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(This paper appears only in the Lick Observatory Bulletin series. It will not be published in any journal)

I. Introduction, General Remarks

In order to accommodate such new information as well as more accurate astrometric coordinates within a double page, 264-column format, it has been necessary to omit some information that is relevant and would have been useful in some cases:

1. IRAS identifications are not included.
2. Light curve classifications are not included, partly because such traditional observations have not kept pace with the volume of other information. Instead, references are given to sources where such information as exists may be found, except in cases where rotational modulation has been detected; such results are given in the Remarks to Table 1.
3. No references are given to polarization information; however, that subject has recently been surveyed very thoroughly by Bastien (l988).
4. The "emission line intensity" classification of the Second Catalog, a rather subjective quantity but all that was available in l972, has been replaced by the equivalent width of H emission, which is now readily determinable as the result of the widespread use of linear, red-sensitive detectors.
5. No references are given to proper motion information.

It was suggested in the Second Catalog that many of the variables in young clusters and associations that were not then known to have line emission would turn out to have bright H or Ca II, H,K lines upon closer examination. This has turned out to be so: many such stars are now included as "weak-line T Tauris" (abbreviation: wt). A large number of such stars have also been recognized as the result of X- ray surveys of obscured regions, particularly the Taurus- Auriga clouds. Walter and co-workers, who have done much of this work, have called these objects "naked T Tauri stars", or NTTS. It is our opinion that these do not constitute a separate class of pre-main sequence stars, but are a quite natural extension of the T Tauri class toward weaker line emission since the cutoff of conventional T Tauri stars at W(H) ~ 5 Å was set only by the limitations of the early objective-prism or -grating surveys. The existence of substantial numbers of such stars was in fact to be expected (Herbig l985) from the shape of the frequency distribution of W(H). We prefer the non-committal classification "wt" for these stars as a group rather than NTTS, partly because the latter implies a physical picture of the phenomenon that is still speculative.

However, one kind of weak-emission star that has been omitted from the Third Catalog are the rapid-rotating G- and K-type dwarfs in young clusters, such as Per and the Pleiades, most of which have emission at H. They have not been included because they lie on or near the main sequence. There are probably such stars in the field as well, and consequently we have omitted objects such as W92/NGC 2264 (= V642 Mon), Gliese l82 (= V1005 Ori), and any others that appear to be BY Dra-like variables. On the other hand, we have included many weak-emission G and K stars in the Orion Nebula region and in NGC 2264, on the grounds that they lie well above the main sequence and are therefore clearly pre- main sequence objects.

The lower boundary of the Orion population, insofar as it is represented in this Catalog, thus is not well defined. Nor is it always apparent whether a late-type star having no more than weak H and Ca II emission is pre-main sequence or not. This is a relatively recent problem. The sample of emission objects that were turned up in the early H surveys were mostly classical T Tauri stars, where emission-line criteria clearly provide the identification. Foreground dMe stars were not detected, because such stars in the field and in older aggregates like the Hyades rarely have W(H) greater than about 6 Å. But in younger clusters like the Pleiades, emission H has now been found in M dwarfs at W(H) values as large as l8 Å, although the most are less than 12 Å (Stauffer and Hartmann 1986). When such stars attract scrutiny as the consequence of some special activity, such as variability or X-ray emission, unless their luminosity is well enough known to locate them above the main sequence, there is no obvious way to distinguish a pre-main sequence star from its young main sequence counterpart. It is possible that refinement of the lithium abundance criterion might clarify this situation.

It must be stressed that the stars listed here have been discovered by a variety of techniques, through searches that have been concentrated in certain areas while other regions have been almost neglected. Therefore, no one should consider the Catalog as complete even to a fairly modest limiting magnitude over any large fraction of the sky.

The Catalog references those sources and papers that were available to us through March 1988. We shall be grateful for any errors that are called to our attention.

II. The Catalog

Table 1 is organized as follows.

Column

1. HBC The running number is followed by n when the star is itself involved in, or illuminates bright nebulosity. An asterisk (*) indicates that a Remark follows the Table.

2. Star This is the preferred designation of the object; if a variable star name has been assigned that is always given preference. If the preferred name is too long, a > symbol indicates that it follows in col. 3.

3. Other designation: The conventional designations (AS, LkH, Haro ...) are explained in HRC. We have found it necessary in some cases to expand the prefix system, usually abbreviating discoverers' names by two-letter symbols rather than one to avoid confusion with variable star designations (thus: CoKu for Cohen and Kuhi). We have also retained the discoverer's name for an object wherever possible, rather than substituting what might seem a more rational designation (thus: P2441/c for the companion of P2441, rather than P2441 B). The prefixes used in cols. 2, 3 are as follows:

      CD       Cape Photographic Durchmusterung
      CoD      Cordoba Durchmusterung
      CoKu     Cohen and Kuhi [93]
      Eggen    [125]
      Elias    Tau-Aur [128]; Oph [127]; IC 5146 [126]
      FK       Feigelson and Kriss [132]
      GlPe     Glass and Penston [157]
      GM       Gyulbudaghian and Magakyan [177]
      HaGr     Hartigan and Graham [186]
      He 3-    Henize [195]
      HH       Herbig [211] and later publications by a variety of authors.
      HJ       Herbig and Jones [218]
      HJM      Hyland, Jones and Mitchell [238]
      HM       Henize and Mendoza [196]
      JH       Jones and Herbig [250]
      Kn       Knacke et al. [274]
      LkCa     Herbig, Vrba and Rydgren [219]
      LZK      Liu, Zhang and Kimura [315]
      MacC     MacConnell 1968: Cep-Cas; 1981: Pup
      MaRy     Marraco and Rydgren [323]
      MC       Cohen [90]
      NTTS     Walter et al. [506]
      OgHa     Ogura and Hasegawa [355]
      P        4 digits:  Parenago [359]
               1 digit:   Mundt et al. [344]
      Par      Parsamian [360]
      PC       Parsamian and Chavira [363]:  PC numbers have been assigned 
               to all the confirmed Tonantzintla discoveries in the Orion
               Nebula region, but Table 1 gives only those that have no 
               Haro 6- designations.
      PH       Pettersson [370, 371]
      PP       Parsamian and Petrossian [362]
      ROX      Montmerle et al [332]
      RNO      Cohen [85]
      S        Sonneberg variable star
      San      Sanduleak [417]
      SS 1     Sanduleak and Stephenson [419a]
      SS 2     Stephenson and Sanduleak [444a]
      SSS      Strom, Strom and Stocke [450]
      SSV      Strom, Vrba and Strom [455]
      St       Stephenson [444]
      Sz       Schwartz [426]
      TH       The:  see Table 3
      vBH      van den Bergh and Herbst [482]
      VSB      Vasilevskis, Sanders and Balz [485]
      W        Walker, NGC 2264 [494]; IC 5146 [495]
      Wa       Walter [502]
      WK       Walter and Kuhi [504]
      Wray     Wackerling 1970
   

4. Right Ascension
5. Declination
6. The coordinates indicated by B in col. 6 were determined by one of us (KRB) with the Lick Automatic Measuring Machine on yellow (in most cases) plates of the Lick astrometric program. Usually 15 to 20 reference stars from the AGK3, with proper motions applied, were used. The epoch (minus 1900), rounded off to the nearest year, follows the B. The indicated by Aw in col. 6 were originally measured by C.A. Wirtanen, from blue plates of the Lick program, for the HRC. The epoch of those coordinates is approximately 1950. We do not regard either B or Aw coordinates to be of astrometric quality. Coordinates drawn from other sources are referenced accordingly. Those brought forward to 1950.0 have not had proper motions applied, so remain at their original epoch.

7. These two columns contain the
8. Galactic coordinates in the lII, bII system

9. These two columns contain the
10. Photometric range if the star is a known variable, expressed in the magnitude system indicated. Values taken from the 4th edition (1985, 1987) of the General Catalogue of Variable Stars, or recent Supplements, are indicated by a C. (Note that the conventional practice is followed in that < means "fainter than".) Stars believed to be variable are indicated var. A number of stars not known to be variable have their mean, or estimated magnitudes in these columns if that magnitude is not visual or in the Johnson V system; otherwise that value is in col. 11.

11. V
12. B-V
13. U-B photometry: for stars observed more than once, unlike HRC practice (where mean values were given regardless of phase) these columns contain the values observed when the star was brightest in V and a full set of UBVRI magnitudes were measured at essentially the same time. In some cases, the colors show a substantial scatter at the same value of V; such colors are marked with a v. For those stars where there is only a small scatter about a mean V, or where a small-range cyclic variation is superposed upon irregular activity, mean rather than maximum-V values are tabulated; such stars have an m following their V magnitude.

14. Photometric references: the first number is the source from which the tabulated values are taken. Additional sources of UBV data follow. For stars having an extensive photometric history, a * means that details are in a Remark to Table 1. An hrc means that some information given in the Second Catalog is not repeated here.

15. The HBC number again.

16. V-R
17. V-I values, usually obtained simultaneously (i.e., at maximum V) with the UBV data of cols. 11-13; this is so if the first reference in col. 19 is the same as the first in col. 14.

18. A single letter (J, C) shows whether the R, I values are on the Johnson or Cousins system. An i indicates an instrumental (r,i) system; conversion relations for the photometry by Rydgren and co-workers are given in [407].

19. References to the V-R, V-I data, as described for col. 14.

20. References for infrared magnitudes, spectrophotometry and spectroscopy. However, low angular resolution far-infrared observations are not usually cited.

21. UV, X-ray references: these usually refer to IUE spectroscopy and to X-ray detections from the Einstein survey.

22. Radio references are to VLA observations or to detection of the star by some other means. No attempt is made to cite radio frequency molecular line observations of the cloud in the general neighborhood of the star.

23. Light curve: references to photometric studies published since HRC. An hrc means that significant references in the Second Catalog are not repeated here.

24. v sini, the projected axial rotational velocity, given only to the nearest km/s. If no radial velocity value appears in col. 25, then that reference is to the source of the v sini; if a value for the radial velocity is given, then the second reference is (usually) the source of the v sini.

25. These two columns contain
26. Radial velocity (heliocentric, in km/s), quality, and reference. In all cases, these velocities are from the absorption line spectrum. Velocities obtained with modern equipment usually replace those obtained at low dispersion by the early observers. The quality letter (a, b, c) expresses our judgment as to the uncertainty of the quoted velocity: a indicates a velocity of the highest quality, with an uncertainty of 1-2 km/s; b means a value with an uncertainty of 3-5 km/s; and c a velocity of still lower accuracy. For some stars we have not given the published velocities at all. Comments on several special objects (*) appear in the Remarks.

27. Spectral type. With the growing employment of red-sensitive detectors, spectral types determined since the HRC have increasingly been dependent upon criteria in the region longward of about 5000 Å. However, it is apparent that significant differences exist in T Tauri spectra between such types and those assigned by the early observers of the 4000-4500 Å region ([498] and Appenzeller 1985). Furthermore, it is not clear whether the spectral types of such stars change during their light variations or at other times. Therefore, it may not be possible to assign a MK type to a T Tauri star without further qualification. We have not faced up to such issues: the types given here for those stars for which more than a single classification is available are either compromise values (usually indicated by :), or in case of conflict that value which seems most reasonable to us. No indication is given of the spectral region in which the type was assigned. Several special cases are explained in the Remarks. Many of the types in HRC were based on unwidened, very low-dispersion, often underexposed Lick spectrograms; in all but a very few cases, those classifications have here been disregarded. The conventions in col. 27 are as in HRC: type K7, M0 means either K7 or M0, while K7-M0 means a type between K7 and M0. If the Li I 6707 Å line has been detected in absorption, the type is followed by (Li). The very fact that the star is included in this Catalog indicates that emission lines have been detected (except in a very few special cases, all explained in the Remarks), so the suffix e for emission is not printed for types G and later in col. 27 although it properly is a part of the classification; the e should be added if these types are quoted. However, in order to avoid possible misunderstanding, that e has been included for all the B, A and F types where line emission is present. An hrc means that some significant information either in the Second Catalog, or referenced there, is not repeated.

28. References to the source of the type quoted. Information in col. 27 which does not appear in the papers cited is usually from unpublished Lick material; a blank reference has that specific meaning.

29. These two columns contain
30. Equivalent width of H emission (in Å): These are from the original sources, and are often mean values. Different observers at different times sometimes quote very different results and it is often uncertain whether this represents real variation or is an instrumental effect; when real variations seem to be present, the mean is given followed by a v. A number of cases where the W(H) value from slit spectroscopy seems incompatible with the fact of detection of H on an objective- prism plate are mentioned in the Remarks. A hk in col. 29 means that there is no information on H, but that emission is present in the H,K lines of Ca II. A pr means that H emission has been detected, but that no value for the equivalent width is available. An abs means that H is in absorption. An em means that unspecified emission lines have been observed [238]. A * means that there is a Remark.

31. Spectrum references show where the spectrum is reproduced (either photographically or as a scan), or the spectrum is described or discussed.

32. Type gives our judgment as to which group the star belongs. The abbreviations are:

       tt   T Tauri star
       wt   weak-line T Tauri star, usually having W(H) less
            than about 10 Å and no other emission in the
            optical region except Ca II H,K.  This includes
            most of the so-called "Naked T Tauri Stars".
       su   A star like SU Aur:  type late F to K, weak
            emission at H and Ca II, very broad absorption
            lines (v sini > 50 km/s), and relatively high
            luminosity.
       ae   An Ae or Be star such as those described in [203].
       fu   A star of the type of FU Ori.
       ?    Type uncertain:  the information is adequate, but
            the object does not fit into any established
            group;  these stars are usually described in more
            detail in the Remarks.  Also, one of the original
            criteria for membership in the Ae, Be group was
            that the star illuminate bright nebulosity, but
            now a number of irregular variables are known
            which are photometrically and spectroscopically
            similar but are not nebulous or associated with
            obvious obscuration (UX Ori, WW Vul, SV Cep, BO
            Cep, ...).  These questionable objects are also
            marked ? , or in some cases a?, in the Table.
       --   A blank means that the observational information
            is inadequate.
    

33. Reference to an identification chart or photograph.

34. The name of the bright nebulosity, dark cloud, cluster, association, or other object with which the star is associated or projected upon. A number of southern cloud complexes are designated by the abbreviations used by Schwartz [426]; note that these are not the T-association designations of Kholopov (1959) or the R associations of Herbst (1975).

        The prefixes used are:
                  B    Barnard (1927)
                  FS   Feitzinger and Stuwe (1984)
                  Gum  the Gum Nebula region
                  L    Lynds (1962)
                  Ori  the Orion Nebula region
                  Sh   Sharpless (1959)
    

We are greatly indebted to A. Klemola for his help with the astrometric measurements, to B.F. Jones for unpublished coordinates and other assistance, and to many colleagues for preprints and unpublished information. We are also very grateful for partial support by the National Science Foundation, most recently under Grant NSF AST82-03115, for much of the observational work at Lick Observatory that is included here as well as for the preparation of the Catalog itself.

REFERENCES

Barnard, E.E. 1927, Carnegie Inst. Wash. Publ. 247.

Bastien, P. 1988, in Polarized Radiation of Circumstellar Origin (Vatican Conference, June 1987).

Feitzinger, J.V. and Stuwe, J.A. 1984, Astr.Ap. Suppl. 58, 365.

Herbig, G.H. 1962, Adv.Astr.Ap. 1, 47.

Herbig, G.H. and Rao, N.K. 1972, Ap.J. 174, 401.

Herbig, G.H. 1985, Birth and Infancy of Stars, ed. R. Lucas, A. Omont, and R. Stora (North Holland), p. 535.

Herbst, W. 1975, Astr.J. 80, 503.

Kholopov, P.N. 1959, Sov.Astr.-A.J. 3, 291, 425 [36, 295, 434].

Lynds, B.T. 1962, Ap.J. Suppl. 7, 1.

MacConnell, D.J. 1968, Ap.J. Suppl. 16, 275 (Cep-Cas).

MacConnell, D.J. 1981, Astr.Ap. Suppl. 44, 387 (Pup).

Stauffer, J.R. and Hartmann, L.W. 1986, Ap.J.Suppl. 6l, 531.

Wackerling, L.R. 1970, Mem. R.A.S. 73, 153.