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NOTES FROM OBSERVATORIES

OBSERVATIONS OF THE SPECTRUM OF THE COMPANION TO BD +4o4048

George H. Herbig Lick Observatory, University of California

The star having the lowest luminosity known at the present time is the common proper motion companion of the M3 dwarf star BD +4^4048.1 The fainter star was discovered by Van Bies- broeck,2 and lies 74^ from the primary. The magnitude has been 3 4 determined by Baade as mPg— 19.2, and by Luyten and Jose

as mVg = 19.5. The color index was estimated by both observers to be +1.4 mag. The trigonometric parallax of the system is given in the 1952 edition of the Yale General Catalogue of Trigo- nometric Stellar Parallaxes as 0^168 =b CK/CXH, which corresponds to a value of about +19.0 for the visual absolute magnitude of BD +4o4048(B). The M-type dwarf of lowest luminosity whose spectrum has previously been observed is Wolf 359, of type dM6e

on the Mount Wilson system, whose Mv is about +16.5. Observation of the spectrum of BD +4o4048(B) presents some problems due to the faintness of the star (m^ = 17.9) and to its appreciable proper motion (1^4 annually). The system is located in a rich region of the Milky Way in Aquila, but a recent direct photograph taken with the Crossley reflector shows that at the present time the companion is in a favorable position for observation, in that no field stars are near enough to contaminate its spectrum.5 Three spectrograms of BD +4o4048(B) in the photographic region were obtained on September 3, 7, and 8, 1956 (UT), with the nebular spectrograph of the Crossley reflector and exposure times of about four hours. The dispersion is 430 Â/mm at Ηγ. Although the star could be seen faintly by looking through the slit jaws at the focal plane of the telescope, it was positioned initially by placing the slit in the proper position angle (determined by measurement of the direct photograph) through an easily visible fifteenth-magnitude star about 30^ away. The continuous spectrum of BD +4o4048(B) on all the

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spectrograms is overlain by a heavy sky spectrum, and classi- fication is most difficult and uncertain. The strongest TiO band heads can be discerned on all three plates, and Ca ι λ 4227 as well is suspected on the first spectrogram. All that the writer is will- ing to hazard from the present material is that the band strengths correspond to an intermediate subclass of type M. The type is not later than that of Wolf 359, so that a very uncertain classi- fication of dM5± on the Mount Wilson system seems reasonable. No emission whatsoever is visible on the September 7 and 8 spectrograms, hut on the plate of September 3 extraordinarily intense bright lines are present at the hydrogen lines (from Η β through H9) and at Η and Κ of Ca n. There is no obvious change in the visibility of the absorption spectrum between the three spectrograms, but the continuum extends farther to shorter wave- lengths on the exposure showing the bright lines than it does on the other two plates. Presumably a flare occurred during the September 3 exposure. The centering of the star in the slit jaws was checked a num- ber of times during the 4.5-hour exposure on September 3, and no conspicuous change in brightness was noted on these occasions, but a flare that lasted only about half an hour could easily have been missed between these inspections. The general brightness of the star seemed, visually at least, to be about the same on all three nights. The intensities of the bright lines of BD+4o4048(B) are greater with respect to the continuous spectrum on the plate of September 3 than in any other Me dwarf that has been observed by the writer. The case of Ηβ is particularly interesting. This emission line is not obliterated in Me dwarfs by overlying TiO as it often is in M-type long-period variables, but even so, Ηβ is not an outstanding feature in the band structure between λ 4700 and λ 5000 in low-dispersion spectra of M4e-M6e dwarfs. In BD-f-4o4048(B), however, Ηβ stands out far above the continuum as a strikingly intense emission line on the plate of Sep- tember 3 (see Plate I). It is not known whether this is due to the great strength of the entire bright-line spectrum on that plate or whether the emission on that occasion originated at a higher level where there was less interference from TiO.

L726-8 AB

d M 5.5 e φ fi inw <Μι..φι mm»· ^

+ 4° 4048 Β-

- Sept. 3,1956

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- Sept. 7

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- Sept. 8

Above: The upper two spectra (of different exposure times) are of L726-8(AB), type dM5.5e + dM5.5e, for comparison with the bright- line spectrum of BD+4o4048(B). The following component of this pair is Luyten's flare star UV Ceti. Below: Three spectrograms of BD+4o4048(B) ; the position of its continuous spectrum is shown by lines in the right-hand margin. Bright lines of hydrogen and Ca n appear only on the exposure of September 3. The strong emission lines extending across the spectrum on all three ex- posures are Hg ι λ 4047 and λ 4358, which are due to scattered city lights. The overexposed star spectrum just above the spectrum of BD -l-4o4048(B) is that of a near-by fifteenth-magnitude star.

If BD 4-4o4048(B) is a flare star in the usual sense of that term, it differs from other members of that class in not possessing bright lines at minimum light.6

ι BD +4o4048 = HD 180617(Ma) : α = 19*12^0, Ô = +5^(1900),

mv = 9.1. 2 G. Van Biesbroeck, AJ., 51, 61,1944. 3 Carnegie Inst. Washington Yearbook, 43, 9, 1944. 4 W. J. Luyten and P. D. Jose, Harvard Announcenient Card No. 697, 1944. 5 This is not the case for another star of very low luminosity whose observation has also been attempted: L745-46(B) at the present time lies within a few seconds of a much brighter field star. It will be perhaps a decade before proper motion opens up the pair to the point where L745-46(B) can be observed separately at the scale of the Crossley reflector. 6 The "flash" stars found by G. Haro and his collaborators in the Orion Nebula and in the Taurus dark clouds do not generally exhibit emission lines at normal light, but the relationship of these variables to the near-by dMe flare stars like UV Ceti and AD Leonis is not yet entirely clear.

A LATE-TYPE STAR OF VERY LARGE RADIAL VELOCITY*

George W. Preston Berkeley Astronomical Department, University of California AND William P. Bidelman Lick Observatory, University of California

Several months ago Dr. G. H. Herbig noticed that the star HD 2320781 appeared to be a very red object on Lick copies of the National Geographic Society-Palomar Observatory Sky Sur- vey plates, and he suggested that it might prove to be of interest. A low-dispersion spectrogram was subsequently obtained by one of us (W.P.B.) ; it was apparent on inspection of this spectrogram that this star was an unusual late-type object with an

* Presented at the Berkeley joint meeting of the Astronomical Society of the Pacific and the American Astronomical Society.

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