1. 2 months to go: time to be serious about observing run preparations

2. getting ready for our (any!) observing run
YOU THE OBSERVER should never be the cause of this:

3. What is the scientific goal?
or …
how did we manage to fool the telescope allocation committee?

4. questions you should be able to answer
do I know what the point is?
what astrophysical idea is being considered?
could I explain it to children, friends, other science teachers?
do I understand if my telescope/instrument can attack this?
have I assembled a reasonable list of stars (or nebulae/galaxies)?
can I observe any/all of these objects?
observatory location; time of year?
appropriate magnitudes?
am I comfortable with magnitudes and colors?
can I translate from target star coordinates to where they are in the sky?
do I understand my telescope?
basic optical configuration?
startup/shutdown, moving between targets, tracking targets?
dangers: mechanical limits of telescope; weather restrictions?
do I understand my instrument?
optical design (not trivial for our instrument)?
what are its “parameters” (how faint can it go, at what spectral resolution, at what noise level)?
can I tell by looking at an output image whether I have done something stupid?
how do I save the data safely?
can I interpret a spectrum that is obtained?
what does “interpret” really mean when I am sitting at the telescope at 4AM
do I know the stuff to be done after the observing run?
extraction of a “clean” spectrum?
analysis to get desired results?

6. fred

7. Ege University is in Izmir, near the western edge of Turkey
fred
Ege University is in Izmir, near the western edge of Turkey
Izmir is located in the Aegean province, which, of all the seven geographical regions of Turkey, enjoys the finest climate. In population it is the third city in Turkey.It is located in an area whose magnificent history has made it a tourist centre. It lies at the centre of the most important land, air and sea communication network in the ancient Aegean region.

8. In June we are observing red giant stars

9. Thumbnail sketch of stellar evolution

10. Hydrogen fusion powers most stars

11. The alternate way of H-fusion interests us more
Supposed to do the same thing: four H nuclei fuse to form one He nucleus + energy
Cycle doesn’t complete every time; net result is buildup of 13C and 14N
These products get mixed to the stellar surfaces as stars age to become red giants
C and N atoms form molecules, like CH and CN
We can observe these molecules in cool stars, and so we can check out enhancements in N and depletions in C and changes in 12C/13C ratios

12. The red giant clump is really well-known and understood

13. Remember: color is temperature, and absolute magnitude is luminosity

14. The red giant clump is really well-known and understood: here is a color-magnitude diagram for nearby stars
Red giants
main sequence
subgiants

15. The red giant clump is really well-known and understood: so, so … what are these things?
Red giants
subgiants
main sequence

16. For very old, low mass stars the clump spreads hotter into the “horizontal branch”
De Boer et al. 2011, A&Ap
where the red giant clump should be
MSTO = main sequence turn-off; RGB = red giant branch; RHB = red horizontal branch; BHB = blue horizontal branch; BSS = blue straggler stars; FG = foreground (ignore)

17. A simple question, too long ignored: why are there apparently so many bright RHB stars in the young disk population surrounding our Sun?
De Boer et al. 2011, A&Ap
RGB clump
our target RHB stars
the task: identify true giant stars that are a few hundred K warmer than they should be, and do a detailed analysis of them to see if chemical clues can uncover their secrets …

18. We will also be studying red giant chemical compostions of open clusters
Most open clusters have only a few RGB stars, and it is tough to pick out cluster members from the general Galactic field population

19. Melike is in charge of assembling the target list
Her summary of the selection process, and my comments in blue:
The stars we are interested in are RHB stars.
First we did a literature scan and learned about our stars, finding out what temperature and absolute magnitude/luminosity range they have (location on the HR-diagram). We had to understand how temperature and luminosity (theoreticians’ units!) translate into colors and magnitudes (observers’ units!).
Then we used this information to sort out the catalogs, mainly using SIMBAD and HIPPARCOS. These were our basic star information sources.
We threw out the stars outside the temperature and luminosity range (if available) that we are interested in. This is an imperfect process, with uncertainties in all published quantities! We knew that some promising targets would turn out to be duds.
In our case, the Galactic latitudes of the stars are also important since we want to observe stars in the Galactic thin/thick disk and halo.
We used both spectral type and V-K color index in order to determine the temperatures. We also calculated the absolute magnitudes when the distance information was available. As always in astronomy, lack of accurate distances for every target is the biggest limitation for us.

20. photometric bandpasses? Most of us are familiar with the “UBV” system
remember for example: V = mV, that is the apparent magnitude in the “visual” (yellowish) bandpass, close to the human eye response

21. we also used infrared “K” magnitudes when available
the colors B-V, V-I, and especially V-K are good indicators of temperature
and the V (= mV) magnitude, IF YOU KNOW THE DISTANCE (PARALLAX) can be translated into absolute magnitude MV

22. SIMBAD http://simbad.u-strasbg.fr/simbad/sim-fid

23. HIPPARCOS

24. an actual star we need to observe in June!
¡Ay, caramba! Star names can be a headache

25. RA, Dec, KT, UT, LST, HA RA = right ascension Dec = declination
UT = universal (Greenwich) time
LST = local sidereal time
HA = hour angle
KT = kitchen (o’clock) time
first point of Aries = Vernal Equinox

26. Galactic coordinates

27. Visualizing Galactic coordinates

28. Our Smith Telescope at McDonald Observatory
° N, ° W

29. Summary of 2.7m Smith Telescope properties

30. The desire is for spectra of our targets we’ve all seen general stellar spectra before
Na I “D” Hα
CH “G”
Mg I “b”

31. Reminder of basic spectrograph design

32. Echelle spectrographs are a bit more complex

33. A solar echelle spectrum

34. A solar echelle spectrum
Telluric O2 Hα
Na I “D”
Mg I “b” Hβ CH Hγ

35. Our spectrograph: the Tull echelle
circa 1968?? left to right:
Harlan Smith, Gerard de Vaucouleurs
Bob Tull, Terry Deeming, Frank Edmonds

36. Very complex drawings designed to make you stop asking questions

37. What you will see at telescope
Telluric O2
What you will see at telescope
Which you can “display” thusly: Hα
Na I “D”
Reduction and analysis: to be continued …

38. HELP!
TELESCOPE:
SPECTROGRAPH:
NIGHT REPORT:
WEATHER:

39. fred