Astron. Astrophys. 362, 984-1003 (2000)

4. Discussion of individual IRAS objects

10256-5628: The position of the IRAS counterpart agrees with that of a m(red) = 17.1 mag star in the USNO catalogue. The K magnitude of García-Lario et al. (1997) is in agreement with our value.

11159-5954: This object has an USNO counterpart with m(red) = 21.0 mag. This is the only star for which the K magnitude derived from the Br spectrum is significantly brighter than the one determined from the K -band image. Hence this star may be variable. Its optical spectrum shows that this is an M-type star (Van de Steene et al., in preparation).

13356-6249: Our value for the K magnitude is in perfect agreement with the magnitude mentioned by García-Lario et al. (1997). The position and magnitude are also in excellent agreement with the data published by the DENIS project (Epchtein et al. 1994). This object appears extended in our TIMMI image.

13416-6342: According to Hu et al. (1993), the source is a highly reddened G1I star with R  = 17.4 mag. Taking into account the photometry of Hu et al. (1993), this object seems to have become brighter since the 1987 observations of van der Veen et al. (1989) by J  = 0.74 mag, H  = 0.46 mag and K  = 0.21 mag respectively. However in the L -band the star became fainter by 0.30 mag.

13428-6232: This is a very nice bipolar showing Br in emission. The magnitude of van der Veen et al. (1989) is somewhat fainter than ours. Considering its size, possibly part of the flux was missed in their 10" diaphragm.

13529-5934: In the CASPIR images we see two faint stars less than 4" apart. The top one is closest to the IRAS position and the reddest source, and therefore the most likely counterpart. The correct identification of the IRAS counterpart needs to be confirmed at 10 µm. The spectra of the objects are completely blended in the IRSPEC image. Their combined spectrum shows no Br in absorption or emission. We won't discuss this spectrum any further.

14325-6428: This object is associated with a bright GSC star of V  = 11.8 mag. It was also observed by the DENIS project. Their K magnitude is in good agreement with ours.

14488-5405: This IRAS object is also associated with a bright V  = 11.5 mag GSC star. This star shows Br in emission.

15066-5532: The counterpart at the IRAS position is a bright m(red) = 14 mag USNO star. Its magnitude is K  = 9.46 mag. However, our TIMMI position, and hence the object for which we obtained a spectrum with IRSPEC , is to the west. It is the reddest of the two and its magnitude is K  = 8.95 mag. It showed a flat Br spectrum. The object appeared extended in our TIMMI image. The K magnitude determined by García-Lario et al. (1997) is brighter than each one of ours, but he may have had both neighbors in its 15" aperture. The correct identification of the IRAS counterpart needs to be confirmed at 10 µm. We won't discuss this spectrum any further.

15144-5812: The K magnitude determined in the CASPIR image is 1 mag brighter than the magnitude determined from the IRSPEC continuum spectrum. We see this bright object and the fainter star towards the south both in the slit. Because of this and the Br in emission, easily visible in the spectrum of the brightest star, there is no doubt that the difference in magnitude is not due to an identification error. Hence this source could be variable.

15553-5230: Our K magnitude is 4 mag fainter than the value determined by García-Lario et al. (1997). These determinations cannot correspond to the same source. In the K -band image we see four objects close together. The K magnitude of the brightest star to the west is K  = 6.21 mag and does agree with the value determined by García-Lario et al. (1997). There is a fainter, very red, extended object just eastward of this bright source. It has an elliptical morphology. Most likely this is the correct IRAS counterpart.

16086-5255: Our USNO counterpart is significantly fainter than the magnitude K  = 7.30 mag determined by Hu et al. (1993). Their magnitude is in agreement with our magnitude of the bright, red USNO star to the south. Its spectral type would be M3I. Our position is within 3" of the IRAS position, while the southern star is more than 16" away. We therefore adopt our identification as the true IRAS counterpart.

16130-4620: In the K -band image the object corresponds to two sources 4" apart. Hu et al. (1993) associated the southern star (V  = 16.7 mag) with an M5Ib star. Our magnitude is in agreement with his measurement. However the top one is by far the reddest of the two, invisible in the optical. This makes it a much stronger candidate for being the IRAS counterpart. The spectra of both objects were blended into one extended source in the IRSPEC observations. We shall not discuss this spectrum any further.

16279-4757: Our K magnitude is 0.1 mag fainter and our L magnitude 0.7 mag fainter than the values measured by van der Veen et al. in 1987 and Hu et al. in 1990. However, the J - and H -band values are in perfect agreement. This difference could be due to measurement errors, or the object may be variable. Hu et al. (1993) determined R  = 18.4 mag and classified it as a G5 star based on its optical spectrum.

16594-4656: Our magnitude is in perfect agreement with what was measured by García-Lario et al. (1997). HST images show the presence of a bright central star surrounded by a multiple-axis bipolar nebulosity with a complex morphology and a size of (Hrivnak et al. 1999). In our K -band images we do not see any evidence of the bipolar nebula. The counterpart of this object is a m(red) = 12.4 mag USNO star.

17009-4154: Our magnitudes obtained in 1998 are fainter than the 1990 value of García-Lario et al. (1997), but brighter than their 1992 values. This source seems variable. It is a post-AGB star with Br in emission surrounded by a faint nebulosity. The object is 7" in diameter and would have fitted in the aperture of García-Lario, if well centered.

17088-4221: This source has been observed by van der Veen et al. (1989) and García-Lario et al. (1997). Their K magnitudes are about 1 mag brighter than ours. The position given by van der Veen et al. (1989) corresponds to the bright, red USNO star west of the IRAS position. We measured a magnitude K  = 9.08 mag for this star in our image, in agreement with their value. The star for which we obtained the Br spectrum corresponds to the USNO star south of the IRAS position. This object is further away from the IRAS position. The northern star is more likely to be the IRAS counterpart, although the correct identification needs to be confirmed at 10 µm. We won't discuss this object any further.

© European Southern Observatory (ESO) 2000

Online publication: October 30, 2000
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