• SCUBA data from February 1998. The contour intervals are
  • 1, 2, 3, 4, 5, 10, 25, 50 and 75% of peak at 850um and
  • 2, 4, 6, 8, 10, 25, 50 and 75% of peak at 450um.
• The excess noise in the west of the 450um map is due to less overlap of coadds in that region of the map.

Click here for a postscript (508kB) image of OH231.8, IRC+10216 and CRL2688.

As with CRL2688, OH231.8 could be marginally extended. At 450 micron a FWHM of 8.7" is obtained, but there are no planet data to compare with. A target object observed during one of the nights give a FWHM of 8.1", while a single map of CRL618 gives 8.5". It may therefore be classified as 'compact' until more accurate maps are available. Examination of integrated fluxes suggest excess emission of < 200 mJy in a 30" radius at 850 micron and less than 600 mJy at 450 micron, which argues for OH231.8 being a point source.

OH231.8 is variable at 850 microns, and probably at 450 microns also. However, the scatter in the data at 450 microns is too large to fit a curve to, and hence OH231.8 CANNOT BE USED FOR 450 MICRON CALIBRATION. If you need to calibrate your 450 micron data and have no other calibrator, we suggest you use the general FCF information posted here. The 850 micron fits for peak and integrated fluxes against modified julian date, along with their residuals, are shown below.

	Peak flux	Integrated flux
Best fit
Residuals
Formula (Y in decimal year)	S (Jy) = 2.35 + 0.45sin (2π (Y - 1999.17)/1.65)	S (Jy) = 2.60 + 0.50sin (2π (Y - 1999.17)/1.65)
(Y in MJD)	S (Jy) = 2.35 + 0.45sin (2π (Y - 51240)/602.4)	S (Jy) = 2.60 + 0.50sin (2π (Y - 51240)/602.4)