WD2256+249
Basic Info

    2MASS 22584811+2515439, GD 245, EG232, KUV2256+249
    RA/DE = 22:58:48.1 +25:15:44
    V = 13.68, Bt=13.955, Vt=12.579, r'=13.861, J=11.675, K=10.915

According to Schmidt et al (1995) this is a binary system, consisting of a hot WD (spectral type A2, Teff = 22,170 K) and brown dwarf (spectral type M3.5 MS, Teff = 3560 K). The LC variation is due to the WD heating the co-rotating front side of the brown dwarf, which then radiates at hotter temperature. The authors also write "The sinusoidal modulation is indicative of reprocessing of white dwarf emission by the orbiting secondary." I'm confused by whether they are invoking both effecst to account for the sinusoidal modulation. They give the following ephemeris:  HJDmax = 2449627.0524(8) + 0.173661(14) × E. The orbital period corresponds to 4.16786(34) hours. The LC by Ayiomamitis has maximum brightness at  HJD = 2455807.47604. This means that E = 35589 ± 3. Since the SE on E >> 0.5, we are unable to refine the period. To improve on the period accuracy by factor 10 would require two LCs like that of Ayoimamitis 100 days apart. Or, we could match the Schmidt et al period accuracy every 10 days. 
Observation Summary

This target was abandoned as soon as I realized that it is a well-studied WD/M4 binary. Here's an article about it: link



  YYYYMMDD  Length   JD start - JD end  Filter Observer     RMS10    Sine Amplitude & Period 

  20110902  7.8 hrs  5806.662 - 5806.989  C    Foote, Jerry 1.6 mmag, 50.6 ± 0.3 mmag, 4.20 hr 
  20110902  7.8 hrs  5806.664 - 5806.988  C    Foote, Cindy 2.5 mmag, 51.7 ± 0.5 mmag, 4.18 hr 
  20110903  8.2 hrs  5807.663 - 5808.005  Rc   Garlitz      3.7 mmag  81.8 ± 0.8 mmag, 4.18 hr
  20110902  5.1 hrs  5807.226 - 5807.435  C    Ogmen        2.0 mmag  60.5 ± 0.4 mmag, 4.44 hr
  20110902  8.1 hrs  5807.268 - 5807.605  C    Ayiomamitis  4.0 mmag  49.1 ± 0.8 mmag, 4.22 hr

Light Curves 


 raw spo 


raw spo   
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raw  spo  
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  raw  spo  Maximum brightness is at UT = 23.290 ± 0.015, or HJD = 2455807.47604 ± 0.00063. 

Finder Images



Aladin image.
   
WebMaster: B. Gary.  This site opened:  2011.09.01.  Last Update:  2011.09.06