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

September 17, 2017

The star list has over 6500 star systems, going out to about 108 LY. Parallaxes 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. 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.

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

Updates

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, 2017. All rights reserved.