New emission lines in M dwarfs.

Abstract

view Abstract Citations (3) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS New emission lines in M dwarfs. Wildt, Rupert Abstract A number of ultraviolet spectra of K and M dwarfs were obtained with the Qf/2 camera, dispersion about 65A/mm at X325o, attached to the spectrograph of the 8 -inch McDonald reflector. The exposure times were chosen as long as feasible, in order to record the ultraviolet at wave lengths less than X35oo. A cursory inspection of the first exposure of the star BD 2002465 (dM4e) revealed 3 emission lines below X33oo, where the continuum of the star had already faded out; their existence was confirmed by a second exposure. Bright lines of HI and CaiI had been noticed in this star by Swings and Struve,1 and recently it has become famous as a flare-star.2 No photoelectric magnitudes were recorded at Lick during the nights the spectrograms were taken at McDonald, 1950 February 5, 8:oI U.T. and February 7, 6:56 U.T. Since Swings and Struve had stressed the similarity of the emission spectra of BD 2002465 and YY Gem, this star too was examined for emissions in the far untraviolet. Only one spectrogram with an exposure time of 6 hours is available. It shows the continuum extending to about 3250, making it more difficult to disentangle faint emission lines. Omitting two doubtful ones, 6 emission lines were recognized in BD 2002465 and 4 of these also appear in YY Gem. However, their character is quite different in these two stars. In BD 2002465 the emission lines stand out 556 1/2 5.56 3/2 13/2,2 4.63 5.53 7/53/2 z4D0 4.62 549 z6D0 5/2 4.60 7/2 ~4175 9/2 i5 1.69 Figure. 1/32/ 1.09 1.66 ~3/29 4 2 1.07 a4D 3/71/3 1.04 0.96 Fell emissions in M dwarfs. lines observed in BD +20e2465, Q lines observed in VY Gem (Castor C). sharply against the background fog, and there is no doubt about their nature as "lines"; an exception is the rather diffuse emission at X3228 where there is some vignetting by the spectrograph. In YY Gem the emissions are quite diffuse. In particular, X3256 looks nearly 2A wide; and X3278 appears unsymmetrical, the continuous background being of different density to the red and ultraviolet of this line, as if the emission line coincided with the edge of an absorption band degraded toward th ultraviolet. It is fair to say that the existence of these emissions in YY Gem could hardly have been established from a single spectrogram if it had not been for for their previous discovery in BD 2002465. All the lines were identified with the strongest members of two low-excitation multiplets in the spectrum of Fell; they are entered in the term diagram shown in the figure, which also contains the appropriate excitation potentials. The same two multiplets of Feii, including their fainter members, appear in emission in a Herculis (M ) and a Scorpii (MI), according to G. Herzberg's observations.1 He proved that Feii emission does not originate in the atmospheres of the early-type companions of these stars, but is characteristic of the giants themselves, which also have bright H and K lines. Herzberg also lists 8 unidentified emissions; one of them, at X329o.I5, may be identical with a doubtful emission at X3290.o in BD 2002465. Both a Herculis and a Scorpii have also bright H and K lines. Thus there is suggested remarkable parallelism in emission characteristics between dwarfs and supergiants of spectral type M. Further investiagtion of this point seems 1n- dicated. This investigation was supported by the Office of Naval Research. I.Pub. A.S.P. 53, 244, 1941. 2.K. C. Gordon and G. E. Kron, Pub. A.S.P. 6i, 210, 1949. 3.Ap. J. 107, 94, 1948. Yale University Observatory, New Haven, Conn. Publication: The Astronomical Journal Pub Date: 1951 DOI: 10.1086/106629 Bibcode: 1951AJ.....56S..51W full text sources ADS | data products SIMBAD (4)