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Hem Yorti 14609 USA (716) 482 - 0500 - Phone (716) 288- 5989 -Fo» y^^^ ^^CtK^ ^Hx.,y4t>-*U^U^ ar-r>i>5Z^l,rvA-n>^ pLO RSHINTIID r«OM THt JODRNAI. Of Thk Royal Astronomical SociKTY Or Canada, May -June, 1911 ECD nOM THE MMINIOR OBSEIUTOIY THE ORBIT OF c GEMINORUM BY W. E. HARPER \ <-• ' ^ >>x DEC 2 n 1911 THK ORBIT OF -4. was aiiiioiiiiced * as a spectroscopic binary bv Reese in litO.5. The four measures given about cover the total range in its v-lcK-ity. During 1!)()7, 1910 ami the present year thirty eight sjiectrG- j;rams of this star have l)een obtained. Numbers (>2S and i^'A were made on Seed 27 plates using the Universal Spectroscope, disjiersion at //; 1S(! tenth-metres per millimetre ; numl)ers;51S-2 and 3l'.'57 on Sigma plates with a three-prism of the same disper- sion ; while nnmljers ;!2.S6, ;!;{()!) and .•13:'..-. were made on Sigma plates with three-prism dispersion of liOl' tenth-nictrts per milli- metre. The remaining plates were made on Seed 27 enuilsion with the single-prism instrument having a dispersion at the same region of 'X\A tenth-metres per millimetre. The spectrum is of A' type and should yield mea.surements with a small probable error. The probable error of a jilate of ± 217 km. per sec. obtained from our observations is larger than one should expect for a star of this type, but there are many ways in which this may l)e accoutited for. The u.se of the coarse-grained plates when three prism dispersion was used, made necessary from the faintness of the star ; the low dispersion for the great majority of the spectrograms, with consequent blend- ing of the spectral lines, and the fact that none of the plates, however poor, have been rejected. m:iy he given as possible reasons for the large probable error of an ob.servation. Reese's comment upon the spectrum, in announcing it as a binary, was : " Numerous lines, haxy yet trustworthy. " An attempt was made to measure the plates on the spectro- comparator, which, in the ca.se of .stars having many spectral lines, •/Ml. (Mv,-, .-„/„/,. lUilhUii, \ul. II.. p, ji, i()oj. Thf O'hH of » (ifmiwntm 22i|.(i( + 7«-9 9 "54 JOAViX' 33" ^i■7 9 .Ui7 72.S-t.73 .4 723 3.ZS0 7.i<>''7 ' .. M . **■" 4 .Ut"» 74l-(x.4 1(1 .05 42-0 ■1 .mi S74S-(iii.i J-441 74 -x i| 397" iK>(>7 75J S-.J09 I8-I 5 J,)qS ,kS,}7S5 5 .Uh 50-0 7 4022 i)i)5-(>7i 17-222 59-0 4 4<>3^ ()i^>'fi ^\ 1X-1S4 "7-3 7 4'"7 <)'>9-5'7 1 •4''3 70 -s 5 ■4"'5S lixvsiS 2.464 74 1 6 4070 103h,So 5-020 55 5 (i 4(i.Sii 104719 o-n*)5 493 40S9 106 641 .S-5S7 27-7 S 41<>2 l(K)-6<>q I. -015 105 7 412S 1 IO-()*i,S 12-014 ()-ii 4120 II2-6S7 i4-'>.i3 ^>i.>i S 41.54 1 l6-(i?i is-577 IMh N 4'.?7 120042 2-9X3 79-6 S 4"44 124719 7-o<>o 35-6 5 4 "55 1 29709 1 2 050 120 4II12 1 JO 700 13041 is-o 7 4'".? 1 5t)(>7o 19-011 70-7 7 4177 '.i7-5>f7 •333 S,;-8 S 4lSn ijSs.^j 1-320 ,Vo-0 S 4i'K. 141 (119 4-355 ()7-0 7 42<>2 i4S-5')i S-321) 276 5 4211 14'>'5«>> 9 •304 21-0 S 4221 147-650 10-560 x-x 3 4228 I4S-599 ■'•.535 ')■<) 4247 '5'-5y7 •4-333 ^yi 425,? ■52-54S 15.2S4 .1' - ' 7 42OJ 1 53-000 ■0-345 jo-X 5 4271 ■55-55^ i8-2S,S 09-7 4 42S0 i(>o-500 3-697 734 5 4^91 9<'ii-55.'! 4-6X6 + 6S-2 7 '■5 7-2 «p- : 37 44 0-5 0-5 44 15 4 " 20 3S 5" I -n 0-1) 2-7 4-0 5-5 o-s 0-1 2-0 3 '4 0-7 2-3 i-o 0-0 0-0 0-4 o-o ■•5 y^ 2-4 "•3 2-7 • 4 4-0 0-9 4-2 ■A 2<>2 U: /■:. Hat pet For convenience of reference the l.ick observations are ^iven here. Ohskkvatioxs at Lick Ohskkvatory Daw Julian Ddto Ph.w V«llKitV KetMlual IriMi) -I I.H)-' Mar.h 10 J4I5Hl^7* 17 -1- 74- - 6' l'l"i laritiary \i hli77 g.» filjS 7 IO<> •V 4* l'cljru!ir\ IS (>|6I7 4 4 -♦ fM| + V * The (lecim il t»r .t dax )> ii^iiiiiieossible systematic differences in tlic measures would cause the residuals from the curve to l)econie very much smaller, but the increase of period would affect our secon«! obser- vation making the residual, already large, much ureatcr. Hence the period decided U]X)n, lll'(!(l.') days, was an attempt to equalize these discrepancies. With this period the ob.servations were grouped, according to phase, into sixteen normal jilaces, and weights assigned to the groups which were in general the sums of the weights of the individual plates. XoKMAI, ri.ACKS Mean Phax Mean Vel. + 7'>I4 Wt. '-5 -- c '45 Mean Phase Mean Vcl. - i3-"i Wt. 2-5 -C lO-jSl - '61 2-457 77 -.(O •«-5 '■-'3 10 I2<)().S 12 71 2-1) ^ -05 3 ■407 7J-70 20 75 1 I "3 •037 •i—,'- "-5 t 2'IM» 4S»I 67 -go "-5 t 2-K) 12 14-93" 2.r''i ••5 ■So 5470 5577 '•5 •60 ' j i6(XJ.'j .!7-5" '•5 4-1(1 6 6844 43-07 1 ^ >-34 '4 "'■735 i2 22 1 "O + 2-411 7 7 933 30 SS •5 + -12 15 iS-37<> "^■35 2-0 + I 51 K 8 7ii + 24-01 '•5 + -02 I(> lO-S"'^ - 7769 1-5 + 2-12 The observations are well represented l>y a sine curve ; the eccentricity is so small that it cannot l>e differentiated from zero by graphical methods, hence the values of 7" and 01 are indeter- minate in this way. Recourse was had to the method of least squares for finding the most ]irobable values of the elements. Since the numlK-r of unknowns remained constant it was assumed that the elements w'lich gave the least value for "^fyvv would he Till' Orbit 01 T liemiiiotuin 9W the most probable. Several solutions were tnaile iisinj; the follow- iiiR preliminary values : 1 /• - li»«<).-> davs (• 270°, .TUr, atMt'' ! I'reliminarv r- J. I). 241.'>S'.>()-7.VJ . , 401'.i . . :.fi.->3 \ Klements A' :!:{•:■'. km. y = + 4o 7"< km. I A value of <« l!M)"gave^' negative. The following table shows the main result of the solutions. I'cr a circular orbit V'-.' T'.ll. •1) he 5/>i';' 270'' -oii 70-5 Jjo" MUi 68 -i) j(>o'' -012 7JX The values of the other elements varied but little in each solution. In none of the solutions did the residuals as obtained + Sf) ■ ■■ r ,.., < ^ ■^v ■ - -■ 7" Y\ N \ — — / \ y / \ 40 \ 1 — I 4 \ JO \ / , — -^ — . \ 10 ^V>. — - I . .. — Dav. 4 '' Vki.ocitv Cikvk ok «■ {'.k.minori.m Tht Otbil of'' CemiHotHm •J04 . ... ■ »,v a.n.imt«"K '»'^**^"> "" " . q.,,„„„,, there i» UttU- to .„.au..n. a.ffer n...re '>'- ^ '^.^''^ ^.^^aecuWa to accept that a...,e ..twee, the v-"- * -^ ; ,^ ,,,„,, .alue. The then. a» follow- 1 <»('.(!.') tlilVH .0-22 • OJH XM)" »-V I" "•'■' :j4 -21 km. ''f* km + 4.-, so km. ' ^'- *i"' J. I). •241.">Hi4 Ot« J :{4 ,sr> km. 'if = :•,:{.'»<', km. ^ ,i„ ,• . -..■J2«. UK) km Y I'iiial Value* mil i • • — -n.e curve shown repre«.«ts these final x-bUk- .^^ Dominion OiiSicKV.\ToKY, OTT.XWA, CAN.\1>.^. June, 1911. ^