Eighty-two UV-bright stars have been found on 17 two-color 48-inch Schmidt plates centered on the galactic plane, and on one high-latitude plate. The sources are divided into three categories according to their apparent (U-B) values: (a) sources bluer than (U-B) ~ -0.8, (b) sources bluer than (U-B) ~ -0.5 but redder than (U-B) ~ -0.8, and (c) marginal sources bluer than (U-B) ~ -0.3 but redder than (U-B) ~ -0.5. Some of the most prominent sources are discussed, and finding charts are included for all sources listed.
A program recently completed at Hale Observatories entailed the photographing of the northern galactic plane (l = 0 deg - 227 deg), to latitudes of +/- 9 deg, in the blue and ultraviolet with the 48-in (122-cm) Schmidt. The 35x35 cm (43 square degree field) plates used for the survey were double exposed on a 103a-O emulsion through GG13 and UG1 filters with an image separation of 12 arc seconds. The multicolor photographic technique has been described elsewhere (cf., Haro and Herbig 1955). Exposure times, corrected for air mass, were scaled to produce a decided difference in image size between the two-color images for objects redder than (U-B) ~ 0.0 and bluer than (U-B) ~ -0.4. Plates were taken by J. Kristian, A.R. Sandage, R.J. Brucato, and the author. The original purpose of the survey was to search for ultraviolet-bright (UV) objects as possible candidates for X-ray sources. During inspection of the plates, however, many UV-bright objects fainter than 10th magnitude were seen in the general field. These are interesting in themselves, for example as possible candidates for low-luminosity stars, and it was decided to publish a catalog for the use of other observers.
The data presented here were found following a careful examination of 17 plates but it should not be assumed these data represent a complete survey of the fields examined. On an additional plate, five high-latitude sources were noted in the vicinity of the Hercules X-1 field (Giacconi et al. 1972). Included among these objects was HZ Herculis, the rapid irregular variable (Kukarkin et al. 1970) which has been suggested as a candidate for the optical identification of the X-ray source (Liller 1972). Three peculiar objects, which appear to be associated with nebulosity, are discussed in section IV.
Tables I-III list 82 ultraviolet objects found on the plates. These have been placed into three categories, depending upon eye estimates of the relative brightness of the ultraviolet and blue images. The categories were roughly calibrated against photoelectric (U-B) measures, but a full scale calibration program, including magnitude effects, etc. was not done. The numberical (U-B) limits of the tables should not therefore be taken precisely. The photometry of stars in galactic cluster fields determined by Hoag et al. (1961) was used for many of the fields surveyed. Photometry collected in the catalog of Blanco et al. (1970) and photometry by the author was used in the remaining fields. The blue magnitude of the sources in the finding list has been estimated using these photoelectric values as a guide. These estimates should be considered accurate to only +/- 0.5 mag. due to the difficulty of adjusting to the various plate characteristics.
The format of Tables I, II, and III is the following:
Col. 2 -- Right Ascension (1950) epoch
Col. 3 -- Declination (1950) epoch
Col. 4 -- Estimated photographic blue magnitude (+/- 0.5 mag.)
Col. 5 -- Remarks.
The Lowell Proper Motion Survey of Giclas, Burnham, and Thomas (1971) and the Bruce Proper Motion Survey (BPM) (Luyten 1963) were searched for possible identification of the UV sources found in this survey. Two Giclas stars and one BPM star were determined to coincide with UV sources presented here and are given in the remarks in their respective tables. Other identifications of UV sources with catalogued stars or central stars of planetary nebulae are also given in the remarks.
TABLE 1
Sources With Large UV Excess ((U-B) < ~-0.80)
Approximate
Source RA DEC Photographic B Remarks
No. (1950) Magnitude(+/-0.5)
1 00 18 40 +67 58 47 18.5:
2 01 00 04 +69 30 40 17
3 01 16 22 +70 05 27 18:
4 01 22 31 +68 46 34 16
5 02 09 43 +61 50 34 20:
6* 02 38 22 +62 41 17 ... See Plate II
7 02 40 49 +57 32 40 20:
8 05 18 07 +37 18 55 14.2
9 05 19 38 +34 58 24 16.5
10 05 30 10 +36 57 58 15.5 see Horne, Lanning, Gomer (1982)
11 05 57 20 +29 08 42 12
12 06 06 15 +16 43 00 19:
13 06 16 33 +18 39 34 19:
14 06 40 39 +01 33 06 15
15* 16 56 10 +34 47 47 18.5 B2 1656+34
16* 18 17 42 -16 12 12 ... BD-16 4818
17 18 20 22 -04 38 58 20: See Plate I
18* 18 45 06 +01 54 21 12
19 19 31 38 +18 45 32 15.5
20 19 41 18 +18 17 26 12
21 19 42 51 +22 38 39 16
22 19 58 09 +18 59 21 14.7
23 22 47 52 +58 18 55 14
*Notes to TABLE I
6: Strong UV excess of south preceding star, surrounded by
nebulosity. No blue magnitude estimate is given because of
contamination of the image by the nebulosity.
15: Very strong UV excess; suggested as radio identification of
B2 1656+34 by Grueff & Vigotti (1972)
16: Located in the Omega Nebula (M17). The AGK1 m(V)=9.6. No
estimate of the blue magnitude was attempted due to the
heavy nebulosity in the field.
18: Luyten (1963)
TABLE II
Sources With Moderate UV Excess (-0.5 > (U-B) > -0.80)
Approximate
Source RA DEC Photographic B Remarks
No. (1950) Magnitude(+/-0.5)
24 01 20 31 +68 58 08 19:
25 02 26 25 +63 04 14 11.6
26 02 31 28 +59 55 36 19:
27 02 45 03 +62 19 47 12.7
28 03 04 57 +50 23 58 17
29 03 14 11 +52 53 20 17
30 03 25 18 +50 25 18 14.3
31* 05 14 59 +38 17 29 14.5 RY Aur
32 05 16 36 +36 31 37 15.7 [DEC error in Paper
corrected for WWW]
33 06 03 21 +27 18 59 12
34 06 05 26 +20 31 00 18:
35 06 10 06 +17 01 07 20.5
36* 06 15 55 +15 18 00 13 Planetary Neb.
37 06 18 22 +27 21 12 10.5
38 06 40 24 +00 06 40 11.3
39 06 51 24 +03 02 46 13.5
40 06 52 23 -02 19 51 13.5
41 16 59 35 +35 16 17 20:
42 17 08 07 +34 25 32 20:
43* 18 43 55 -07 59 12 9.53 BD-8 4702
44 19 38 45 +26 19 58 13
45 19 43 09 +18 51 45 13.5
46* 19 43 18 +16 20 00 14.04 EG 134; G142-50
47* 19 53 02 +29 09 29 16 Planetary Neb.
48 20 01 01 +16 10 07 12
49 20 04 04 +17 34 47 14.5
50* 20 05 18 +17 33 00 15.3 EG 136 (WZ Sge)
51* 21 17 22 +54 00 07 12.5 G231-40
*Notes to TABLE II
31: Observed near minimum. Kukarkin et al. (1970) gives
m(pg) = 11.7 - 14.0; eclipsing (algol)-spectral type - B9.
36: Central star of 195-0 1 (Perek & Kohoutek 1967)
43: HD 173637. Photoelectric B magnitude (Blanco et al. 1970);
U-B = -0.66; B1 IV.
46: Photoelectric B magnitude (Blanco et al. 1970);
U-B = -0.86; WDA.
47: Central star of NGC 6842 (Perek & Kohoutek 1967).
50: Photoelectric B magnitude (Blanco et al. 1970);
U-B =-0.72; WDA.
51: Suspected white dwarf (Giclas et al. 1971).
TABLE III
Marginal Sources (-0.3 > (U-B) > -0.50)
Approximate
Source RA DEC Photographic B Remarks
No. (1950) Magnitude(+/-0.5)
52 02 40 18 +61 07 20 12
53 02 43 37 +61 28 36 14
54 02 43 45 +58 08 20 12.7
55 02 47 26 +60 24 03 13
56 03 00 10 +51 27 58 13.2
57 03 06 26 +52 57 51 17
58 03 16 35 +49 08 39 14
59 03 20 20 +54 24 16 13
60 03 22 39 +50 51 44 19:
61 03 26 47 +48 56 17 13.5
62 03 27 37 +52 53 41 17
63 03 29 51 +51 06 24 13.7
64 05 07 28 +36 16 05 11.3
65 05 07 28 +36 17 55 10.5 +36 1030
66 05 07 32 +36 16 46 11
67 05 07 22 +35 07 14 10.5
68 05 14 14 +38 02 22 9.0 +37 1122
69 05 21 43 +38 02 29 12.7
70 06 02 10 +28 34 58 11
71 06 04 18 +27 26 01 12
72 06 21 12 +16 12 07 12.7
73 06 22 28 +17 06 00 13.8
74 06 48 58 +17 36 00 13
75 06 39 54 -00 12 04 14
76 06 48 58 +02 53 49 13.5
77 16 54 25 +35 14 46 19:
78* 16 56 01 +35 25 04 13
79 18 25 33 -17 34 50 11
80 19 50 50 +15 23 01 14.5
81 19 51 33 +16 10 01 12
82* 21 24 47 +55 00 41 14
*Notes to TABLE III
78: Rapid irregular variable (Kukarkin et al. 1970);
m(pg) = 13.0 - 14.5. HZ Her has been suggested as the possible
optical indentification of Her X-1 (Liller 1972).
82: Giclas et al. (1971).
Finding charts are given in Plates I-XI for all the sources listed and are arranged in order of increasing right ascension. All the charts have been reproduced from the blue prints of the Palomar Sky Survey (PSS) unless otherwise noted. The scale is approximately 20.5 arc second/mm, the full field 15' on a side. In all charts north is up and east is to the left.
A number of the sources in the finding list deserve some discussion due to the peculiar appearance of their images.
Source No. 17. The faint source no. 17 (Table I) is variable. It was very prominent on the two-color plate as a result of its large UV excess [Plate I(a)]. In addition, the image appeared to be nebulous in character. The most striking nature of the object, however, was the absence of any image on the PSS blue print Plate I(b). An image near the plate limit on the PSS red print [Plate I(c)] was measured and compared to the two-color print, and is believed to be the same object. A subsequent two-color print plate partially overlapping the first was taken 13 months later and shows no trace of the UV object.
Source No. 6. No. 6 (Table I) is interesting because of the UV bright star surrounded by nebulosity [Plate II(a)]. The star is hidden from view by the nebulosity on both the PSS blue and red prints. The nebulosity itself is much more prominent on the PSS print, a photo of which is shown in Plate II(b). The Catalogue of Galactic Planetary Nebulae (Perek and Kohoutek 1967) was searched but no object was found at this position. Present evidence, however, is too limited to suggest this source is a planetary. Its importance here is directed principally to the strong UV excess of the coincident stellar source. No estimate of the blue magnitude was attempted because of the apparent association with nebulosity.
Source No. 15. A third object from Table I, no. 15, is a high-latitude source (b = +37.4 deg) approximately 1 degree south of the Hercules X-ray source, which is probably too far from the X-ray error box to be associated with that source. The object has a very large UV excess ((U-B) < -1.0)) and has been suggested as the optical identification of the Bologna radio source B2 1656+34 by Grueff and Vigotti (1972). Its estimated blue magnitude is approximately 18.5 mag.
Finally, attention is drawn to the peculiar object east of no 25, and designated by the arrow. This source does not show any UV excess but was of interest because of its nebulous image, apparent on both the red and blue PSS prints and the two-color plate. The 1950 coordinates for this object are:
The investigation of the two-color plates in this survey is expected to be a continuing project.
The author would like to thank Dr. R. J. Brucato for his assistance in the examination of some of the photographic plates for this two-color survey. Also, special thanks should go to Mr. John Bedke and Mrs. Felice Woodworth for help in the preparation of the finding charts. This work was supported in part by the National Aeronautics and Space Administration uner grant NGR 09-140-009 to the Carnegie Institution of Washington.
Giacconi, R., Murray, S., Gursky, H., Kellogg, E., Shreier, E., and Tananbaum, H. 1972, Ap. J. 178 281.
Giclas, H. L., Burnham, R., Jr., and Thomas, N. G. 1971, Lowell Proper Motion Survey-Northern Hemisphere. The G Numbered Stars. (Flagstaff: Lowell Observatory).
Grueff, G., and Vigotti, M. 1972, Astr. and Ap. Suppl., 6, 1 (No. 1)
Haro, G. and Herbig, G.H. 1955, Bol. Obs. Tonantzintla y Tacubaya, 12, 33
Hoag, A. A., Johnson, H. L., Iriate, B., Mitchell, R. I., Hallman, K. L., and Sharpless, S. 1961, Pub. U.S. Naval Obs. 17 (part 7), 345 (2nd series)
Kukarkin, B. V., Kholopov, P. N., Efremov, Yu. N., Kukarkina, N. P., Kurochkin, N. E., Medvedeva, G. I., Perova, N. B., Fedorovich, V. P., and Frolov, M. S. 1970, General Catalogue of Variable Stars, 3rd ed. (Moscow: U.S.S.R. Academy of Sciences).
Liller, W. 1972, I.A.U. Circ. No. 2415.
Luyten, W. J. 1963, Bruce Proper Motion Survey - The general Catalogue 2 (Minneapolis: University of Minnesota).
Perek, L., and Kohoutek, L. 1967, Catalogue of Galactic Planetary Nebulae (Prague: Czechoslovak Academy of Sciences).
UV Survey Intro Page