we propose an isocam/isophot search at 6.7/15 and 60/100 microns for faint circumstellar disks around very young (1-2 myr) stars of low mass in the most nearby ob association (sco-cen or orion depending on the launch window). all these stars are weak-line, x-ray (einstein, rosat) selected t tauri stars (wtts). it has been suggested that such stars are truly naked (diskless). the sensitivity of iso is such that we can probe the presence of disk dust masses up to a factor of 100 lower than ground-based observations (i.e. of order earth masses). by concentrating on the youngest wtts, we will find out whether wtts are genuinely naked or whether wtts only lack the innermost disk and, correspondingly, the signatures of accretion (e.g. large halpha equivalent widths). therefore the proposed observations go a long way to understand the difference between weak-line and classical t tauri stars. indeed we expect to find faint dusty disks and will investigate their properties (dust mass, dust temperature) in a well-defined nearly coeval sample (each object is placed in the hr-diagram). the 7/15 micron data will probe the presence of warm inner disks at radii of the order 1 au, important for the formation of terrestrial planets. the 60/100 micron data bear on the presence of cold outer disks with a scalelength of the order of 100 au, important for the formation of very low-mass binary companions. models suggest the disks are likely to be optically thin at each of the 4 wavelengths, in which case the dust mass of both the inner and outer disks can be determined. this will respresent an enormous quantitative advance in our understanding of young disks (disk dissipation timescale as a function of stellar mass), in an environment where most of the field stars are believed to form.
Instrument
CAM01 , PHT22
Temporal Coverage
1997-08-04T00:34:21Z/1997-08-24T06:02:58Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the world's 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, 1999, Are X-Ray Selected Very Young Weak-Line T Tauri Stars Born Nakedquestionmark A Study Of Faint Disks Around Low-Mass Stars In An Ob Association, 1.0, European Space Agency, https://doi.org/10.5270/esa-2a6wlud
