NStars

NStars is a personal program intended to help me build and maintain a list of Nearby Stars. The original version of the program was written back in 2006 and 2007, and used the (now long defunct) NStars website, ARICNS, and the Recons 100 list as input. Output was in CHView *.lst. It was of great use to me in producing my Clusters of Nearby Stars page.

With the release of the GAIA DR1 dataset, which includes the Tycho-GAIA Astrometric Solution (parallaxes for over 2 million stars), I decided to dig out my old program and adapt and improve it. I ended up making a great many changes. Although my revised star list is not completely satisfactory yet, I have decided to make both the program and my updated star list available to anyone who might want it.

Currently, NStars can..


Downloads

November 4, 2018

The star list has over 8100 star systems, going out to about 108 LY (there are some more distant systems, but this is due to parallax changes for not yet deleted systems). Parallaxes from Gaia DR2 are offset by 0.029 mas, those from the TGAS are offset by 0.25 mas. I've weeded out most stars with bad parallaxes and I've checked and corrected many bad luminosities and spectral types, but there are still some doubtful stars in the list (especially some binary star components from Gaia DR2). Please note that I've mostly avoided importing systems/stars with photometric distance estimates unless they use the latest CCD photometry, and when it comes to the URAT Parallax Catalog, I ended up removing many of the systems, even after restricting my import to stars with errors under 6 mas, because the magnitudes of the stars seemed too dim for the spectral colors. Many stars with URAT parallaxes are only left in the list because they are likely within 110 LY, even if the URAT distances seem quite wrong. Gaia DR2 has gone some way to correcting that, but Gaia DR2 itself is far from perfect.

If you download or make use of any of the above, please contact me for any questions, comments, or suggestions.

Updates

November 04, 2018:The program has more visble updates than last time. In the listbox, the system name is now (most times) colored based on the spectral type of the primary. I've moved many former Tool menu items to a new menu called Position (the Tools menu was getting too long). A new menu item in the Import menu can be used to try and get UCAC4,DENIS, and Gaia DR1 ids for the current star from VizieR. Some addition flux transforms have been added (the most useful probably being G to V for Red Dwarfs). Finally, when adding new Gaia DR2 stars, they will be skipped if the Gaia DR2 id is already in the list.

The list now has Gaia DR2 stars out to a parallax of 40 mas (unless they are clearly wrong), thus completing the 25 parsec radius sphere that is often considered to be Nearby by many. I do not plan to stop there. Keep in mind some binarys still have divergent parallaxes, and there plenty of Ultracool Dwarfs and White Dwarfs whose spectral types are just guesses at this point. The list has almost 8200 stars now.

September 30, 2018: The program has only a few changes, the most notable being some revamped flux transforms from Gaia DR2 magnitudes to 2MASS magnitudes (better for redder stars, but beware of unusual colours!), and a menu option to download and insert Gaia DR2 data (if you have the Gaia id).

For the star list, I've added DR2 stars with parallaxes between 50 and 45 mas, and assigned spectral types and magnitudes for all of these. Some old stars with photometric parallaxes have been shown to be Binary, and are now either removed from the list or moved much further out.

August 4, 2018: For the program, I've changed the mass estimations for Red Dwarfs to a new MKs fit from 'How to Constrain your M dwarf II' (Mann+ 2018, the paper has been submitted, but not posted to arXiv). Also, the mass estimations for AFGK main-sequence stars now use multi-linear relations from 'Empirical relations for the accurate estimation of stellar masses and radii' (Moya+ 2018), which use TEff and [Fe/H] as well as luminosity. Right click menus have been added to location editors, to help enter positions in decial (and for secondaries, a few other things). Some new filters have been added to help identify systems with certain problems.

The list has almost no new stars. The improvements come from: going over stars within 20 parsecs and, where applicable, tweaking the magnitudes and spectral types. Matching with Gaia DR2 stars with parallaxes between 10 mas and 30 mas, resulting in a few hundred updated parallaxes (and the stars are now beyond 108 LY, so I'll probably delete most of them eventually). Checking for binaries with mismatched Epochs (the positions are from 2 different dates) and fixing them. Finally, adding some missing Gaia DR2 ids, and picking system parallaxes for some systems where the previous per-star parallaxes places them too far apart.

June 23, 2018: When it comes to the program, some improvements have been made. Internal flux transforms have been added to estimate VRI from G − J and G − RP for certain edge cases. The catalog names store has been rewritten, which means that name duplicate matches are faster and Gaia ids are now correctly formatted with two internal spaces instead of 1. There is a new menu option to swap the order of system components, and merging stars into one system now handles most catalog ids better. Some filter option have been added to find internal name collisions and position mismatches.

The list has now added Gaia DR2 stars out to 20 parsecs (65.2 LY). Some name collisions, spectral types, and fluxes have been fixed, but a more through checking will have to come later.

June 3, 2018: The second post Gaia DR2 release. One change you might notice is that I've removed anything related to ARICNS (which has not been updated since the late 90's), and the RECONS nearest 100 list (too limited). I've fixed various bugs, I've created new (and quite useful) flux transforms to estimate B V Rc Ic J H Ks from Gaia DR2 G BP RP, and the Gaia DR2 import for new stars has a new section to specify rules to automatically discard objects.

New stars from Gaia DR2 have been added to the list going out to about 56.2 LY. This includes a nice selection of Red Dwarfs (many not in Simbad), some White Dwarfs, and a few Ultracool Dwarfs that I have not yet assigned spectral types for (and some others that were already known). The Gaia magnitudes and transforms have been quite useful in cleaning up some binaries (some previously not known to be binary), but close separations of under 2″ mess up even Gaia DR2 photometry, so many binaries are still in a 'unfinished' state.

May 17, 2018: The first post Gaia DR2 release. I've added custom importers for Gaia DR2 (since my usual importers skip binaries and don't let you review the stars / browns dwarfs being imported, which is bad for DR2). I've added better enabling and disabling of menu items, fixed some bugs, and added both Gaia DR2 magnitudes to the display, and photometric conversions of BP−RP to V, Rc and Ic using the provided polynomials (which unfortunatly do not go redder than around M3).

For the list, I've matched DR2 parallaxes of more than 30mas (with a 0.029 mas offset) to as many stars as possible. A fairly small quantity of new stars has been added out to around 40.7 LY (80 mas), including a new White Dwarf. A strong note of caution here: Gaia DR2 does not handle close binaries all that well, and parallaxes that seem more precise are sometimes less accurate than older parallaxes (sometimes vastly so). The difference is not necessarily known to me. Also, newly added stars include some binary components, for which I have not yet gotten around to estimating magnitudes and spectral types.

April 17, 2018: With GAIA DR2 just around the corner, this update will soon become very obsolete. However, I have made many changes, so here one last release before DR2. You might notice the program now includes an embedded Icon. I have added importers for the recently published URAT South Catalog (using the .tex files in the sources). A few hundred stars have been added, but the quality of URAT parallaxes still seems to be fairly bad. Related to this is a tool that lets you swap the current parallax with one of the saved 'old' parallaxes. The download of APASS magnitudes is fixed.

Also, because of a lack of photometry, I ended up spending quite a bit of time deriving polynomial and multilinear fits to convert some types of photometry to B, V, Rc, and Ic, for K and M dwarfs. So the APASS conversion is now much better for Rc, there are options in the tool menu to input URAT, UCAC4, and CMC15 r' magnitudes for conversion, and the Simbad download will try and 'improve' magnitudes that come from the USNO B Catalog, and will also convert UCAC4 to Rc, if Simbad is using that for R.

February 23, 2018: Some additional issues in CHView .lst output have been fixed. I've added a new binary type, White Dwarf Secondary, for unresolvable binaries where the secondary is beleived to be a white dwarf (details unknown). A new tool has been added to set the position of a secondary from a separation and the position angle. Minor updates to the star list (mostly setting some systems to use the white dwarf secondary type).

February 16, 2018: The program has few changes. These are generally bugfixes to try and eliminate some types of crashes which I uncovered when I started to redo the cluster information. The starlist has a selection of accumulated changes, with some new red and brown dwarfs and various other minor changes.

September 17, 2017 : The program has relativly few changes, most of them minor adjustments to the intrinsic colours used to estimate spectral types. The list has more changes: I've finished importing TGAS and New Hipparcos stars out to 30 mas (~108.7 LY), and I've imported new parallaxes for Red Dwarfs and Subdwarfs from The Solar Neighborhood XXXX. New Young Stars near the Sun (Bartlett+ 2017), The Solar Neighborhood XLII. Identifying New Nearby Subdwarfs Using Tangential Velocities and Locations on the H-R Diagram (Jao+ 2017), and CCD Parallaxes for 309 Late-type Dwarfs and Subdwarfs (Dahn+ 2017).

August 20, 2017 : Many internal changes, but few that show up to an end user, other than a re-organization of the interface: instead of 2 sets of tabs per system, there is now one, with system data on the first tab, components (stars and pairs of stars, and brown dwarfs) on the second, and fictional info on the third. The White Dwarf mass estimates now take into account thermal bloating (using info from the same files I use to estimate Bolometric corrections), and for hot stars, I now use an interpolated Bolometric Correction instead of treating the stars as Blackbosy radiators. For the list, a have pushed the outer limit a bit further with TGAS and Hipparcos stars. Some errors have been fixed.

July 20, 2017 : No changes in estimation, but I have added a few more importers and expanded the Star List. New Trigonometric parallaxes from The Solar Neighborhood XXXIX have been added for many white dwarfs (including many not previously in the list), and I've also added a few hundred Red Dwarf systems with photometric parallaxes from The Solar Neighborhood XXXXV and UCAC4 Nearby Star Survey. I also imported some other lists from VizieR, but they yielded only a handful of systems.

March 22, 2017 : I've decided to adopt polynomial V-J based TEffs and Bolometric Corrections from the paper ‘How to Constrain your M Dwarf’ (Mann+ 2015), this reduces the Bolometric Luminosity of some stars by as much as 20% over what I had previously. For Ultracool Dwarfs, Luminosities will be calculated using Polynomial Fits from ‘Individual Dynamical Masses of Ultracool Dwarfs’ (Dupuy and Liu, 2017) if possible. The earlier Mass Estimates for Red Dwarfs turn out to be flawed, and I've replaced it with a reverse lookup using a different equation from the same paper (SN 37). I've also added an import for ‘An All-Sky catalog of Bright M Dwarfs’ (Lépine and Gaidos, 2011) as well as Photometry from ‘The Solar Neighborhood XXXV’. My star list has been updated with almost 90 M Dwarfs from these two catalogs, and I've done some more ‘weeding’ to correct or get rid of stars that have bad parallaxes.

March 12, 2017 : Log g has been added as a possible datum for stars and brown dwarfs. For the estimations, I've added bolometric corrections for White Dwarfs (instead of assuming they are blackbodies) from Bergeron and Kowalksi, et al, improving White Dwarf estimates for almost every White Dwarf in my list (except LHS 3250). To cover Giant Stars, I have implemeted polynomial fits from Alsonso et al (1999) for the hotter stars, and an equation to calculate the bolometric correction from TEff, from Buzzoni et al (2010), for cooler giants. I've replaced the mass-luminosity relations I got from Wikipedia with another set from Eker et al (2015). Finally, in those cases where I still use Blackbody-based estimations, a proper Johnson V filter curve is used (instead of assuming 100% for all wavelengths between 380 and 750 nm). The list has non been changed much, but I fixed a few systems where I left question marks at the start of a spectral type (like Algol).

March 5, 2017 : A few bug fixes, but the primary changes are to the estimates. Late K and M Dwarves now have interpolated TEffs and Bolometric corrections, based on V-K, which should lead to better Bolometric Luminosities and Sizes (if K is available). These also extend to late K and M subdwarfs, which makes the estimates for those far better than before. Mid F to Mid K stars now have TEff and Bolometric Corrections calculated from V-K or B-V, and Fe/H (as per Casagrande+ 2010). Also, I corrected a wrong value for the Sun's absolute Visual Magnitude, which will noticibly change the Visual Luminosity for all stars (except the Sun). The star list has been improved, with a few new white and red dwarfs (one deleted), some photometry added and altered, and some new metallicties. The CSV file contains the new estimates as well.

Please Note :

It has to be noted here that as a personal tool, the interface for NStars is cluttered and somewhat buggy. Also, NStars was never intended to do things in a completely automated way: the list that I have produced required a lot of system by system checking, especially since the data (usually the Fluxes) downloaded from Simbad or ARICNS may itself be bad.

In particular..


Acknowledgements

After all of the work I've done, I have not really kept good track of my sources. However, I will list a few here...


Copyright© John Q. Metro (johnqmetro@hotmail.com), 2018. All rights reserved.