Catalogue of candidate emission-line objects in the Small Magellanic Cloud

H\alpha and [O III] narrow band, wide field (7 * 7 degree), CCD images of the Small Magellanic Cloud were compared and a catalogue of candidate planetary nebulae and H\alpha emission-line stars was compiled. The catalogue contains 131 planetary nebulae candidates, 23 of which are already known to be or are probable planetary nebulae or very low excitation objects. Also, 218 emission-line candidates have been identified with 113 already known. Our catalogue therefore provides a useful supplement to those of Meyssonnier & Azzopardi (1993) and Sanduleak, MacConnell & Davis Phillip (1978). Further observations are required to confirm the identity of the unknown objects.Comment: 8 pages, accepted by MNRA

Spectrophotometric Libraries, Revised Photonic Passbands and Zero-points for UBVRI, Hipparcos and Tycho Photometry

We have calculated improved photonic passbands for the UBV RI, Hipparcos and Tycho Hp,BT,VT standard systems using the extensive spectrophotometric libraries of NGSL and MILES. Using the Hp passband, we adjusted the absolute flux levels of stars in the spectrophotometric libraries so their synthetic Hp magnitudes matched the precise Hipparcos catalog value. Synthetic photometry based on the renormalized fluxes were compared to the standard UBVRI and BT, VT magnitudes and revised synthetic zero-points were determined. The Hipparcos and Tycho photometry system zero-points were also compared to the V magnitude zero-points of the SAAO UBVRI system, the homogenized UBV system and the Walraven V B system. The confusion in the literature concerning broadband magnitudes, fluxes, passbands and the choice of appropriate mean wavelengths is detailed and discussed in an appendix.Comment: 44 pages, including 16 figures and a 12 page appendi

First detection of a low-mass stellar halo around the young open cluster Eta Chamaeleontis

We have identified several lithium-rich low-mass (0.08<M<0.3 Msun) stars within 5.5 deg of the young open cluster Eta Chamaeleontis, nearly four times the radius of previous search efforts. Of these stars we propose 4 new probable cluster members, and 3 possible members requiring further investigation. These findings are consistent with a dynamical origin for the current configuration of the cluster, without the need to invoke an abnormal Initial Mass Function deficient in low-mass objects. Candidates were selected on the basis of DENIS and 2MASS photometry, NOMAD astrometry and extensive follow-up spectroscopy.Comment: 5 Pages. 5 Figures and 1 Table. Accepted for publication in MNRAS Letters. Higher resolution figures available at http://www.mso.anu.edu.au/~murphysj/

The Initial Mass Function and Young Brown Dwarf Candidates in NGC 2264. IV. The Initial Mass Function and Star Formation History

We have studied the star formation history and the initial mass function (IMF) using the age and mass derived from spectral energy distribution (SED) fitting and from color-magnitude diagrams (CMDs).We also examined the physical and structural parameter

Measuring the Balmer Jump and Effective Gravity in FGK Stars

It is difficult to accurately measure the effective gravity (log g) in late-type stars using broadband (eg. UBV or SDSS) or intermediate-band (uvby) photometric systems, especially when the stars can cover a range of metallicities and reddenings. However, simple spectroscopic observational and data reduction techniques can yield accurate values for log g through comparison of the Balmer jumps of low-resolution spectra with recent grids of synthetic flux spectra.Comment: 20 pages, 13 figures and 4 table

The Schizophrenic Spectrum of LSR 1610-0040: a Peculiar M Dwarf/Subdwarf

We present a moderate resolution (R=2000), 0.8-4.1 micron spectrum of LSR 1610-0040, a high proper motion star classified as an early-type L subdwarf by Lepine and collaborators based on its red-optical spectrum. The near-infrared spectrum of LSR 1610-0040 does not fit into the (tentative) M/L subdwarf sequence but rather exhibits a mix of characteristics found in the spectra of both M dwarfs and M subdwarfs. In particular, the near-infrared spectrum exhibits a Na I doublet and CO overtone bandheads in the K band, and Al I and K I lines and an FeH bandhead in the H band, all of which have strengths more typical of field M dwarfs. Furthermore the spectrum of Gl 406 (M6 V) provides a reasonably good match to the 0.6-4.1 micron spectral energy distribution of LSR 1610. Nevertheless the near-infrared spectrum of LSR 1610 also exhibits features common to the spectra of M subdwarfs including a strong Ti I multiplet centered at ~0.97 microns, a weak VO band at ~1.06 microns, and possible collision-induced H_2 absorption in the H and K bands. We discuss a number of possible explanations for the appearance of the red-optical and near-infrared spectrum of LSR 1610-0040. Although we are unable to definitively classify LSR 1610-0040, the preponderance of evidence suggests that it is a mildly metal-poor M dwarf. Finally, we tentatively identify a new band of TiO at ~0.93 microns in the spectra of M dwarfs.Comment: Accepted for publication in the Astronomical Journa