view Abstract Citations (2) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Nature of the Infrared Excesses in T Tauri-like Stars. Poveda, Arcadio Abstract It has been argued (Poveda, Bol. Ton. & Tac. 4,15, 1965) that very young stars may be accompanied by a thick circumstellar cloud, extremely bright in the infrared, that can evolve into planetary systems. Mendoza's (Astrophys. J. 143, 1010, 1966) discovery of the large infrared excesses in T Tauri stars supports the initial hypothesis that R Monocerotis is an early stage of the protoplanetary cloud where only about 1/100 of the star's luminosity leaks out in the visible, while FU Orionis' hundredfold increase in luminosity in 1937 occurred because the particles coalesced into large planetesimals, or because they were blown away by the stellar wind. Mendoza's observations show two types of infrared excesses: (a) stars whose infrared luminosity is at least 100 times larger than the visual one, like R Monocerotis, and (b) stars where the infrared luminosity is one to three times the visual, like T Tauri. In (a) the infrared luminosity results from the transfer of the star's electromagnetic radiation through the circumstellar cloud, while in (b), at a more evolved stage, the planetesimals capture only a fraction of the radiation, too small to explain the infrared excesses. These could be produced by the stellar cosmic rays (50-100 MeV), since they heat the matter of the dense stellar winds at intermediate distances. The cosmic rays generated in the chromospheres move outward isotropically, guided by Parker's magnetic spirals, whereas Kuhi's (Astrophys. J. 140, 1409, 1964) results show the existence of enough mass in the stellar winds to absorb the stellar cosmic rays. Thus, infrared excesses of class (b) require that the stars should dissipate more energy in cosmic rays than in thermal radiation. This unexpected result is not too surprising, considering that the energy lost by some T Tauri stars in stellar winds is also somewhat larger than their visible luminosities. Thus, infrared excesses of class (b) may exist even in the absence of protoplanetary systems. Publication: The Astronomical Journal Pub Date: September 1967 DOI: 10.1086/110337 Bibcode: 1967AJ.....72..824P full text sources ADS |