WiggEB
On June 29, 2009, Patrick Wiggins (Utah, MPC 718) observed a transit of HD 149026. During his image processing and analysis he noticed that one of his reference stars exhibited a transit of its own! It had a depth of 110 mmag, much deeper than the HD 149026 depth of 3 mmag. Sebastian X searched the NSVS (Northern Sky Variability Survey) catalog and found that the star is an uncataloged EA-type exlipsing binary and calculated an approximate ephemeris based on NSVS data. Subsequent observations by Patrick Wiggins and friends confirmed the primary transit with high accuracy for both depth and mid-transit times. Eventually a secondary eclipse was observed, and confirmed by friends. This is an interesting story and as far as I know it's the only case of an exoplanet and EB that are so close to each other (2.3 'arc) that they can be expected to be within the FOV of all observers. This object, which I refer to as WiggEB, will undoubtedly be the subject of professional investigations. This web page summarizes early results of observations by amateurs.
Links Internal to this Web Page
    Basic Info
    Summary of results to date
    Primary LCs
    Secondary LCs
    Finder chart

Basic Information

RA/DE = 16:30:21.0, +38:19:10
aka: GSC 03063-01707, 2MASS 700553553
Observing season centered on June 1
B ~ 13.01, V = 12.27, R ~ 11.84, I ~ 11.54, J = 11.340, K = 10.875 (B-V ~ 0.75, J-K = 0.465)
Spectral type: G5 to K4 (based on J-K) [Mv ~ +5.5, Ms ~ 0.85×Msun, Rs ~ 0.9×Rsun, Teff ~ 5500 K]
Primary Transit:
    Ephemeris: 5020.7904 + E * 0.74640781 (observed several times, in BV R bands).
    Depth = 119 mmag (B-band), 110 ± 3 mmag (V-band), 100 mmag (R-band)
    Length  = 2.06 hr (B-band), 2.08 hrs (V-band), 2.09 hrs (R-band)
Secondary Eclipse:
    Ephem:  5021.1636 + E * 0.74640781 (observed 4 times)
    Depth = 14.2 ± 1.5 (I-band)
    Length = 2.5 ± 0.1 hr (I-band)

Summary of Results to Date

Primary transits have been observed many times (Patrick Wiggins, Yenal Ogmen, Jerry Foote, Bruce Gary) and secondary eclipses have been observed 4 times (Patrick Wiggins, Jerry Foote, Bruce Gary). Foote observed one primary transit in three colros (BVR). Several attempts at detecting a secondary eclipse were "no shows" but in almost every case these observations were made with a R-band or C-band filter. The 4 positive measurements of the secondary eclipse were all made with an I-band filter, implying that the secondary is very cool. The secondary eclipse is longer than the primary transit.



Depth decreases with wavelength (according to Jerry Foote's measurements), implying that impact parameter, b < ~ 0.73 (which assume primary's limb darkening is like the sun's). The ratio of B-band to R-band depth is 1.19 +- 0.03. For a solar type star (for the primary) the greatest this ratio can be is 1.12. But we know this isn't a solar type star, and I think cooler stars have greater limb darkening effects.

The depths can be used to estimate the size of the secondary star if we assume the secondary is much cooler (smaller surface brightness) than the primary. Using 100 mmag (R-band) yields Rsecondary/Rprimary = 0.27 (for a central transit).

The fraction of time of partial transit is Fp = 0.41 +- 0.01 (R-band), so for a central transit this corresponds to Rsecondary/Rprimary = 0.41/(2-0.41) = 0.26 +- 0.01. Since non-central transits are possible, and these produce larger Fp, we can accomodate Rsecondary/Rprimary < 0.26 (which we don't need to do, since depth calls for 0.27).

Rsun. If the primary star produces most of the light, and it's a G5 to K4 star, then Rprimary = (0.85 +- 0.05) × Rsun. If Rsecondary/Rprimary = 0.26 +- 0.02, then Rsecondary = (0.22 +- 0.03) × Rsun. If the secondary is a main sequence M6 star, for example, it will have a mass of ~ 0.15 × Msun, and it will be a red dwarf (not a brown dwarf).

I think the data so far indicates that the secondary is a red dwarf.

The OOT data by Yenal Ogmen (Cyprus) reveal that the WiggEB primary is ellipsoidal. An observing project is underway to refine the OOT shape using a set of specific reference stars with a V-band filter, which should allow combining of LCs from different observers.

 
These two figures came from Christopher Lloyd, showing mostly observations made by Yenal Ogmen (Cyprus).

Preparations are underway for a coordinated series of V-band observations of this object using a specified set of reference stars. Details of this project will appear here when the observing and analysis instructions are ready.


Primary Transit Light Curves


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090714-WiggEB(R)-FJ2-sys  Jerry Foote's R-band LC for 20090714.


090714-WiggEB(R)-FJ2-pro  Same data as above but in "pro" format.


090714-WiggEB(V)-FJ2-sys  Jerry Foote's V-band LC


090714-WiggEB(V)-FJ2-pro  Same data as above but in "pro" format


090714-WiggEB(B)-FJ2-sys Jerry Foote's B-band LC.


090714-WiggEB(B)-FJ2-pro Same data as above but in "pro" format.

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090708-WiggEB-WPK-sys This LC has systematic effects present.


090708-WiggEB-WPK-pro  This version of the same data has systematic effects removed.

Secondary Transit Light Curves





9817WPK

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090817-WiggEB2-GBL-pro  


090817-WiggEB2-GBL-sys  

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090811-WiggEB2-FJ2-pro  


090811-WiggEB2-FJ2-sys  

-------------------------------------- separator for observations of different event  (date or observer) ---------------------------------------------




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090727-WiggEB2-GBL-pro


090727-WiggEB2-GBL-sys

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090718-WiggEB2-WPK-pro  


090718-WiggEB2-WPK-sys  

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090712-WiggEB-GBL-sys  and 090712-WiggEB-GBL-pro


090712-WiggEB-KPW-sys and 090712-WiggEB-KPW-sys   

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090710-WiggEB2-WPK-sys


Finder Chart


FOV = 12.5 x 11.9 'arc, north up, east left. Note that exoplanet system HD 149026 is a mere 2.4 'arc away.


Return to Bruce's Astrophotos

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WebMaster: B. Gary.  This site opened:  2009.08.19.  Last Update:  2009.08.19