1954Apjs...1...39J SPECTROSCOPIC

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1954ApJS....1...39J lines ofdifferentelementsandmultipletsispeculiar.Ingeneral,thevelocitiesfrombright increase withphase,butthehydrogenvelocitiesshowapproachuntilphase+65daysandthenjoin cycle. Ineachcycle,maximumvelocityofrecessionusuallyoccurredshortlyafterlight,but variation, indicatefluctuationsfromcycletoinamountscomparablewiththerangewithinasingle spectroscopic behaviorofMiraCetithanwaspossiblewithlowerdispersions.Eighty-eightspectrograms were measuredforvelocity. curve ofthemetals.Withrespecttoreversinglayer,velocitiesarealwaysoutward.Bright-line lines aremoreregularthanthoseoftheabsorptionlines.Thevelocitiesrecessionmetallic Fe linesarecorrelatedwiththeexcitationpotential. the observationsnearmimmumlightaretoofewtopermitconclusionswithregardtheirapplication indicate thattheperiodoflight-fluctuationmaybeabout12-14years.ThesharpreversalinbrightH effects. velocities arealsocorrelatedwithexcitationpotential.Certainlinesgreatlyenhancedbyfluorescent and Klinesshowsavelocityof+52.3km/sec,whichmaybethestar.Nootherabsorp- to thepulsationtheory.Differentelementsyieldslightlydifferentvelocities.Thedisplacementsof tion linesoccurexceptthestrongPCygniabsorptionaccompanyinghydrogenlines. velocity resultsfromabsorptionandemissionlines. Thenumberoflinesusedindeter- persions of2.3and9.1A/mmwereobtainedbyI.S.Bowenatthe200-inchHaletele- tion ofthewholestarisopentoquestion. and forrecordingthevariationsindifferentcycles.Whiletheseobservationshavenot Mount WilsonbyP.W*Merrill,W.S.Adams,andA.H.Joyforvariousinvestigations Mira Cetiwasissued,manycoudéspectrogramsofthestarhavebeenobtainedat computed fromthemaximaofTable2.Themeasurement hasbeensharedbyMissSylvia scope. Inaddition,117spectrogramswithdispersions of36and75A/mm,exposedatthe a morepreciseexaminationofmanydetailsthanhasheretoforebeenpossible.Atthe been systematicorexhaustive,theuseofconsiderablyhigherdispersionmakespossible mining thevelocityfromeachplateappearsinparentheses. Thedispersionofthespectro- dispersion was,attimes,increasedto2.9A/mm.In1950afewspectrogramswithdis- advantage atallphasesexceptnearminimumlight.Atofgreatestbrightnessthe coudé spectrographofthe100-inchtelescopeadispersion10.3A/mmwasusedtogood accidental errorsarenearlyidenticalinamount. Becauseoftheaccuracyattainedin grams isinthelastcolumn.Thephasesfrommaximum light,inthefourthcolumn,are 60- and100-inchreflectors,wereusedforchecking andcomparison. Burd. Themeansystematicdifferenceinourmeasures islessthan0.1km/sec,andour 1 1 Absorption lines.—Radialvelocitiesdeducedfrom70selectedlines,representing16cyclesofthestar’s The useofcoudéspectrogramswithdispersionsupto2.3A/mmpermitsamorecriticalstudythe Emission lines.—Theintensityoftheemissionvariesindifferentcycles,andincidencevarious Discussion.—Velocity variationswithinthecycleareconfirmed,butevidenceforvolumepulsa- The visualcompanion.—Variationsintherelativeintensityofspectrumcompanion A.H.Joy,Mt.W.Contr.,No.311;Ap.63,281,1926. In Table1thecoudéspectrogramsmeasuredfor velocityarelisted,togetherwiththe Since 1926,whenanextendedreportonlow-dispersionspectroscopicobservationsof © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem SPECTROSCOPIC OBSERVATIONSOF Mount WilsonandPalomarObservatories Carnegie InstitutionorWashington California InstituteofTechnology MIRA CETI,1934tT952 Received August7,1953 Alfred H.Joy ABSTRACT 39 1954ApJS....1...39J 3703. 3695. 3686. 3279. 2426. 3216. 2423. 2173. 2141. 2140. 2120. 2119. 2133. 2118. 2115. 2114. 1785. 1774. 1524. 1518. 1513. 1472. 1315. 1287. 1870. 1868. 1843. 1801. 1775. 1319. 1298. 1290. 1540. 1209. 1286. 1208. 987. 975. 890. 885. Coudé Plate © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem 1945 Jan.1 1943 Sept.22 1940 Sept.22 1939 Sept.4 1938 Sept. 1937 Sept.15 1937 Jan. 1936 Oct. 1935 Dec.6 1935 Jan.24 Date Jan. 26 Jan. 3 Oct. 21 Feb. Nov. 12 Oct. 11 Nov. 29 Oct. 21 Jan. Dec. 30 Dec. 29 Jan. 25 Sept. 29 Sept. 21 Sept. 21 Sept. 21 Sept. 4 Dec. Nov. 13 Oct. 18 Dec. 29 Dec. 23 Oct. Oct. 20 Dec. 23 Oct. Dec. 12 Sept. Sept. Oct. 19 31 25 26 4 1 2400000 + 30990 27827 9895 9914 9597 9558 9558 9536 9528 9528 9528 1482 9511 9511 9262 9180 9151 8826 1459 1457 9263 9236 9145 9145 8827 8825 8792 8566 8565 8538 8532 8468 1041 8851 8526 8526 8467 8180 8143 7828 JD Velocity ObservationsofMiraCeti - (Days) Phase +221 +170 - 2 - 25 + 94 + 75 +116 + 77 + 77 -l 55 + 47 + 47 + 30 + 47 + 30 + 77 - 27 +104 +103 + 21 + 21 + 85 + 84 + 57 + 51 + 45 + 45 Max. - 8 - 38 + 30 + 24 + 24 - 14 - 14 - 3 - 4 - 5 - 13 - 14 - 7 from TABLE 1 +61.9(21) +60.3 (56) +59.9(61) +53.2 (19) +61.6(11) +63 !2(66) +63.5 (8) +64.4(24) +61.2 (10) +59.7(50) +68.3 (20) +62.4(25) +57.0 (37) +57.9(27) +58.2 (30) +56.6(11) +62.4(31) +63.7(20) +63.4(16) +67.1 (7) +57.2 (51) Absorption 40 +53.4 (3) +49.9 (9) +49.2 (10) +50.2 (5) +51.0 (6) +47.8(10) +49.2 (4) +50.1 (6) +48.4(15) +50.1 (11) +48.8(12) +48.0 (7) +49.3 (5) +52.6(10) +51.0 (5) +43.7 (1) +47.8 (11) +43.5 (1) +44.4 (6) +46.3 (17) +52.5 (1) +45.1 (3) +44.6 (1) +45.1 (1) +44.2 (2) +45.7 (1) +46.4 (9) +45.9 (6) +45.2 (1) +45.0 (1) +42.7 +43.1 (1) +42.6 +45.8 (9) +48.3 (6) Velocities (Km/Sec) Neutral Bright (3) (1) +50.2 (1) +45.2 (2) +46.9 (1) +40.8(1) +51.6(1) +43.6(1) +46.3(2) +48.6(1) +47.7(1) +49.8(1) +47.2 (2) +40.8 (1) +42.4(2) +48.6(1) Bright Hôy +50.1 (3) +53.6(3) +52.3 (3) +54.6(1) +54.1(3) +56.0(4) +55.3 (3) +56.4(2) +56.9 (2) +52.6(1) +55.8 (1) +57.8(3) +61.0(1) +56.5 (2) +51.4(1) +50.6(1) +53.9 (3) +50.5 (2) +53.0 (1) +54.0 (2) +47.7(1) Bright Fe n 10.3 10.3 10.3 20.0 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 Disp. Mu) (A/ 2.9 2.9 2.9 2.9 2.9 2.9 2.9 2.9 2.9 2.9 3.1 2.9 2.9 2.9 3.1 3.1 3.1 3.1 3.1 2.5 3.1 3.1 7.9 7.9 2.3 7.9 7.9 1954ApJS....1...39J P 39. P 17. 4109. 4102. P 36. P 24. P 11. 4127. 4108. 4103. 4079. 4077. 4042. 4141. 4138. 4104. 4078. 4057. 4047. 8516. 5486. 4457. 4180. 6028. 5981. 5352. 5042. 4576. 4547. 4502. 4170. 6446. 6166. 6088. 5925. 5814. 5319. 5314. 5307. 5306. 5056. 4984. 4926. 4476. 5809. 4915. 4464. 7221. Plate Coudé © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem 1952 Nov.28 1951 Aug.1 1946 Jan.10 1950 Aug.7 1950 Jan.5 1949 Aug.3 1948 Aug.23 1948 Jan.3 1947 Oct.6 1945 Oct.25 1947 Jan.11 1946 Oct.11 Date Dec. 22 Feb. 23 Jan. 19 Feb. 17 Feb. 14 Feb. 5 Nov. 29 Nov. 17 Feb. 5 Jan. 18 Jan. 15 Oct. 28 Dec. 11 Aug. 23 Dec. 28 Nov. 13 Aug. 4 Oct. 13 Dec. 2 Dec. 13 Dec. 23 Dec. 23 Dec. 11 Dec. 11 Nov. 29 Nov. 20 Sept. 23 Oct. 8 Sept. 11 Oct. 23 Nov. 8 Oct. 13 Dec. 23 Nov. 13 Sept. 12 Sept. 10 2400000 + 301754 4345 3860 3638 3615 3198 3133 3603 3548 3501 3336 3287 3234 3170 3132 2897 2838 2522 2482 2465 2168 3583 2807 2806 2787 2787 2570 2554 2222 2197 2133 2105 2107 1831 1818 1813 1813 1813 1801 1801 1789 1857 1839 1836 1780 1869 1866 1773 JD (Days) Phase + +194 + 54 +116 + 96 + 61 +183 +134 + 81 + 42 + 33 + 13 Max. +151 +128 + 14 + 45 + 17 + 78 + 19 + 90 + 74 + 2 -}■ 58 + + 46 -F 34 + 16 + 43 - 20 - 21 - 12 - 13 - 32 - 15 FROM - 32 TABLE 1—Continued 43 31 22 22 34 59 57 50 69 10 10 10 8 4 5 +59.8 (32) +62.5 (23) +58.5 (34) +57.5 (43) +62.9 (25) +69.3 (34) +59.0 (26) +66.3 (36) +62.6(68) +60.4 (78) +61.5 (29) +59.7(15) +63.3 (30) +63.8 (29) +62.7 (31) +63.1 (26) +61.5 (29) +60.5 (22) +63.4(32) +61.7 (34) +60.5 (93) +60.1 (32) +58.7 (46) +59.0 (35) +58.8 (40) +57.9 (59) +57.3 (32) +57.9 (22) +59.8 (43) +57.9 (42) +59.2 (39) +57.5 (30) +60.2 (29) +59.6(19) +62.2 (29) +62.4 (29) +63.2 (35) +63.6(31) +62.7 (34) +62.2 (34) +62.3 (37) +59.9 (32) +58.1 (51) +62.2 (19) +60.9 (32) +61.5 (33) +61.8(40) Absorption 41 +46.6 (4) +48.9 (4) +51.7 (10) +48.3 +48.6 +44.4 +44.2 +50.3 (12) +51.0(14) +54.5 (12) +50.3 (3) +48.7 (11) +48.4 (5) +47.8 (3) +47.6 (1) +51.1(11) +47.0 (2) +44.0 (1) +45.7 (1) +45.4 (1) +49.4(16) +49.3 +48.1 +49.9 +48.4 +46.7 +46.9 +46.8 +46.4 +48.1 +46.7 +42.6 +43.2 +44.0 +43.8 +44.2 +43.5 +51.6(11) +46.2 +44.5 +45.8 +46.1 +43.6 +45.1 Velocities (Km/Sec) Neutral Bright (7) (6) (3) (5) (6) (3) (5) (3) (3) (1) (1) (2) (2) (1) (5) (3) (2) (3) (2) (1) (1) (1) (1) (1) (1) (1) +50.8(2) +49.4(2) +44.8(2) +51.5 (2) +53.5 (1) +49.3(1) +46.0(1) +47.7(1) +47.1(1) +50.4(2) +46.7(1) +49.6(2) Bright Hôy +55.1 (3) +53.2 (1) +54.1 (3) +58.0(6) +53.7 (3) +53.4(2) +51.5(1) +58.1 (1) +54.0(3) +52.6(3) +54.0(3) +54.8(3) +55.2 (2) +55.7(2) +55.6(2) +56.7 (2) +55.2 (3) +52.5 (2) +54.9(2) +55.5 (1) +50.9 (1) +53.3 (1) +56.3 (1) +58.3 (1) +53.0(1) Bright Feu 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 Disp. 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 10.3 Mm) (A/ 9.1 9.1 9.1 2.3 2.3 1954ApJS....1...39J 42 ALFREDH.JOY mean intervalfrommaximumtominimumis205days.Themajorchangesinthespec- tion ofVariableStarObserversarelistedinTable2.Maximafrom1926to1935 and courteouslysuppliedbyRecordersLeonCampbellMargaretW.Mayall.The seems justified. days frommaximumarereproduced. from 68coudéspectrogramsrepresenting16cycles ofthestar’slight-variationfrom variations inthecomparisonlinesofironarc. lines ofcertainelements,andphysicaleffects such asexcitationpotential,well the measures,adetailedstudyofvelocitiesindifferentcyclesyears1935-1952 varied frommagnitude 2.7to4.7,andthetimeinterveningbetween maximaranged limited tothebrighter phases. Inordertoillustratethevelocityresults indifferent lished laboratorywavelengths,differencesdue tothesystematicdisplacementof few exceptions,theyhavemoderateintensities,andtheirexcitationpotentialsaregen- trum areillustratedinFigure1,wherespectrogramsatphases—50,+17,and+134 between 316 and349days.Themaximum velocityfora cycle variedbetween+60.5 an averagegoodplate.Elevenpairsofplateswith datesdifferingby5daysorlessshow few plates.Thelineschosenarefreefromtroublesomeblendsandbrightedges.With used. Somelinesfromotherregionswereincludedforcomparisoninthemeasuresofa The StoryofVariableStarsbyCampbellandJacchia;thoselaterdatewerecompiled km/sec inFebruary, 194r6,and+63.8 km/secinSeptember, 1949. the stariscapable,marked fluctuationsareevident.Themaximumlight inthisinterval sponding toaninternalprobableerrorof0.13km/sec forthevelocitydeterminedfrom of 10A/mm,theaveragedeviationasingleline fromthemeanis±1.1km/sec,corre- a meanvelocitydifferenceof0.6km/sec.These deviationsincludeerrorsinthepub- erally lessthan1volt.Theresultsdependdirectlyonlaboratorywavelengths. 1926 Oct.19. cycles from1945to1950. Althoughthisintervaldoesnotexhibittheextremes ofwhich cycles, theobservedvelocities wereplotted(Fig.2)againsttimeforthe 6consecutive 1928 Aug.22. 1927 Sept.26 1935 to1951.Only3cycleswereunobserved.The coudéobservationswerenecessarily tween X3770and4290wereselected,thebestoftheselinesoneachplate 1930 June22. 1929 July17. 1939 Aug.5.. 1938 Sept.17. 1937 Oct.23. 1935 Dec.13. 1932 Apr.18. 1931 May18. 1936 Nov.8. 1934 Dec.31. 1933 Mar.10. 1934 Feb.1.. The datesofmaximumlightMiraCetifromobservationsbytheAmericanAssocia- The averagenumberofabsorptionlinesmeasured is33perplate.Withadispersion For measurementofthevelocitiesfromabsorptionspectra,70atomiclinesbe- Radial velocitiesfrommeasurementoftheselected absorptionlinesweredetermined © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Date VELOCITIES FROMABSORPTIONLINES Mag. 4.0 4.7 4.3 4.1 2.9 3.4 3.5 3.0 2.7 2.5 3.8 4.1 2.8 JD24 + 24808 9481 9159 8830 8481 8150 6150 5150 6816 5810 5481 6480 7803 7470 7142 Maxima ofMiraCeti Interval 322 329 349 347 331 333 326 330 340 331 342 319 328 336 329 TABLE 2 1952 May18. 1951 June8.. 1950 July24. 1949 Aug.24. 1945 Jan.28.. 1944 Mar.2.. 1942 May18. 1941 June18. 1940 July9.., 1948 Sept.24. 1947 Oct.21.. 1946 Dec.9.. 1943 Apr.5.. 1946 Jan.2... Date Mag. 4.3 4.0 3.1 3.1 4.0 3.6 3.6 3.7 3.3 3.9 3.4 2.7 3.2 2.8 JD24 + 30164 29820 0820 0498 3153 3806 3487 4151 2819 2480 2164 1152 1484 1823 Interval 332 334 339 334 341 339 332 322 344 319 339 316 345 334 Fig. 1.—Spectra of Mira Ceti at w rlíj'ífc SlnprtrnPTams bv P. W. Merrill.

In the whole 16-year interval of observation these extremes were: maximum light, 2.5-4.4 mag.; period, 311-355 days; maximum observed velocity, +57.2 in January, 1936, to +68.3 km/sec in the following cycle in October, 1936. While these extreme velocity maxima are based on few observations, the general accuracy of the measurements and the good quality of the plates indicates that these velocity variations are probably real. m M mMmM mMmM mM m

|FlG. 2 .—Radial velocities of Mira Ceti in six consecutive cycles, 1946-1950. Absorption above; emission below.

Fig. 3.—Plot showing correlation of maximum velocity with apparent magnitude in different cycles

The highest velocities attained in different cycles evidently vary by several kilome- ters per second. Usually greater positive velocities accompany maxima of greater brightness, as shown in Table 3 and Figure 3. The scatter is rather large for a direct physical relationship, but some connection between high velocity and high luminosity seems more than a coincidence. Possibly this correlation would be found to be more precise if complete velocity observations and more accurate magnitudes were available. In each cycle having sufficient observations, a maximum value of the velocities observed occurs, on the average, 25 days after maximum light. Since the height of this maximum velocity changes from cycle to cycle and the time of its occurrence with respect to the observed epoch of maximum of light varies many days, the usual procedure of combining observations from different cycles according to phase, to form a character- istic mean curve, is justified only as a first approximation, showing the over-all com- posite movements of the star’s atmosphere. A mean curve of this kind (Table 8, a; Fig. 4, a, solid line) representing the coudé observations may be compared with the low-dispersion-curve of 1926. TABLE 3 Magnitude at Maximum and Highest Positive Velocity

Magni- Magni- Magni- Year tude at Highest Year tude at Highest tude at Highest Maxi- Velocity Maxi- Velocity Year Maxi- Velocity mum mum mum 1934. 2.5 +67.1 1939. 2.8 +64.4 1947 3.1 +63.6 1935. 4.2 +57.2 1940. 3.8 +61.8 1948 3.4 +62.4 1936. 2.5 +68.3 1945. 2.9 +62.0 1949 2.8 +64.0 1937. 4.4 +58.5 1946. 4.0 +60.5 1950. 3.9 +61.5 1938. 4.0 +62.5 1946. 4.3 +62.7

If, however, the velocities from different cycles are reduced to a standard maximum velocity and the phases to an average time lag of maximum velocity after maximum light, a mean curve which may have some significance may be plotted. A standard curve corrected in this arbitrary fashion was formed by reducing the velocities of each cycle to a standard maximum of +63.0 km/sec and by correcting the phases for each cycle by the number of days necessary to reduce the time of observed velocity maximum in the cycle to the average value of +25 days. In this adjusted mean curve (Fig. 4, a, dashed line) the velocities of recession reach a maximum at about 20 days after maximum light. In 112 days preceding its maximum the curve rises 2.2 km/sec, and after its maximum falls 4.0 km/sec in 116 days. The lack of observations does not permit the extension of the curve through minimum light. Coudé observations of other long-period variables by P. W. Merrill2, ^ 4> 6’6 indicate that the velocities from the absorption lines are also subject to considerable irregularity. In different cycles these velocities are not precisely repeated. In 1943 R Aql showed no certain velocity variation between phases +5 and +70. In the same year R Leo had a definite velocity maximum at phase +50 days, rising 3.2 km/sec in 118 days and thereafter falling 0.8 km/sec in 30 days. In the next cycle in 1944 the rise was 1.0 km/sec 2 ML W. Contr., No. 713; Ap. 102, 347, 1945. 3 Mí. W. Contr., No. 720; Ap. 103, 275, 1946. 4 Mt. W. Contr., No. 717; Ap. J., 103, 6, 1946. *Mt. W. Contr., No. 730; Ap. J., 105, 360, 1947. 6 Mi. W. Contr., No. 735; Ap. J., 106, 274, 1947.

© American Astronomical Society • Provided by the NASA Astrophysics Data System MIRA CETI 45 between phases —18 and +17 days, and the decline was 1.5 km/sec from +17 to +101 days. Measures of the postmaximum decrease in velocity for R Leo, R Hya, R And, and X Cyg are summarized in Table 4.

Fig. 4.—Mean velocities plotted according to phase from maximum light, a, Absorption lines; b, 19 standard emission lines (Table 9) ; c, groups of emission lines of different excitation potentials; d, emission lines of ionized metals and hydrogen; e, Si, Co, and Mg emission lines;/, hydrogen emission lines measured by P. W. Merrill; g, emission of 19 standard lines minus mean absorption velocities; h, hydrogen emission lines minus mean absorption velocities. The numerals represent the number of measures included in the means.

The premaximum behavior is not so regular. In 1944 the U Ori curve declined 0.9 km/sec between phases —38 and —3 days, and the velocities of R Hya fell continuously throughout the whole period of observation from phase —45 to +95 days, with a total range of 10.0 km/sec. With allowance for considerable irregularity, we may conclude that the variation in the absorption velocities of several long-period variables resembles in some degree that of Mira. The velocity changes are small, but usually a maximum velocity occurs near the time of maximum light. In this respect the measures of higher precision agree with

© American Astronomical Society • Provided by the NASA Astrophysics Data System 46 ALFRED H. JOY the previous results obtained from low-dispersion spectrograms of Mira, but the total velocity range in any single cycle is probably smaller than that shown by the 1926 curve.

VELOCITIES EROM DIFFERENT ELEMENTS The average residual from the mean for the lines of elements generally measured in Mira are collected in Table 5. Merrill’s mean residuals for the same elements (not neces-

TABLE 4 Postmaximum Velocity Decline in Long-Period Variables (Merrill) Compared with o Ceti

Range of Star Velocity Phase Year Decline (Days) (Km/Sec)

R Leo. (1943 0.8 +49 to + 81 \1944 1.5 +17 to +101

RHya. J1943 7.4 +21 to +125 \1944 5.3 +38 to + 95 X Cyg. 1944 2.7 +70 to +162 fl944 +102 R And. 2.8 +10 to \1945 1.9 +27 to + 54 R Aql. 1943 0.0 + 5 to + 70 o Cet. . 1935-52 4.5 +45 to +174

TABLE 5 Relative Displacement of Absorption Lines of Different Elements

Mira Mira 7 Me Stars 7 Me Stars Mean Resid- Mean Resid- Element Element ual (Merrill) No. Mean ual (Merrill) No. Mean Residual (Km/Sec) Residual (Km/Sec) Lines (Km/Sec) Lines (Km/Sec) Sc. 4 +0.10 +0.65 Fe. . 29 +0.26 +0.52 Ti. 11 + .33 - .60 Co. . 6 - .58 + .08 V. 10 - .41 - .28 Ni. . 3 + .84 + .22 Cr 4 -0.88 -0.70 Sr ii. 2 +0.33 (-0.4) sarily the same lines) of seven other stars are entered for comparison. Except for Ti, the agreement is close. The deviation of velocities derived from different elements is doubtless real and may amount to nearly 1.5 km/sec. The reason for this difference is not evident. ANOMALOUS RESIDUALS The residuals from several lines are so large that the lines were omitted from the means. The ultimate potassium lines, X 4044 and X 4047, are displaced shortward with reference to the mean by 2.7 km/sec (10 plates) and 2.0 km/sec (7 plates), respectively. A similar displacement of even greater amount was found for these lines by Merrill in each of seven long-period variables. No emission components are involved.

The lines X 3906.482 Fe (4), low E.P. 0.1, and X 4045.815 Fe (43), E.P. 1.5, have much larger residuals than other lines of their multiplets. For X 3906 the mean displacement is — 2.8 km/sec (32 plates), and for X4045 it is +3.1 km/sec (34 plates). The measures are not affected by emission, which is extremely weak or absent in both lines in Mira. The mean displacement of seven other lines of multiplet (4) is —0.2 km/sec; that of four other lines of multiplet (43) is +0.4 km/sec. In Figure 5 the variation of the residuals of X 4045 with phase is shown. For X 3906 the change with phase is negligible.

-60 DAYS 0 +60 +120 +180 Fig. 5.—Residuals from the mean of absorption velocities of X4045 Fe and the Mn lines XX 4030,^4033, 4034, and 4035. The numerals represent the number of measures included in the means.

TABLE 6 Anomalous Residuals of x 4045 Fe and Mn Absorption Lines

X 4045.815 Fe X 4030.755 Mn X 4033.073 Mn X 4034.490 Mn X 4035.728 Mn Phase (Days) No. Resid. No. Resid. No. Resid. No. Resid. No. Resid. Plates (Km/Sec) Plates (Km/Sec) Plates (Km/Sec) Plates (Km/Sec) Plates (Km/Sec) -49. 7 +4.0 5 -1.1 -5.0 8 +1.8 8 +7.8 -11. 14 +2.3 10 -1.2 -4.8 14 +0.8 12 +7.6 +31. 12 +2.1 9 -2.2 -4.9 14 +1.4 9 +6.9 +72. 6 +7.4 6 +2.2 -1.4 8 +3.6 7 +7.0 +122, 5 +9.4 4 +7.7 +2.5 4 +6.3 5 +4.6

The manganese lines XX 4030.755, 4033.073, and 4034.490 from the ground level of multiplet (2) and X 4035.728 (5), E.P. 2.1, have anomalous displacements which neces- sitate their omission from mean velocities. The mean displacements of these four lines are —1.2 (24 plates), —4.5 (24 plates), +1.3 (36 plates), and +7.1 (28 plates) km/sec, respectively; but, as shown in Table 6 and Figure 5, the variation during the cycle of

© American Astronomical Society • Provided by the NASA Astrophysics Data System 48 ALFRED H. JOY light-change is large, indicating that these manganese atoms are peculiar. They tend to follow the motions of absorbing atoms of other elements near maximum light, but after phase +30 days their velocities of recession increase for at least 100 days. The problem is complicated by the presence of emission (see p. 51 and Fig. 6) on the shortward edge of X 4030 and X 4034; but the velocity changes do not seem to be well correlated with the strength of emission, and X 4033 has similar velocity changes, although the emission is extremely weak or absent in this star. Contrary to the laboratory intensities, X4033 always appears stronger in absorption than X 4030. The behavior of X 4035.728 of multiplet (5) is most peculiar. It has a large longward displacement but does not share the velocity changes during the cycle shown by X4045 and the Mn lines of multiplet (2). Four other lines of multiplet (5) have normal displacements. Faint emission on the shortward edge appears for several days near phase +30 days and on both edges from minimum light until — 50 days. It is hardly possible that the velocity measures are much affected by the emission, but an unidentified absorption line of slightly longer wave length may be present. At times, the line appears somewhat wide and hazy. In addition to these lines of K, Fe, and Mn, the lines XX 3875.075 V, 3906.482 Fe, 4113.518 V, and 4202.031 Fe, with mean residuals of +3.9, —2.8, +2.6, and +3.7 km/sec, respectively, were omitted from the means on account of their large discord- ances. The measures of the first three may be affected by blends and the last by emission on the shortward side having high intensity from phases +25 days until well after minimum light. SHIFTS VARYING WITH EXCITATION POTENTIAL In agreement with the results obtained by Adams7 for o Ceti and of Merrill2,3’4’5’6 for U Ori, R Ser, R Hya, R And, and x Cyg, the present measures of Mira indicate that 17 dark lines having excitation potentials greater than 0.9 volts (mean E.P. 1.40 volts) have mean residuals of +1.12 km/sec with reference to 50 lines having low excitation potentials (mean E.P. 0.10 volts). For the absorption lines identified within the bright hydrogen lines of Mira, a larger range of excitation, 2.32 volts, was covered, giving a difference in velocity of +3.4 km/sec.8 The five iron lines, XX 3865.527, 3872.504, 4005.246, 4063.597, and 4071.740, of multiplets (20) and (43) were measured on many plates but show no variation of displacement with phase when compared with lines of low excitation potential. The line X 4045.815 Fe (43), however, has extraordinary longward shifts at phases 60-120 days, as shown in Figure 5. These lines have excitation potentials rang- ing from 0.99 to 1.60 volts.

EMISSION LINES The emission spectrum of Mira Ceti is conspicuous, especially at postmaximum phases, but the bright lines are less numerous and less intense5, 6 than in R And and X Cyg. Estimates of the approximate phases at which the bright lines of different elements become definitely visible, together with the times of maximum intensity and of disappearance, are in Table 7. Only the chief lines of the different multiplets are entered. The emission varies greatly in different cycles. Bright lines are stronger and more numerous in cycles of high maximum brightness (Fig. 7).

HYDROGEN The Balmer lines of hydrogen are outstanding at all phases except for a few weeks near and shortly after minimum light. Their total width decreases from 70 km/sec at phase —50 days to 45 km/sec at +170 days. From the time of their appearance until phase about +110 days, the hydrogen emission lines are severely mutilated by the absorption 1 Mt. W. Contr., No. 638; Ap. 93, 19, 1941. 8 A. H. Joy, Mt. W. Contr., No. 737; Ap. J., 106, 288, 1947.

X «É§ H;

''I I

■ * 04 I -ï«g la CD « Ä Ä1 m 00 to i é». H 04 . çpiO Ä- ^ ^ I _ OJ S ?' CD ro B mm

f # J; #m-■ ■ Fig. 7.—Spectra of Mira Ceti at the same phase after high and low maxima. The unidentified emission features XX 3956, 4906, 4098, 4104, 4138 are marked. Above, Ce 1290, phase +51 days, maximum = 2.7 mag.; below, 4180, +46 4.0 mag. Spectrograms by P. W. Merrill.

© American Astronomical Society • Provided by the NASA Astrophysics Data System MIRA CETI 49 of many lines of the reversing layer of the star.7, 8’9> 10 At later phases this absorption is no longer present, probably because of a relative uplift of the hydrogen sources, as Merrill has suggested, and the relative intensities of the Balmer lines take their laboratory values. The Hß and Hy lines rise above the absorption of the titanium oxide bands. The absorption of by H (Ca n) is noticeably reduced at phase +20 days and has little effect at phases greater than +50 days.

TABLE 7 Occurrence of Chief Bright Lines

Maximum Multi- Chief Appearance Disappear- Element Phase ance Phase plet Line (X) (Days) Phase (Days) (Days) Int. Hy 4340 -65 0 Strong +215 m. 4101 -70 0 Strong +190 4571 +45 +180 15 +300 Mgi 3838 0 + 80 2 +180 4102 -70 0 5 +200 Sii. . 3905 -60 + 80 4 + 180 Sc I.. 3907 +30 +100 3 +180 Ti n. 3759 +20 + 80 1 + 170 3685 +10 + 80 2 +170 4030 0 + 90 4 +210 Mn I. 4035 -70 0 1 + 45 4375 -15 +130 5 +215 4216 +10 +130 5 +210 4307 0 +135 10 +260 Fe I. 4063 +25 + 70 2 + 90 3949 0 + 80 3 + 150 3852 0 + 80 8 +200 3938 +33 + 60 5 +160 Feu. 4233 -20 + 50 5 +220 4178 -70 + 85 3 +200 4121 -10 + 40 2 +100 3995 -10 + 40 2 +100 Co I. 3935 -40 0 2 +100 3997 -10 + 40 1 +100 Sru 4077 +45 + 80 2 +190 In i. 4511 -70 +140 3 +190

If the hydrogen lines are strongly overexposed, fairly reliable velocity measures are possible at all phases. As Merrill has shown for other long-period variables, the velocity- curve of the hydrogen emission is quite different from that of the metallic lines. In order to determine the motions of the strata in which the hydrogen emission arises, the measurements of Hy and Hb are the most useful because these lines are visible over the longest time interval and happen to be less severely affected by overlying absorption than do other hydrogen lines. Table 8, d, and Figure 4, d and/, indicate the course of the velocity variations of the Hy and Hb emission sources in Mira Ceti (M6e) and, for com-

9 C. D. Shane, Lick Obs. Bull., 10, 133, 1922. 10 P. W. Merrill, Pub. A.S.P., 57, 178, 1945.

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1954ApJS....1...39J 989. 762. 195. 179 97. 41 48. 10. 14. 10. 12. 13. 14. 6 8 6 4. 4. 4. 4. 9. 2. Lines No. © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem XX 3938,4173,4178,4233 Selected RadialVelocitiesofMiraCeti a) MeansofAbsorption (Days) Phase +134 + 82 + 45 + 174 - 11 - 55 + 43 Mean + 31 + 7 + 43 +167 + 53 +129 + 90 - 52 XX 4206,4216,4375 d) EmissionFen d) EmissionSrn c) EmissionFei c) EmissionFei 173 129 110 126 165 183 Lines byPhase X 4063,X4202 X 4077,4215 90 68 49 84 74 Velocity (Km/Sec) +59.4 +46.3 +44.4 +55.2 +47.1 Mean 61.9 60.2 57.4 59.3 61.6 49.0 48.9 47.6 46.3 46.2 47.9 48.4 51.6 46.6 48.1 54.2 51.1 55.1 50.7 53.8 54.5 TABLE 8 133. 29. 30. 52. 39. 78. 11. 25. 15. 11. 14. 11. 13. 9. 5. Lines No. b) Meansof19Metallic Emission LinesbyPhase (Days) + 24 +131 + 76 + 44 Phase +184 - 11 - 47 + 19 + 47 + 52 Mean + 127 + 69 + 26 - 10 XX 3852,3949,3977 d) EmissionTtn c) EmissionFei c) EmissionFei 134 185 146 146 d) EmissionH X 3759,X3761 X 4101,4340 84 87 84 51 (Table 9) X 4307 Velocity (Km/Sec) +44.7 +46.3 +40.2 +47.2 +48.6 Mean 46.9 45.8 49.0 47.9 51.2 50.6 43.2 48.4 53.8 53.8 49.8 57.5 52.0 48.4 41.3 45.6 50.0 1954ApJS....1...39J 634 parison, in%Cyg(M6e+S),RLeo(M8e),andHya(M6e),fromMerrill’smeas- phases ofthestar’svariation.Theemissionisfirst seenontheshortwardsideofab- an epochsomewhatbeforemaximumlightuntil atimesome2monthsaftermaximum, emission layersshowincreasingvelocitiesofapproach fromtheirfirstmanifestationat sorption lines,anditisoftendifficulttodetermine theexacttimewhenemissioncan ures ofnumeroushydrogenlinestoB18.Inthese fourstarswefindthatthehydrogen lines ofmetalsoccurringinMiraCeti,andsome ofthemarepresentatpracticallyall tion potential,especially thoseofFei,arefirstseen.Later,thelines lowerexcitation Ni i,InTin,Feand Srn,emergeinconsiderablenumbers.Lines ofhigherexcita- increases enormously,and linesofadditionalelements,suchasSci,F Oi,MwCo first bedistinguished.As thelightdecreasesaftermaximum,number ofemissionlines appear ingreatnumbers. when theaccelerationlevelsofforreversesitsdirection. The linesofneutralMgi,SiandFeiarethe most prominentofthemanyemission © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem 155 34. 21. 27. 21 23 25 10. 11. 71 11 6. 4. 5. 8. 7. Lines No. (Days) + 24 Phase + 133 + + + 3 - 18 - 55 +134 + 83 +163 + 41 Mean - 7 g) “19Bright’-Dark - 48 XX 3997,4045,4121 e) EmissionCoi e) EmissionSii X 3905,4102 93 63 84 33 54 Displacement ofEmissionLines Velocity (Km/Sec) +43.9 TABLE 8—Continued +49.0 -14.8 Mean 47.6 44.7 49.1 48.3 53.5 49.1 53.9 51.8 12.2 15.0 14.9 MIRA CETI 6.6 7.9 METALS 35. 15. 10. 12. 9. Lines No. XX 3829,3832,3838,4571 (Days) + 19 Phase + 45 + 123 + 34 + 6 Mean - 16 e) EmissionSci h) Bright¿7-Dark e) EmissionMgi 181 132 140 46 80 94 63 X 3907 Velocity (Km/Sec) +46.3 +48.2 Mean 47.8 49.8 48.7 48.3 51.0 51.2 50.6 11.0 15.3 11.3 10.1 51 52 ALFRED H. JOY

FLUORESCENT EFFECTS As described by Merrill for other long-period variables of type Me and for R And of type Se, the Fe i (42) lines X 4202.031 and X 4307.906 from the zzG\ level and Fe i (73) X 3852.574 from the level have by far the strongest emission in their respective multiplets. Their extraordinary intensity is well accounted for by excitation effects of MgTL X 2795.53, as first suggested by Thackeray and Merrill.11 They are seen in Mira Ceti from maximum until well after minimum light. Although it is fainter in the laboratory, X 4202 appears first and is stronger than X 4307 until phase +100 days, after which X 4307 becomes more intense and endures for a longer time after minimum; X 3852 also appears at maximum, but, although it reaches nearly the same intensity, it fades out somewhat earlier than the lines of multiplet (42). The Zr i singlets, XX 4166.51, 4240.44, and 4242.61, observed by Merrill12 in x Cyg, show only a trace of emission in Mira. In the only accessible multiplet oí In the complete fluorescent mechanism is manifest. The line X 4101.764, the shortward member of the doublet, has nearly the same wave length as Hb. It is present in absorption13 within the strong Eh emission line until phase + 130 days. The energy absorbed raises many of the In electrons to the 62Si/2 level, from which they are able to radiate X 4511.310, the other member of the doublet. While this emission line never attains great intensity, it has a long lifetime, nearly coincident with 2 that of Eb. The Sc i line X 3907.476 (8) from the y F21/2 level is much strengthened in emission and is well seen between phases +30 and +180. The low-term line from the same level of this multiplet is X 3933.381, which may be excited by emission of K {Ca n). The only visible emission in the K region is that of the broad displaced line which Mer- rill3’4’5’6 found to be of considerable strength in R Leo, R Hya, and R And and x Cyg but which is weak in Mira. No evidence of an absorption line at K corresponding to X4101 of In i at Eb is visible. The bright line X 4372.3 was tentatively identified by Thackeray and Merrill11 with the singlet Ti i (277) from the ViPJ level. It occurs in Mira between phases +75 and +220 days, with a maximum strength of about 5 at +130 days, but is not so strong as in x Cyg, R Leo, and R And. Measurements indicate that the line is displaced long ward on the basis of this identification by 4-5 km/sec; but if it is identified with the [Fe n] line X 4372.43 (21F), the displacements agree with those found for Fe n. Much the same result was found by Merrill for R Leo and R Hyd. The line X 4372 appears earlier and attains greater intensity than the other members of multiplet (2IF). The identification remains uncertain. The bright line X 4172.05 attributed by Merrill to Ga i is barely visible in Mira Ceti.

VELOCITIES FROM LINES OF METALS Since the bright lines of metals are sharp and of moderate intensity, they can be measured with high accuracy. On spectrograms of the highest dispersion, between phases +50 and +100 days, the strong emission lines XX 3852 Fe i, 3905 Si i, 4102 Si i, and 4307 Fe i are divided by a sharp absorption reversal. The separation of the emission components is about 0.2 A. Without exception, the emission lines are displaced shortward with respect to the absorption lines. When the emission first appears, the displacement of 15 km/sec is sufficient to separate the emission from the absorption lines, and the velocity measurements are not affected; but as the bright lines increase in strength, their displacements diminish (Table 8, g, and Fig. 4, g), and they encroach upon the absorption lines originating at a lower level. Thus the dark lines are apparently displaced longward. This effect is clearly shown (Fig. 4, c) in measures of the Fe i lines X 4202 and X 4307 of multiplet (42). Weaker absorption lines, such as X 3852.574 Fe i (73), are completely covered by emission at later phases. 11 Pub. A.S.P., 48, 331, 1936. ™Ap. 106, 283, 1947. 13 P. W. Merrill, Mt. W. Contr., No. 713; Ap. 102, 352, 1945; Mt. W. Contr., No. 720;^^. /., 103, 285, 1946; Ap. /., 116, 20, 1952; and A. H. Joy, Mi. W. Contr., No. 737; Ap.J., 106, 292, 1947.

Although great numbers of bright lines of metals may usually be measured between maximum and minimum light, the most accurate determination of the changes in velocity of the emission strata of the star’s atmosphere can be derived by limiting the measures to moderately strong lines which have a long lifetime covering as much as possible of the cycle of variation. For this purpose the nineteen bright lines of Table 9 were chosen, and the mean velocities determined from such of these lines as were measured on each plate are shown in the sixth column of Table 1. The number of lines used is in parentheses. The resulting mean velocity-curve from the “19 standard emission lines” is found in Figure 4, b (Table 8, b), and the corresponding curves for each successive cycle between October, 1945, and De- cember, 1950, are shown in the lower part of Figure 2. The curves of emission lines show less irregularity than those of absorption lines. As seen from the sun, the velocities of

TABLE 9 19 Standard Bright Lines

Upper Upper Line Element Multiplet E.P. Line Element Multiplet E.P. (Volts) (Volts) 4571.096. Mg I 2.7 4375.932 Fel 2 2.8 3829.355. 5.9 4206.702 3 3.0 3832.300. 5.9 4216.186 3 2.9 3838.293. 5.9 4202.031 42 4.4 4307.906 42 4.4 4102.926. Si I 4.9 4063.597 43 4.6 3905.527. 5.1 3949.954 72 5.3 3977.743 72 5.3 3907.476. Sc I 3.2 3852.574 73 5.4 4121.318 Co I 28 3.9 4045.386 31 4.1 3997.901 32 4.1 recession increase steadily from the time of the appearance of the lines, shortly before maximum, until their disappearance near minimum. The apparent change in the direc- tion of the mean curve at +130 days results from combining different cycles which are not exactly alike. In relation to the absorbing strata, the motions of the emission atmosphere are always outward. The difference in velocity is small at minimum light (Table 8, g; Fig. 4, g). The mean velocity-curves for single lines and groups of similar lines of neutral atoms are plotted in Figure 4, c (Table 8, c and e), and those of ionized atoms in Figure 4, d (Table 8, d). The Sr n, Ti n, and Fe n emission lines show small velocity variations with phase, but, as for the absorption-line velocities, they vary with excitation potential (see accompanying tabulation). The Fe i bright lines also show velocities correlated with ex-

Mean Upper Mean Element E.P. Velocity (Volts) (Km/Sec) Sr II. +47.5 Ti II, +48.9 Fe II. +54.3

© American Astronomical Society • Provided by the NASA Astrophysics Data System 54 ALFRED H. JOY citation potential, as Merrill14,15 has found in R Leo and in the variables T Cas, R LMi, W Hya, and T Cep. The lines XX 3852.574 (73), 3949.954 (72), and 3977.743 (72) (Table 8, c; Fig. 4, c), with mean E.P. of 5.3 volts, give consistently higher positive velocities than do XX 4063.597 (43), 4202.031 (42), and 4307.906 (42), with mean E.P. of 4.5 volts. The low-temperature lines XX 4206.702 (3), 4216.186 (3), and 4375.932 (2), E.P. 2.9, have nearly the same velocities as X4063 and X4202 until phase +100 days, after which the velocities of the low-level lines fall rapidly. The mean difference between the high- and low-excitation groups is about 2.5 km/sec from phases +40 to +110 days and +13.3 km/sec from +110 to +170 days. The line X 4307, for some unexplained reason, has a greater velocity range than X 4202 of the same multiplet (42).

MAGNESIUM At minimum light the ground-level intercombination line X4571.096 Mg\ (1), 31Sq—33PJ, reaches great intensity in emission, covering the absorption line completely. When its intensity is low, both before and after minimum light, it is seen on the shortward edge of the moderately strong absorption line. It usually appears at about +45 days and remains visible through minimum until about a month before the following maximum. The intensity varies in different cycles. At the minima of 1925, 1930, 1944, and 1946, X 4571 was barely seen on low-dispersion plates and disappeared after minimum. Except at the lowest temperatures, this line is weak in the laboratory because of its low transition probability; but, in the rarefied atmospheres of the Me and Se variables, its occurrence in great strength is generally permitted near the time of minimum light. The violet triplet of multiplet (3), XX 3829.355,3832.300, and 3838.293, with high excitation potential 5.92 volts, has a remarkably long lifetime with moderate intensity. CALCIUM The red triplet of C^n, XX 8498.018, 8542.089, and 8662.140, was observed in emission on five spectrograms taken near the bright maximum of December, 1936. The bright lines are superposed upon the wide absorption lines and appear fairly sharp, with intensities about 2, 3, and 4, respectively. The mean velocity from four plates with a dispersion of 20.7 A/mm is +45.6 km/sec. One plate by R. F. Sanford, taken on August 28, 1939, phase +23 days, gives a mean velocity of +49.1 km/sec for the three bright lines.

DISPLACED LINES OP Al I AND Cd II Merrill found that wide emission lines on the shortward wings of the strong absorption lines X 3944, X 3961, Al i, and X 3933, X 3968, Ca n (K and H), occur in several M- and S-type variables. In the spectrum of Mira Ceti X 3968 Ca n reaches considerable intensity, but X 3933 and the lines of Al are wide and weak, with maximum intensity at about + 140 days (Fig. 6). The bright Ca n lines become narrower with increasing phase, and their displacements (relative to the dark-line mean) become less, as shown in Table 10, in agreement with Merrill’s measures in other stars in which they attain greater intensity. The mean displacement of K is about 9 km/sec greater than that of H. The broad lines are unsymmetrical, the longward wing being stronger, and measures are affected by the intensity of the exposure. A similar displaced emission line of X 4226 Ca i ap- peared in September and October, 1943, but was not observed at other times. SILICON The singlets X 3905 (2) and X 4102 (3) of Si i are remarkably strong, and they are nearly as persistent in emission in Mira as are the hydrogen lines. Their high E.P. is 5.0

14 Ap. 116, 337, 1952. 344.

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1954ApJS....1...39J 6 1 6 asymmetry, themeasurement ofthelinesisnotgreatprecision. greatly atdifferentphases(Fig.6).ThelineX 4033.073 (2),themiddlememberof level ofX4172.05Gai, which isbrightinseveralofthelong-periodvariables. InMira double. Merrillsuggests thatenergyfromX4033maybetakenupin fillingtheupper ing considerablestrengthat+90days.Thegeneral appearanceoftheselinesvaries lines” istoolargeby0.181A.ThevelocitychangesresemblethoseoftheFenlines. triplet, isdepressedinsome starsobservedbyMerrillandshowsvery faint emissionin may bebrightattimes,butitisdoubtfulbecause ofthebandstructureinthatregion. uncertain. ThelineX3688.069(29)ispossiblypresent.measuredreachesanin- Ceti, however,X4172is extremelyweak.TheMnemissionispeculiar. Onaccountof Mira. InRAnditispresent inemission,andxCygitisstronger than X4034and X 4034.490haveemissionontheirshortwardedges frommaximumtominimum,reach- Other emissionlinesofCrareweakanduncertain. short-lived, showingbetween+20and+120days, withmaximumintensityatabout because themeasuredwavelengthfromsixplatesbasedonvelocityof“19bright mation aboutthevelocity-curve. placement asthe“19brightlines/’agreeswithlaboratoryvaluewithin0.01A.The strong lineofthemultiplet,X3911.810,doesnotappear.Theradialvelocitiesfrom E.P. 5.30,assuggestedbyThackerayandMerrill,isnotentirelyconvincing,largely +50 days.Thechieflineofthemultiplet,X3703.584, isblendedwith2716. X 3907(Table8,e)fallbetweenthoseofMgandSibutaretoofewtogivecertaininfor- tensity. TheidentificationofastrongbrightlinewiththesingletX4372.383Til(277), tensity of3,anditswavelengthreferredtothe “19brightlines”isX3687.968.It +134 may besufficienttoexciteelectronsofX3933.381Sci,whichhasthesameupperlevel only strongbrightlineofthiselement.AssuggestedbyMerrill,theemissionK(Can) -f 80 + 46 (see p.52).Thewavelengthfrom15plates,assumingthatithasthesamevelocitydis- mum light,noemissionappearsonanyofourplates. volts. ThelineX4102ismuchstrongerthan3905.NootherSiilinesfallintheregion three timesasstronginabsorptionX4045.815Fei(43)atphasesjustprecedingmini- usually observed. Mean Phase 2 ‘The ground-levelMni(2)tripletisstrongin absorption. ThelinesX4030.755and Although theabsorptionlinesofVarenumerous,theiridentificationinemissionis The greatground-levellinesofCri(1)showno emission.ThelineX4325.073(104) The emissionofTiiissurprisinglyweak,butseverallinesoiTinoccurwithlowin- The lineX3907.476Sci(8)aD—yF°seemscorrectlyidentified,althoughitisthe Although theground-levellinesX4044.145and4047.214Ki(3)becometwoor (Days) © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem X 3944,X3961 -47.2 (2) -47.9 (2) Mean Dis- placement (Km/Sec) the irongroup:Sc,Ti,F,O,Mn,Fe,Co,Ni Displacement ofWideBrightLines - 59.5(3) - 86.0(3) -107.4(1) Mean Dis- placement (Km/Sec) KandH Al IANDCaII MIRA CETI POTASSIUM TABLE 10 +170 +158 Mean Phase (Days) X 3944,X3961 Mean Dis- placement (Km/Sec) - 38.7(2) - 55.4(1) Mean Dis- placement (Km/Sec) K andH 55 1954ApJS....1...39J 14 56 represented moreorlesscompletelyintheFeiemission.TheupperE.P.levelsarefrom Multiplets (2),(3),(4),(20),(23),(24),(72),(73),(74),and(76),nearlyallquintets,are lines ofFengenerallyhavetheiroriginintheM-typestarandnotcompanion. mum light. prisingly longlifetime,coveringallthestar’speriodexceptafewweeksfollowingmini- maximum, muchlikethatoftheneutralemission;butotherFenlineshaveasur- of thecombinationmultiplet(3)representedbyX3914and3938takesplaceafter 2.8 to5.5volts.Thestrongerlinesappearatmaximumlight,reachtheirin- variables. TherelativeintensitiesoftheselinesonCe3216(September,1943,phase the first,levelsarequartetswithupperE.P.from4.8to5.6volts.Theappearance The spectrogramsnowavailablemakeitclearthatthepermittedandforbiddensharp in thespectrumofMirafromphase+130daysuntilminimumsomecycles(Fig.8,a). in xCyg(M6e+S),areTable11.Theyevidentlystrongeratsomeminimathan Me variablesobservednearminimum,buttheyhavenotbeennotedinS-,R-,orN-type tensity about100dayslater,anddisappearatminimumorsoonafter. Sharp brightlinesof[Fen]havealsobeenidentifiedbyMerrillinthespectraallother + 170days),togetherwithMerrill’sintensitiesofthesamelinesatanadvancedphase found inemission. for observation,butfive low-excitationlinesofmultiplets(2),(30),and (33)havebeen ness ofthestarattheseminimawasaboutnormal. The\Fen]emissionreachedgreatest low intensities. independent ofthesourcesluminosityin starandmayoriginateinfluctuating at others.Observationsbetweenphases+130and +240daysweremadein25ofthe39 identified. Theyappearabout10daysbefore maximum lightanddisappearatphase strength atthenormalminimaof1943and1945. Apparently,theintensityissomewhat that \Fen]mayremainconstantinintensitywhile thestarvariesinbrightness. streamers whichcanbeobservedonlyatminimum light.InRLeo,Merrillsuggests cycles, 1918-1952,but\Fen]lineswerecertainly presentinonly11cycles.Thebright- shortward edge oftheabsorptionlines andlastnearlyuntil minimum,attaining only + 100days,withgreatestintensityat+40days. TheNilinesarenotfavorablyplaced The forbiddenlinesofFen(6F),(7F),and(21F)aredefinitelypresentinemission Great numbersoflinesbothneutralandionizedFeatomsappearinemission. Several Fenmultiplets—(3),(27),(28),and(38)—aregenerallypresent.Exceptfor The SrnlinesX4077and X4215appearinemissionwellaftermaximum lightonthe Several faintbrightlinesofCöiinmultiplets (28), (29),(31),(32),and(34)were © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem 4243.97. 4287.40. 4276.83. 4352.78. 4319.62. 4305.90. P. w.Merrill,Mt.W.Contr.,No.735;Ap.106,274,1947. Line Multi- plet 21 21 21 21 21 7 ( +170 Days) o Get Forbidden LinesofFen Intensity ALFRED H.JOY X Cyg* ( +162 Days) 0.8 3 5 1.5 1 1 STRONTIUM TABLE 11 4416.27. 4413.78. 4359.34. 4358.37. 4457.96. 4452.11. Line Multi- plet 21 6 6 7 7 7 (+170 Days) o Get Intensity X Cyg* ( +162 Days) 0.8 3 3.5 2.5 1 1 1954ApJS....1...39J © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem

Fig. 8.—-a, Spectrum of Mira Ceti, XX4175-4495, Ce 3216, phase +170 days, showing [Feu\ lines..Spectrogram by P. W. Merrill, b, Spectrum of the companion of Mira Ceti. Ce 8516, November 28, 1952. Spectrogram by O. C. Wilson. MIRA CETI 57

INDIUM The presence of the In i line X 4511.310 in emission in moderate strength is well estab- lished. The bright line has the same long lifetime as Hb (see p. 52). UNIDENTIFIED LINES The strong emission lines of Table 12 have no satisfactory identifications. The wave lengths have been corrected for the mean velocities of the chief neutral metallic bright lines of each plate. The table shows two groups of lines. The lines XX 3735,4372, and 4455 have similar behavior. They appear about 2 months after maximum and disappear at minimum, reaching maximum intensity at about phase +180 days. They are sharp and resemble the neutral metallic bright lines in appearance. For X 3735.3 and X 4455.3 the TABLE 12 Strong Unidentified Bright Lines

Max. Strength Plates Possible Identifications Wave Length Meas- and Remarks ured Phase Int. 3735.351. 6 + 180 days X 3735.325 Fei (388)? 3956.082. 9 + 50 Wide, X 3956.270 Coi (2)? 4006.772. 7 + 50 Wide 4098.940. 9 + 50 Wide 4104.455. 8 + 50 Wide 4138.483. 5 + 50 Wide 4372.564. 7 +180 X 4372.383 Ti 1(211)7 4455.310. 10 + 180 X 4455.321 Ti i (113)? measured wave lengths suggest the identification of the last column. Unless their occurrence can be explained by fluorescence, these identifications seem unlikely because of their high excitation potentials. Lines of equal or greater strength in multiplets Fe i (388) and Ti i (113) do not appear in emission, although two other lines in the Ti I (113) multiplet have the same upper level as X 4455.321. The velocity changes are similar to those of X 4202 Fe I and X 4307 Fe I. The identification of X 4372 with Ti i (277) is doubtful on account of its wave length (see p. 52; also Thackeray, Observatory, 73, 83, 1953). All three of these prominent lines are stronger in Merrill’s spectra of x Cyg (M5e + S)6 and R And (Se)5 at phases 162 and 103 days, respectively, than in Mira Ceti. Their pref- erence for S-type sources may be a clue to their final identification. The five remaining lines of the table are quite different in appearance and behavior. They are wide (Fig. 7, Ce 1290) like the displaced lines oí Ah and Ca n described by Merrill in other long-period variables. On account of their nebulous appearance, they are often assumed to be bright spaces between absorption lines. Their high intensity and their position with reference to adjacent absorption lines indicate that some other explanation is needed. No identification for any of the five is evident. They have a short lifetime of from —15 to +90 days, with a maximum intensity at about +45 days. On some of the spectrograms of highest dispersion they appear to be made up of two or more components. The measures of velocity are reasonably accordant, considering the character of the lines, and show no variations which can be definitely correlated with phase. Merrill5 has measured X 4098 and X 4138 in R And but none of the five in x Cyg. THE VISUAL COMPANION Observations by double-star observers show no certain change in distance or position angle of the two components of the visual pair greater than the errors of measurement,

© American Astronomical Society • Provided by the NASA Astrophysics Data System 58 ALFRED H. JOY except that in 1926 G. van Biesbroeck estimated that the distance had diminished and Aitken16 made an uncertain measure of distance of 0''3 and position angle of 188°, when Mira was brighter than the sixth magnitude. This discordant observation deserves little weight, and Aitken17 suggests that it may have been an illusion. Nevertheless, a consider- ation of the distance of the companion from the primary and the masses involved leads to the conclusion that the motion of the companion in its orbit must have been sufficient to make an easily measurable change in its position since its discovery in 1923.18 Follow- ing this reasoning, P. P. Parenago19 has computed a probable orbit assuming periastron in 1927.0. The elements are: P= 14 years e = 0.7 0-131° a=0?50 ¿ — 85° co —150° Our spectrograms are not timed to contribute evidence either in support of, or in contra- diction to, this proposed orbit. It is possible that, with special care, spectrograms could be made which could be measured to find the displacement of the spectrum of the companion with reference to that of the M-type star, as was done at the time of the discovery of the companion, but such methods are subject to large errors on account of atmospheric

Fig. 9.—a, Visual estimates of the brightness of the companion of Mira Ceti by various double-star observers; b, estimates of the intensity of the spectrum of the companion from Mount Wilson spectrograms. dispersion and poor seeing. Visual double-star measures are more dependable, but they must be made when the red star is close to minimum light in order to be trustworthy. Estimates of the brightness of the companion before 1939 have been compiled by P. Baize.20 These magnitudes, together with additional values by W. H. van den Bos21 (1940-1945), P. Couteau22 (1952-1953), and eight estimates (1935-1951) by van Bies- broeck, kindly supplied in advance of publication, are plotted in Figure 9, a. The 1953 point at 10.5 mag. is from a Aw estimate of 1.7 mag. made by G. H. Herbig with the 36- inch refractor of the Lick Observatory on January 31 and reported in a personal letter. The total brightness of the double star on that date was 8.6, according to the A.A.V.S.O. observers. The values of the brightness of the companion are computed from estimates of the total brightness and the difference in magnitude of the components. The consist- ency of the estimates is poor on account of the difference in color of the components. Van Biesbroeck’s estimates {circles) are fainter than those of other observers. This lack of agreement may be, in part, due to instrumental differences. The curve indicates a real variation in brightness. Sudden changes have also been suspected by most observers. Systematic observations of this star are badly needed.

™Pub. A.S.P., 38, 334, 1926. 21 Union Obs. Circ., No. 108, p. 315, 1949. 17 Ibid., 42, 60, 1930. 22 /. des observateurs, 36, 46, 1953. 18 R. G. Aitken, Ibid., 35, 323, 1923. 19 Variable Stars, 7, 199, 1950. 20 Bull. Soc. astr. de France, 53, 360, 1939.

In comparison with the light-observations, the relative intensity of the spectrum of the companion at minimum light in successive cycles is shown in Table 13 and Figure 9, b. These estimates are subject to considerable uncertainty because the observations were made at different phases and the exact position of the star image on the spectro- graph slit is not known. Poor seeing and atmospheric dispersion may have disturbing effects. Nevertheless, a variation in the intensity of the spectrum of the companion relative to that of the Me variable is clearly indicated. More than two complete cycles with periods of 12-15 years have been covered by observations. Maxima of intensity of the companion occur about 1922-1924,1933-1935, and 1948-1950, with minima about 1927- 1929 and 1941-1943. These extremes of intensity are corroborated to some extent by the light-curve, which has maxima about 1922-1924 and 1936-1937 and minima at 1927- 1929 and 1942-1944. The minima of intensity correspond approximately to the times of periastron of Parenago’s elements. The explanation of such a coincidence is difficult unless, as seen from the earth, absorbing matter between or surrounding the stars cuts down the light of the companion when it is near periastron.

TABLE 13 Relative Intensity of Spectrum of the Companion at Different Minima

Minimum Int. Minimum Int. Minimum Int. May, 1918. Jan., 1930. Jan., 1942. Apr., 1919. Jan., 1931. Nov., 1942. Max., 1920 Dec., 1931. Oct, 1943. Jan., 1921. Nov., 1932. Sept,1944. Dec., 1921. Oct., 1933. Sept., 1945. Oct, 1922. Aug., 1934. July, 1946. Oct, 1923.. Aug., 1935. June, 1947. Sept., 1924. July, 1936. May, 1948. July, 1925. June, 1937. Mar., 1949. June, 1926. May, 1938. Mar., 1950. May, 1927. Apr., 1939. Feb., 1951. Apr., 1928. Mar., 1940. Jan., 1952. Mar., 1929. Feb., 1941. Dec., 1952.

While there are changes in the wide bright hydrogen lines and the accompanying absorption from time to time, the fluctuations are probably slow and not related to the 332-day cycle. On most of the plates showing hydrogen emission lines the violet emission component is weak or entirely absent, but in the years 1921, 1923-1925, 1933-1934, and 1944-1946 it was seen in moderate strength, although the high intensity shown in Plate Xc of Contribution No. 3111 is not equaled on any other plate. At the minima of 1924 and 1925 many fuzzy emission lines from the z4D° multiplets of Fe n were seen, apparently in the spectrum of the companion; but these lines have not been found in other years. Sharp lines of Fe n and [Fe n], which are frequently seen near minimum light, doubtless have their source in the atmosphere of the M-type star. The wide emission H and K lines of Ca n are cut by a narrow absorption line (Fig. 8, b). This line doubtless originates at a high level in the atmosphere of the companion and may indicate an expanding calcium shell. Probably it is not greatly affected by in- terstellar absorption. The velocities from measures of this line are given in the accompanying tabulation. Although the luminosity of the companion is certainly much fainter than that of stars of the main sequence, its spectrum resembles in many respects that of certain P Cygni stars of much higher luminosity. For example, the bright lines of hydrogen and their absorption components (Fig. 8, b) are much like those of BD+47°3487

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1954ApJS....1...39J 2324 28 27 7 variable butonthisplateareconsiderablywiderthaninBD+47°3487.Thecompanion lines. Thehydrogenseriesextendsto7720inemissionand7730absorption,while absorption componentssuchasarepresentintheFenlinesofBD+47°3487. is peculiar,inthatithas,exceptforthePCygnicomponentsofhydrogenlinesandi in thecompaniontoMiraCetibothbrightanddarkhydrogenlinesareseen7722on Beals estimatestheabsolutemagnitudeas—2.7fromstrengthofinterstellar 60 are 5-6Ainwidth.Thesebrightlinesapparentlyundisplacedandhavenoshortward He I,andperhapssometimeswideFenlinesappearinemission.TheiFeu O. C.Wilson’sspectrogramCe8516,November28,1952.Bothbrightanddarklinesare the narrowcoresofHandK,nootherabsorptionlines.Strongwidefuzzy convective zonewithcyclicmotionsaccountsformostoftheobservedphenomena.The proposed byMerrillinhisreportsonMeandSestars. realm ofspeculation.Satisfactoryexplanationsanumbertheactivitieshavebeen ances andthefundamentalcausesofrhythmicoutburststhesestarsarestillin fidence inourknowledgeofthesuperficialprocessestakingplaceatmospheres velocity rangethanthatpreviouslyfound,butadefinitevariationwithineachcycle ponents ofthedoublelinesisnotsufficienttoshow onotherplates.Recurrentturbulent rising andfallingofstrataatlowlevelsareneeded toaccountfortheobservedmotions tions nearminimumareinsufficienttocompletethecurve. light. Precedingandfollowingmaximum,thepositivevelocitiesareless,butobserva- high temperatureofthisstratummaysupplytheenergynecessaryforemissionlines. Mira Cetiandotherlong-periodvariablestarshasbeensecured.Theoriginofthedisturb- (MWC 374)B3eqdescribedbySwingsandStruveC.S.Beals.Forthisstar phase +55daysandattributedtheeffecttodifferential motionsintheatmosphereof seems certain.Maximumvelocityofrecessionoccursnearorshortlyaftermaximum confirmed. Themoreaccuraterecentobservationsofabsorptionlinesindicateasmaller be timedtocontributeevidenceconcerningthe possibilityofexplosiveorshockeffects, and tosupplyenergyforthevastarrayofemission features.Furtherobservationsshould effects mightbedifficulttodistinguishfrompulsation byvelocityalone. the star,assuggestedbyLymanSpitzer,Jr.The separationof0.2Abetweenthecom- lines ofMni,CrandninoCetionthe high-dispersion spectrogramCe2133at such aswerefoundbyR.F.SanfordinWVir. Adamsdiscoveredwidenedanddouble 26 2i 26 21 28 26 Pw¿. ^.5.^,64,222,1952. Pub. Dom.Ap.Obs.Victoria, 9,88,123,1951. ™Ap. 91,577,1940. As aresultoflargeobservationaleffortwithpowerfulequipment,considerablecon- McKellar andOdgersfindthattheapplicationofnotionalow-lyinghydrogen Explanations onthebasisofgeneralvolumepulsation areopentoquestion,butthe Ap./.,116,331,1953. Ap./.,90,494,1939. A.S.Eddington,M.N.,101, 177,1941. In general,theresultsofpreviousstudywithlow-dispersionspectrogramsarewell © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem P 39. P 36. P 24. Plate (Days) -f-116 +151 +128 Phase ALFRED H.JOY (Km/Sec) Velocity +52.0 +52.2 +52.4 DISCUSSION Ce 8516... Mean. . Plate (Days) +194 Phase (Km/Sec) Velocity + 52.7 +52.3 1954ApJS....1...39J ity fluctuations. layer fromphase—16daysuntil+40andthenseemstosubside,whereas tion. Thehydrogensourceincreasesitsvelocityofascentwithrespecttothereversing measurements ofthespectrograms. Wilson forspectrogramstakenatcriticalphasesandtoMissSylviaBurdmuchas- clusions, forthemostpart,areoutcomeoffrequentdiscussionsbetweenus. a dispersionof10.2A/mm,andhismethodattackhasbeencloselyfollowed.Thecon- is someindicationthatthesevariationsarecorrelatedwiththeluminosityandtempera- hydrogen displacements.ThecurveofemissionvelocitiesshowninContributionNo.311 ture atthemaxima,itmaybethatmeasureddifferencesarenotentirelyduetoveloc- is evidentlyacompositeofhydrogenandmetalvelocities. the sourceofemissionmetalsmaintainsaconstantnegativevelocitydifference sistance inanalyzingtheextensivematerial,aswellforhercontributionofprecise which isofthesameordermagnitudeasvariationwithinasinglecycle.Sincethere Ceti istheconclusionthatvelocitymaximavaryfromcycletobyanamount the spectraofM-andS-typevariables.Heobtainednearlyallspectrogramswith 15 km/secfrom—50daysuntil+40days,afterwhichthecurvefollowsthatof (Fig. 4,k)emissionlinesrelativetotheabsorptionspectrumisinterestinginthisconnec- The differencebetweenthedisplacement-curvesofmetallic(Fig.4,g)andhydrogen This paperonMiraCetishouldbeconsideredoneoftheseriesbyP.W.Merrill My thanksarealsoextendedtoW.S.Adams,I.Bowen,R.F.Sanford,andO.C. An importantresultofthesurveyvelocitiesfromabsorptionlinesMira © American Astronomical Society MIRA CETI61 Provided bytheNASA Astrophysics DataSystem *