we propose to search for nearby brown dwarfs as companions to nearby white dwarfs within 20 pc from the sun selected from the gliese/jahreiss catalog, a complete sample of 50 targets. these white dwarfs are old objects (several gyr) so that any companion brown dwarfs are expected to have cooled to 200-1000 kelvin, ideal for detection of an infrared excess in the 3-15 micron range. in fact, white dwarfs are the perfect targets to search for brown dwarf companions, as their radius is 10 times smaller than brown dwarf radii so that the brown dwarf blackbody emission curve can cross and exceed the white dwarf blackbody emission in the infrared. our search is different from the zuckerman and becklin surveys which concentrated on young (< 1 gyr) white dwarfs so that any young brown dwarf companions could be detected from the ground at 1-2 microns. by choosing a sample of old white dwarfs we make sure that any infrared companion must be a bona fide brown dwarf (ie an object with a temperature much lower than that of an m8-m10 main sequence star, hence a mass below the hydrogen burning limit). we need iso because ground-based observations do not have the necessary sensitivity by a factor of 100 (1 mjy at 10 mu is needed). we will use isocam (1.5/pixel) with the sw1, lw2, and lw3 filters. isocam is also 2 orders of magnitude more sensitive than iras at 12 mu, enough to detect cool (e.g. 750 k) brown dwarfs at 20 pc. the choice of 3 filters ensures that we can cover the range of effective temperatures expected for brown dwarfs with ages 3-10 gyr. isocam is preferred over isophot since imaging with isocam allows us 1) to register any infrared excess emission coincident with a white dwarf, 2) to discover cool companions near the white dwarfs, and 3) to check that there is no confusion with cool background objects (e.g. obscured high-z protogalaxies which we may happen to detect).
Instrument
CAM01
Temporal Coverage
1996-07-27T08:37:47Z/1998-03-19T17:24:24Z
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, ZINNECKER et al., 1999, 'BROWN DWARFS: A SEARCH FOR COOL INFRARED COMPANIONS AROUND NEARBY OLD WHITE DWARFS', 1.0, European Space Agency, https://doi.org/10.5270/esa-9zwq4il
