THE FIRST BYURAKAN SPECTRAL SKY SURVEY. BLUE STELLAR OBJECTS. IX. THE ZONE +69 ~ _< $ _< +73 ~ AND ADDITIONAL OBJECTS FROM PREVIOUS REGIONS

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1 Astrophysics, Vol. 37, No. 3, 1994 THE FIRST BYURAKAN SPECTRAL SKY SURVEY. BLUE STELLAR OBJECTS. IX. THE ZONE +69 ~ _< $ _< +73 ~ AND ADDITIONAL OBJECTS FROM PREVIOUS REGIONS G. B. Abramyan and A. M. Mikaelyan UDC We present the ninth list of blue stellar objects of the second part of the First Byurakan Spectral Sky Survey (FBS). We publish 61 objects in the zone +69 ~ < ~f < +73 ~ 3~5 '~ _< a ~ 18~1 '~ and P3 additional objects from the previous 5 zones of the survey. Of the 84 objects, 6,~ are discovered for the first time. We give the equatorial coordinates, stellar V magnitudes, color indices, and preliminary classes of the objects with respect to slitless low-dispersion spectra. For the ~3 objects we give approzimate types, among which there are 5 candidates for quasars, one for a Seyfert galaxy, 3 UV-excess galaxies, 9 white dwarfs, cataclysmic variables and one probable planetary nebula. 1. Introduction. Since 1987 we have been searching for blue stellar objects on the plates of the First Byurakan Spectral Sky Survey (FBS). The identification, cataloguing, and classification of blue stellar objects constitutes the second part of the FBS. In the eight published lists [1-3] there are 855 objects, of which 516 are discovered for the first time. The present paper continues the study of objects with high from the north celestial pole. In the zone +69 ~ < g _< +73 ~ we have detected another 61 blue stellar objects. In addition, on the basis of a revision of the results of the previous papers, we have analyzed the quantitative tests for selecting objects and included in the survey 23 additional objects. At the same time we have conducted a spectral [4] and polarimetric [5, 6] study of the objects of the second part of the FBS in order to classify all the objects and study the most interesting of them in detail. The description of the second part of the FBS, the method of selection, and the principles for the preliminary classification of the objects are given in [1]. In [2] we carried out a comparison of the lists with other similar surveys and analyzed the preliminary classification of the authors by comparing them with the generally accepted spectral classification for known objects. The papers [3] contain some statistical analysis of the sample of the present survey; in particular, the galactic distribution of the objects of the second part of the FBS is studied. In [7] the method of determining the coordinates and stellar magnitudes from the charts of the Palomar Sky Survey is described. 2. The zone $ = +71 ~. The FBS zone /~ = +71 ~ occupies the region from +69 ~ _< ~ _< +73 ~ and 3h5 m _~ a _~ 18h1 m with 19 survey fields each 4 ~ x 4 ~ photographed with a step of 45'. The total area of the zone is 28 square degrees. The maximum size of the V plates, determined using the charts of the Palomar Sky Survey by the method described in [3] varies within the limits 16.5m-18.9 'n, the mean value being 18.1 m. This is 1 m higher than had been previously thought (for example, [8]). In 1993 we examined each of the plates three times looking for blue stellar objects. Table 1 gives a list of 61 blue stellar objects of the FBS in the given zone. The successive columns of the table give: 1, the notation for the objects in the FBS according to the recommendations of IAS Subcommittee No. 28; 2, the number in the survey; 3 and 4, the equatorial coordinates for the epoch 195, within 2s ((~) and.1' (~); 5, t he visible stellar magnitude V within.3m; 6, t he color index CI within.3 m; 7, the survey type of the objects according to the classification of shtless spectra; 8, an estimate of the type of the objects also according to low-dispersion spectra; 9, the identification of known objects (the number of the corresponding source in the list of literature). The equatorial coordinates are determined from the charts of the Palomar Sky Survey by the direct vision method. The stellar magnitudes and color indices CI are also determined from the charts of the Palomar Survey using the gauge of the "diameter of the image/stellar magnitude" relation according to [22] and correspond to the standard photometric V magnitude of the Johnson system, which is established in [7], within.3 m. Translated from Astrofizika, Vol. 37, No. 3, Original article submitted May 19, /94/ $12.5 (~) 1995 Plenum Publishing Corporation

2 LIST OF BLUE STELLAR OBJECTS OF THE FBS ZONE Table 1 FBS No. ~195 ~195 m~, CI Surv. type Est. type Lit h13m43 s +72~ N N B N2e: B B Nle: Ble: N1 qso Bla B B BI B B2a O B B2a B2 DA [11,13] [9,18] B3a DA B B3e QSO B2a DA: [9, B3e: QSO: BI [9,17] B2a DA We also determined an empirical relation between the color indices CI and the photometric B - V values, expressed by the formula B - V =.6CI +.7. Prom this formula one can determine the standard B - V color indices within.2". As shown in [1], the length of the UV portion of the low-dispersion spectrum (classes 1-3) correlates in first approximation with the U - B color index of the objects. On the basis of averaging of the U - B color indices for more than 1 known FBS objects of various survey types we computed the mean U - B values for classes 1 (-1.3), 2 (-.85), and 3 (-.54). We remark that the estimates of the U - B color for the lengths of the UV portion of the spectra 1-3 done by Markaryan [23] coincide nlmost perfectly with our determinations on the basis of averaging a large number of data. 3. Additional objects of the previous survey zones. Besides the objects published in the papers [1-3], in the course of the survey we also selected many other reserve objects that did not go into the lists 225

3 Table 1 (continued) B2a Blv CV B1 [9,18] B1 [9,17] B3a DA [11,13] B3a: B1 [9,17] Nle CV [9,16,19] B Bla DA 18. -O.3 N B B3a DA Nle B B1 [9,17] B1 [9,12,14] Ble PNN N B B1 [9,18] B B Nlev CV: [9,16,19] B1 [9,1,18] B2e: CV: B2 [9,18] Nlv: QSO: [9,2,21] of the corresponding zones because we were not sure they satisfied the accepted criteria. These objects were not published, but were kept in reserve to test observations or a number of characteristics of similar objects (U - B colors as functions of the length of the UV portion, object type as a function of the spectral distribution in the low-dispersion spectrum). A secondary examination and analysis of the reserve objects, as well as spectral observations of some of them, made it possible to include in the general list an additional 23 blue stellar objects of the 14 reserves. Some of the additional objects are compact galaxies with starshaped spectral images on the lowdispersion plates which were not accepted after verification of their extent on the charts of the Palomar Survey. However, from the low-dispersion spectra these galaxies satisfy our criteria and may prove to be interesting objects. It should be said that even in the published lists there were several galaxies that were selected in order to find Seyfert and other emission galaxies, and also in part to supplement the first part of the FBS. 226

4 Table 1 (conclusion) B2a B1 [9,18] B Bla [12,15,17] Ble: 15. -O.6 B B B2 Remarks: On the FBS plate m A probable cataclysmic variable. Noted by B. E. Markaryan The dwarf nova DO Dra. Luminosity variable within the limits (B) SS UMi: Dwarf nova of UG type. V Quasar with z = Weak IR source IRAS , probably variable: on the plate 14 '~. According to the POSS charts V = 13.7; in the IRAS and PG quasar catalogs V = Table 2 gives a list of the 23 objects added to the survey from the previous zones. The order of the data and the notations are the same as in Table 1. The numbering of the objects continues from the zone ~ i.e., starting with number 917. In the commentary at the end of the table, in particular, we give several reasons for accepting one object or another into the second part of the FBS. It is interesting that among the added objects is FBS , which is in the Palomar-Green catalog and was detected but not at first accepted because of the insufficient length of the UV-continuum. Thus at present we have selected a total of 939 objects with UV excess. 4. Estimating the type of the objects. Besides the classification of the slitless spectra described above, an attempt was made in the course of the survey to identify the types of many objects. Certain emission and absorption lines show up well on the slitless spectra. On the basis of the slitless spectra and (sometimes) the images on the charts of the Palomar survey, one can recognize the following types: white dwarfs, subdwarfs, cataclysmic variables, planetary nebulae, quasars, and Seyfert galaxies. The objects that can be identified most reliably from the slitless spectrum are the white dwarfs. Almost all dwarfs with the Balmer absorption series are recognizable even from an examination of the low-dispersion plates. In Tables 1 and 2 they are denoted DA, including, besides DA, also other white dwarfs (DAB, DBA, DAZ). In this category one may include a number of objects without any noticeable UV excess (with short blue portion of the spectrum), which are also undoubtedly white dwarfs. However, such exceptions were made only in rare cases, when the length of the blue portion was close to the preliminary class "3." Certain objects (for which the presence or width of the Balmer lines is doubtful) were denoted DA:. In many cases it is possible to identify subdwarfs from the low-dispersion spectrum. This is possible only for objects with optimal exposure (14"-15 m) for which the Balmer series is also observed in absorption. Objects whose lines are narrow are denoted by the estimated type sdb, to which the spectral classes sdb, sdb-o, and sdoa belong. On the whole, the majority of objects for which no estimated type is determined are subdwarfs. In the case of emission object~ with narrow lines the estimated type is determined according to the approximate identification of the Balmer series and the forbidden lines. The notation CV (or CV:) is used for objects with Balmer emission lines, and PNN (or PNN:) for objects suspected of having forbidden lines (mainly N1 and N2). In one case (FBS ) 4-5 forbidden lines were observed. This object was reliably classified as a PNN. As a rule bright quasars can also be recognized from the low-dispersion spectrum. All objects that 227

5 LIST OF ADDITIONAL BLUE STELLAR OBJECTS OF THE FBS FBS No. ~ m~ CI Surv. type Est. type Table 2 Lit h51m46 ~ 67"14' N N B3a: Sy: DA: [1] A N3 QSO: B B B B3a B B N d2e: s2 Gal ds3 Gal B3a: B3a B2 DA: [9,1s] B3a: B s3 Gal sd3e B B2a: B3 Remarks: is an object noted by B. E. Markaryan as a candidate for a compact galaxy. On the POSS charts it has a point image. The object is not blue, but has a noticeable UV excess on the slitless spectrum is blue, possibly an emission galaxy. On the blue and red POSS charts it has a nearly circular shape with a diameter around 1" and 8" respectively. We do not attempt to distinguish the type of galaxy; possibly it is a compact galaxy is accepted as a galaxy with UV excess. It may have been omitted from the first part of the FBS due to its faintness. Its slitless spectrum has a very long UV part. On the POSS charts it resembles a spheroidal galaxy is accepted as a galaxy with UV excess. It may have been omitted from the first part of the FBS due to its faintness. It slitless spectrum has a long UV part. On the POSS charts it is a spiral galaxy elongated from north to south The slit spectrum of this object was observed on the 2.6m zenith telescope. Its preliminary spectral class is sdb is accepted as a galaxy with UV excess. It may have been omitted from the first part of the FBS due to its faintness. Its slitless spectrum has a long UV part. It was observed on the 2.6m ZTA; no emission lines were observed. Its preliminary classification is Gal is an emission galaxy. According to the POSS charts it is a nearly spheroidal galaxy with starshaped nucleus (a halo is noticeable around the nucleus). Its diameter on the red chart is about 12". It may turn out to be a Seyfert galaxy The slit spectrum of this object was observed on the 2.6m ZTA on Its preliminary spectral class is DBA: The slit spectrum of this object has been observed twice on the 2.6m ZTA ( and ). Its preliminary spectral class is HBB:. 228

6 Est. Type COMPARISON OF THE ESTIMATED TYPES AND SPECTRAL CLASSES OF OBJECTS No. Obj. With Spec. Type Ident. Obj. Pct. Corr. Ident. No. Known Obj. Table 3 Pct. Ident. DA % 1 24% DB PNN IO CV Bin QSO 4O Sy 11 3 Gal 3 1 Total % % are suspected of being quasars from their spectral distribution are denoted by the estimated type QSO:, while evident quasars (QSO) were reliably identified only in the presence of wide emission lines. For objects denoted Sy (or Sy:) the width of the emission fines is moderate. The bulk of quasars, unfortunately, cannot be identified due to the faintness of the spectra (since there are very few bright quasars), but certain faint objects nevertheless have the estimated type QSO: in view of the presence of possible emission. It is mainly DC objects, the majority of subdwarfs, HBB's, and all overexposed or underexposed objects whose spectral details were not observed that remain without an estimated type. In all an estimate of the type was made for 145 objects of the entire set of 939 blue stellar objects of the FBS. However in the first 8 lists of the survey this characteristic was not presented. For that reason it is of interest to compare our rough types with the spectral classes for known objects and determine the probability that the identification of individual categories of objects from slitless low-dispersion spectra is correct. Table 3 gives such a comparison. In its successive columns are: the estimated type; the number of objects denoted as a given type (taking account of the FBS objects of all the published lists); the number of known spectrally classified objects among the number denoted as the given type; the number of objects of the given spectral classification identified from slitless spectra; the percent of correct determination of the given type of objects; the total number of spectrally classified objects of the given class in the FBS sample; the percent of identification of the given class of objects from low-dispersion spectra. It is interesting that for almost all the types of objects the preliminary estimate turns out to be correct in 75-1% of the cases; however only about a fourth of the known (relatively bright) objects (not counting subdwarfs) can be identified from the low-dispersion spectrum, and only 15% of all objects. 5. Conclusion. In the zone +69 ~ _< 6 < +73 ~ of the FBS survey 61 blue stellar objects have been detected, of which 43 were discovered for the first time and 18 were identified with earlier published objects from other surveys. Among these 18 objects we find 1 quasar, 7 white dwarfs, 2 cataclysmic variables, 6 hot subdwarfs, and 2 blue stellar objects whose spectral class is as yet unknown. As pointed out in [3], this distribution cannot give the true picture of the composition of the objects in our list, since quasars and white dwarfs can also be discovered by several other methods. However the new objects of type N (8 in all) are candidates for cataclysmic variables and extragalactic objects, in particular quasars. Among the new objects there is also a number of candidates for white dwarfs. The hot subdwarfs seem, as before, to constitute the majority of objects in our lists, as is natural for relatively bright blue stellar objects. Of the 18 known objects 15 can be found in the most complete Palomar-Green survey (PG) [9]. In the PG survey there is a total of 17 objects in the zone +69 ~ < 6 < +73% Two objects not detected by us did not meet our criteria (no UV excess was observed in the slitless spectr,,m). On the other hand, 229

7 in the region intersecting the PG survey in this zone, we have discovered an additional 22 objects not in the Palomar-Green survey. Of these FBS (V = 15.7, CI = -.7) satisfies the restriction in the visible magnitude and the color criteria for selection by the PG, and seems to have been omitted in that survey. Thus the FBS supplements the existing surveys of blue stellar objects both with previously unstudied regions and with new objects in the intersection regions. The authors are grateful to the American Astronomical Society for support of the present paper. Byurakan Astrophysical Observatory, Armenia Literature Cited 1. G. V. Abramyan, V. A. Lipovetskii, and Dzh. A. Stepanyan, Astrofizika, 32, 29 (199). 2. G. V. Abramyan, V. A. Lipovetskii, A. M. Mikaelyan, and Dzh. A. Stepanyan, Astrofizika, 33, 213, 345 (199); 34, 13 (1991). 3. G. V. Abramyan and A. M. Mikaelyan, Astrofizika, 36, 19 (1993), in press; 36 (1993), in press; 37 (1994), in press; 37 (1994), in press. 4. G. V. Abramyan and A. M. Mikaelyan, Astrofizika, 35, 197 (1991). 5. A. M. Mikaelyan, M. A. Eritsyan, and G. V. Abramyan Astrofizika, 34, 351 (1991). 6. M. A. Eritsyan and A. M. Mikaelyan, Astrofizika, 36, 23 (1993). 7. G. V. Abramyan and A. M. Mikaelyan, Soobshch. Byurakan. Observ., 66 (in press). 8. B. E. Markarian, V. A. Lipovetski, J. A. Stepanian, L. K. Erastova, and A. I. Shapovalova, Comm. Spec. Astrophys. Observ., 62, 5 (1989). 9. R. F. Green, M. Schmidt, and J. Liebert, Astrophys. J., Suppl. Set., 61,35 (1986). 1. W. J. Luyten, "A search for faint blue stars," Observ. Univ. Minn. ( ). 11. W. J. Luyten, Proper Motion Survey with the Forty-eight Inch Schmidt Telescope, University of Minnesota Press, Minneapolis ( ). 12. H. L. Giclas, R. Burnham, Jr., and N. G. Thomas, The Lowell Proper Motion Survey of the Northern Hemisphere. The G Numbered Stars, Lowell Observatory, Flagstaff, AZ (1971). 13. H. L. Giclas, R. Burnham, Jr., and N. G. Thomas, The Lowell Proper Motion Survey, Lowell Observ. Bull. No. 166, Vol. VIII, No. 6, Flagstaff, AZ (198) J. Eggen and J. L. Greenstein, Astrophys. J., 141, 83 (1965). 15. J. L. Greenstein, Comm. Astrophys. Space Phys., 1, 62 (1969). 16. N. N. Samus', gen. ed., General Catalog of Variable Stars [in Russian], Vol. IV, Nauka, Moscow (199). 17. G. P. McCook and E. M. Sion, Astrophys. J., Suppl. Ser., 65,63 (1987). 18. D. Kilkenny, U. Heber, and J. S. Drilling, South Aft. Astron. Observ. Circ., 12, 1 (1988). 19. H. Ritter, Astron. and Astrophys., Suppl. Ser., 85, 1179 (199). 2. M.-P. Veron-Cetty and P. Veron, A Catalog of Quasars and Active Nuclei, Sixth Ed., ESO Sci. Rep. No. 13 (1993). 21. Joint IRAS Science Working Group (ed.), Infrared Astronomical Satellite Catalogs and Atlases, Vol. 2, The Point Source Catalog, Declination Range 9 ~ > 6 > 3 ~ NASA, Washington, DC: U.S. Government Printing Office 22. I. R. King and M. I. Raft, Publ. Astron. Soc. Pacif., 89, 12 (1977). 23. B. E. Markaryan, Astrofizika, 8, 165 (1972). 23