CSO Memo M1000-001A
August 19, 1998

CO_point_star catalog

CO point star catalogs have been in somewhat of a disarray: on VAX side there are and in cat_dir, and on bck, orrery accesses yet another CO point star catalog. contains some 26 entries, and appears to be a subset of with 60 stars, but some of the star positions differ by as much as 3-4 arcsec and has somewhat updated info of stars' proper motion. Rather than chasing the source of the two catalogs, it appears to be easier to start from scratch by finding out the latest observations on these stars.

Two papers came to be of great help: ``Catalog of CO/HCN Observations of Circumstellar Envelopes'' by Loup et al. (A&A Suppl. 99, 291, 1993) and ``A CO (J=1-0) and (J=2-1) Atlas of Circumstellar Envelopes of AGB and Post-AGB Stars" by Neri et al. (A&A Suppl. 130, 1, 1998). The Loup paper contains an exhaustive listing of 444 circumstellar objects and their past CO/HCN observations by various submillimeter telescopes. Positions were given in both B1950 and J2000, but there is no proper motion information. The more recent Neri paper reports fully sampled observations (IRAM interferometer+IRAM 30-m) for 46 stars in the Loup list. The positions were listed in J2000, and most of the stars have size information. Again, there is not proper motion information.

Combing through the Loup list, 76 sources are selected covering our visible sky based on their CO line strength. The sources include almost all of that listed in, minus a few known weak ones. To obtain proper motion for the sources, various alias object names for each source as listed in the Loup paper prove to be very useful: they were used for keyword searches in the Hipparcos Input Catalog to find the corresponding matches, and these entries invariably come with proper motion at J2000 epoch and position listing in both B1950 and J2000 which are usually within 4-5 arcsec of radio positions listed in the two papers. We have hence adopted the Hippacos positions for these sources. About 60% of the selected sources were matched with proper motion information this way. For sources that have not corresponding entries in the Hipparcos Input Catalog but are in Neri paper, the positions are quoted from the latter, but converted to B1950. For the still few that are in neither, the B1950 positions as listed in the Loup paper are used. Two other source in, IR0121P61 and IR0433P16, are of unknown origin, and are not in the Loup list either. They are assumed to be in the for good reasons, and are therefore carried over to be included in the selected source list. In all, there are 78 sources in the new, and the old catalog is renamed CO_point_star.old_cat.

The information orrery accesses on bck is also consolidated to reflect changes made to the CO pointing star catalog. Annotations for individual stars, which can be viewed by clicking on the star on an orrery display, are also added/expanded with information regarding the star's size and CO line temperatures. There are however some 28 stars with no CSO measurement of their CO line temperatures. We will post the list in the control room to encourage observers to observe them if they happen to be in the area and are with right receiver tunings (CO 2-1, 3-2, or 4-3). Or we could use engineering time to observe the sources.

To compare the differences between the new and old, common entries in both catalogs are used to calculate the positional offsets. The medium value of the B1950 positions is 0.72", with 80% of the source positions agree within 4". In four cases the positional differences are in the range of 8"--12". The differences in proper motion between the two catalogs would introduce on average a positional difference of 0.14" to current positions of CO pointing stars. While 80% of the such positional offset is under 1", it can be as large as 6.5". Clearly, with more updated positions and proper motion measurements, the new CO pointing star catalog should represent a marked improvement over the existing catalog.

Ruisheng Peng (