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Light Echo Detection of Circumstellar Disks around Flaring Stars

✍ Scribed by Eric J. Gaidos


Publisher
Elsevier Science
Year
1994
Tongue
English
Weight
656 KB
Volume
109
Category
Article
ISSN
0019-1035

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✦ Synopsis


Light echoes can be used to detect and characterize disks around flaring stars. Such disks are thought to be a hallmark of planet formation but are very difficult to detect by ordinary means. Dwarf emission-line (M) stars experience flares with luminosities comparable to their quiescent photospheres on time scales of minutes, less than the light travel time across a disk many astronomical units in extent; they are thus ideal candidates for such a search. Bromley (1992, Publ. Astron. Soc. Pac. 104, 1049-1053) calculated that the detection of Jupiter-sized companions using light echoes requires photometric accuracies better than 1 part in (10^{6}). However, a disk consisting of grains or small bodies will scatter a much larger fraction of the light than a planet of similar mass. I estimate the light echo amplitudes from plausible geometries of circumstellar material and present simulated light curves. The light echo amplitudes are typically (1 %) of the flare and I conclude that such events will be detected best in cases where the flare is eclipsed by the star. An examination of the time scales associated with internal processes in a protoplanetary disks around (\mathrm{dM}) stars indicates that any primordial disks may become undetectable in (10^{4}) years and will have completely disappeared by (10^{8}) years, the estimated age of dMe stars in the solar neighborhood. However, searches for light echoes might constrain the amount of material continuing to fall into these young stellar systems in the form of comet-like objects. O 1994 Acondemic Pres, Irac.


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