Initial Steps

In August 2010, RECONS began from scratch, but with the experience of NStars and a far greater understanding of how to construct the database of nearby stars, brown dwarfs, and planets. Like NStars, we started with the Yale Parallax Catalog (van Altena et al. 1995), as the vast majority of nearby stars can be found there. To this we added the HIPPARCOS

catalog. Where NStars folded in the original HIPPARCOS reduction, RECONS began with the new van Leeuwen (2007) HIPPARCOS re-reduction. RECONS also has the benefit of all our published parallaxes (Jao et al. 2005; Costa et al. 2005, etc.) which added a sizable amount of systems.

Angelle Tanner and I independently cross-matched YPC and the new HIPPARCOS, her by automation and I by hand (later, I also did an automatic cross-match). The first step

was to merge the YPC and re-reduced HIPPARCOS catalogs, as they contain _∼90% of the currently known systems. Accordingly, the initial work involved extracting and formatting the lists to be identical; sorting the lists together, and sifting them manually in GNUemacs. If a match was discovered, I merged the lines, overwriting YPC information with HIPPAR- COS information; the only information from YPC that survives a match is the list of names (including YPC ID) and the YPC parallax.

This task was made difficult by errors in YPC (which was, again, attempting to homog- enize an enormously heterogeneous dataset); sometimes coordinates for stars were off by arc-minutes, and occasional typos in the names or coordinates made it worse. There were additional difficulties matching up the correct set of components to each other, which often required paying attention to the V magnitude, proper motion, or other sources of informa- tion about the stars. While there was no hard limit (this being a by-hand sort), the rough parameters used were: match to within_±30′′

in either RA or DEC;V within 0.2 mag, proper motion to within 0.1′′ _yr−1_{, position angle to within 10}◦_{. Leniency was granted in the more}

obvious cases, under the assumption that, for example, there would not be more than one 4th_{magnitude star moving at 2}′′

yr−1 _{within a few arcminutes, and so on. Companions often}

appeared as discrepancies inV magnitudes (or multiple matches in the same catalog). The sorting and final list production was done by October 2010.

The nagging issue here, however, is that one cannot simply download a list of all stars within 25 pc in both catalogs and match them up. Some stars do appear in the other catalog, but not within 25 pc. For instance, YPC and the original HIPPARCOS (Perryman et al.

1997) put Mizar and Alcor within 25 pc; the new HIPPARCOS (van Leeuwen 2007) does not9_{. The second phase of the sort involved running the entire list of coordinates from the}

first phase through the VizieR versions of YPC and HIPPARCOS to find parallax matches

not within 25pc to stars within 25pc. This was finally completed in November 2010.

The resulting list had good parallaxes, but lacked companions, and lacked stars added by more recent trigonometric parallaxes. All RECONS parallaxes (for new and existing entries) were quickly added to this final table, along with white dwarf systems from the DENSE project10_{. Jen Winters added the RECONS Parallax Database (see§ 3.3) in stages, starting}

with trigonometric parallaxes published between November 1995-January 2000, then 2000- 2005, and finally 2005-2011. Angelle Tanner folded in a table of values from Stauffer et al. (2010) that provided accurate coordinates and GJ names for all systems in any public version of the Catalog of Nearby Stars, as well as additional companions.

At this point, the table was separated out into the three quality sections (VETTED, FLIMSY, BOOTED), plus an additional “confusing” section for entries that proved partic- ularly challenging.

2MASS data (astrometry and photometry) was blindly (closest-entry) extracted from VizieR for the entire sample, and Justin Cantrell’s 2006 NStars photometry list was folded in (creating companions where photometry existed for them). I extracted the list of known verified planets from the Exoplanet Data Explorer11_{, a more thoroughly vetted list than Jean}

9_{With a weighted mean parallax of 39.90±0.13 mas, it is still possible they are within 25 pc, though}

new measurements to settle the question will be difficult. There are few remaining instruments capable of measuring parallaxes for stars that bright.

10_{Subasavage, J.P. http://www.denseproject.com} 11_{http://exoplanets.org/ checked 2012 JUL 15.}

Schneider’s Extrasolar Planets Encyclopædia12_{. Finally, I downloaded all 5835 HTML pages}

that form ARICNS and extracted all the information I could with UNIX ‘grep’ statements; the resulting table and its notes formed a starting point for adding still more well-known companions – these are referred to in the database as CNS98.

Eventually, in June 2011, Ken Slatten was invited to GSU, and work began cross- comparing our extensive list of systems and companions with his database. The hour-by-hour folding in of companions identified in that search continues (largely by Jen Winters).

The confusing entries were eventually resolved by comparison to multiple catalogs, appeal to Occam’s Razor, and eventually the intervention of Ken Slatten, who resolved the last 7 problem cases. They usually resulted from multiple pieces of erroneous or contradictory information between two catalogs (switching the members of a binary by position and name, but not magnitude) or just plain misleading (e.g. the dozen proposed companions to Capella, of which only four are physically linked: Capella A=Aa, B=Ab=P, H, and L.) Another large chunk were members of the Pleiades and Hyades with erroneous parallaxes that put them within 25 pc, and terribly large errors that made them potentially match many members of the Pleiades and Hyades (all of which had similar proper motion vectors). The Pleiades and Hyades members were resolved by assuming more realistic distances of 133 and 38 pc (respectively) for the erroneous entry, and throwing out all “companions” with separations larger than 63,000 AU (_∼1 ly). The erroneously high-parallax entries were themselves kept, though, in the FLIMSY and BOOTED sections.