Red dwarfs are by far the most common but also the most inconspicuous type of star. They are cool, small (7% to 60% of solar mass), main sequence stars found towards the lower right hand corner of the Hertzsprung-Russell diagram. Some red dwarfs are flare stars with frequent eruptions that greatly increase their brightness for a short time. These flares only take a few minutes to reach maximum brightness and flare stars erupt at irregular intervals with flares spaced anything between an hour and a few days apart.
Photometric techniques have been developed to identify red dwarf stars and the table below is extracted from the article "Updated colors for cool stars in the SDSS".
The AAVSO Photometric All-Sky Survey (APASS) is still work in progress but for those areas of the sky where measurements have been taken it is possible to extract results for stars where (r-i) > 0.62 as the first stage of identifying and characterising red dwarf stars in the APASS field.
Once a list of candidate red dwarf stars has been obtained it is cross referenced against the Third U.S. Naval Observatory CCD Astrograph Catalog (UCAC3) catalog. Only stars with a total proper motion greater than 60 mas/yr go forward for further analysis. This proper motion test distinguishes between nearby red dwarfs and far more distant red giants.
Bochanski et al (2010) The Luminosity and Mass Functions of Low-Mass Stars in the Galactic Disk: II. The Field - Link
When I came to study this article I was confused by the equations and graphs on page 9. If you substitute (r-i) = 1 into the second equation you don't get the same answer as you get by examining the graph provided. There is a misprint and the second equation should read 5.025 + 4.548(r-i) ....!
Full details - including location, absolute magnitude, distance, spectal type and total proper motion - of the 73 red dwarfs in the field can be found here.
Over the last few years I have carried out many astronomical data mining or data analysis projects. Most remain unpublished and this series of papers aims to put them all into the public domain. I welcome constructive feedback from readers and encourage colleagues to take the work forward, perhaps as far as peer reviewed publication. I can be contacted by email. and this address is monitored daily.
Martin Piers Nicholson - Shropshire, United Kingdom.
This page was last updated on July 7th 2011.