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


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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