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G. Schneider (Steward Obs., U. of Az.), E.E. Becklin (UCLA), B.A. Smith (U. Ha.), P.J. Lowrance (IPAC), M. Silverstone (Steward Obs., U. of Az.), NICMOS IDT/EONS Team
During HST Cycle 7/7N we conducted an H-band coronagraphic imaging survey of 29 nearby M-dwarf stars using NICMOS Camera 2 searching for faint companions. The sample included stars which were a) very nearby (within 6 pc) with spectral types later than M3.5V; b) younger than 100 Myr with d less than 25pc; and c) spectrally the latest known at the time of the survey (i.e. "ultra-cool" dwarfs later than M8V). The imaging strategy adopted permitted appx. 25 minutes of total integration time for each target in a single HST visibility period where the coronagraphically occulted star was observed at two field orientations rolled 30 degrees about the target axis. The system sensitivities achieved, after self-subtraction of the target star's coronagraphic PSF enabled imaging of candidate companions with delta-H's of appx. 12, 14, and 15.5 at 1, 2 and 3" from the target star, respectively, at the 5- sigma level to a limiting H-magnitude of appx. 23. We discuss the results of the survey in terms of its spatial coverage and detection limits with the added constraint of correlated detection of unresolved field objects imposed by the differential rotation of the field. We also discuss the status of ground-based follow-up of specific candidates objects which were found, and the prospects for the application of this survey method with the return of NICMOS in HST Cycle 11.
This work is based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc. under NASA contract NAS2-6555 and supported by NASA grants NAG5-3042 to the NICMOS IDT and EONS teams.
The author(s) of this abstract have provided an email address for comments about the abstract: gschneider@as.arizona.edu