view Abstract Citations (7) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Herbig-Haro Objects Near NGC 1999 Haro, G. ; Minkowski, R. Abstract Haro Objects Near NGC 1999. G.HARO, 0 bservatorio Tonantzintla, Mexico, AND R. MiN ows i, Mount Wilson and Palomar Observatories, Carnegie Institution of Washington, California Institute of Technology. Photographs of the Haro-Herbig objects in the visual region with the 200-inch telescope show that Object No. 1, like Object No. 2, consists of small condensations on a background of faint unresolved nebulosity. A revised analysis of the observations (Bo hm, K. H., 1956, Astrophys. J. 123, 379) of Object No. 1, leads to visual magnitudes from 18.4 to 21.5, electron densities from 1.3x 10 to 2.7x 10 cm-2, and masses from 3 x 10 ~ to 3 X 1028 g for the individual condensations in both objects. None of the condensations contains a star as bright as Mv=2l. Infrared plates taken in Tonantzintla and with the 48-inch telescope on Palomar do not show any star brighter than MT 19.5. Therefore, the emission lines of H and K and the faint continuous spectrum observed by Herbig and investigated by Bo hm cannot be of stellar origin. The faintness of the objects in the infrared is out of line with the color B-V 1.7 found by B6hm for the continuum. The nature of the continuum remains an open question. Since no star brighter than Mv + 13 is observed in the condensations and, since no external source of excitation is visible, the most attractive hypothesis is that the condensations contain a protostar and that the excitation is due to nonradiative processes on the surface of the protostar. The similarity of the spectrum to the spectra of T Tauri stars suggests that the protostar is an early stage in the evolution of a T Tauri star and that the nonradiative processes remain active during the later stages of evolution and are the source of excitation of the emission spectrum of T Tauri stars. The sudden appearance of new condensations {Herbig, G. H., editor, 1957, Non- Stable Stars, I.A. U. Symposium No. 3 (University Press, Cambridge), p. 31 may be because of a sudden start of the excitation at a certain stage of the contracting evolution of the protostar. An alternate possibility which might deserve theoretical investigation is a slow growth of the excitation and a rapid transformation of a residual dust cloud around the protostar into a gas cloud. Publication: The Astronomical Journal Pub Date: 1960 DOI: 10.1086/108160 Bibcode: 1960AJ.....65S.490H full text sources ADS | data products SIMBAD (1)