On the Variable Star U Herculis
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ASTRON 0 MI S CHE NACHRICHTEN. Nr. 4381. Band 183. 13. On the variable star u Herculis. By Naazo Zchznohe. Although the variability of u Herculis was discovered Phase Steps brag. Nr. Phase Steps Mag. Nr. by Schmidt early in 1869, the nature of its light-curve was od67 &'.'3 4m68 5 Id33 6?7 41185 4 remaining unknown until last year and the star was con- 0.70 7.1 4.81 6 1.39 6.7 4.85 4 sidered as a variable having an irregular period, of about 0.73 6.3 4.88 5 1.47 5.6 4.q7 4 forty days. Thus, it was rather surprising for me to read 0.77 7.1 4.81 5 1.54 7.3 4.18 5 an announcement by Prof. Schlesinger stating that u Herculis 0.82 7.8 4.72 6 1.59 T.5 4.77 4 is a short period variable of t9 Lyrae type. According to 0.88 7.6 4.74 5 1.62 7.7 4.74 4 him, this nature was revealed from the simultaneous obser- 0.96 7.6 4.74 4 1.72 7 .O 4.81 5 vations both by the Allegheny observers, spectroscopically, 1.01 5.7 4.95 4 1.85 6. I 4.9' 5 and by the Harvard observers, photometrically. So far as 1.08 6.6 4.86 4 1.93 6.8 4.84 6 I know, such an attempt with success was the first and I 1.14 5.4 4.98 5 2.01 5.3 4.98 5 think it is very interesting. When I saw the announcement, 1.25 5.2 5.0' 6 ~ my curiosity was turned to this star but especially my at- tentions were collected on it after Mr. Baker's orbit of the star was published in the Publications of the Allegheny Ob- servatory Vol. I, No. I I. The whole number of my observations on this star is 154 between July 12 of 1906 and Aug. 19 of this year. These were provisionally reduced, adopting Baker's period, and the results of this reduction are as follows. The stars taken for the comparisons were: 111 Herculis o?o 5m1 5m3 dD I .6 5.6 5.3 C) 5.5 5.7 5.2 en 7.2 4.8 4.7 I Fig.D I. 53 )) 8.5 5.6 54 An 9.8 4.6 4.5 The graphical representation of these values in Fig. I shows that the light curve of Herculis is surely of ,d Lyrae e )) I 3.0 4.4 4.1 u type and the following elements are derived from the exami- The second column shows the brightness of the stars nation of the curve. derived from my observations expressed in steps; the third and fourth the magnitudes of the stars from the Potsdam and Principal minimum = 2418125.93 Gr. m. t. + 2do5102 E Harvard photometry, respectively. Rut the comparisons with Mt-mm, = 0d57 m-Mt = od48 J&-mm,.= od51 53 Herculis were omitted in this discussion as these show Aft = 4m75 ?ti2 = 41195 Al, = 4Y78 nil = 57L30. too discordant results. Comparing these with the velocity-curve by 'Baker as At first, I took the entire number of observations shown in Fig. 2 we see that the times of principal and and these were reduced taking the time of periastron, secondary minimum exactly coincide with the times of zero 2418125.80 Greenw. m. t., as the initial epoch, and T= velocity. The variation of brightness is quite gradual without = zdo51oz as the value of period. The result came out P indicating any stop at maxima as well as at minima. as follows. Here, the magnitude is of the Harvard scale. Thus, we know that the dimensions of these bodies are Phase Steps Mag. Nr. Phase Steps Mag. Nr. comparable with that of the orbit. 0d04 4?2 5m1o 6 od30 6?6 4m85 8 The above confirms the nature of the ,d Lyrae type. 0.09 2.9 5.23 6 0.36 5.5 4.91 5 But it seems quite strange that for a star having such a 0.13 2.2 5.31 6 0.41 6.4 4.88 4 gradual change of light we should have been so long re- 0.17 3.0 5.23 5 0.50 6.8 4.84 6 maining in ignorance of the true period, though the dis- 0.22 3.9 5.14 3 0.61 8.2 4.68 4 coverer Schmidt observed this star very frequently. When '3 tm Y' Y' Fig. 2 I consulted some observations by him, published in the A.N., I found very a curious thing. His observations are given in every alternate day. Then, the question naturally comes up whether Schmidt could keep observing the star so re- gularly. I think it more probable that he was following the star every day when the conditions allowed. The fact that he could not find the true period of nearly 49 hours seems 0.74 6.8 4.84 4 1.71 6.2 4.90 3 to show something peculiar in this star and I took it as a 0.78 7.4 4.77 4 1.93 5.7 4.95 3 suggestion. 0.96 6.4 4.84 3 2.01 5.4 4.98 4 Although my observations are not sufficient to decide whether the light-variation of this star was exactly repeating the same curve or not, I tried to discuss it dividing the whole material into three parts. The first series contains only 33 observations made at the Yerkes Observatory be- tween 1906 July 12 and 1907 June 20; the second 42 made here between 1907 Oct. 31 and 1908 Oct. 19, and the last contains 79 observations made also here between 1909 Jan. 24 and Aug. 19. These three series were reduced using the same period and initial epoch as above and the results are as follows: First series. Phase Steps Mag. Sr. I Phase Steps Mag. Br. I odo 5 I?IO 6?9 41'82 2 0.34 1~29 7.9 4.71 .-j 0.55 1.48 7.1 4.81 3 0.78 1.58 9.2 4.59 3 0.85 8.4 4.66 3 1 1.75 8.8 4.62 2 0.96 8.0 4.70 3 , 1.92 8.1 4.70 3 Second series. odo8 3?7 51'16 2 1 1d07 5?4 4'!'98 3 0.17 3.7 5.16 3 1.26 5.3 4.98 2 0.28 5.7 4.95 2 1 1.40 6.9 4.82 3 0.47 7.4 4.77 3 1.54 6.5 4.87 4 0.69 5.9 4.93 4 1.65 6.8 4.84 3 Perhaps, we may conclude as follows: (I) The three 0.84 7.6 4.74 4 1.76 6.7 4.85 2 1 series coincide in respect to the time of the principal niini- 0.96 6.4 4.88 3 1.94 5.2 5.00 4 mum but the brightness at this phase differs, (2) the sym- Third series. metry of the curve with respect to the secondary minimum odog 37'6 57118 odr7 2'!6 5mz8 3 will be fairly seen in the first as well as second series, but 0.08 0.22 4.9 5.03 3 for the third we see .a marked difference, but (3) the time 0.10 3.0 5.23 0.29 5.3 4.98 3 of secondary minimum does not occur at the exact middle 0.12 0.33 5.8 4.94 4 of the period for all series; the ratios are I 14 : 9 I, I 16 : 89, Astronom. Nachr. Bd. 184. E. C. Pickering. Determination of absolute wavelengths with objective prisms. Fig. I. Spectra with Grating. Fig. 2. Pleiades. Fig. 4. 'pl Orionis. Fig. 5. p Aurigae. Fig. 3. a Canis Minoris. Fig. 6. p Orionis. C. Schaidt, Kiel and I 3 2 : 7 3 ; thus, speaking in general, the secondary mini- of observations used in the present reductions is not suf- mum takes place a few hours later than the middle of ficiently large, especially for the first and second series and period and lastly, (4) the mean brightness is decreasing (3) the distribution of the observations is not uniform, from the first to the last series. especially for the third series. Thus, further observations Of course these results are greatly liable to suspicion on this star will be very much needed in order to arrive from the following reasons, (I} the observation of the star to safer conclusions, but I think it would be very interesting according to Argelander's method is not easy, (2) the number to reduce the old materials obtained by Schmidt and others. The Astronomical Observatory, Tokyo, 1909 Sept. 8. Nmzo Ichinohe. Measures of double stars. By B. D.Roe, Jr. The following double stars were measured with the to the nearest second of time and minute of arc for 1910 6.5 in. Clark refractor and Gaertner micrometer described (neglecting proper motion) by Mr. Lindsey. When a pair in A. N. Nr. 4338. was not in the BD Catalogue, I obtained ,.fa and Ad with Besides the pairs found in Burnham's General Cata- reference to some near BD (comparison) star as follows: logue, a list of sixteen others found by the writer is given.