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Peremennye Zvezdy (Variable Stars) 27, No. 3, 2007 Received 20 April; accepted 28 April.
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Article in PDF |
Harvard-Smithsonian Center for Astrophysics, Cambridge,
MA 02138, U.S.A.;
e-mail: bmarsden@cfa.harvard.edu
Of the 379 candidate variables listed by F.E. Ross during 1925-1931, 97 appear in the NSV catalogue, and 51 of these were recorded on a single night. Ross recognized that some of the single-nighters were likely to be minor planets, and a few years ago J.R. Bedient identified six such cases. The present author has identified nine further Ross objects as long-known minor planets. |
Bedient (2003) identified six of the "New Variable Stars" listed by Ross (1925, 1926a, 1926b, 1927a, 1927b, 1928a, 1928b, 1929, 1930, 1931) as minor planets. These were cases where F.E. Ross' comparison of plates taken with the Bruce photographic telescope at the Yerkes Observatory by E.E. Barnard during 1904-1915 and those taken by Ross himself with the same instrument during 1924-1930 showed the "variable" to be present only on a single night. Photographic defects had (presumably) been eliminated, since each observation consisted of a pair of duplicate images with 10-inch and 6-inch lenses. In the preamble to his third list Ross (1926b) had remarked that "while a certain small percentage of the stars listed as variables in the present survey may actually be asteroids [sic], to prove that such would be the case for any individual star would be an exceedingly difficult matter".
The majority of the 379 objects have either been fully recognized as variables or been shown not to vary, but as many as 97 remain in the New Catalogue of Suspected Variable Stars (Kukarkin et al., 1982), and of the latter, the 51 objects collected in Table 1 are single-night detections. In such cases the non-detection was indicated either by a limiting magnitude (invariably 15 for the cases of interest) or - for the third through seventh lists - by the notation "n.s." (not seen), where it is also reasonable to presume a limiting magnitude of 15.
Ross 5 = NSV 01488 | Ross 114 = NSV 13523 | Ross 231 = NSV 04352 |
Ross 11 = NSV 02913 | Ross 115 = NSV 13558 | Ross 249 = NSV 11953 |
Ross 17 = NSV 02911 | Ross 130 = NSV 14097 | Ross 271 = NSV 12941 |
Ross 21 = NSV 08638 | Ross 136 = NSV 00308 | Ross 279 = NSV 13086 |
Ross 24 = NSV 09124 | Ross 144 = NSV 01760 | Ross 301 = NSV 10876 |
Ross 25 = NSV 09194 | Ross 152 = NSV 01809 | Ross 310 = NSV 11971 |
Ross 26 = NSV 09248 | Ross 160 = NSV 03506 | Ross 321 = NSV 12374 |
Ross 29 = NSV 09437 | Ross 166 = NSV 04168 | Ross 323 = NSV 12985 |
Ross 30 = NSV 09457 | Ross 168 = NSV 06188 | Ross 324 = NSV 13021 |
Ross 36 = NSV 09668 | Ross 182 = NSV 00907 | Ross 326 = NSV 13047 |
Ross 38 = NSV 04748 | Ross 190 = NSV 02777 | Ross 329 = NSV 13179 |
Ross 39 = NSV 04796 | Ross 204 = NSV 04018 | Ross 331 = NSV 13449 |
Ross 40 = NSV 04849 | Ross 206 = NSV 05338 | Ross 344 = NSV 14721 |
Ross 41 = NSV 09200 | Ross 208 = NSV 08001 | Ross 349 = NSV 01797 |
Ross 77 = NSV 12634 | Ross 218 = NSV 12168 | Ross 352 = NSV 01982 |
Ross 79 = NSV 12682 | Ross 225 = NSV 14640 | Ross 353 = NSV 02490 |
Ross 89 = NSV 13752 | Ross 230 = NSV 04333 | Ross 369 = NSV 06249 |
Following the recent publication (Samus and Antipin, 2007) of the identity of DU Aqr with (57) Mnemosyne, Samus (2007) suggested to the present author that Ross 168 was likely to be a minor planet and requested assistance in identifying it. In response, and unaware of the work by Bedient (2003), the present author quickly identified Ross 168 and, further, checked to see which of the 50 other objects listed in Table 1 were detections of identifiable minor planets. The work was simplified by the availability of a new on-line version of the NSV catalogue that includes equinox 2000.0 versions of the equinox 1875.0 positions originally provided by Ross.
The other prerequisite was the availability of computer files at the Minor Planet Center containing osculating J2000.0 orbital elements of all 155,368 numbered minor planets for epochs at 200-day intervals back in time to well before Barnard exposed his plates.
This of course rendered it an "exceedingly easy matter" to conclude that just 15 of the 51 entries in Table 1 refer in fact to minor planets. Seven of the minor planets were recorded during 1904-1915, seven during 1925 or 1927 and - intriguingly - one in 1925 and 1927. The observations of these minor planets are listed in Table 2.
Object | R.A.(2000)Decl. | Obs. | Minor planet | UT | Computed | ||
mag. | position | ![]() |
|||||
Ross 11 | 06![]() ![]() ![]() ![]() ![]() |
13 | (449) | Hamburga | 1925 Feb. 17.1 | 40/43.4 | 12.9 |
Ross 38* | 10 08 14 +12 28.0 | 11.5 | (24) | Themis | 1925 Mar. 31.0 | 14/28.0 | 11.5 |
Ross 39* | 10 15 27 +12 10.5 | 10 | (39) | Laetitia | 1925 Mar. 31.1 | 27/10.5 | 11.0 |
Ross 40 | 10 25 20 +17 45.9 | 11 | (162) | Laurentia | 1907 Apr. 1.0 | 20/45.6 | 12.8 |
Ross 89* | 21 31 18 -17 47.4 | 11 | (115) | Thyra | 1904 June 20.3 | 19/47.4 | 11.4 |
Ross 136* | 00 49 19 +04 51.4 | 12 | (137) | Meliboea | 1925 Nov. 14.2 | 19/51.4 | 12.6 |
Ross 168 | 13 20 01 -03 19.1 | 11 | (106) | Dione | 1905 Feb. 13.3 | 01/19.3 | 11.1 |
Ross 190 | 06 00 50 +15 48.0 | 13 | (714) | Ulula | 1909 Nov. 12.3 | 50/48.0 | 12.8 |
Ross 204 | 08 21 09 +17 31.3 | 12 | (554) | Peraga | 1927 Mar. 9.1 | 09/31.3 | 12.5 |
Ross 206* | 11 47 43 +05 31.3 | 11 | (26) | Proserpina | 1909 Apr. 10.1 | 43/31.3 | 11.1 |
Ross 230 | 08 59 06 +07 45.0 | 10 | (389) | Industria | 1915 Mar. 20.2 | 06/45.0 | 11.8 |
Ross 231 | 09 02 06 +02 22.2 | 12 | (242) | Kriemhild | 1915 Mar. 20.1 | 04/22.2 | 13.3 |
Ross 329 | 20 37 43 -19 24.0 | 12 | (24) | Themis | 1927 Oct. 18.1 | 44/24.0 | 13.2 |
Ross 344 | 23 49 32 -06 34.3 | 12 | (59) | Elpis | 1927 Nov. 26.0 | 32/34.2 | 12.2 |
Ross 352* | 05 26 37 +26 43.5 | 11 | (451) | Patientia | 1927 Feb. 22.1 | 37/43.3 | 11.8 |
Here the equinox 2000.0 positions in the on-line NSV catalogue
have been rounded to the precision of the 1875.0 positions
tabulated by Ross. The observed magnitude is that for the
positive observation supplied by Ross; it should be noted that the
NSV catalogue deliberately gives a number 10 fainter. Since
the precise time of observation is unknown, the UT date given
corresponds to when (to 0
1) the computed position (for which
just the end figures in R.A. and Decl. are given) was closest to
the observed position of the indicated minor planet. These UT
dates are one day later than the local dates provided by Ross. To
start the local date at noon was standard astronomical practice
during 1904-1915, and it appears that Ross continued this
practice following the actual introduction of UT in 1925. The
computed magnitudes for the minor planets are in the
system.
It should be noted that all these minor-planet identifications are absolutely sure, and that no remotely questionable cases were found among the other 36 Ross objects. For six of the minor planets, (26), (59), (115), (389), (449) and (451), astrometric positions are available from other observatories (mainly Heidelberg, but also Greenwich, Marseilles and Algiers) at the same opposition. The 1909 observation of (714) Ulula, the minor planet with the highest number in the whole set, is in fact the earliest known for that object, which was discovered from Heidelberg in May 1911. By curious chance, (24) Themis was observed both as Ross 38 on 1925 Mar. 31 and as Ross 329 on 1927 Oct. 18. That Ross 39 should turn out to be (39) Laetitia is also fortuitous.
In no case was the computed brightness more than 1
8
different from the observed magnitude given by Ross. The mean
brightness discordance was 0
6 in the sense that the computed
magnitude was systematically fainter than the Ross magnitude.
Given that the Ross observations are photographic, it would be
reasonable to use the computed
magnitude, which is typically
0
8 fainter than
. The mean discordance would therefore be
1
4. Although the brightness discordance is obviously affected
by the low precision of the Ross values, the computed magnitudes
do support the decision by the compilers of the NSV catalogue
consistently to add 1
0 to the Ross figures.
The six cases previously identified by Bedient (2003) are indicated in Table 2 by means of asterisks following the Ross number. Ross 352 was also independently identified by Schmeer (2003). However, four more of the objects, Ross 40, 168 (the object that inspired this investigation), 230 and 329, were incorrectly characterized by Bedient in his Table 2 as "not to be solar system objects". They are most certainly (162) Laurentia, (106) Dyone, (389) Industria and (24) Themis, respectively. The present author also disagrees with the notation in Bedient's Table 3 that Ross 231 and 344 "had ambiguous search results" and "cannot be characterized". The present work clearly shows that they are (242) Kriemhild and (59) Elpis, respectively.
References:
Bedient, J.R., 2003, Inform. Bull. Var. Stars, No. 5478
Kukarkin, B. V., Kholopov, P. N., Artyukhina, N. M., et al., 1982, New Catalogue of Suspected Variable Stars, Moscow: Nauka
Ross, F.E., 1925, Astron. J., 36, 99
Ross, F.E., 1926a, Astron. J., 36, 122
Ross, F.E., 1926b, Astron. J., 36, 167
Ross, F.E., 1927a, Astron. J., 37, 91
Ross, F.E., 1927b, Astron. J., 37, 155
Ross, F.E., 1928a, Astron. J., 38, 99
Ross, F.E., 1928b, Astron. J., 38, 144
Ross, F.E., 1929, Astron. J., 39, 140
Ross, F.E., 1930, Astron. J., 40, 34
Ross, F.E., 1931, Astron. J., 41, 88
Samus, N.N., 2007, personal communication
Samus, N.N. and Antipin, S.V., 2007, Peremennye Zvezdy (Prilozhenie), 7, No. 10
Schmeer, P., 2003, personal communication to N.N. Samus