Comments on Catalog III/246 
(First Byurakan Survey Late Type Stars catalog)

Cécile Loup, CDS VizieR Help

1  General comments

The Vizier catalogue file III/246 is described by his author as mainly a compilation of 14 lists of late-type stars published from 1989 to 2003 by Abrahamyan, Gigoyan, Hambaryan, & coll. Late-type stars candidates have been extracted from the First Byurakan Spectral Survey. In addition of the compilation, and according to the Readme Vizier file, the author provides : (a) accurate coordinates, (b) systematic cross-identification with various optical catalogues and with 2MASS, (c) some new spectral types, (d) a rough luminosity class for all the objects.

The major difficulty I see with this compilation is that it has not been published anywhere. The Readme file is intended to be a short abstract, but it does not give any accurate explanation on the new columns added by the authors. The compilation provides "accurate coordinates", but it is not explained how they have been determined, or which catalogue they come from. The methodology used to perform cross-identifications with optical catalogues and 2MASS is not explained, so that it cannot be checked. For some stars which had no spectral types in the original lists a new spectral type has been determined, but as it used the same photographic material, it would be required to explain how these spectral types have been determined and why they were left blank in the previous works. Finally, the determination of the luminosity class is poorly explained, and turns out to be incorrect.

My opinion is that this compilation could be interesting mainly because of the various cross-identifications, but that it should not be made available at CDS as long as a paper explaining the work performed has not been published in a referee journal.

2  Detailed comments

  1. The total number of stars from lists I to XIV amounts to 1001. The compilation III/246 contains 995 stars, so 6 are missing : FBS L 5-10, 7-12, 7-29, 9-52, 9-56, 9-87. It should be explained why these 6 stars are missing compared to the original catalogues.

  2. The compilation III/246 gives a luminosity type "giant" or "dwarf" based on the 2MASS (J-K) color. However it is not explained anywhere precisely which criteria are used nor to which extent it has a physical explanation. As far as I can see, it has just been set that stars with (J-K)>1 are giants, while those with (J-K)<1 are dwarfs. This is incorrect. Early M-type and C-type giants may well have (J-K)<1. Conversely, some late M-type dwarfs may have (J-K)>1. 75 C stars candidates thus appear to be dwarfs in the compilation, 53% of the total of C stars in the sample. Hydrogen deficient C stars might be dwarfs in an interacting bynary system. However such objetcs are very rare. To find that more than half of the C stars would be dwarfs is obviously in contradiction the present knowledge based on observations and theory. The column "luminosity type" should be removed.

  3. Detailed checks of the list number X (169 stars)

    It has to be noted that in addition of the original list X and the compilation III/246, a check of optical identifications and cross-identifications with IRAS based on finding charts and coordinates has been performed by an expert, B.Skiff, often collaborating with the CDS and known to usually provides a very reliable work. His work is available in Vizier together with the original data of list X at : J/other/Ap/41.356.

    Here I have cross-checked the three lists for : GCVS or NSV identification and IRAS cross-identifications. I also checked the consistency of the spectral types between list X and III/246.

    There are certainly 6 incorrect optical identifications in III/246. In addition 2 stars are listed with a spectral type C instead of M in list X. These 8 problems must be corrected.

    There are also quite a few stars with missed optical identifications or IRAS counterpart; it would be better to take advantage of the work made by B.Skiff, or to explain any disagreement if required.

    Finally, III/246 sometimes gives an IRAS identifier in the FSC rather than in the PSC. This is I think better as the FSC provides better flux measurements than the PSC for faint sources.

    ||No  ||List X   ||Compil.III/246   ||Expert B.Skiff ||
    ||Major discrepancies ||
    ||10-029  ||...               ||ER Eri            ||... ||
    ||10-040  ||SX Eri            ||...               ||SX Eri ||
    ||10-041  ||NSV 1765          ||SX Eri            ||NSV 1765? ||
    ||10-060  ||not T Hya         ||T Hya             ||T Hya. List X incorrect. ||
    ||10_072  ||...               ||...         ||NSV 4902. FBS coordinates incorrect. ||
    ||10-079  ||...               ||...               ||NSV 18658 ||
    ||10-123  ||W Oph             ||V868 Sco          ||V868 Sco ||
    ||10-124  ||...               ||W Oph             ||W Oph ||
    ||10-124  ||M6-7              ||C(N)               ||||
    ||10-137  ||...               ||MQ Aqr            ||... ||
    ||10-158  ||M5-6              ||C(R)        ||||
    ||Disagreements requiring 
      checks or explanations||
    ||10-010  ||...               ||ER Cet            ||ER Cet ||
    ||10-032  ||...               ||IRAS F04142-0919  ||IRAS F04142-0919 ||
    ||10-043  ||NSV 1780          ||...               ||NSV 1780 ||
    ||10-047  ||NSV 4114          ||...               ||NSV 4114 ||
    ||10-048  ||IRAS F08288-0958  ||...               ||IRAS F08288-0958 ||
    ||10-049  ||IRAS 08315-0757   ||...               ||IRAS 08315-0757 ||
    ||10-056  ||IRAS F08473-0707  ||...               ||IRAS F08473-0707 ||
    ||10-070  ||...               ||NSV 18400         ||NSV 18400 ||
    ||10-073  ||...               ||IRAS F10509-0802  ||IRAS F10509-0802 ||
    ||10-109  ||...               ||GP Lib            ||GP Lib ||
    ||10-113  ||IRAS F16083-0835  ||...               ||IRAS F16083-0835 ||
    ||10-116  ||...               ||...               ||IRAS F16132-0725 ||
    ||10-133  ||NSV 13155         ||...               ||NSV 13155 ||
    ||10-142  ||IRAS F20506-1035  ||...               ||IRAS F20506-1035 ||
    ||10-148  ||...               ||EY Aqr            ||EY Aqr ||
    ||10-154  ||IRAS F21309-0930  ||...               ||IRAS F21309-0930 ||
    ||Small differences: IRAS PSC 
    		versus IRAS FSC.||
    ||10-002  ||IRAS 00015-0835   ||IRAS F00015-0835  ||IRAS 00015-0835 ||
    ||10-034  ||IRAS 04179-1031   ||IRAS F04179-1031  ||IRAS 04179-1031 ||
    ||10-045  ||IRAS 08267-0719   ||IRAS F08267-0719  ||IRAS 08267-0719 ||
    ||10-081  ||IRAS 11181-1018   ||IRAS F11181-1018  ||IRAS 11181-1018 ||
    ||10-102  ||IRAS 14544-0657   ||IRAS F14544-0657  ||IRAS 14544-0657 ||
    ||10-151  ||IRAS 21218-0756   ||IRAS F21218-0756  ||IRAS 21218-0756 ||
    ||10-155  ||IRAS 21427-0858   ||IRAS F21427-0858  ||IRAS 21427-0858 ||

Cécile Loup, 19 July 2007
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