some iras lrs sources can not be identified in the optical poss charts and even were not detected in near-infrared. they are peculiar objects in that the very sharp change of energy distribution happens between 12 micron and near-infrared. both the brightness at far infrared and invisibilty at optical band indicate a cold and thick circumstellar envelopes. so such objects without near-infrared detection proposes one question that why the thick circumstellar envelopes do not emit much in the near-infrared, i.e. k band magnitude fainter than 10 or flux density weaker than 0.067 jy at 2.2 micron. the mystery can be caused by two factors. one is that the circumstellar envelopes contain some special dust components which absorb much between 12 micron and 2 micron or emit much in the far-infrared. the other is that the sources are not point-like but extended. the non-detection at k band is caused by the smaller diaphragm compared with iras diaphragm. since optical and near-infrared observation can not provide any information about them at present on the ground, iso will be the only way to study them in mid- and far-infrared from space. furthermore, they are iras bright which make them very appropriate for iso detection. these very few sources stand for a peculiar group and may be in a special evolutionary stage between agb star and planetary nebula.
Instrument
CAM01 , SWS01
Temporal Coverage
1996-12-19T20:28:16Z/1997-07-31T14:13:51Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the worlds first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, JIANG et al., 1998, 'THE NATURE OF IRAS LRS SOURCES WITHOUT NEAR-INFRARED DETECTION', 1.0, European Space Agency, https://doi.org/10.5270/esa-tiz1bdd
