30 october 2010 aavso #1 rs sge observations & preliminary analyses jerry horne aavso fall...

30 October 201030 October 2010 AAVSOAAVSO ##11

RS Sge RS Sge Observations &Observations &

Preliminary Analyses Preliminary Analyses

Jerry HorneJerry Horne

AAVSO Fall MeetingAAVSO Fall Meeting

30 October 201030 October 2010

30 October 201030 October 2010 AAVSOAAVSO 22

OutlineOutline AbstractAbstract BackgroundBackground Previous ObservationsPrevious Observations Current ObservationsCurrent Observations Looking for EclipsesLooking for Eclipses ConclusionsConclusions


AbstractAbstract

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


OutlineOutline AbstractAbstract BackgroundBackground Previous ObservationsPrevious Observations Current ObservationsCurrent Observations Looking for EclipsesLooking for Eclipses ConclusionsConclusions


IntroductionIntroduction RS Sge first appears as a variable in the German Publication RS Sge first appears as a variable in the German Publication

Astronomiche Nachrichten Astronomiche Nachrichten in 1905in 1905..

It was also noted as a variable by Walter Baade in 1928, It was also noted as a variable by Walter Baade in 1928, who provided more precise coordinates.who provided more precise coordinates.

Apparently, the first detailed study of the star was Apparently, the first detailed study of the star was published by V. Tsessevich in 1977. He reported both published by V. Tsessevich in 1977. He reported both “fast” and “slow” fluctuations in the light curve over an “fast” and “slow” fluctuations in the light curve over an approximately 20 year period. approximately 20 year period.

Two Algol-like “fades” were reported by V.I Kardopolov and Two Algol-like “fades” were reported by V.I Kardopolov and G.G. Filip’e in 1985G.G. Filip’e in 1985


IntroductionIntroduction 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 It is the only RV Tauri star in the GCVS which is also

indicated as an eclipsing binary (EA)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 daysThe period is listed as: 82.395 days

710011 |RS Sge *|195706.4+195944 |RVB+EA | 11.7 | 15.9 |p |


BackgroundBackground Interest in RS Sge appears in several AAVSO Interest in RS Sge appears in several AAVSO

communications, most recently:communications, most recently: • Eyepiece Views:Eyepiece Views:

July 2007 - July 2007 - A DIFFERENT VIEW OF RV TAURI STARSA 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


BackgroundBackground

R.A. 19 57 06.42 Dec. 19 59 43.7 (2000.0)

N

E



R.A. 19 57 06.42 Dec. 19 59 43.7 (2000.0)

N

E


BackgroundBackground RV Tauri stars:RV Tauri stars:

• Are regular or semi-Are regular or semi-regular variablesregular variables

• Are luminous stars of F Are luminous stars of F or G at maximum light or G at maximum light and G or early K at and G or early K at minimum light. minimum light.

• Show complex light Show complex light and spectral changesand spectral changes

• Have Periods between Have Periods between 30 and 150 days 30 and 150 days



Common RV Tauri characteristics:Common RV Tauri characteristics:• Alternating deep and shallow minima in the Alternating deep and shallow minima in the

light and color curveslight and color curves• Secondary minima depths are more variable Secondary minima depths are more variable

that primary minima depthsthat primary minima depths• A mean phase lag exists between the color A mean phase lag exists between the color

index and light curvesindex and light curves• The RVb subclass, exhibits a long term The RVb subclass, exhibits a long term

variability, beyond the alternating minima, with variability, beyond the alternating minima, with periods from hundreds to thousands of days. periods from hundreds to thousands of days.


OutlineOutline AbstractAbstract Introduction and BackgroundIntroduction and Background Previous ObservationsPrevious Observations Current ObservationsCurrent Observations Looking for EclipsesLooking for Eclipses ConclusionsConclusions


RS Sge Previous ObservationsRS Sge Previous ObservationsIBVS 1371 (1977). From observations by Tsessevich:


RS Sge Previous ObservationsRS Sge Previous Observations

Long Term variability of RS Sge. From observations by Tsessevich published in 1977



Long Term variability of RS Sge. From observations by Tsessevich published in 1977


RS Sge Previous ObservationsRS Sge Previous ObservationsV.I. Kardopolov and G.K. Filip’e (1985) focused on the short term variability and reported:

• Concerning the alternating minima of RV Tauri stars:

― Max I: 11.1 mag Min 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



Short Term variability of RS Sge. From photoelectric observations by V.I. Kardopolov and G.K. Filip’e published in 1985

11.0

12.0

~90 d



Long Term variability of RS Sge. From observations submitted to the AAVSO (Trend line added).

RS Sge - AAVSO Observations

10.5

11

11.5

12

12.5

13

13.5

14

14.5

2454800 2454900 2455000 2455100 2455200 2455300 2455400

JD

V m

ag


RS Sge Previous ObservationsRS Sge Previous ObservationsPojmanski, in 2008, published observations on RS Sge as part of the data from the All Sky Automated Survey (ASAS) for 2003-2008:

RS Sge - Long Term Variablity

10.0

11.0

12.0

13.0

14.0

15.0

2452500 2453000 2453500 2454000 2454500 2455000

JD

V M

ag



Visual magnitude of RS Sge. From ASAS observations from 2003-2008

RS Sge - Long Term Variablity - 1174 d

10.0

11.0

12.0

13.0

14.0

15.0

2452500 2453000 2453500 2454000 2454500 2455000

JD

V M

ag

Eclipses?


ASAS RS Sge DataASAS RS Sge DataSome 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.


ASAS RS Sge DataASAS 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 don’t know the length of the eclipse, this variance could be minutes to hours in size.


ASAS RS Sge DataASAS RS Sge Data

Mid Point of EclipseASAS

Cutoff Mag

+/- Timing Variance

Typical Eclipse Light Curve


Current RS Sge ObservationsCurrent 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.


RS Sge ObservationsRS Sge Observations

Visual magnitude of RS Sge. From AAVSOnet observations in 2010

RS Sge - 79.64 d period

10.8

10.9

11

11.1

11.2

11.3

11.4

11.5

5260 5280 5300 5320 5340 5360 5380 5400

MJD (2450000 +)

V M

ag



Comparison of light curve for RS Sge. From AAVSOnet observations in 2010 (left) and photoelectric observations by V.I. Kardopolov and G.K. Filip’e published in 1985 (right).

10.75

11

11.25

11.5

2455260 2455280 2455300 2455320 2455340 2455360 2455380



Visual magnitude of RS Sge. From observations by the author in 2010

RS Sge 2010

11.00

11.10

11.20

11.30

11.40

11.50

11.60

11.70

5345 5355 5365 5375 5385 5395 5405 5415 5425 5435

MJD (2450000 +)

Vm

ag



Ic magnitude of RS Sge. From AAVSOnet observations in 2010

RS Sge

7.8

8

8.2

8.4

8.6

8.8

5270 5280 5290 5300 5310 5320 5330 5340 5350 5360 5370 5380

MJD (2450000 +)

I Mag



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


RS Sge EclipsesRS 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 Filip’e (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?


RS Sge EclipsesRS Sge Eclipses

Iterate over various Eclipse Periods

ASAS Cutoff Mag

That minimizes the difference between the period and the ASAS data


RS Sge EclipsesRS 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.


RS Sge EclipsesRS Sge Eclipses• The resulting candidate periods:

Interval (d)Interval (d) Period (d)Period (d)

1 - 21 - 2 1.7088351.708835

2 - 32 - 3 2.3795102.379510

3 - 43 - 4 3.9146743.914674

4 - 54 - 5 4.6682284.668228

5 - 65 - 6 5.9452045.945204

7 - 87 - 8 7.2844867.284486

9 - 109 - 10 9.1014389.101438

13 - 1413 - 14 13.98005113.980051


RS Sge EclipsesRS Sge Eclipses• Observational data vs candidate periods:

Interval (d)Interval (d) Period (d)Period (d)

1 - 21 - 2 1.7088351.708835

2 - 32 - 3 2.3795102.379510

3 - 43 - 4 3.9146743.914674

4 - 54 - 5 4.6682284.668228

5 - 65 - 6 5.9452045.945204

7 - 87 - 8 7.2844867.284486

9 - 109 - 10 9.1014389.101438

13 - 1413 - 14 13.98005113.980051


RS Sge EclipsesRS 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 Filip’e 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


ConclusionsConclusions• Current and recent observations of RS Sge:Current and recent observations of RS Sge:

Confirmed the RVb classificationConfirmed 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 daysPeriod probably ~28 days

• More observations neededMore observations needed Especially starting in Mar 2011Especially starting in Mar 2011


References References American Association of Variable Star Observers, 2010, American Association of Variable Star Observers, 2010,

http://www.aavso.org/; http://www.aavso.org/; http://www.aavso.org/publications/eyepieceviews/0707.pdfhttp://www.aavso.org/publications/eyepieceviews/0707.pdf

General Catalog of Variable Stars, Sternberg Astronomical General Catalog of Variable Stars, Sternberg Astronomical Institute, Moscow, Russia. Institute, Moscow, Russia. http://www.sai.msu.su/groups/cluster/gcvs/gcvs/http://www.sai.msu.su/groups/cluster/gcvs/gcvs/

Kardopolov, V. and Filip’e, G, 1986, SvA, Kardopolov, V. and Filip’e, G, 1986, SvA, 3232, 424K, 424K Pojmanski, G. 2002, Acta Astron. Pojmanski, G. 2002, Acta Astron. 5252,397,397 Pollard, K.R., P.I. Cottrell, W.A. Lawson, and A.C. Gilmore, Pollard, K.R., P.I. Cottrell, W.A. Lawson, and A.C. Gilmore,

1996, 1996, Monthly Notices of the Royal Astronomical SocietyMonthly Notices of the Royal Astronomical Society, , 279279, 949-977, 949-977

Tsessevich, V., 1977, IBVS 1371Tsessevich, V., 1977, IBVS 1371 Skiff, B, 1997, IBVS 4459 Skiff, B, 1997, IBVS 4459

30 October 201030 October 2010 AAVSOAAVSO ##4141

Questions?Questions?

30 october 2010 aavso #1 rs sge observations & preliminary analyses jerry horne aavso fall...

Documents

background rv tauri

days slide

introduction rs sge

rvb tauri type star

rs sge designation

new observations

aavso communications

p slide