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Coordinates and identifications for the Ackermann red stars
In the late 1960s Gerhard Ackermann published two lists of extremely red
stars (1968ZA.....69..130A and 1970A&A.....8..315A), including what appeared
to be reliable spectral classifications for a few hundred stars. For several
years I have gone over the longer second list iteratively in hopes of
recovering the stars, though handicapped by the approximate coordinates for
these rather faint objects. But even with such new catalogues as 2MASS and
MSX, many ambiguities remained. The 1970 paper indicated that charts were
prepared for the stars, and it was clear that they could not be recovered
without them. Various attempts to locate the author were unsuccessful.
Recently, however, I located him via the Technische Fachhochschule in Berlin,
where he is recent past president of this institution. Hooray for Google!
Professor Ackermann was kind enough to respond to my query and also to
quickly provide a copy of his original Heidelberg dissertation that contains
charts for all the stars. The charts are very clear, so it was easy to go
through the list once more in a definitive way.
The two published papers provide details of the observing and analysis.
In particular, the 1970 A&A paper presents in English nearly all the
information contained in the dissertation 'auf Deutsch'.
Briefly, the spectral classification was done on plates taken with the
25cm f/3.6 Schmidt camera at Heidelberg together with a 10-degree UBK7 prism
yielding a dispersion of 3500A/mm at the atmospheric A band (7700A). Exposures
on ammonia-hypersensitized Kodak I-N emulsion + RG665 filter were obtained
along with direct plates on I-N emulsion as well as 103a-E + OG550, totalling
101 exposures in all. The observing was done on 24 nights between June and
October 1968. The spectra were classified by following the precepts of
Cameron & Nassau (1955ApJ...122..177C) and Nassau & Velghe
(1964ApJ...139..190N).
Because the calibration of the photometry on the direct plates was by
necessity rather crude, and much better data exist now, I have chosen to
completely ignore Ackermann's photometric results. The procedures used were
sufficient to identify the reddest stars, but not for much else. I show
at least approximate V magnitudes instead for all the stars. For the most
part these are merely averages of the photo-blue and -red magnitudes in both
GSC-2.2 and USNO-B1.0, but their zero-point and scale should be reliable at
the few-tenths magnitude level in this range.
Ackermann initiated photoelectric observations at I and K, but obviously
the Heidelberg weather was not conducive to pursuing this.
Coordinates were drawn from either UCAC2 or 2MASS depending mainly on
Declination, since UCAC2 extends only to about +40 Dec in this area.
The UCAC2 positions should be good to < 0".1, and those from 2MASS < 0".2.
In a few cases, such as gross overexposure in 2MASS, I have adopted positions
from various Schmidt survey catalogues, as indicated with each entry.
GSC-ACT continues to come in handy on occasion.
After obtaining coordinates for the stars, I matched the lists in VizieR
against various useful catalogues. I also searched each position in SIMBAD
(3' search radius) for additional identifications. In the remarks I show just
one useful alternate name if space allows.
The first short list is from the concluding volume of the Zeitschrift fur
Astrophysik. It includes 13 very red stars in various parts of the sky and
gives charts. In the 1970 paper, Ackermann refers to these stars using the
acronym HDK, which is adopted here. The published table gave rather rough
arcminute-precision positions (for equinox 1965). Star 6 was recovered
1 degree east of the nominal place, and identified with the variable star
WX CMi. Along with the positions and IDs, the table below shows V magnitudes
and the spectral types given in the original paper. Some of the stars are
within the region covered by the ASAS-3 survey, so reliable V magnitudes are
available along with beautiful lightcurves.
Ackermann's second much longer list contains rough photometry from the
POSS-I prints for some 400 very red stars in the Cygnus starcloud, and for
254 of these spectral types were also determined. The stars without spectral
classifications comprise a diverse group including both red/reddened late-type
stars and greatly obscured hotter stars, but no real astrophysical information
is given for any of them beyond sheer redness. I have therefore decided to
omit these stars from the tables below. The survey was a first reconnaisance
with the limited resources available to the author, so could not be expected to
be comprehensive.
The second list is arranged identically as the first, but GSC names
are omitted since the stars are in general much fainter. The name scheme
includes the approximate galactic longitude and latitude as the first two
elements, followed by a serial number within each field. These names are
already provided for in the Lortet et al 'Dictionary'. Note that two stars
([A70] 78-0- 36 and 78-12- 9) have identifications from the IRAS faint- and
serendipitous-source surveys, but the remainder are ordinary point-source
objects. At low galactic latitudes, the MSX6C survey provides much improved
flux data in the mid-infrared.
The table format extends to 124 columns, so only a few stars require
separate notes at the bottom of each table, indicated by an asterisk next to
the star name.
In consultation with Prof Ackermann, the following changes have been
made to the spectral types. For stars shown in the original table with a
hyphen between two types (e.g. M5-M6), this was to show that the type was
uncertain to that degree (i.e. M5 or M6). I have changed these to the
'slash' notation of Nancy Houk, thus M5-M6 becomes M5/6. One star,
[A70] 78-0-144, exhibited a range in types, and it is shown as M7-M9.
Ackermann also indicated a number of stars as being of very-late type
with VO present (separable from the A-band), but where the star was too faint
to classify accurately. He agrees these are likely to be in the range
M7 to M9, and I again show these in the slash-style notation as M7/9:,
with the colon added to indicate uncertainty since the types were not explicit
in the original, and sometimes a question mark for those already marked as
uncertain in the original. These changes were made so that machine parsing
schemes will be better able to handle the classifications.
As best I can tell from the 2MASS J-K colors (large!) and the
near-complete IRAS and/or MSX detections, all the stars here are ordinary
very-late-type giants; there are no T Tauri stars or other sorts among them.
These stars complement similar far-red surveys for M and C stars by other
observers in the same regions, and provide spectral types and (now) visible-
light identifications for many 'anonymous' IRAS/MSX sources, not to mention
known and future variables.
Francois Ochsenbein has already allocated a spot for the catalogue in
the VizieR system as item II/260:
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?II/260
...soon to be filled in with complete information and data.
I am extremely grateful to Gerhard Ackermann for sending a copy of his
dissertation, which allowed the preparation of this list, and thus making it
available in machine-readable form at last. The Web site for TFH-Berlin is:
http://www.tfh-berlin.de (some principal pages in English)
Professor Ackermann's Web page is here:
http://www.tfh-berlin.de/~ttrans/ff/Ackermann.htm
===============================================================================
Coordinates and identifications for the Ackermann red stars
version: 7 Aug 2005
position sources (column 's'):
b USNO-B1.0 (2003AJ....125..984M, I/284)
g GSC-2.2 (2001yCat.1271.....S, I/271)
G GSC-ACT (1999yCat.1255.....G, I/255)
M 2MASS (2003yCat.2246.....C, II/246)
U UCAC2 (2004AJ....127.3043Z, I/289)
-------------------------------------------------------------------------------
source: 1968ZA.....69..130A
ACKERMANN G., FUGMANN W., HERMANN G., and VOELCKER K.
Zeitschr. Astrophys., 69, 130-139 (1968)
Neue Infrarot-Sterne.
HDK RA (J2000) Dec s GSC UCAC2 IRAS MSX6C V spec remarks
1 3 30 29.72 +22 35 52.0 U 1798-0308 39792432 03275+2225 10.3 M7
2 3 51 25.35 +15 45 17.7 U 1248-0771 37305083 03486+1536 11.2 M6.5
3 4 12 22.71 +51 09 47.3 M 3340-0962 04085+5102 G151.7507-00.1037 14. C CGCS 625
4 4 25 27.21 +16 33 23.2 U 1265-0539 37659233 04225+1626 10. M8 VX Tau
5 6 09 57.01 +17 32 35.9 U 1318-1151 38038522 06070+1733 G192.6535-00.8784 12.5 M8 GH Ori
6* 7 11 57.55 +07 29 58.6 M 07092+0735 G208.5465+07.9562 13. M9 WX CMi = NSV 3412, crowded
7 7 31 12.43 +28 08 20.1 U 1922-0334 41703641 07280+2814 G190.9680+20.5203 11.1 M8 DO 13073
8* 20 35 24.03 +40 57 55.5 M 20335+4047 G080.1863+00.2545 17. [A70] 78-0-103
9 20 43 00.71 +41 22 18.6 U 46180383 G081.3804-00.6350 13. M: [A70] 78-0-120, not V1589 Cyg
10 20 45 14.17 +39 15 20.0 M 20433+3904 G079.9816-02.2791 17. M9: [A70] 78-0-127
11 20 47 15.58 +40 59 18.9 U 46034082 G081.5777-01.4987 14.5 M7 [A70] 78-0-136
12 23 09 32.39 +51 12 25.8 M 3635-1332 23072+5056 13. M8
13 23 13 13.35 +56 36 12.4 M 4006-0523 23110+5619 G109.6811-03.7196 12.5 M8 V562 Cas
Notes
6 original coordinates have -4m RA error.
8 no strong TiO or VO bands.
-------------------------------------------------------------------------------
source: 1970A&A.....8..315A
ACKERMANN G.
Astron. Astrophys., 8, 315-334 (1970)
Extreme red stars in Cygnus.
Dictionary: Appendix: <[A70] LL-BB-NNN> N=166+86+12+134.
Notes
95-0- 7 Ackermann magnitudes seem to be for nearby CGCS 5182,
but spectral type is for this brighter star.
95-0- 57 western of two red stars 21" apart; second star is much fainter and
redder, and associated with MSX6C G093.5063+01.3003
(21 21 26.33 +51 45 01.2, 2MASS). the nearby IRAS sources have no
certain links.
