scientific abstract we want to study young intermediate mass stars, in two stages: the youngest completely embedded yso. stage, and the very young, already visible, herbig ae/be stars with sizable dust envelopes still around them. these stars have masses of 2 to 10 msun, and ages up to a few million years. it is generally assumed that disks play a pivotal role in the earliest evolution of very young stars, and indeed several authors make models for herbig ae/be stars that include disks (e.g. hillenbrand et al. 1992), but a few authors have recently shown that dusty envelopes alone may suffice to explain their near-infrared emission (e.g. hartmann, kenyon and calvet 1993). our goal is to determine whether intermediate mass yso.s and herbig ae/be stars have disks, and to study the geometry and physical conditions of their extended atmospheres, winds and infalling material, if any. the program stars are in different stages of their evolution: massive envelopes (and disks?) close to the star, less massive extended envelopes, and stars that are still recognizably young by their extended atmosphere. all of iso.s instruments are used to study these objects. this proposal emphasizes the sws. commonality between similar proposals of lws, pht and cam has been sought. apart from images with cam, and full spectra with pht-s, sws and lws, important lines are studied with a higher s/n using sws-aot2, and occasionally sws-aot3. we expect that these observations and the application of recently published models will lead to a three-dimensional picture of the complicated surroundings of young stars in the mass range 2 to 10 msun. the sources are well-spread in priority and location on the sky such that even observing a small sample will further the goals of the program. observation summary for some objects we perform complete scans of the sws and/or lws range using sws-aot1 and lws-aot1. the length of the planned sws-aot1 observation gives implicitly the spectral resolution (see sws observers manual). the lines we wish to observe in the sws and lws range are listed completely in the scientific justification. section. very recently it has become apparent that both yso.s and herbig ae/be stars have often complicated surroundings with a few sources in an area of 10 by 10 arcsec. we perform therefore three cam observations with the highest spatial resolution (2 minutes per exposure) for each object using the filters lw4, 8, 9 at about 6, 11.5 and 15 micrometer, unless cam plans to observe these objects already. for efficiency reasons, the observations of other groups have been merged with ours, for a few objects. this concerns the sws proposal of van dishoeck et al. for t tau and r cra, that of whittet et al. for elias 1 and iras 12496-7650 and the water lines for a few stars in collaboration with ceccarelli of lws. research using ground-based facilities is vigorously being pursued by many astronomers on these objects. the identification of iras sources evolves with time for some sources. it may be anticipated that the coordinates selected for the objects of this proposal have to be adapted just before the launch of iso.
Instrument
LWS02 , LWS04 , SWS01 , SWS02 , SWS06
Temporal Coverage
1997-06-04T04:49:52Z/1997-09-27T08:01:12Z
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.
