Simultaneous U, B, V, and X-ray measurements of a burst from 4U/MXB 1636-53

A. Lawrence, L. Cominsky, C. Engelke, G. Jernigan, W. H. G. Lewin, M. Matsuoka, K. Mitsuda, M. Oda, T. Ohashi, H. Pedersen, J. van Paradijs

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Data are presented on the first simultaneous X-ray and optical burst to be measured in more than one optical color. Various analyses agree that, to a first approximation, the optical burst is produced through blackbody reprocessing of the X-ray burst, with a short delay. Depending on the technique used, the value of the delay is 2 or 3 s. The smearing of the optical signal is determined to be less than 3 s. The temperature of the optical reprocessor ranges from approximately 25,000 K at quiescence to approximately 50,000 K at burst maximum. An extinction toward the source is derived from the color-color diagram, suggesting a distance greater than or approximately equal to 2 kpc. The projected effective area of the blackbody reprocessor is approximately 5 x 10 to the 21st (D/5 kpc)-squared sq cm. The fraction of the total X-ray burst energy converted into optical energy at all wavelengths is, within an order of magnitude, approximately 3 percent. These parameters are discussed in relation to the 4 hr orbital periodicity in the system reported by Pedersen et al. (1981).
Original languageEnglish
Pages (from-to)793-803
JournalAstrophysical Journal
Publication statusPublished - 1 Aug 1983


  • Ubv Spectra
  • X Ray Sources
  • Bursts
  • Color-Color Diagram
  • Colorimetry
  • Optical Measurement


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