Carina Nebula

Astronomy 61: Current Problems in Astronomy and Astrophysics

Prof. David Cohen

Spring 2015
Friday 11:30 to 12:20
SC 113 (seminar room)


Townsley image windtabs transmission windtabs fit HD93129





posted 3/1

We'll catch up; make sure we can all do the multi-temperature fitting, with the ISM absorption, etc. And then we'll add the last ingredient to our models: wind absorption.

Archive of old announcements.



posted 3/1

The first four data guides are on the old assignments page. Here is a list of things everyone should send to me:

(1) A plot of the HD93129 spectrum, with the best-fit blackbody spectrum overplotted. This plot should be made outside of xspec.

(2) A plot of the same spectrum, but with your best-fit two-temperature APEC model. Please also include either on the graphic or in a separate text file, the best-fit model parameters and the chi-square value of the fit.

(3) A plot of the same spectrum, with a two-temperature APEC model that also includes interstellar absorption, via the TBABS model in xspec. Here too, you should also provide me with the best-fit model parameters and the chi-square value. You should see a significant improvement when you include interstellar absorption.

(4) (This is similar to something I asked you to do, but now I'm telling you to do it and make me a plot showing what you've done): Take your best-fit two-temperature model that includes wind absorption (from (3)) and plot it in model space by typing "plot model" in xspec after you've done the fit. Then do the "iplot" "wdata filename" sequence and the new file you've created will be the model (no data) in model space (photon flux, rather than counts). Make a plot of this model and label the two strongest lines with the ion that gives rise to each line (use ATOMDB webguide to figure it out).

All four of these tasks and associated plots in addition to the fit information, are things you should get done by the middle of this week (Wednesday night).

I will provide instructions soon on the next step: adding wind absorption. You will also have to complete that step and make an associated plot by Friday's class.

We will discuss data fitting/modeling issues in class this week – both practical issues (bring your computer) and discussing what the fit parameters mean. And we will also revisit Fig. 8 in the Leutenegger et al. (windtabs) paper and the spectral fitting information in the XSPEC manual (see last week's assignments to remind yourself of the details).

Archive of old assignments.



Class information

Class Moodle page

class information (posted before the semester)


Useful resources

Local computing information

ADS: for papers
astro-ph: for more papers
SIMBAD: for objects
Astronomical Catalogs: for catalogs

X-ray astronomy

Chandra X-ray Center
XSPEC manual: spectral fitting
ATOMDB webguide (line list)

General astro research information

Astrobetter – lots of useful information about the nitty-gritty of astronomical research and many aspects of being an astronomy student and astronomer

Astrobites – very short summaries of interesting research papers, written for undergraduates by graduate students.




This page is maintained by David Cohen
cohen -at-

Last modified: February 26, 2015