# Is there a website out there where I can find/compare data on stellar parameters for the brightest stars?

I'm looking for some kind of catalog/repository which lists stellar parameters (e.g. mass, radius, temperature) in a similar vein to NASA's Exoplanet Catalog (but except for stars), for the brightest stars in the sky, with $$m_v<4$$. I'd rather not have to refer to Wikipedia as they only list data from one source (or an average of several uncited sources).

I'm aware of SIMBAD, but that site doesn't have a very intuitive UI and doesn't list mass measurements. I've also tried CDS (http://cdsportal.u-strasbg.fr/), but I can't find distance measurements from Gaia (although apparently Gaia doesn't measure distance and I need to put some kind of external study into a Gaia search query which I haven't got a clue how to use).

• Mass of stars is not measurable unless you have a multiple-star system.SIMBAD is the canonical reference and the query interface is not bad. You better spend the time to get to know its interface than searching for alternatives which are less accurate, complete and vetted – planetmaker Sep 20 '20 at 11:17
• Does it show the masses of stars in multiple systems? If not, where can I find that information aside from trawling through research papers for every star of interest (which I'm not prepared to do). – Will Sep 21 '20 at 11:32
• Also, taking Alpha Circini as an example, CDS (cdsportal.u-strasbg.fr/?target=alpha%20Cir) has much more data than SIMBAD (simbad.u-strasbg.fr/simbad/…). Why is this? The only data SIMBAD lists on stellar radius is completely at odds with any other source. – Will Sep 22 '20 at 9:59
• Regarding your last comment, the stellar diameter of 2.7e6 km listed in Simbad converts to a stellar radius of 1.95 R_Sun, which seems pretty consistent with other sources. – Eric Jensen Sep 25 '20 at 0:17
• Yeah. Accidentally forgot to halve it for radius. That's embarrassing. – Will Sep 25 '20 at 14:02

As you’ve discovered, there are a lot of different catalogs out there, and many ways to search them. It would help if you could narrow your question a bit - what kind of data are you looking for? You seem to want stellar masses at least - what else? As noted above, there are few stars for which mass is measured directly, but there are robust ways of estimating it from other information, just as effective temperature can be determined from spectral type or photometry.

One catalog that might meet your needs is the TESS Input Catalog (TIC) or its brighter subset, the TESS Candidate Target List. It compiles information from a lot of other sources, and includes magnitudes from optical through infrared, as well as estimates of stellar mass, radius, temperature, metallicity, luminosity, and surface gravity. It also includes stellar parallax (i.e., distance) and proper motion from Gaia.

In addition to the ways of searching given in the above link, you can search it through Vizier here - I find the Vizier interface a little easier to navigate than MAST, though both have a lot of options.

Now this catalog may be overkill for what you want: it has 471 million stars, though “only” 27 million of those have mass estimates, and “only” 2 million have distances. :-) So knowing more about what you want could help narrow things down.

Edit: The above numbers refer to an earlier release of the catalog, prior to Gaia DR2. The updated version (which is what I linked to from Vizier) has about 1.7 billion stars, of which 1.27 billion have distances and 455 million have mass estimates.

Edit 2: After clarification in the comments that the goal is finding information only for very bright stars, this isn’t the best catalog to use. While it does include entries for some bright stars (e.g. Vega, Betelgeuse), the information included is very limited, presumably because they are saturated (overexposed) in most surveys.

In general it is much harder to get homogeneous data for very bright stars because of this. There is a wealth of data on them individually, but because they are saturated in systematic surveys, there aren’t uniform sources of data on them to which known relations can be applied in bulk.

The Yale Bright Star Catalogue (searchable here) is a good source of basic data (photometry, spectral type, distance, multiplicity), but for derived quantities like mass or radius you would have to apply known relationships yourself (if you need the data in bulk) or go to individual references for particular stars if you don’t need a lot of them. Honestly Wikipedia isn’t a bad starting point in the latter case - it is generally clear about what references the numbers come from.

• Can you revise the summary of the catalog contents to match the updated TIC catalog that you are discussing. In particular, there are something like half a billion mass and radius estimates and a billion stars with parallax-based distances. The paper to refer to is arxiv.org/abs/1905.10694 – ProfRob Sep 25 '20 at 7:02
• Thanks for your reply. I'm looking for all kinds of measurements including mass, radius, temperature, luminosity, rotational velocity and distance (preferably calculated from Gaia). I've been making do with the CDS portal, but I've hit a road block when it comes to multiple star systems in that either the parameters of only one star get reported (and it's completely unclear which component is being referred to), or the whole system is treated is one star for some bizarre reason (although I understand this can be unavoidable for spectroscopic binaries). Does the TESS catalog remedy this? – Will Sep 25 '20 at 10:29
• Also: I'm only interested in stars brighter than magnitude +4.00 at the moment. What difference does it make if a choose the "brighter subset" CTL over the TIC? If it only means I see fewer dim stars in the search, then that's fine, but if it affects the data of the target, then that would not be ideal. – Will Sep 25 '20 at 10:43
• @Will It maybe that multiple systems are unresolved and that the parameters are not available for the two stars separately. You really do have to understand the data and catalogues that you are using and be prepared to a bt of work to clean it in the bespoke way that you appear to require. The properties of the TIC/CTL catalogs are described in the link in my comment above. – ProfRob Sep 25 '20 at 11:01
• Update: when I entered the target Alpha Lupi into both CTL and TIC, it gave me data for everything but the object I was interested in. Why isn't there data on the target star? – Will Sep 25 '20 at 11:17