COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 985 Konkoly Observatory Budapest 1975 April 12 NEW VARIABLE STARS IN THE FIELD OF M 16 - M 17 Eight years ago the writer noticed the marked increase of the number of Mira type variables when a field of stars is observed in infrared radiation (Maffei, 1967). At that time he also observed some differences in the behaviour of a few variable stars of different type when blue-infrared comparison was made. This finding was based on the photographs of stars fields just a few square degrees wide, and the Mira stars involved were only fifteen. In order to begin again the research on a statistical ground the writer started a systematic photographic search and observation of variable stars, in blue and infrared radiation, in 5 fields of some 25 square degrees each, at different galactic longitudes. The collection of the plates was effected with the two Schmidt telescopes of the Osservatorio Astrofisico of Asiago (mainly with the 90/65 cm telescope) beginning from the summer of 1967. 103a-O (without filter) and I-N (hypers.) + RG5 were used. The examination of the first of these fields, centred on alpha=18h14m delta=-14deg50' (1900.0), containing the objects M 16 and M 17, has led to the discovery of 198 new variable stars, almost all visible on the infrared plates only. The plates were compared by, means of the blink microscope of the Asiago Observatory. This operation was based on four pairs selected from 50 plates. A comparable number of plates obtained in blue light yields only 2 new variables. The main characteristics of the 198 variables are listed in Table I. The variables have been arranged in order of discovery. This numeration, characterized by the prefix M, will be continued in the remaining fields. The lack of some numbers is due to the exclusion of a few variables, not confirmed during the investigation following the discovery. The identification charts, light curves and a detailed account will be published, in a short time, in a more extensive work. Table I Var. A. R. (1950.0) Dec. m_{ir} Type P E N. 24...... M 1 18h7m14s -15deg14'38" 11.7 15.4 M 193d 40814 M 2 6 48 14 56 13 14.8 16.2 M or SR 320:: M 3 6 1 14 9 4 13.2 15.7 M 237 41110 M 4 8 8 14 26 43 13.8 16.1 SR: 390: 40404 M 5 8 10 14 23 50 15.6 16.5 M 6 12 8 15 49 17 15.4 16.2 SR: 350:: M 7 14 9 15 19 27 11.2 15.7 M 280 41198 M 8 9 26 14 25 26 12.4 16.0 M 460 41048: M 9 16 17 14 48 59 13.1 16.1 M 486: 40072: M 10 22 30 15 33 43 13.1 16.2 M 417 39758 M 12 13 1 19 39 48 11.2 15.1 M 334 41260: M 13 13 29 12 46 42 14.7 16.1 M or SR 288: 40810 M 14 17 14 12 45 21 13.9 16.2 M or SR M 15 26 31 15 9 59 14.3 16.2 M 362 39746 M 16 10 41 16 14 44 8.4 11.0 M 279 40784 M 17 8 52 15 9 41 11.7 15.9 M 510 40520: M 18 11 32 15 32 0 12.0 15.8 M 394 41220 M 19 7 6 14 21 21 14.5 16.2 M or SR M 20 6 38 14 8 25 14.2 16.1 SR:: 375:: 41246:: M 21 11 16 15 7 27 14.8 16.2 M 22 12 12 14 8 48 13.0 16.0 M: 400: 41040: M 23 24 30 16 17 32 14.2 16.9 SR:: 366:: 39680:: M 24 27 6 15 20 43 14.0 15.8 M 25 12 38 12 58 32 14.3 16.1 M 247 41143 M 26 24 23 15 51 28 13.5 17.1 M 444 41118 M 27 18 37 13 13 19 15.4 16.4 L: M 28 18 48 12 44 24 14.7 16.3 M 29 14 40 17 43 26 13.3 16.0 M:: 450:: 39748 M 30 5 30 15 24 32 14.0 15.9 SR 270: 41164 M 31 5 43 15 8 8 13.7 16.0 RV:: M 32 5 48 15 10 8 13.9 16.2 M 270 41178 M 33 7 32 15 23 2 13.2 15.9 M 338: M 34 8 10 15 36 37 12.8 15.9 M 202 41096 M 35 15 35 17 26 51 15.5 16.2 M 36 15 54 17 45 7 12.3 15.6 M or SR 396:: M 37 16 33 17 49 6 12.3 15.8 SR:: 135:: 41138: M 38 9 33 15 46 10 12.9 15.9 M 336 40806 M 39 9 25 15 48 11 12.3 15.3 M 204 40804 M 40 9 5 15 40 12 13.0 16.2 M 531 41128 M 41 9 28 15 23 29 13.8 16.4 SR:: M 42 7 37 15 8 35 13.6 16.4 M 482 41226 M 43 7 14 14 49 58 12.6 15.7 M 478 40815 M 45 9 15 14 55 37 12.6 16.2 M 285 40762: M 46 11 6 15 22 54 14.2 16.0 M 47 18 48 17 33 33 12.3 15.0 M 208 41144 M 48 18 28 16 44 23 12.0 15.6 M 49 9 17 14 45 33 14.6 16.5 M 210: 40840: M 50 7 47 13 52 1 11.8 15.6 M 434 40032 M 51 11 50 15 4 51 14.8 16.2 M 52 21 15 17 5 18 14.1 15.8 M or SR 390:: M 53 21 31 17 5 36 13.8 16.3 M 54 21 45 17 6 45 12.8 15.8 M:: 290:: M 55 13 54 15 10 39 11.4 13.6 SR: 490: 40836: Table I (cont.) Var. A.R. (1950.0) Dec. m_{ir} Type P E N. 24...... M 56 18h12m11s -14deg34'39" 13.0 15.5 SR 210d:: M 57 22 16 16 38 7 11.6 15.2 M: 442:: 41214 M 58 23 55 16 23 34 14.7 17.2 M: 298 41100 M 59 24 48 16 23 50 13.8 17.6 M 405: 41152: M 60 24 54 16 9 2 11.2 15.4 M 312: 41162 M 61 23 44 15 52 30 14.2 17.3 M 290 39745 M 62 12 31 13 9 51 12.8 16.2 M:: 500: 41066: M 63 24 23 15 34 19 14.0 16.4 M 384: 40754 M 64 25 14 15 56 45 13.5 17.0 UG or RW M 65 26 20 15 39 41 15.6 17.2 M 250:: 41238:: M 66 25 27 15 27 47 12.9 15.9 M 313 40055 M 67 25 50 15 24 52 12.6 15.3 M 298 40458 M 68 25 39 15 21 22 13.7 16.4 M 315 39740: M 69 23 17 14 49 5 12.1 14.7 SRc M 70 13 31 12 45 6 14.9 16.1 L: M 71 22 9 14 19 56 12.2 15.9 M:: 522:: 41142 M 72 24 8 14 43 41 7.6 11.6 M 400 39758 M 73 25 5 14 50 35 12.5 16.8 M 322 40478: M 74 25 29 15 7 58 12.8 16.4 M 310 40082 M 75 25 44 14 58 17 13.2 16.0 M 319: 39749 M 76 27 59 15 39 37 12.8 16.2 M: 41164 M 77 28 44 15 29 8 10.0 15.5 M 468 41158 M 78 28 33 15 20 31 12.1 15.6 M 428:: 40137:: M 79 26 10 14 45 52 12.0 15.4 M 312 39720 M 80 26 3 14 31 20 12.1 15.4 M 477 40804 M 81 17 10 12 37 35 12.4 15.9 M 310 40826 M 82 17 48 12 9 59 13.8 15.8 M: 304 39730 M 83 21 23 13 17 35 14.5 16.0 L: M 84 27 23 14 27 22 11.4 15.0 M 302 41100 M 85 27 53 14 54 53 11.3 14.1 M 264 41170 M 86 13 52 16 53 20 12.6 15.5 SR:: 365: M 87 24 60 13 45 3 12.9 13.9 L: M 88 14 39 17 33 13 14.9 16.0 SR: 39744 M 89 8 13 16 13 40 13.4 15.2 M or SR 360:: M 90 5 34 15 35 37 11.2 16.0 M 256 40860 M 91 5 38 15 34 20 15.4 16.3 M 92 5 44 15 4 30 12.0 14.0 R CB: M 93 8 31 15 38 12 14.4 16.3 SR or M 210 41222 M 94 8 41 15 45 1 14.2 16.7 SR: 320:: M 95 9 2 15 40 58 13.1 16.0 M 396 40790 M 96 16 33 17 47 6 13.8 15.8 M:: 400:: 39750:: M 97 17 2 17 44 28 12.9 15.4 M:: 450:: 40424:: M 98 8 57 15 38 5 13.4 16.4 M 465: 40928:: M 99 17 24 14 52 9 14.0 16.1 M100 6 27 14 38 44 14.5 16.6 M or SR M101 5 21 14 34 49 10.9 15.9 M 358 41244 M102 5 3 14 31 52 14.0 16.4 M:: 360:: 40860:: M103 5 35 14 18 37 14.3 16.4 M or SR 400:: 41136 M104 6 44 14 27 14 14.5 16.0 SR M105 7 8 14 51 52 12.2 15.4 M 316 40410 M106 8 48 14 47 49 11.7 15.4 M 434 41092 M107 9 42 15 21 46 14.5 16.2 SR: M108 18 14 17 7 46 13.7 16.3 M or SR Table I (cont.) Var. A. R. (1950.0) Dec. m_{ir} Type P E N. 24...... M 109 18h20m12s -17deg22'43" 13.3 14.8 M or SR M 110 14 5 15 54 30 13.1 16.2 M:: 365:: 41224 M 111 19 6 16 35 35 14.8 16.4 M 112 21 24 17 9 0 13.3 15.8 M or SR 390:: 41144:: M 113 22 11 17 5 42 14.6 16.0 M 114 14 45 15 3 35 11.2 12.1 E M 116 8 27 13 36 22 14.3 16.4 M or SR M 117 11 56 14 9 7 11.6 14.7 M 213 40808 M 118 18 31 15 43 10 14.5 16.1 M or SR M 119 21 34 16 11 47 13.8 17.2 M 608 39734 M 120 22 46 16 35 33 11.2 15.3 M 379 41247 M 121 16 45 14 40 48 11.6 12.7 M: 226: 41124 M 122 15 49 14 46 2 12.0 15.1 M: 388 41100 M 123 23 54 15 59 23 14.7 17.2 M 374 37556 M 124 24 59 16 24 3 14.4 17.4 M 410:: 40432:: M 125 25 2 16 23 30 16.1 17.4 M 126 25 26 16 23 9 13.2 16.6 M: 510:: 41092: M 127 25 45 16 5 25 15.0 16.9 M or SR 41186 M 128 24 2 15 42 17 14.1 17.4 SR: 227:: 39722 M 129 13 58 13 15 45 11.7 16.2 M 450 40844 M 131 12 38 12 51 21 13.9 16.2 M or SR M 132 13 44 12 43 22 14.8 16.6 M 134 26 31 15 49 31 11.5 15.4 M 450 39712 M 135 26 40 15 50 43 11.7 15.2 M 716 40394 M 136 27 10 15 30 35 15.0 17.0 M or SR M 137 27 22 15 29 29 14.6 17.2 SR:: M 138 22 49 14 44 49 12.7 15.3 SR 400:: 39684:: M 139 17 28 13 10 38 14.3 16.0 380:: M 140 17 11 13 11 0 12.9 16.0 M 506 40448 M 141 15 25 12 11 35 12.0 15.8 M 407 41058 M 142 15 26 12 28 18 12.3 15.8 M 420 41220: M 143 16 34 12 25 7 12.1 15.8 M 410 40424 M 144 16 49 12 35 47 13.6 15.9 SRc: M 145 25 42 14 58 31 13.9 16.0 M 366 41164 M 146 25 26 14 14 20 11.3 15.2 M 378 41098 M 147 20 27 13 3 12 14.4 16.4 SR: 486:: 40020:: M 148 17 36 12 30 5 13.9 15.8 M 259: 40798: M 149 21 34 12 53 49 10.4 15.4 M: 600: 40388:: M 150 25 21 13 46 30 14.4 15.8 M 151 26 50 14 2 21 12.2 15.6 M 468 41104 M 152 27 8 14 12 16 13.5 16.1 M 416:: 41064:: M 153 27 46 14 18 28 14.0 15.6 M 354: 41214: M 154 27 38 14 23 41 12.9 15.4 M 405 41120: M 156 9 28 15 5 50 11.6 12.7 EA M 159 18 54 13 2 10 14.1 15.5 EA M 161 14 24 17 35 16 15.3 15.9 M 162 8 20 16 4 9 14.7 16.5 SR:: M 163 6 17 15 51 53 13.2 16.4 M 288 41238 M 164 6 32 15 20 7 10.1 13.4 M 239 41214 M 165 6 14 15 19 8 13.0 15.7 M 166 7 32 17 32 39 15.2 16.4 M 167 8 20 15 46 5 14.8 16.3 SR:: 330:: M 168 16 39 17 49 57 12.4 15.6 M 286: 39720 Table I (cont.) Var. A. R. (1950.0) Dec. m_{ir} Type P E N. 24...... M 169 18h17m 4s -17deg32'54" 14.7 16.0 L: M 170 15 59 17 19 45 14.1 16.0 M 172 5 45 14 48 5 14.5 16.7 M 173 5 11 14 44 38 14.0 16.3 M or SR M 174 6 23 14 30 20 15.0 16.2 M 175 13 51 15 52 13 13.8 15.0 M 176 10 2 14 47 4 14.2 16.0 M or SR 200:: 41190: M 177 7 37 14 26 43 13.1 16.3 218 39720 M 178 13 15 14 59 54 14.4 16.5 SR: 280:: M 179 12 46 15 6 35 15.1 16.4 M: 298:: 39738 M 180 13 10 15 19 6 12.5 15.9 M 458 41104 M 181 12 34 14 3 7 14.5 16.4 M or SR M 182 14 51 14 36 8 13.7 16.4 L: M 183 22 54 15 13 32 16.0 16.8 M 184 22 17 16 12 19 16.2 17.2 M 185 21 49 16 10 51 15.5 17.2 M:: 268: 40800 M 186 13 56 13 42 22 15.3 16.4 M 187 22 10 15 42 49 14.3 16.8 M:: SR:: 400:: 41152 M 188 23 0 15 33 55 14.4 16.7 M: 416 41240 M 189 15 9 13 6 4 13.8 16.0 M 290 41192 M 190 17 49 13 34 10 12.8 15.0 M 190 41160 M 192 25 37 15 8 25 13.8 16.8 M: 418: 40849: M 193 25 21 15 16 34 13.6 16.4 M 478:: 41164 M 194 14 47 12 40 29 13.2 15.4 M or SR 700:: M 195 16 1 12 25 0 11.9 16.0 M 196 16 24 12 36 13 13.6 16.0 M 197 17 57 12 54 12 13.0 15.8 M 400 41186 M 198 26 11 14 48 56 12.5 16.1 M 335: 37558 M 199 27 2 14 59 56 14.1 15.8 M 330 39720 M 200 28 50 15 14 24 12.0 15.8 M 448:: 37870: M 201 26 48 14 48 11 14.4 16.0 M 318 41168 M 202 27 25 14 33 31 11.0 14.9 M 400 39758: M 203 20 21 12 39 32 14.6 16.1 SR 400 M 204 24 45 13 40 44 12.3 15.6 M 376 37570 M 205 27 24 14 23 39 12.9 15.5 M 301: 41126: M 206 28 34 14 45 58 12.7 15.9 M: 460:: 39690: M 207 10 8 14 55 19 13.3 16.6 M 480 40756 M 208 27 6 14 44 52 12.9 14.6 SR:: Of the 198 new variables, 108 have-been classified as Mira type stars and 25 as SR. Before this research only 31 variables were known in the field. From this number we have excluded 52 variables of RWn type, found by Walker (1961) in the cluster M 16, fainter than m_{pg}= =20 and therefore below the limit magnitude of our research.Those of Mira type were 7, all discovered by the writer, with the same infrared technique. This result confirms the very strong increase of the number of Mira type stars when the observations are made by means of infrared technique. Moreover the most frequent period of these new infrared Miras is some 100 days longer than that of the known Mira stars,in the direction of the galactic centre. This is shown in Fig. 1, where the histogram constructed with the periods of the new Miras is compared with that obtained by Romano and Di Tullio (1970) for the Miras in the zone of the galactic centre given in GCVS. [FIGURE 1] Fig.1 Number of Mira variable stars (normalized at SummaN = 100) as function of the length of the period. Left: the results of Romano and Di Tullio, for the region of the galactic centre; right: present results. The increase of the period's length proves that the rise in number of Mira stars must be mainly due to physical effect and not only to the diminished effect of the interstellar absorption by using infrared technique. In other words, while, till now, the blue variable stars have been favoured by the photographic or photoelectric (U,B,V) techniques of observation, the study of the Mira stars can start to advance toward a reasonable completeness only at present, through these infrared observations, which favour the stars which are redder, cooler, imbedded in circumstellar envelopes, etc. Other prospects appear from the study of the light curves in the infrared. The first result on this subject will be published in the next issue of the IBVS. PAOLO MAFFEI Cattedra di Astrofisica dell'Universita di Roma References: G. Romano and G. Di Tullio (1970) - Mem. SAIt vol. 41, p. 495 [BIBCODE 1970MmSAI..41..495R ] P. Maffei (1967) - Astrophys.J. vol. 147, p. 802 [BIBCODE 1967ApJ...147..802M ] M.F. Walker (1961) - Astrophys.J. vol. 133, p. 438 [BIBCODE 1961ApJ...133..438W ]