The Yale Parallax Catalog (van Altena et al. 1995) contains the sum-total of all annual trigonometric parallaxes reported in scientific literature, as of November 1995. HIPPARCOS
has another ∼1500 relevant parallaxes. Trigonometric parallaxes continue to be reported, however, and the only way to get the best set of stars within 25 pc is to track down all of the publications.
Where YPC made a massive effort to remove systematic errors and re-weight parallax solutions, the RPD makes no attempt to correct the parallaxes or errors of various programs. The values published in papers are simply taken as-is, despite our reservations about some papers and authors – several do not correct parallaxes to absolute, several others do not say if they did or not. Ultimately, most recent parallax programs have published so few stars that corrections on the level of what YPC did would be impossible. Not counting HIPPARCOS
re-reductions, 1071 stars have been measured in the past 16 years in 178 papers; most are single-star papers, while RECONS alone accounts for 279 of the parallaxes published with only 9 papers, and the largest paper, Riedel et al. (2010)16, with 67 parallaxes to 64 star
systems (see§ 5.2).
The RECONS Parallax Database properly exists in three parts: A list of all papers known to contain trigonometric parallaxes, with a check of whether they’ve been added to our tables; a table of all ground- and space-based parallaxes; and a table of HIPPARCOS
re-reductions. The actual table of ground- and space-based parallaxes is rather informal, as we have only systematically collected information for stars within 25 pc. The table of
HIPPARCOS re-reductions, on the other hand, is fairly complete. Inasmuch as the RPD only exists to feed the RECONS Database with new parallax data, its value and existence as an independent project are questionable. The RPD may never be published formally, though the list of known papers is already online17.
16Recently exceeded by Faherty et al. (2012), 70 parallaxes.
3.3.1 Ground-Based and Space-Based
This category essentially contains every parallax published using either a ground-based op- tical/infrared observatory, long-baseline radio interferometry, or Hubble Space Telescope parallaxes, mostly done with the Fine Guidance Sensors (HST-FGS), though several papers have used the Wide Field/Planetary Camera 2 (HST-WFPC2) or even the Advanced Cam- era for Surveys (HST-ACS). This section of the RPD was originally designed and curated by Jennifer Winters, though others (including myself) have added to it as well.
The list of papers contains many notable entries: the final publications of the Yale parallax program (Weis et al. 1999); the final McCormick Observatory (Virginia) parallaxes
(Ianna et al. 1996); the (possibly) last publications from Allegheny Observatory (Gatewood & Coban 2009); the last (at least thus far) photographic plate-based parallax (Deacon et al. 2005b).
Contained within the list are the first VLBI parallaxes Bradshaw et al. (1997) (which are typically accurate to 10 µas), and all HST parallaxes.
Other notable entries include Gatewood et al. (2001) and Gatewood (2005), both of which include ground-based and space-based parallax measurements, and Lucas et al. (2010), the only instance I’m aware of where two CCD-based sources of astrometry were combined in a parallax solution.
3.3.2 HIPPARCOS re-reductions
This category does not include the van Leeuwen (2007) re-reductions, as those were done from scratch. Rather, this category concerns the massive number of publications that have re-
analyzed Hipparcos Intermediate Data (HID) (van Leeuwen & Evans 1998) to obtain better parallaxes. These intermediate data evidently already have the raw transit scans reduced to absolute sky positions on the ICRS grid, but with no other processing done.
HIPPARCOS re-reductions generally fall into two categories: Stars with incorrect po- sitions in the HIPPARCOS input catalog (if the star did not pass through the center of the astrometer’s grid, the automated reduction pipelines had problems), and multiple star systems (where the orbital motion was often incorrectly modeled into the parallax or proper motion). The most famousHIPPARCOS re-reduction (and the only one used by the NStars team) was S¨oderhjelm (1999), who combined Hipparcos Intermediate Data with TYCHO-2 data and speckle measurements to re-calculate parallaxes to 205 nearby binary systems.
He was not, however, the only one. There were 240 systems with improved results included in the notes to the original HIPPARCOS catalog (Perryman et al. 1997). Many authors have published papers re-reducing HIPPARCOS data with constraints of known orbits (or, in Guillermo Torres’s case, solving the entire 3D orbit, parallax, systemic radial velocity and proper motion at once, Torres & Ribas 2002).
Originally, I divided the papers into groups based on which of a short series of authors had worked on them (Dimitri Pourbaix, Fran¸cois Mignard, Valeri Makarov, and Guilliermo Torres are on most re-reduction papers), with the intent to discern whose re-engineered so- lutions were more accurate, and which (if any) should be preferred over van Leeuwen (2007). Eventually, it was decided that more recent papers should supercede older papers, and all
van Leeuwen (2007). In any event, van Leeuwen (2007) released new Hipparcos Intermedi- ate Data, which have already been used in a paper by Ramm et al. (2009).
3.3.3 Problems
Not all papers can be smoothly incorporated into the RPD or RECX25.
Several HIPPARCOS re-reductions claim to have re-evaluated all the astrometry but do not publish the new values, or at worst only publish deltas between the old and new values- this is especially bad for Sozzetti & Desidera (2010), whose deltas are apparently relative to the original HIPPARCOS reduction and Intermediate Data, but did not explicitly say so.
Several other papers (Ianna et al. 1996; Bartlett et al. 2009; Khrutskaya et al. 2010) only published relative parallaxes. Ianna and Khrutskaya do include corrections to absolute, the absolute parallaxes need to be calculated explicitly.
Superceded values are occasionally tricky to deal with. Martinache et al. (2009) re- reduced the parallax data from Pravdo et al. (2004) (by reading values off a graph!) and thus supercedes Pravdo et al. (2004) despite no involvement from any of the authors of Pravdo et al. (2004). Tinney (1996) updates parallaxes from Tinney (1993) which were included in YPC; in those cases YPC has been made obsolete, and we assume Tinney (1996) has none of the systematics YPC corrected for. Ianna et al. (1996) is particularly difficult, as it updates McCormick observatory results for many stars that were already included in YPC as the mean of many observations, and thus supercedes onlypartof the published YPC value. It is unlikely that we will go back to the original YPC data (in Volume II) and re-run their mean parallaxes.
Most of the other confusing cases are statistical, orbital, microlensing (stereoscopic) or pulsar timing parallaxes, though Boden et al. (2006) still manages to confuse by deriving an orbital parallax using re-reduced HIPPARCOS data.