PMS-OBJECTS IN THE STAR FORMATION REGION Cep OB3. I. STARS WITH Hα EMISSION

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1 Astrophysics, Vol. 56, No. 1, March, 2013 PMS-OBJECTS IN THE STAR FORMATION REGION Cep OB3. I. STARS WITH Hα EMISSION E. H. Nikoghosyan Results are presented from a detailed analysis of PMS stars located in the star-formation region that includes the bright part of the ionization front of the molecular cloud Cep B. Slitless spectroscopy is used to detect 149 stars with Ha emission. Models for the distribution of the spectral energy are constructed for 203 PMS stars based on photometric data in the visible and infrared and their basic parameters are determined. A good correlation is observed between the Hα emission intensity and the infrared excess. The relative disk mass and degree of accretion for stars with EW (H α) > 10Å and α > 1.8 are about an order of magnitude greater than for the other stellar objects. The average distance and age of the PMS stars in the cluster are 890 pc and 0.74 million years, respectively. The stars with EW (H α) > 10Å and α > 1.8 are more than 0.5 million years younger than the others. Keywords: star-formation regions: stars: emission: young stellar objects individual: Cep OB3b, S 155, Cep B 1. Introduction The molecular cloud Cep B and the adjacent eastern part of the association Cep OB3 are an active starformation zone. The association consists of two main groups of stars, Cep OB3a and Cep OB3b, with ages of and , respectively [1]. The younger of these is Cep OB3b which appears to be the result of a secondary wave of star formation [2] and adjoins the molecular cloud. Between the molecular cloud and the association there is a V. A. Ambartsumyan Byurakan Astrophysical Observatory, Armenia; elena@bao.sci.am Original article submitted November 20, 2012; accepted for publication December 5, Translated from Astrofizika, Vol. 56, No. 1, pp (February 2013) /13/ Springer Science+Business Media New York

2 bright, extended HII region, Sharpless 155, which is nothing other than an ionization front caused by the interaction of the short wavelength radiation from hot stars in the association with dense cold matter in the molecular cloud [3,4]. The entire region is estimated by various authors to lie at a distance of from 725 to 850 pc [5]. The search for and study of the young stellar population in this star-formation region have led to the discovery of more than 30 stars with Hα emission [6], several hundred x-ray sources, and stars with an infrared excess [7,8]. A compact group of young infrared stars has been discovered [9] based on data from the 2MASS survey in the neighborhood of the IRAS source, which is associated the Cep B nebula. This paper is devoted to the search for and study of young stars in this star-formation region, specifically, stars with Ha emission. The results of the search are described in Section 3. In Section 4 we examine the relationship between the color indices in the near and middle infrared for these emission stars. 2. Observations and data analysis Images of the region being studied were obtained at the primary focus of the 2.6-m telescope at the Byurakan Observatory with the aid of the SCORPIO camera and a pixel CCD array. The field and scale of the resulting images are 14 14' and 0.42"/pixel, respectively. The FWHM of the images does not exceed 2".5. V and I filters in the Cousins photometric system were used for the photometric observations. Stellar magnitudes of the cluster NGC 7006 were used as photometric standards. Slitless spectroscopy with a grism that has a dispersion of 2.1 Å/pixel and a narrow band Hα interference filter (λ c = 6560 Å and Δλ = 85 Å) were used to search for Hα emission objects. Images were obtained in four slightly overlapping zones. The coordinates, observation dates (day.month.year), and total acquisition times (s) for each zone are listed in Table 1. The standard procedure was used for initial processing of the images. The stellar magnitudes were determined using the IRAF program. The error in the stellar magnitudes are less than ~0 m.04. The equivalent with EW ( Hα) was measured using the MIDAS program. The errors in the equivalent width were determined using a formula taken from Ref. 10: ( W ) = + Fc F ( Δλ W ) ( S N ) σ 1, where Fc is the average continuum level, F is the emission in λ λ TABLE 1. Observation Log Zone RA (2000) Dec (2000) Hα V I Hα V I I II III IV

3 the spectrum line, and S/N is the signal-to-noise ratio. For objects with R < 17.0 the errors in measuring EW ( Hα) are less than 30% and for fainter objects the errors increase to 40% of EW ( Hα). For some of the objects we determined stellar magnitudes within the ranges of the IRAC camera at the Spitzer telescope. For this purpose we used publically available images from this data base (AORKEY: , , ). Stars in these same images for which the stellar magnitudes were already known were used as secondary standards. We also used photometric parameters of stars from the 2MASS and WISE data bases [11,12] and V and I stellar magnitudes taken from Ref Stars with Hα emission The search for stars with Hα emission was conducted in an area of ~20 20' that includes the northeast part of the association Cep OB3b, the HII region S 155, and the northwest part of the molecular cloud Cep B. An image of this region is shown in Fig. 1. The zone for the emission star search was specially chosen so that it coincided with the regions of x-ray and infrared observations, so that about 650 PMS stars were identified [5,7]. This allowed us to make a comparative analysis of the signs of activity in young stellar objects within different spectral bands. A total of 135 stars with Hα emission were found. Their parameters are listed in Table A1 (see the Appendix), which includes the following data: (1) sequence number. The sequence number of the objects in Table 1 of Ref. 7 are given in parentheses which provided data on the x-ray sources found within this zone; (2) and (3) coordinates of the objects determined using the DSS2 R charts. Two of the objects (37 and 38) form a very close pair and all the parameters except the coordinates were determined jointly for these objects; and, (4) the equivalent width EW ( Hα). This quantity was not determined for a large number of these objects (indicated by f.c. for faint continuum), either because of the low brightness of the object or because very bright Ha emission from the field was projected on it. In those cases where EW ( Hα) of a given object was not determined, this is indicated in parentheses. References on the existence of Hα emission for these stars are also given in the parentheses. In two cases (objects 45 and 99) there was a substantial spread in the estimates of EW ( Hα). Besides the above mentioned 135 stars within the region being studied, another 14 stars with Hα emission have been found earlier but were not resolvable in our images. Weak absorption was observed for another 8 stars that had been previously noted as emission objects. The major parameters of these objects are listed in Tables A2 and A3, respectively. The designations of the columns are the same as in Table A1. Weak absorption in the Hα line has also been detected in 39 of the x-ray sources in Table 1 of Ref. 7. Data for these are given in Table A4. The other PMS objects indicated in these references [5,7] were not adequately resolved in our images. Models of the spectral energy distribution for PMS stars, described in detail elsewhere [14,15], have been constructed for all of these stellar objects (except for three). The spectral energy distributions were constructed using the following photometric data: V, I [13], BRJHK (2MASS), 3.6, 4.5, 5.8, and 8.0 μm (Spitzer, IRAC), and 3.4, 4.6, 12, and 22 μm (WISE). The distance to the cluster was taken to be within the interval from 700 to 900 pc [16,17] 28

4 50'00" Decl. (J2000) 40'00" +62 o 30'00" 22 h 58 m 00 s 57 m 00 s 56 m 00 s 55 m 00 s R.A. (J2000) Fig. 1. A DSS2 R image of the region being studied. The dashed box indicates the search region for Hα emission stars. The smooth box outlines the search region for x-ray sources [7]. and the absorption (A V ), within the interval from 0 m.1 to 15 m [5]. Of all the proposed models, the most probable 2 was chosen; for the overwhelming majority of the stars χ does not exceed 150. The stellar magnitudes in the optical (V, I) and MID (4.5 and 8.0 mm) ranges for some of the stars were not known previously and were determined by us. The photometric results are listed in Table 2. The tables on the internet ( "On line data.pdf") provide more detailed information on the parameters of these stellar objects derived from the models of the spectral energy distribution. These parameters include the slope α of the spectral energy distribution in the range from 3.6 to 8.0 μm, which characterizes the evolutionary status of a stellar object. Objects with α > 1.8 and a gently sloping spectrum belong to evolutionary class II with a distinct optically thick disk component. A slope α > 2.56 corresponds to objects in evolutionary class III, for which the disk component has evolved to a great extent and which have a very slight infrared excess. The objects with 2.56 < α < 1.8 belong to an intermediate evolutionary class with an optically thin disk (Class II/III) [18]. The tables also list the absorption, distance, age, mass, temperature, bolometric luminosity, disk mass, and degree of accretion. The internet tables also give photometric data for these stars taken from the above mentioned data bases. Overall, we found 135 stars with Hα emission; emission had been reported previously for only 26 of them. In effect, we were able to detect the presence or absence of emission for all the objects brighter than V = The difference in the estimate of whether emission is present or absent (see the objects in Table A3) can be explained either by differences in the method of observation or by the variability of an object. A model of the spectral energy 29

5 TABLE 2. Stellar Magnitudes Object V I 4.5 μm Table A1 8.0 μm Object V I 4.5 μ m 8.0 μm Table A Table A Table A distribution was constructed for 203 of the stars. Most of them are x-ray sources. We now compare our parameters with those reported previously. The interstellar absorption A V ranges from 0 m.1 to 8 m.2 in our case, with A V = 1. 9, while the average distance of the stars, i.e., the distance to the cluster, is 790 pc. Based on the position of the stars on an HR diagram (J/J-H) for a fixed distance of 725 pc, the same sample of stars yielded [7] a value of A 3 m V =. 1. That is, in our case the average interstellar absorption is ~1 m smaller, but then the distance to the cluster is larger. Note that a gradient in the interstellar absorption has been observed 30

6 TABLE 3. Percentage of x-ray Sources and Objects with Different Slopes of the Spectral Energy Distribution Group N X ray α > < α < -1.8 α < EW(H α) > 10Å (64%) 39 (100%) - - EW(H α) < 10Å (92%) 24 (32%) 9 (12%) 42 (56%) Faint cont (38%) 23 (68%) 6 (18%) 5 (14%) Absorption (95%) 5 (9%) 7 (12%) 45 (79%) within the region being studied. In Cep OB3 A V is lowest at ~1 m.5, while in S 155 and Cep B it rises to 3 m.0. These values are in good agreement with published data [16]. With respect to EW(Hα), the stars are conventionally divided into two main groups. The first is CT Tau objects with EW ( H α) > 10Å up of WT Tau objects with EW ( H α) < 10Å, for which Hα is mainly produced as a result of accretion activity. The second group is made, for which the emission is manly produced by chromospheric flares. These objects are in a later stage of evolution. Those stars whose equivalent width was not measured because they are not bright enough, probably also belong to the first category, but they will, nevertheless, be examined separately. A fourth group is made up of stars for which absorption is observed in the Hα line. Table 3 gives the percent of x- ray sources and objects with different spectral slope a for each of these four categories. The data of Table 3 show clearly that all the objects with strong Hα emission, as well as most of the stars for which EW(Hα) was not measured, have a gently sloping spectral energy distribution, which can be explained by the presence of an optically thick disk component. In terms of their spectral energy distribution, most of the stars with faint emission and absorption, however, belong to later evolutionary classes. In fact, in the latter case the percentage of objects in class III is considerably higher. It should be noted that 13 of the 24 stars in the second group with α > 1.8 have EW(Hα) > 7 Å It is possible that errors in the determination of EW(Hα) could lead to incorrect classification of an object. The percent amount of x-ray sources among the CT Tau stars is considerably lower than among the WT Tau stars. This is entirely to be expected. A similar pattern has been observed in other young stellar clusters [19]. The lower percentage of x-ray sources in the third group appears to be explained by the relative faintness of these stars, which also meant that their EW(Hα) could not be determined. Table 4 lists the averaged data (age, relative disk mass, and degree of accretion) for objects in these four groups chosen with respect to EW(Hα) and stars with different slopes of their spectral energy distribution. These data show clearly that the relative mass of the disk and the degree of accretion in the youngest (from the standpoint of evolution) categories (EW(Hα) > 10 Å and α > 1.8) is almost an order of magnitude higher than for the others. A massive optically thick disk can substantially absorb the star s x-ray emission, which usually accompanies the accretion process. This can to a certain extent explain the relatively low percentage of x-ray sources 31

7 TABLE 4. Age, Relative Disk Mass, and Degree of Accretion Group EW(H α) > 10Å EW(H α) < 10Å Faint cont. Absorption α > < α< -1.8 α< N Age M disk /M star Deg. accretion among the emission stars. The objects for which the equivalent width was not determined also have a relatively more massive disk component, but their degree of accretion is essentially the same as for the other groups. Most likely, a small fraction of these stars nevertheless belong to the WT Tau stars, which is also reflected in the data of Table 3, and this distorts the overall picture somewhat. The stars in the first and third groups have the lowest ages. As the Hα activity decreases, the median age increases. The difference in age between CT Tau and the absorption stars is ~10 6 years. Roughly the same picture is observed when the stellar objects are sampled with respect to their spectral characteristics. As the slope α of the spectral energy distribution increases, the median age of the objects also rises, with the difference between stars in the first and third evolutionary groups also being ~10 6 years All objects Hα emission Hα absorption log(n) log ( M ) M Fig. 2. The distribution of mass 32

8 The median age for all the stars in Tables A1-A4 is 0.74 million years. Thus, the mean values of the distance and age for the region as a whole are 890 pc and 0.74 million years, respectively, in good agreement with the second estimate of these parameters given in Ref. 5, 890 pc and 0.5 million years. Note that no significant difference was observed between the distances and ages of stars lying in different regions. Figure 2 shows the distribution of log ( M ) M. It is very similar to the mass distribution in Ref. 5 derived from a large number of objects, where the mass was determined from the HR diagram for fixed values of the distance (725 pc) and age (1 million years). A small deficit of objects with mass ~ 1 M and a distinct maximum in the range M is also observed among the emission stars; this is difficult to explain. The deficit of low-mass stars among the absorption objects compared to the emission objects appears to be explained by selectivity in the sample. In addition, a deficit of low-mass stars is also observed in Cep B and S 155. The median mass of the stars in these regions is ~0.75 M, and in Cep OB3, ~0.44 M. This is evidently a consequence of the difference in the interstellar absorption in these regions. Based on the mass distribution, we can effectively conclude that the emission stars in the association Cep OB3 are complete up to objects with masses greater than 0.45 M. With respect to the values of the temperature T, the overwhelming majority of the emission stars belong to spectral classes ranging from F2 to M7. Five of the objects have earlier spectral classes of B7-B9. No significant difference between the spectral classes of the CT Tau and WT Tau stars was observed. 4. Near and mid infrared photometric data Two-color diagrams for the objects in Tables A1-A4 are shown in Fig. 3. Photometric data were taken from the 2MASS (JHK), IRAS Spitzer (3.6, 4.5, 5.8, and 8.0 μm) [5], WISE (3.4, 4.6, 12.0, and 22.0 μm) data bases to construct these diagrams. It should be noted that ~20% of the objects from Tables A1-A4 are, nevertheless, not complete in terms of stellar magnitudes in the mid infrared range, so their are fewer of them in the diagrams than indicated in Table 3. The JH/HK diagram. The position of the main sequence (MS) is taken from Ref. 20. The formulas from Ref. 21 were used to construct the reddening vectors. It is quite clear from the diagram that there is fairly good correlation between the Ha emission intensity and the color indices in the near infrared. All except two of the stars with strong emission lie within the region of the T Tau locus [22]. The overwhelming majority of the star with faint emission lie near the MS. Of the 15 objects which fall into the region of the T Tau locus (H-K > 0.4), 14 have α > 1.8. Of these, 7 have values of EW ( Hα) high enough that they could, to within the error in measuring the effective width, be classified as CT Tau stars. The overwhelming majority of the f.c. (faint continuum objects lie in the region of the CT Tau stars. Only 7 are localized at the MS. Two of these have α > 1.8. Most of the absorption stars also lie in the region of the MS. Only two of them have a significant infrared excess, in one case with α > 1.8. Two of the five emission stars with early spectral classes lie in the region of Ae/Be Herbig stars [23]. Their masses equal 2.3 and 3.3 times that of the sun. 33

9 J - H Å Å faint continuum absorption [3.6] - [4.5] H - K 1.0 [5.8] - [8.0] [3.4] - [4.6] [3.4] - [4.6] [4.6] - [12] Fig. 3. Two-color diagrams [12] - [22] Spitzer (IRAC). The boundary values for the positions of the stars in the various evolutionary classes were taken from Ref. 24. The formulas from Refs. 25 and 26 were used to construct the reddening vectors. The position of the stars on the diagram is well reflected in the data of Table 3. The WT Tau stars with α > 1.8 also have color indices that correspond to evolutionary class II. They also include the objects for which EW(Hα) is largest, as noted above. Of the stars in the f.c. group only those for which α < 2.56 fell into the region of evolutionary class III. The position of the absorption stars is also in good agreement with the data from Table 3. Objects with α > 1.8 are found in the region of evolutionary class II. WISE (Wide-field Infrared Survey Explorer). We have also used photometric data from this relatively recently completed survey for classifying the PMS stars. Its spectral ranges correlate fairly well with the ranges of the IRAC and MIPS cameras of the Spitzer telescope. The position of the MS stars are taken from the website of this data base. The formulas from Refs. 25 and 26 were used to construct the reddening vectors. It can be seen clearly in the diagrams that objects in evolutionary classes II and III have essentially the same positions with respect to the color indices [ ] as in the Spitzer-a diagram with respect to the [ ] range. This result is fully to be expected, since the ranges essentially overlap and are in good agreement with the position of stars in classes II and III on an analogous diagram in Ref. 27. With respect to the color index [12-22], the objects have much wider scatter 34

10 than with respect to [ ], which is entirely explainable from the standpoint of the features of the radiation from the disk component of PMS stars. An increase in the brightness at ~10 mm can be seen in many cases in the spectral energy distribution of PMS stars in evolutionary classes II and III; this is reflected in the diagram. This is typical for stars that have sufficiently developed disks with a nonuniform structure and a significant deficit of dust is observed in the interior regions located near the star, which leads to red shift of the spectral energy distribution of the disk component [14,28-30]. In this regard the 24 mm band of the MIPS camera in the Spitzer telescope is very productive for diagnostics of the stars in evolutionary class III [14,28-30]. This is also reflected in the second two-color diagram for WISE, where it can be seen clearly that all objects in class III are shifted to the right from the MS, i.e., all the objects have an infrared excess in this range. 5. Discussion and conclusion Slitless spectroscopy in a region covering the bright part of the ionization front of the molecular cloud Cep B has revealed 135 Hα emission stars. This emission has been discovered for the first time for the overwhelming majority of these stars. Taking earlier reports into account, a total of about 150 emission stars have been found in this region. In terms of the richness of a population with Hα emission, this region can be compared with the Herbig fields, in particular with the clusters IC 348 [32], Lk H α 101 [33], L988 [34], and IC 5146 [35]. Based on visible and near and mid infrared photometric data, models of the spectral energy distribution have been constructed [14,15] for all the stars and their major parameters determined: mass, temperature, age, absorption, distance, disk mass, etc. In addition, the equivalent width for Ha absorption has been measured and spectral energy distributions have been constructed for another 49 x-ray source stars [7] which are well resolved in our spectral images. A significant gradient in the interstellar absorption has been observed in the region under study. The average interstellar absorption in Cep OB3 is A 1 m V =. 5, or almost a factor of two higher than in S 155 and Cep B. These values are in fairly good agreement with previous work. The average distance of 890 pc and the median age of the stellar objects in the cluster of 0.74 million years are in good agreement with a second, younger variant derived for young stars on the basis of x-ray and mid infrared data [5]. In the overwhelming majority of the cases examined here, the emission objects are low-mass stars with a fairly wide range of spectral types from F2 to M7. Some of the stars belong to an earlier spectral type B. Of these, two can be classified as Ae/Be Herbig objects in terms of the position on the 2MASS diagram. A good correlation is observed between the intensity of the Hα emission and the excess of radiation in the near and mid infrared. Essentially all the objects with ( H α) > 10Å EW can be classified as belonging to evolutionary class II in terms of the magnitude of their infrared excess, and the stars with EW ( H α) < 10Å, mostly to class III on the basis of their infrared color indices (their position on the two-color diagrams and the slope of the spectral energy distribution). In some cases, however, there is an inconsistency between the Hα emission intensity and the infrared excess. Even if we exclude those cases where this kind of inconsistency between the optical and infrared bands may be caused by an erroneous determination of the Hα emission equivalent width and, therefore, by an incorrect classification of the object, it is still true that about 20% of the stars with ( H α) < 10Å EW have a substantial infrared 35

11 excess. A significant infrared excess was also observed in some of the absorption stars. The diagrams based on the WISE infrared survey data base showed that data from this survey can also be used to classify stars in evolutionary classes II and III. In addition, the long-wavelength 12 and 22 mm bands are very productive for detecting stars with highly evolved disks, in which hot dust lying near the photosphere is not observed, so that the thermal emission is shifted to longer wavelengths. Between the objects in different evolutionary classes, both with respect to the Hα emission and to the slope of the spectral energy distribution, there is a significant difference in terms of the mass of the disk component and the degree of accretion. For objects in a later evolutionary class, both parameters are considerably smaller. In a sample of the stars with respect to the parameter α (the slope of the spectral energy distribution), this dependence shows up better. The relative mass of the disk and the degree of accretion for a star with α > 1.8 are essentially an order of magnitude greater than for the other stars. There is also a difference in age between objects in the different evolutionary classes. Stars with EW ( H α) > 10Å and α > 1.8 are more than half a million years younger than the others. Here we can advance two propositions. First, all the young stars were formed simultaneously, but some of them for whatever reason move along the evolutionary path faster and their color indices correspond to an older generation. It has been suggested that the more rapid breakup of the disk may be caused by a gravitational interaction with a nearby pair [37]. It is also possible, however, that the stellar objects were not formed simultaneously, but in a certain sequence, e.g., along a star-formation wave which presumably propagates from west to east in this cluster, in the direction from the previously formed OB association toward the molecular cloud Cep B [2,17,18]. We note, however, that selectivity with respect to the distribution of stars with different ages over the field of the cluster has not been observed. Of the stars with weak emission, the percentage of x-ray sources is higher, in very good accord with data for other clusters [19]. However, x-ray emission is also observed for a large number of stars with strong emission. If the x-ray emission in the first case is mainly a product of chromospheric bursts, then among the CT Tau stars, it is caused by accretion activity which also assumes the presence of a massive disk. On the other hand, a massive disk can absorb a significant fraction of the x-rays. This, rather than an absence of x-ray activity, is presumably while the x-ray emission in a large number of the CT Tau stars lies below the detection threshold in this range. An optically thick disk can also absorb Hα emission, and this can lead to a discrepancy in the signs of activity in young stars in the visible and infrared. Of course, this discrepancy can be caused by variability in the Hα emission, as such, owing, for example, to variability in the degree of accretion. It is also possible that photometric errors or the presence of a close pair may contribute to discrepancies between the manifestations of activity in young stellar objects in different spectral bands. 36

12 TABLE A1. Stars with Hα Emission N RA (2000) Dec (2000) EW (Hα) (1) (2) (3) (4) 1 22 h 55 m 25 s o 32'53" f.c. 3 (4) ([38]) 4 (5) f.c. 6 (8) f.c.. 8 (11) (13) (14) f.c. 12 (17) (21) (22) f.c (25) (28) f.c. 20 (32) (33) (35) f.c (-28 [39]) 25 (36) 56 m s (39) (43) (44) (47) (49) (52) (62) (68) (67) ([40.41]) 35 (72) (76) N RA (2000) Dec (2000) EW (Hα) (1) (2) (3) (4) (81) ([40]) 39 (85) f.c.. 41 (88) (89) (93) f.c.. 44 (99) (101) (-7 [38]) 46 (118) f.c. 49 (125) f.c (135) f.c. 53 (136) (137) f.c (141) f.c. 59 (149) (151) (152) (153) f.c (161) (-5. [6]) 67 (163) f.c f.c. 69 (165) (170) (182)

13 TABLE A1. (Conclusion) N RA (2000) Dec (2000) EW (Hα) (1) (2) (3) (4) 73 (185) (189) f.c f.c. (-18 [6]) f.c. 77 (194) (196) f.c. 79 (193) (197) (-10 [6]) 82 (199) f.c. (9 [6]) 84 (201) (-7 [6]) 85 (203) (206) (211) (212) f.c f.c. 90 (217) f.c f.c. ([6]) 92 (232) (233) (-6 [6]) 94 (237) (246) f.c. (-6 [6.16]) f.c. (-55 [6.16]) f.c. 98 (248) (254) (-5 [6]) f.c. (-19 [6]) 101 (265) f.c. 102 (267) (266) N RA (2000) Dec (2000) EW (Hα) (1) (2) (3) (4) f.c. (-10 [6]) 105 (282) (286) f.c. (-10 [6]) 107 (287) (293) f.c. 110 (298) (300) f.c. (-2 [6]) 113 (306) f.c. (-3 [6]) 114 (315) 57 m 00 s (319) (321) f.c. ([6.16]) 118 (337) ([6]) 119 (339) ([6]) 120 (344) ([6]) 121 (352) (356) f.c. ([6]) f.c. 124 (368) f.c.(-28 [6.16]) 125 (369) f.c. ([6]) 126 (372) f.c. ([6]) 127 (382) (396) (399) (402) (413) (419) (422)

14 TABLE A2. Stars with Hα Emission from other Sources (1) (2) (3) (4) (1) (2) (3) (4) 1 22 h 56 m 38 s.2 62 o 40'59" (-30 [6]) (f.c. [6]) (-33 [6]) 9 (323) (-4 [6]) (-26 [6]) 10 (325) (-3 [6]) 4 (290) (-5 [6.16]) 11 (349) (-3 [6]) (f.c. [6]) (-14 [6]) 6 (310) (-21 [6.16]) 13 (370) (-10 [6]) 7 (313) 57 m (-16 [6.16]) 14 (385) (-2) TABLE A3. Stars with Hα Emission from other Sources, but with Absorption According to the Present Data (1) (2) (3) (4) (1) (2) (3) (4) 1 22 h 56 m 13 s o 42'39".6 2 ([41]) 5 (160) ([30]) ([41,16]) 6 (181) ([38,41]) 3 (149) ([38,41]) ([41]) 4 (156) ([39]) 8 (400) 57 m (-3 [38]) TABLE A4. Stars with Hα Absorption (1) (2) (3) (4) (1) (2) (3) (4) 1 (3) 22 h 55 m 35 s o 42'34" (106) (18) (113) (30) (120) (53) 56 m 05 s (121) (56) (130) (57) (138) (58) (140) (60) (143) (61) (146) (71) (166) (83) (168) (94) (174) (95) (178) (104) (184)

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