ASTR 110L                                                                                                                          Name:

Fall 2009

# Variable Star Observing Project — Beta Lyrae  &Delta Cephei

1.  Use the following worksheet to keep track of your observations of the brightness of b (beta) Lyrae and d (delta) Cephei throughout the Fall semester.  You should try to make a minimum of 12 observations of each star over the next two to three months, but more is better!  Observations may be made both in lab and at home, but you should not observe more than once per night.  Observations do NOT need to be on consecutive days, and any time of night (that the constellation is up!) is fine.  Attach an additional page if necessary.  Record:

Date & Time (HST)  (“Phase” will be calculated later)

Magnitude that you observe

Comments (examples: bright moon, interference from clouds, bad city light, low to horizon, or name of observer for any borrowed data).

BETA  LYRAE

 Date (HST) Time (HST) PHASE (days) MAGNITUDE Comments

DELTA  CEPHEI

 Date (HST) Time (HST) PHASE (days) MAGNITUDE Comments

Later, at end of project:  (you will be provided more information later in the semester)

2.  Calculate the phase (in days) for each of your observations above.  You will be shown how to do this, and you will be given a table to aid in your calculations.  (You do NOT need to show your worked-out calculations on the worksheet that you turn in.)

3.  On the provided graphs, plot the magnitude of each star versus Date of Observation, and again versus Phase.

• Plot your own data as big solid dots: Ÿ, and plot any data borrowed from other people as crosses: ´.

• Include error bars to denote uncertainty, if you wish.

• Draw a smooth curve that mimics the light curve of either a pulsating variable or for an eclipsing binary amongst/between your plotted points, perhaps touching only a few, but do NOT “connect the dots”!

4.  Is each light curve more consistent with that of an eclipsing binary or a pulsating variable?  Briefly discuss.