Astron. Astrophys. 346, 441-452 (1999)

2. Observations

In this paper we report on the results of several new sets of observations. The new observations include: CO J=2-1 mapping and sub-mm continuum photometry with the James Clerk Maxwell Telescope, near IR wide-band images taken with the United Kingdom Infrared Telescope, and optical spectroscopy obtained at the Isaac Newton Telescope.

2.1. JCMT observations

Observations of IRAS 05327+3404 in the submillimeter regime were made with the 15m James Clerk Maxwell Telescope (JCMT) on Mauna Kea in the fall of 1995. Both continuum and line observations were made. The observations were performed by the on-site staff, with the authors in remote contact. Continuum observations were made at 350, 450, 800 and 1100 µm using the UKT14 receiver. For each of the bands, the position of the optical star was observed with an aperture of 65 mm, which corresponds to 18:002 at 1100µm and roughly 16:005 at the three other wavelengths. Sky subtraction was performed with chopping every 16 seconds. Photometric measurements were made at 800 and 1100 µm data on Aug 24, 1995 using W3(OH), GL 490 and NGC 2071IR as calibration sources. The night was not photometric, and the opacity varied during the observations, so that the calibration is uncertain at the level of 10%. Observations at 800 µm were also performed using the 47mm aperture (13:002 beam). The comparison of the two 800 µm observations suggests that the source may be slightly extended at these wavelengths, though the difference could be the result of calibration errors. Observations were performed at 350, 450, and 800 µm on Aug 26, 1995 when the sky transparency was significantly better. Calibration was performed with GL 490. The second observation at 800 µm with the 65mm aperture was significantly different from the first, suggesting some 15% calibration error the first night. The measured flux densities are listed in Table 1, which includes only the 800 µm flux from the second (better) of the two nights.

Table 1. Photometry data for IRAS 05327+3404 (Holoea)

In addition to the continuum observations, a raster-map of a large region surrounding IRAS 05327+3404 (Holoea) was made of the CO J=2-1 transition. These line observations were observed using the Digital Autocorrelating Spectrometer with the On-The-Fly mapping mode. The CO J=2-1 beam size of the JCMT is 20". We imaged a region, which was fully sampled with 10" grid spacing in RA and 5" in Dec.

2.2. UKIRT observations

Observations of Holoea were made with the 3.8m United Kingdom Infrared Telescope (UKIRT) on Mauna Kea. The observations were made as part of the Service Time program, during the night of November 20, 1995. The weather during the night was photometric. Observations were made with IRCAM3, a near-IR imaging camera which uses a InSb array. The pixel scale of the array is roughly 0:0028. Observations were taken with each of the three wide filters J, H, and K, and the narrow continuum filter nbL (similar to but narrower). UKIRT Faint Standards FS 12 and FS 15 (Casali & Hawarden 1992) were used as standards for the J, H, and K observations, while HD 40335 was used as a standard to convert the nbL photometry to magnitudes. For each filter, a series of offset images were taken and mosaicked together. IRCAM3 allows for on-chip averaging of series of exposures, avoiding problems with the limited well depth compared to the high background typical in IR observations. The total effective exposure time in each filter is listed in Table 1. Image pre-processing (flat-fielding and mosaicking) were performed by the UKIRT staff.

The central source in the J, H, and K images is roughly stellar but it is surrounded by extended emission which makes photometry difficult. We used a template point spread function made by averaging several nearby stars to make a better determination of the photometry of the central stellar source. The template was scaled and subtracted from the image of Holoea. The scaling of the template was chosen to minimize the amplitude of the residuals. This process was done by eye because some of the residual emission is due to real extended emission, so some judgement had to be made as to the correct amount of residual to leave behind. The J, H, K, and nbL photometry of the central source are listed in Table 1. The errors in the J, H, and K photometry are dominated by the uncertainty in remaining real extended emission after the template was subtracted. The nbL photometric errors are dominated by calibration error since there is no evidence of extended emission in these images.

2.3. NOT observations

Two images were obtained at the 2.5m Nordic Optical Telescope (NOT) November 8, 1994 using R and I filters. These images have been reported in Paper I. We have made improved photometric calibrations of these images using observations in R and I taken in September 1993. As with the J, H, K images, the central source is roughly stellar but surrounded by extended emission. We used the technique described above to fit a stellar profile to the central source. The resulting R and I photometry is listed in Table 1. We have also listed improved photometry for the central source in B and V from images taken in September 1993 and discussed in Paper I.

2.4. INT observations

Low-resolution spectra of Holoea were obtained using the 2.5m Isaac Newton Telescope (INT) at the Observatorio de Roque de los Muchachos, La Palma. These observations were taken on 27 March, 1996 using the low resolution R300V grating on the IDS spectrograph. The projected pixel size is 0:007. We used a wide (3:0025) slit to get as much light of Holoea as possible. This gives us a wavelength resolution of 5Å. Total on-target integration time was one hour. The orientation of the slit was North-South, i.e. along the optical tail. The spectrum of the star was extracted from the inner 4" centered on the star, where the stellar flux dominates the extended emission. The visible extent of the tail was 15:005. The data have been bias subtracted and flatfielded in the standard way, using the ESO MIDAS reduction program. Wavelength calibration was done using a CuAr calibration spectrum. The resulting tail and star spectrum were flux calibrated using the spectrophotometric standard star Feige 34 (Massey et al. 1988). A spectrum with less exposure time was also obtained a year earlier, on March 17, 1995. No significant variation is seen between the two spectra.

© European Southern Observatory (ESO) 1999

Online publication: May 21, 1999
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