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Johnson, Hugh M.

Publications and source records attributed to Johnson, Hugh M..

Low-energy X-ray observations of the Wolf 630 system

The Exosat channel multiplier array is used to resolve the septuplet of M dwarfs into three components (Wolf 630ABab, Wolf 629ab, and VB 8AB) with widely different X-ray characteristics. An isothermal plasma temperature of between 800,000 and 550,000 K (which is very low in the known range of coronal temperatures) is found for any relatively quiescent state of VB 8. It is shown from the count rate during 18,112 sec of effective exposure with Exosat that VB 8 flared once in 0.05-2 keV flux.

Johnson, Hugh M.↗

The Draco cloud as a matrix of potential protostars

The Draco molecular cloud is inbound at a z distance of a few hundred parsecs, according to previous observations. IRAS Point Source Catalog data for a 36 sq deg area that includes most of the cloud and a comparison area around it are tabulated, illustrated, and discussed. The sources are classified as 56 unidentified, 38 identified extragalactic objects, and 44 identified stars. The unidentified and unresolved 100 micron sources appear to be globule-like clumps that are candidates for producing protostars, although the data cannot demonstrate currently accreting protostars in the globules. An undetermined percent of 100 micron sources may be artifactual, but only a small percent of them may be galaxies because of the adherence to the Draco cloud. Sources detected also at 60 micron or only at 60 micron do not adhere to the cloud and are probably galaxies. Unless artifactual the unidentified and unresolved 100 micron sources may provide considerable new information about the cloud components and therefore about potential star formation in a new class of sites and origins. Six unidentified sources have 12-25 micron stellar spectral distributions, but neither they nor the identified stars have 12-25 micron spectra characteristic of T Tauri stars.

Johnson, Hugh M.↗