 0.034 mag in B. These errors will be greatly reduced with the addition of further data in the future, although the Ðnal precision is fundamentally limited by the photometric errors in the existing lists of calibration stars used to calibrate these data.

We present the results of 8 yr of infrared photometric monitoring of a large sample of stars visible from Teide Observatory (Tenerife, Canary Islands). The final archive is made up of 10,949 photometric measures through a standard InSb single-channel photometer system, principally in JHK, although some stars have measures in L 0 . The core of this list of stars is the standard-star list developed for the Carlos Sánchez Telescope. A total of 298 stars have been observed on at least two occasions on a system carefully linked to the zero point defined by Vega. We present high-precision photometry for these stars. The median uncertainty in magnitude for stars with a minimum of four observations and thus reliable statistics ranges from 0.0038 mag in J to 0.0033 mag in K. Many of these stars are faint enough to be observable with array detectors (42 are K > 8) and thus to permit a linkage of the bright and faint infrared photometric systems. We also present photometry of an additional 25 stars for which the original measures are no longer available, plus photometry in L 0 and/or M of 36 stars from the main list. We calculate the mean infrared colors of mainsequence stars from A0 V to K5 V and show that the locus of the HÀK color is linearly correlated with JÀH. The rms dispersion in the correlation between JÀH and HÀK is 0.0073 mag. We use the relationship to interpolate colors for all subclasses from A0 V to K5 V. We find that K and M main-sequence and giant stars can be separated on the color-color diagram with high-precision near-infrared photometry and thus that photometry can allow us to identify potential mistakes in luminosity class classification.

Extensive light and colour curves for the Type Ia supernova (SN Ia) SN 2002er are presented as part of the European Supernova Collaboration. We have collected UBVRI photometry from 11 different telescopes covering the phases from 7 d before until 619 d after maximum light. Corrections for the different instrumental systems and the non-thermal spectrum of the supernova (S-corrections) have been applied. With the densely sampled light curves we can make detailed comparisons to other well-observed objects. SN 2002er most closely resembles SN 1996X after maximum, but clearly shows a different colour evolution before peak light and a stronger shoulder in V and R bands compared to other well-observed SNe Ia. In particular, the rise time appears to be longer than what is expected from the rise time versus decline rate relation. We use several methods to determine the reddening towards SN 2002er based on the colour evolution at near peak and at late phases. The uvoir (bolometric) light curve shows great similarity with SN 1996X, but also indications of a higher luminosity, longer rise time and a more pronounced shoulder 25 d past maximum. The interpretation of the light curves was carried out with two independent light curve codes. Both find that given the luminosity of SN 2002er the 56 Ni mass exceeds 0.6 M with preferred values near 0.7 M . Uncertainties in the exact distance to SN 2002er are the most serious limitation of this measurement. The light-curve modelling also indicates a high level of mixing of the nickel in the explosion of SN 2002er.

Aims. We present optical photometry and spectroscopy of the afterglow and host galaxy of gamma-ray burst GRB 040924. This GRB had a rather short duration of T 90 ∼ 2.4 s, and a well sampled optical afterglow light curve. We aim to use this dataset to find further evidence that this burst is consistent with a massive star core-collapse progenitor. Methods. We combine the afterglow data reported here with those from the literature and compare the host properties with survey data. Results. We find that the global behaviour of the optical afterglow is well fit by a broken power-law, with a break at ∼0.03 days. We determine the redshift z = 0.858 ± 0.001 from the detected emission lines in our spectrum. Using the spectrum and photometry we derive global properties of the host, showing it to have similar properties to other long GRB hosts. We detect the [Ne iii] emission line in the spectrum, and compare the fluxes of this line of a sample of 15 long GRB host galaxies with survey data, showing the long GRB hosts to be comparable to local metal-poor emission line galaxies in their [Ne iii] emission. We fit the supernova bump accompanying this burst, and find that it is similar to other long GRB supernova bumps, but fainter. Conclusions. All properties of GRB 040924 (the associated supernova, the spectrum and SED of host and afterglow) are consistent with an origin in the core-collapse of a massive star.