Campaign Coordinator: Mark Blackford Professional Advisor: Ed Budding

Ed Budding and Roger Butland are currently investigating this relatively bright but neglected eclipsing binary (range 6.96 to 7.16 V Mag, period 0.980417d). They’ve measured radial velocities from high resolution spectra recorded with the HERCULES spectrometer on the 1m McLellan telescope on Mt John and proposed that V0454 Car is probably another quaternary system – not unlike QZ Car, but a bit less massive.

The RV curve of the close binary system (eclipsing pair) is well covered, and they can get a reasonably good picture of it from both its set of spectral lines. However, the third component shows unexpected short-term variations superposed on a much longer-term trend. They think that it is in a binary arrangement with a lower mass companion having a period of order a week or two. However, they don’t have enough information to form a very clear picture at the moment.

Ed and Roger are requesting assistance from spectroscopists in Variable Stars South to help determine the details of this system. Ideally, they are looking for one spectrum per night for about a fortnight. This is because the short-term variations of the non-close-binary lines suggest a period on that order. The requested data may then point up details on the second binary referred to above.

The exposures might have to be a bit long – but they do not need to use these spectrograms to study the close binary (that has already been done) so a long exposure (say an hour or two) is not a problem.

The expected shifts of the (fairly sharp) lines of the third component have amplitude of about 1 Angstrom at ~6000 A (roughly). So, allowing for some possibilities of averaging different results from different lines and different exposures, a resolution of ~3000 or greater should be ok.

With the HERCULES spectrometer the ‘best’ line is generally the HeI 6678 feature. But 4471 or 5876 could be also good, or indeed the lower Balmer lines although the H lines tend to have inherent complications and are not generally favoured so much for reliable rv determinations.

Multi filter photometric observations of the entire eclipsing binary light curve are also requested for modelling purposes. A partial V filter light curve by Mark Blackford is shown below. As a minimum we require full BVRc light curves; however, U and Ic would also be useful.

A finder chart and comparison star list will be made available on the VSS website shortly. Photometrists are asked to use these comparison stars so our measurements can be directly compared. V0454 Car will culminate at the start of morning astronomical twilight on December 1st so will be well positioned for spectroscopy and time series photometry over summer.

If you can help with spectroscopy or photometry of this interesting target, please contact Ed Budding or Mark Blackford.