1 Visual Variable Star Observing Is Fun What I’ve Been Doing And What You Could Do Too Ben Mullin

2 Why Am I Here Talk about how much fun I’ve been having visual variable star observing (VSO) Basics of VSO and how you could get involved What you can observe –including some variables close to objects you probably already observe How VSO has improved my observing What the data you collect might mean Not going to be a technical talk (I’m not an expert) –A little math can add to the fun

3 My Road To VSO Always known VSO was an option Deep Space Objects are cool What could be fun about observing a single star? Imaging is also fun Eventually I got interested in the processing, plotting, and analyzing aspects of CCD VSO

4 My Road Continued Theoretically I have all of the equipment necessary to do CCD VSO Prime focus imaging with a narrow field of view is really hard So VSO sat on the back burner while I worked on getting things together Somehow decided visual observations would be too difficult

5 My First Observation Realized that it was still going to be a while before I got CCD all sorted out I knew Algol was a regular eclipsing binary that was pretty easy to observe Started with the American Association of Variable Star Observers (AAVSO) Manual for Visual Observing of Variable Stars This gave the basics on how to make an observation.

6 Observing Algol First step is to know when the eclipse is expected –Published in S&T also an applet on the S&T website Get a chart from the AAVSO with comparison stars

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8 My Observations In and out of the house while getting the kids ready for bed (did I mention STI?) 8 observations over 3.5 hours

9 Global Collaboration Looks like I missed the minimum But, what about collaborating with others? Between me and Stanislaw Swierczynski from Poland we captured the minimum.

10 Historical Data How does this compare to historical AAVSO data?

11 Wasn’t That Fun? Collected real data on an astronomical event Collaborated with another observer on another continent Made cool graphs and had data to play with when it was cloudy Increased my observing skills Any excuse to go out and look up is a good one

12 So How Did I Do That? Already mentioned the Manual for Visual Observing, eclipse predictions, and chart What about the actual observations? Is it hard? It’s easy and you can learn to do it in just a few minutes.

13 Making Estimates Making estimates

14 Told You So! Pretty easy isn’t it Other things to consider –Avoid biasing your estimate –Report what you see –Don’t stare at red stars –Number one source of error is mis- identification of the variable

15 Now What? Register as an AAVSO observer It’s easy and free Report your estimate Your estimates could be used by professional astronomers doing cutting edge research

16 What You Need To Report An Observation Your observer initials (free registration with the AAVSO) Designation or name of the star observed Your estimate The chart used The comparison stars used Julian date of the observation

17 Online Submission

18 Putting It All Together Pick a star Get a chart from the AAVSO Make and record your observation Register as an AAVSO observer Report your observation

19 See Your Contribution To Science

20 What Could You Observe? A very brief overview of variable star types and their representative light curves –Not a strength of mine yet Interesting/easy variables you could try

21 Broad Categorization Intrinsic –Pulsating –Cataclysmic Extrinsic –Eclipsing –Rotating

22 Pulsating Cepheid – 1 to 70 days, 0.1 to 2.0 mags RR Lyrae – 0.05 to 1.2 days, 0.3 to 2.0 mags RV Tauri – 30 to 150 days, up to 3 mags, alternating deep/shallow minimum Long Period Variables (LPV) – 30 to 1000 days –Mira – 80 to 1000 days, more than 2.5 mags –Semiregular – 30 to 1000 days, less than 2.5 mags, intervals of semi or irregular variation Irregular

23 Cepheid Light Curve

24 RR Lyrae Light Curve From Koppelman, Huziak, Cooney, Petriew

25 Mira Light Curve

26 Semiregular Light Curve

27 Cataclysmic Super Novae – One in Antennae Galaxy announced 12/19/2007, or M51 a few years ago Novae – One in Puppis announced in November, one in Vulpecula in December Recurrent Novae Dwarf Novae –U Gem – Periods of quiescence then erupt –Z Cam – Like U Gem, but with “standstills” –SU UMa – Like U Gem, but with regular outbursts and super-outbursts Symbiotic stars – Close binary systems R CrB – Dwarf novae in reverse

28 Super Novae Light Curve

29 Novae Light Curve

30 Recurrent Novae Light Curve

31 U Gem Light Curve

32 Z Cam Light Curve

33 SU UMa Light Curve

34 R CrB Light Curve

35 Variables You Might Observe Noteworthy Easy Near other commonly observed objects Interesting We already talked about Algol

36 Omi Cet - Mira Maximum predicted near Feb 3, 2008 Going to become naked eye quickly

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38 Delta Cep Bright Only a 5 day period

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40 Zeta Gem

41 Zeta Gem Cepheid Period days Magnitude range Easy to find, hard to estimate

42 M31/RX And

43 RX And UGZ Z Cam Very Active Outbursts and standstills Magnitude range

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45 M42/S Ori

46 S Ori Mira Period 419 days Magnitude range Also a double star

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48 M81/M82/R UMa

49 R UMa Mira Period 301 days Magnitude range

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51 Double Cluster/S Per

52 S Per SRC Period 822 days Magnitude range

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54 RZ Cas

55 RZ Cas Eclipsing binary 4 hours to complete cycle Binocular object

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57 How VSO Has Helped My Observing Admittedly not an advanced observer to begin with Star hopping Averted vision Contrast, magnification, and eyepieces Concentration Most importantly it has added a fun purpose to my observing

58 Are Math and Astrophysics Fun? They certainly can be Let’s see what my 19 observations of X Cyg can tell us

59 Cepheid Variables A class of variable stars Prototype star is Delta Cepheid discovered in 1784 by John Goodricke Henriette Leavitt discovered that their period is closely correlated to their absolute magnitude Can be used as a standard candle to measure astronomical distances

60 X Cyg is a Cepheid So if we can determine the period we can determine the absolute magnitude of the star Arne Henden, AAVSO director, pointed me to a primer paper, “Time-Series Analysis of Variable Star Data” by Matthew Templeton published in the Journal of the AAVSO Among other techniques, it described the ANOVA (analysis of variance) method for determining the period

61 My Data 19 Observations over 5 cycles in 72 days

62 ANOVA Analysis My 19 points versus all AAVSO points My days versus all AAVSO days versus reported days

63 Period-Luminosity Relationship We have determined the period, we can now calculate the absolute magnitude Period-Luminosity relationship Mv = *Log(P)-.826 Mv = *Log(16.36)-.826 = mag Now we know how bright it actually is and we know how bright we see it as…

64 Magnitude Equation m - Mv - Av*d/1000 = 5*log(d/10) m is the observed magnitude (average) – 6.38 Mv is the absolute magnitude d is the distance in parsecs - unknown Av is extinction in mags/kparsec – 2.8 mags/kpc Use Excel’s Goal-Seek function to find d d = pc = 2339ly

65 Compare That To The Professionals ESA Hipparcos satellite measured the parallax of many stars including X Cyg / milli arcseconds annual parallax for X Cyg d = 1000/mas 456pc-1333pc “centered” at 680pc 680pc compared to 716pc, not too shabby for a set of binoculars!

66 Almost Treat Time I have been having more fun observing than ever Possibly contributing to science Improving my observing skills Adds some fun things to do on cloudy nights

67 Thank You