Further Studies of the Association of Planetary Nebula BMP J16135406 with Galactic Open Cluster NGC 6067

Planetary Nebulae (PNe) that are physical members of Galactic open clusters are powerful probes that allow precise determination of their distance and crucially their initial mass on the main sequence. Here, we revisit the physical association of the PN BMP J1613–5406 with the open cluster NGC 6067 and present our preliminary results based on our new ESO/VLT FORS2 data. Our PN spectral data permit the calculation of a precise radial velocity and reddening to the PN that shows a tight consistency with the literature corresponding cluster parameters including importantly the radial velocity. Our measurements, combined with the agreement between the distances of the two objects and the fact that the PN is located well within the cluster boundaries, confirm that the PN is physically associated with the cluster. The cluster has a turn-off mass of around 5 solar masses that indicates a PN initial mass of around 5.6 solar masses. This is closer to the theoretical lower limit of core-collapse supernova formation than has ever been previously observed, providing a unique opportunity for further stellar and Galactic chemical evolution studies using this system

The post-outburst photometric behaviour of V838 Mon

The unusual eruptive variable discovered in Monoceros in 2002 January underwent dramatic photometric and spectroscopic changes in the months prior to its 2002 June-August conjunction with the Sun. Optical and infrared (IR) photometry obtained at the South African Astronomical Observatory (SAAO) between 2002 January and June (JD 2452280-440) is presented here in an analysis of the star's post-outburst behaviour. The light curve indicated 3 eruptions took place in 2002 January, February and March. SAAO echelle spectra obtained in the week prior to the March maximum indicated the ejection of a new shell of material. JHKL photometry obtained during 2002 April showed the development of an IR excess due to the formation of a dust shell. The shell appears to be largely responsible for the rapid fade in the optical flux during 2002 April-May (Delta V > 6 mag within 3 weeks). Blueing of the optical colours during the decline is likely due either to the revealing of an emission line region surrounding V838 Mon, or the unveiling of the progenitor or a spatially-close early-type star.Comment: 7 pages, 7 figures - accepted for MNRA

V838 Mon: light echo evolution and distance estimate

Following its 2002 February eruption, V838 Mon developed a light echo that continues to expand and evolve as light from the outburst scatters off progressively more distant circumstellar and/or interstellar material. Multi-filter images of the light echo, obtained with the South African Astronomical Observatory (SAAO) 1.0-m telescope between 2002 May and 2004 December, are analysed and made available electronically. The expansion of the light echo is measured from the images and the data compared with models for scattering by a thin sheet and a thin shell of dust. From these model results we infer that the dust is likely in the form of a thin sheet distant from the star, suggesting that the material is of interstellar origin, rather than being from earlier stages in the star's evolution. Although the fit is uncertain, we derive a stellar distance of ~ 9 kpc and a star-dust distance of ~ 5 pc, in good agreement with recent results reported from other methods. We also present JHKL and Cousins UBVRI photometry obtained at the SAAO during the star's second, third and fourth observing seasons post-outburst. These data show complex infrared colour behaviour while V838 Mon is slowly brightening in the optical.Comment: 9 pages, 6 figures - accepted for publication in MNRA

Towards precision radial velocity science with SALT’s High-Resolution Spectrograph

We describe efforts to equip the Southern African Large Telescope (SALT) for precision radial velocity (PRV) work. Our current focus is on commissioning the high-stability (HS) mode of the High-Resolution Spectrograph (HRS), the mode intended to support exoplanet science. After replacing the original commercial iodine cell with a custom-built, precisely characterised one and following established best practice in terms of observing strategy and data reduction, this system now delivers 3-4 m/s radial velocity stability on 5th and 6th magnitude stars. Unfortunately, the throughput is compromised by the HRS dichroic split being at 555 nm (i.e. roughly midway through the 100 nm span of the iodine absorption spectrum). Furthermore, SALT’s fixed elevation axis limits the exposure time available for a given target and hence the depth and/or precision achievable with the iodine cell. The HS mode’s simultaneous ThAr option uses the full 370–890 nm passband of the HRS and does not suffer gas cell absorption losses, so it may be more suitable for exoplanet work. The first step was to quantify the internal stability of the spectrograph, which requires simultaneously injecting arc light into the object and calibration fibres. The HS mode’s optical feed was modified accordingly, stability test runs were conducted and the necessary analysis tools were developed. The initial stability test yielded encouraging results and though more testing is still to be done, SAL a laser frequency comb to support the development of HRS PRV capability