PHAS3332 (Practical Astronomy 3: Field Trip) 2008


The report on "Stellar Spectroscopy with the 1.52-m Telescope" is the third of three reports which all students taking part in the Field Trip should submit. This report should be submitted by the end of the first week of the Third Term. It is worth up to 400 marks.

The spectroscopy report must be submitted separately from the report on photometry. You will lose marks if the two reports are bound together.

The aims and scope of the spectroscopy project are somewhat open-ended; it is likely that an individual student will not have enough time to exploit all of the possibilities presented by the data obtained during the Field Trip. A reasonable strategy would be to concentrate on one aspect of the project. For example, one might aim to model the spectra of some of the chemically peculiar stars, or investigate variations in radial velocity of the stars identified as spectroscopic binaries. Consult the organiser of the Field Trip if you are unsure about the suitability of your proposed investigation of the stellar spectra.

The spectroscopy project should include all of the following items that are appropriate:

1. A title page, which must display your name, the course description (PHAS3332 Third Year Observational Astronomy 3: Field Trip), the title of the project, and the date of submission of the report.

2. An abstract: a statement which summarises the major achievement(s) of your project. Include your most important numerical results, the uncertainties on these, and whether they agree (to within the uncertainties) with any relevant values found in the literature.

3. An introduction. This should set your work in context and include a discussion of some of the literature recently published in your area of study and on the stars that you have selected for study.

4. A section on data acquisition, being a detailed description of your observing sessions on the 1.52-m telescope. Summarise the observations of all of the targets listed in the observing proposal, and state how many spectra were obtained for each.

5. A data reduction section. Describe how you used Figaro and Dipso to calibrate and average your spectra. Discuss any problems encountered, and evaluate the quality of the spectra that you use in your project.

6. A section on data analysis. Examples of things to include here, as appropriate, are: spectrum morphology (e.g., is the spectrum dominated by absorption lines, or any emission lines broad or narrow); the identification of spectrum lines; the doppler shifts and equivalent widths of spectrum lines; use of UCLSYN to estimate parameters of the atmospheres of any of the target stars.

7. A clear and concise statement of your results: for example, abundances for the chemically peculiar stars or doppler velocities for the spectroscopic binaries. Any numerical value should quoted with a precision appropriate to its accuracy.

8. A conclusion: discuss the results you presented in the previous section. How reliable are your results? How do they compare with any values in the literature? What are the implications of your results? Discuss whether the project was an overall success, and how you might do things differently if you embarked upon a similar project in the future.

Aim to cover all of the above points in a report of approximately 5000 words. If you follow the guidelines given above, you should be able to include everything that the markers of your report will expect to read, without writing an excessively long report.

Hints and Resources

Click the following link for my notes on Reducing Your Spectroscopic Data.

A list of thorium and argon emission lines that can be used to wavelength calibrate your stellar spectra: Th-Ar line list.

A plot of the thorium-argon emission line spectrum, extending over three pages. The plot indicates lines that I recommend for wavelength calibration of the stellar spectra obtained during the 2008 Field Trip. Available as a pdf (readable with Adobe(tm) Acrobat), or as a postscript file. There is also a wavelength-calibrated plot of the 2008 thorium-argon spectrum, on a single page, available as a pdf, or as a postscript file.

To aid the identification of features appearing in the stellar spectra, this line list has been extracted from the revised version of the ILLSS Catalogue (R. Coluzzi 1993-1999), VizieR VI/71A.

Log of the observations made with the 1.52-m telescope during the 2008 Field Trip (pdf; size is about 23 Megabytes). Because of cloud and rain, no observations were made on the night of January 29.

If you are fitting model spectra to the observations made during the Field Trip, you will need to refer to the UCLSYN User Guide (B. Smalley, K.C. Smith and M.M. Dworetsky, 2004) (pdf; size is 372 Kilobytes, or 33 pages long).

A table of HgMn star abundances, for use with UCLSYN. Place a copy of this table in the directory where you are starting the program.

A paper on elemental abundances in normal and HgMn stars: Smith and Dworetsky (1993). This is the recommended source for estimated abundances of iron-peak elements in each star (in cases where the system is a double-lined spectroscopic binary, abundances are given for the primary star only).

A paper on neon abundances in normal and HgMn stars: Dworetsky and Budaj (2000). This is the recommended source for stellar temperatures and gravities (and light ratios, for any stars that are obviously double-lined binaries).

Dr. Dworetsky's lectures on Chemically Peculiar Stars and The Use of UCLSYN (both given at the University of London Observatory, UCL, 2008 February 25).

Stephen Boyle
Last updated: 2008 February 28