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30 October 2010 AAVSO #1 RS Sge Observations & Preliminary Analyses Jerry Horne AAVSO Fall Meeting 30 October 2010.

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Presentation on theme: "30 October 2010 AAVSO #1 RS Sge Observations & Preliminary Analyses Jerry Horne AAVSO Fall Meeting 30 October 2010."— Presentation transcript:

1 30 October 2010 AAVSO #1 RS Sge Observations & Preliminary Analyses Jerry Horne AAVSO Fall Meeting 30 October 2010

2 AAVSO 2 Outline Abstract Abstract Background Background Previous Observations Previous Observations Current Observations Current Observations Looking for Eclipses Looking for Eclipses Conclusions Conclusions

3 30 October 2010 AAVSO 3 Abstract New V, B, Ic, and R band photometry or RS Sge is obtained. These new observations, when combined with other published observational data, allowed the determination of multiple period values for each star. From its multi-period behavior and from an examination of other intrinsic parameters, RS Sge was confirmed to be that of an RVb Tauri type star, with an fundamental period of 79.4 days with a longer amplitude modulation of 1174 days. New V, B, Ic, and R band photometry or RS Sge is obtained. These new observations, when combined with other published observational data, allowed the determination of multiple period values for each star. From its multi-period behavior and from an examination of other intrinsic parameters, RS Sge was confirmed to be that of an RVb Tauri type star, with an fundamental period of 79.4 days with a longer amplitude modulation of 1174 days.

4 30 October 2010 AAVSO 4 Outline Abstract Abstract Background Background Previous Observations Previous Observations Current Observations Current Observations Looking for Eclipses Looking for Eclipses Conclusions Conclusions

5 30 October 2010 AAVSO 5 Introduction RS Sge first appears as a variable in the German Publication Astronomiche Nachrichten in 1905. RS Sge first appears as a variable in the German Publication Astronomiche Nachrichten in 1905. It was also noted as a variable by Walter Baade in 1928, who provided more precise coordinates. It was also noted as a variable by Walter Baade in 1928, who provided more precise coordinates. Apparently, the first detailed study of the star was published by V. Tsessevich in 1977. He reported both fast and slow fluctuations in the light curve over an approximately 20 year period. Apparently, the first detailed study of the star was published by V. Tsessevich in 1977. He reported both fast and slow fluctuations in the light curve over an approximately 20 year period. Two Algol-like fades were reported by V.I Kardopolov and G.G. Filipe in 1985 Two Algol-like fades were reported by V.I Kardopolov and G.G. Filipe in 1985

6 30 October 2010 AAVSO 6 Introduction The RS Sge designation in the GCVS is RVB+EA. The RS Sge designation in the GCVS is RVB+EA. An RV Tauri type b star (RVb)An RV Tauri type b star (RVb) It is the only RV Tauri star in the GCVS which is also indicated as an eclipsing binary (EA)It is the only RV Tauri star in the GCVS which is also indicated as an eclipsing binary (EA) The variability is listed as: 11.7 - 15.9 p The variability is listed as: 11.7 - 15.9 p The period is listed as: 82.395 days The period is listed as: 82.395 days 710011 |RS Sge *|195706.4+195944 |RVB+EA | 11.7 | 15.9 |p |

7 30 October 2010 AAVSO 7 Background Interest in RS Sge appears in several AAVSO communications, most recently: Interest in RS Sge appears in several AAVSO communications, most recently: Eyepiece Views:Eyepiece Views: July 2007 - A DIFFERENT VIEW OF RV TAURI STARS July 2007 - A DIFFERENT VIEW OF RV TAURI STARS It is definitely worthwhile to put this and other RV Tauri stars on your observing program. - Eric Broens E Y E P I E C E V I E W S #321 ---------------------------------------- July, 2007

8 30 October 2010 AAVSO 8 Background R.A. 19 57 06.42 Dec. 19 59 43.7 (2000.0) N E

9 30 October 2010 AAVSO 9 Background R.A. 19 57 06.42 Dec. 19 59 43.7 (2000.0) N E

10 30 October 2010 AAVSO 10 Background RV Tauri stars: RV Tauri stars: Are regular or semi- regular variablesAre regular or semi- regular variables Are luminous stars of F or G at maximum light and G or early K at minimum light.Are luminous stars of F or G at maximum light and G or early K at minimum light. Show complex light and spectral changesShow complex light and spectral changes Have Periods between 30 and 150 daysHave Periods between 30 and 150 days

11 30 October 2010 AAVSO 11 Background Common RV Tauri characteristics: Common RV Tauri characteristics: Alternating deep and shallow minima in the light and color curvesAlternating deep and shallow minima in the light and color curves Secondary minima depths are more variable that primary minima depthsSecondary minima depths are more variable that primary minima depths A mean phase lag exists between the color index and light curvesA mean phase lag exists between the color index and light curves The RVb subclass, exhibits a long term variability, beyond the alternating minima, with periods from hundreds to thousands of days.The RVb subclass, exhibits a long term variability, beyond the alternating minima, with periods from hundreds to thousands of days.

12 30 October 2010 AAVSO 12 Outline Abstract Abstract Introduction and Background Introduction and Background Previous Observations Previous Observations Current Observations Current Observations Looking for Eclipses Looking for Eclipses Conclusions Conclusions

13 30 October 2010 AAVSO 13 RS Sge Previous Observations IBVS 1371 (1977). From observations by Tsessevich:

14 30 October 2010 AAVSO 14 RS Sge Previous Observations Long Term variability of RS Sge. From observations by Tsessevich published in 1977

15 30 October 2010 AAVSO 15 RS Sge Previous Observations Long Term variability of RS Sge. From observations by Tsessevich published in 1977

16 30 October 2010 AAVSO 16 RS Sge Previous Observations V.I. Kardopolov and G.K. Filipe (1985) focused on the short term variability and reported: Concerning the alternating minima of RV Tauri stars: Max I: 11.1 magMin I: 12.0 mag Max II: 11.25 magMin II: 11.70 mag A fundamental period of approximately 90 days Algol-like fades on JD 2444837.22 and 2444865.17

17 30 October 2010 AAVSO 17 RS Sge Previous Observations Short Term variability of RS Sge. From photoelectric observations by V.I. Kardopolov and G.K. Filipe published in 1985 11.0 12.0 ~90 d

18 30 October 2010 AAVSO 18 RS Sge Previous Observations Long Term variability of RS Sge. From observations submitted to the AAVSO (Trend line added).

19 30 October 2010 AAVSO 19 RS Sge Previous Observations Pojmanski, in 2008, published observations on RS Sge as part of the data from the All Sky Automated Survey (ASAS) for 2003-2008:

20 30 October 2010 AAVSO 20 RS Sge Previous Observations Visual magnitude of RS Sge. From ASAS observations from 2003-2008 Eclipses?

21 30 October 2010 AAVSO 21 ASAS RS Sge Data Some issues with the ASAS data: Possible eclipses are listed as > 14.5 mag. Apparently this is a cutoff mag, not the eclipse depth. The data contains some probable anomalies: 2453625.58214.5 2453625.58412.84 RS Sge apparently gained 1.66 mags in 3 minutes Close pairs of eclipse data points (e.g.): 2453125.85114.5 2453128.86714.5 Have varying intervals of 2.9, 3.1, and 3.90 days Period and Self-Correlation analysis could not determine a unique period from the eclipse data points.

22 30 October 2010 AAVSO 22 ASAS RS Sge Data Assuming at least some subset of the data actually represents an eclipse; Part of the problem trying to analyze the ASAS eclipse data is the time given for the observation only represents: A time during the eclipse when the magnitude was below 14.5. It is not the midpoint of the eclipse Each time listed includes a variance away from the eclipse mid-point. Since we dont know the length of the eclipse, this variance could be minutes to hours in size.

23 30 October 2010 AAVSO 23 ASAS RS Sge Data Mid Point of Eclipse ASAS Cutoff Mag +/- Timing Variance Typical Eclipse Light Curve

24 30 October 2010 AAVSO 24 Outline Abstract Abstract Introduction and Background Introduction and Background Previous Observations Previous Observations Current Observations Current Observations Looking for Eclipses Looking for Eclipses Conclusions Conclusions

25 30 October 2010 AAVSO 25 Current RS Sge Observations In Dec 2009, a project to observe RS Sge was begun with the AAVSOnet telescopes, chiefly, W30 (Wright-30) a 30-cm Meade LX200 also located at the Astrokolkhoz telescope facility near Cloudcroft, New Mexico SRO, a C14 telescope located at the Sonita Research Observatory in Arizona. Images were captured in BVRI bands. Additional observations were made with a 0.25m SCT in V band, once the monsoon season started in the U.S. Southwest.

26 30 October 2010 AAVSO 26 RS Sge Observations Visual magnitude of RS Sge. From AAVSOnet observations in 2010

27 30 October 2010 AAVSO 27 RS Sge Observations Comparison of light curve for RS Sge. From AAVSOnet observations in 2010 (left) and photoelectric observations by V.I. Kardopolov and G.K. Filipe published in 1985 (right).

28 30 October 2010 AAVSO 28 RS Sge Observations Visual magnitude of RS Sge. From observations by the author in 2010

29 30 October 2010 AAVSO 29 RS Sge Observations Ic magnitude of RS Sge. From AAVSOnet observations in 2010

30 30 October 2010 AAVSO 30 RS Sge Observations V color curve and V – I color Index of RS Sge. From AAVSOnet observations in 2010 Expected Phase Lag V band minima V - I minima

31 30 October 2010 AAVSO 31 Outline Abstract Abstract Introduction and Background Introduction and Background Previous Observations Previous Observations Current Observations Current Observations Looking for Eclipses Looking for Eclipses Conclusions Conclusions

32 30 October 2010 AAVSO 32 RS Sge Eclipses One of the primary reasons for this study is to understand the EA portion of the classification – the eclipses. We do have an upper bound on the period: Kardopolov and Filipe (1985) described two eclipses separated by 27.95 days The period then has to be either < 14 (28/n) days or ~28 days Can the noted time variance of the ASAS data be used to help determine possible periods for the eclipse, and guide subsequent observations?

33 30 October 2010 AAVSO 33 RS Sge Eclipses Iterate over various Eclipse Periods ASAS Cutoff Mag That minimizes the difference between the period and the ASAS data

34 30 October 2010 AAVSO 34 RS Sge Eclipses What needs to be done is: Iterate over a large number of periods Measure the difference between the calculated time of eclipse vs the actual data. Sum the differences for all eclipse data points Find the minimum variance for the various possible period intervals (1-2 days, 2-3, days…). A little programming in Excel can do this.

35 30 October 2010 AAVSO 35 RS Sge Eclipses The resulting candidate periods: Interval (d) Period (d) 1 - 2 1.708835 2 - 3 2.379510 3 - 4 3.914674 3.914674 4 - 5 4.668228 5 - 6 5.945204 7 - 8 7.284486 9 - 10 9.101438 13 - 14 13.980051

36 30 October 2010 AAVSO 36 RS Sge Eclipses Observational data vs candidate periods: Interval (d) Period (d) 1 - 2 1.708835 2 - 3 2.379510 3 - 4 3.914674 3.914674 4 - 5 4.668228 5 - 6 5.945204 7 - 8 7.284486 9 - 10 9.101438 13 - 14 13.980051

37 30 October 2010 AAVSO 37 RS Sge Eclipses Other shorter periods virtually eliminated by a combination of AAVSOnet data and authors observations (~10k images) Only remaining viable period appears to be ~28 days If we use the Kardopolov and Filipe period between observations of the eclipse: 27.95 days There was one eclipse visible in 2010 in U.S. time zones: Feb 16, 0340 Z For 2011: Mar 14 1050 Z, Apr 11 0940Z, May 9 0828Z … This would be somewhat consistent with the ASAS data

38 30 October 2010 AAVSO 38 Outline Abstract Abstract Introduction and Background Introduction and Background Previous Observations Previous Observations Current Observations Current Observations Looking for Eclipses Looking for Eclipses Conclusions Conclusions

39 30 October 2010 AAVSO 39 Conclusions Current and recent observations of RS Sge:Current and recent observations of RS Sge: Confirmed the RVb classification Confirmed the RVb classification ~80 day fundamental period ~80 day fundamental period ~1200 day long term variation ~1200 day long term variation No eclipses seen in 2010No eclipses seen in 2010 Period probably ~28 days Period probably ~28 days More observations neededMore observations needed Especially starting in Mar 2011 Especially starting in Mar 2011

40 30 October 2010 AAVSO 40 References American Association of Variable Star Observers, 2010, http://www.aavso.org/; http://www.aavso.org/publications/eyepieceviews/0707.pdf American Association of Variable Star Observers, 2010, http://www.aavso.org/; http://www.aavso.org/publications/eyepieceviews/0707.pdf General Catalog of Variable Stars, Sternberg Astronomical Institute, Moscow, Russia. http://www.sai.msu.su/groups/cluster/gcvs/gcvs/ General Catalog of Variable Stars, Sternberg Astronomical Institute, Moscow, Russia. http://www.sai.msu.su/groups/cluster/gcvs/gcvs/ Kardopolov, V. and Filipe, G, 1986, SvA, 32, 424K Kardopolov, V. and Filipe, G, 1986, SvA, 32, 424K Pojmanski, G. 2002, Acta Astron. 52,397 Pojmanski, G. 2002, Acta Astron. 52,397 Pollard, K.R., P.I. Cottrell, W.A. Lawson, and A.C. Gilmore, 1996, Monthly Notices of the Royal Astronomical Society, 279, 949-977 Pollard, K.R., P.I. Cottrell, W.A. Lawson, and A.C. Gilmore, 1996, Monthly Notices of the Royal Astronomical Society, 279, 949-977 Tsessevich, V., 1977, IBVS 1371 Tsessevich, V., 1977, IBVS 1371 Skiff, B, 1997, IBVS 4459 Skiff, B, 1997, IBVS 4459

41 30 October 2010 AAVSO #41 Questions?


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