Lunar Occultations of Binary Stars

(supervisor: Tony Cook)

Nature of project: experimental, data analysis

Available to full-time physicists or joint students.

Project description and methodology

By measuring the light curves of stars being hidden (occulted) by the Moon, it is possible to determine if the star is binary or multiple due to level steps in the light curve. The height of the steps in brightness can give the relative brightness of the stars involved. The separation in time between these brightness drops, times by the Moon's angular velocity perpendicular to the limb) can give the angular minimum separation between the double (multiple) star. Results will be checked against the datasets on double or multiple stars at the SIMBAD Astronomical Database: http://simbad.u-strasbg.fr/simbad/ in order to see if the stars have changed at all since the original catalog measurements were made. Comparisons of the occultation light curves can be made with previously published occultation results.

Observations can be made using the robotic telescopes owned by the Physics Department. We have low light sensitive cameras on both scopes that can video down to magnitude 10, or 100x fainter than what you can see with your eyes. As a backup there are some videos of occultations of stars that could be made available if the weather is bad.

Anaylsis of the light curves of occultations will be made either using software that the students write themselves, or using on-line software for occultation analysis e.g. Tangra.

A successful project will develop beyond the above in one/some of the following directions:
1) Use integral plots to look for step changes due to binary or multiple stars

2) Determine signal to noise ratio of occultation

3) Determine magnitude difference between stars

4) Use past occultation data in archives or published, detemine separation of stars in arc sec

When considering where to take your project, please bear in mind the time available. It is preferable to do fewer things well than to try many and not get conclusive results on any of them. However, sometimes it is useful to have a couple of strands of investigation in parallel to work on in case delays occur.

Additional scope or challenge if taken as a Year-4 project: 1) Attempt to measure star diameters during grazing occultations when the approach velocity to the polar limb is effectively slower in terms of angular velocity.

2) Observations made through different coloured filters, or through a low resolution diffraction grating can give information on the temperature colour of the stars involved. Compare this to published values (if known)

Initial literature for students:

  1. Nather, R.E. and Evan, D.S. (1970) Astronomical Journal, Vol 75, p575-582.
  2. Nather, R.E. (1970) Astronomical Journal, Vol 75, p583-588
  3. Nather, R.E. and McCants, M.M.. (1970) Astronomical Journal, Vol 75, p963-968
  4. http://www.hristopavlov.net/Tangra/Tangra.html

Novelty, degree of difficulty and amount of assistance required

Slightly above average in terms of difficulty.

Assistance will be supplied with telescope training by your supervisor.

Project milestones and deliverables (including timescale)

milestoneto be completed by
Telescope training and start observingend of October
Select which stars to attempt to observeChristmas
Practice on archive data + observeend of February
Complete observations and analysisEaster

Students taking this project will have to submit a full risk assessment form