UltracoolSheet

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1	Last update (v2.1.0): 2025-07-03 20:15:47 (UTC)
2	The UltracoolSheet
3	Photometry, Astrometry, Spectroscopy, and Multiplicity for 4000+ Ultracool Dwarfs and Imaged Exoplanets
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5	Maintained by Will Best, Trent Dupuy, Michael Liu, Aniket Sanghi, Rob Siverd, and Zhoujian Zhang
6	ultracool.sheet@gmail.com
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8
9	QUICK START GUIDE
10	What is the UltracoolSheet?
11	This spreadsheet contains a catalog of 4000+ ultracool dwarfs (spectral types M6 and later) and imaged exoplanets, including photometry, J2000 positions, parallaxes, proper motions, multiplicity, and spectroscopic classifications from multiple surveys and numerous sources. The spreadsheet is organized into several tabs. This README tab contains details about the contents of the other tabs.
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13	Which objects are included?
14	UltracoolSheet is intended to be a catalog of all spectroscopically confirmed objects of spectral type L0 or later in the extended solar neighborhood (<~100 pc) that were known as of April 15, 2015, augmented by discoveries from Will Best’s PhD thesis (Best et al. 2015, 2017) and newer objects of particular interest (e.g., all imaged exoplanets). This catalog largely corresponds to the input sample used to define the parallax-based 25-parsec L and T dwarf sample of Best et al. (2021) and L, T, and Y dwarf sample of Best et al. (2024). Late-M dwarfs are included here, but mostly objects that had measured parallaxes prior to Gaia and the catalog is far from complete at these spectral types.
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16	What data are in here?
17	* Astrometry (R.A., Dec., parallax, and proper motion), including calculation of epoch 2000 coordinates for all objects.
18	* Photometry, names, and positions from major sky surveys catalogs: 2MASS, CatWISE2020/AllWISE, Pan-STARRS, UKIDSS/UHS, and Gaia DR3
19	* MKO photometry (YJHKLM bands)
20	* Synthesized MKO and 2MASS photometry derived from SpeX prism spectra for objects lacking such photometry
21	* Spitzer/IRAC photometry (channels 1 and 2) for some sources
22	* Spectral types and gravity classifications (optical and near-IR)
23	* Flags for objects with noteworthy properties in the literature (e.g., low gravity, moving group members, low metallicity, imaged exoplanets, etc.)
24	* Resolved information for binaries and multiple systems, including flux ratios and orbit information
25	* Flag to construct the Best et al. (2021 and 2024) volume-limited samples.
26	* Photometric distance estimates
27	* Companion information
28	* SIMBAD information, including the official SIMBAD name (useful for queries) and alternative names
29	* BANYAN Sigma (Gagne et al. 2018) results for moving group assessment
30	* Citation information for all data, including ADS bibcodes & publication titles.
31	* Tables of median colors and absolute magnitudes as a function of spectral type are available HERE.
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33	Where do I find the object(s) I care about?
34	Data for single sources and integrated-light data for multiple sources are listed in the Main tab. Resolved measurements of multiple systems are listed in the Binaries and Triples+ tabs. (Because of this organization, the imaged exoplanet 2MASS 1207-39b appears only in the Binaries tab. The integrated-light properties of the 2MASS 1207-39Ab system appear in the Main tab, since the primary component is an ultracool dwarf. This is the only notable system for which this occurs.)
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36	Can I sort or make changes to the spreadsheet? Will it inconvenience other users?
37	This is a view-only spreadsheet, and your browser downloads a local copy that only you see. You can safely sort, filter, and zoom the spreadsheet, and only you will see these changes. You cannot make changes to the contents or formatting of individual cells.
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39	What are some handy shortcuts for using the Main tab?
40	* Final astrometry: the columns with the “_formula” suffix contain the recommended choices for J2000 coordinates (e.g. “ra_j2000_formula”), present-epoch coordinates (e.g. "ra_YYYYMMDD_formula"), parallaxes (e.g. “plx_formula”), and proper motions (e.g. “pmra_formula”). The decision tree for picking between different data sources is described in the COLUMN DESCRIPTION text below, with the "ref_" columns giving the choices.
41	* Binaries/Triples+: use the “multiplesystem_unresolved_in_this_table” column to pick (or avoid) known binaries and higher-order multiples. The Binaries tab contains the resolved information for these systems.
42	* Subdwarfs: use the “literature_flag” column to pick (or avoid) objects labels as “subd”. Alternatively, use the “sptnum_formula” column to pick (or avoid) negative spectral types, which we use for subdwarfs.
43	* Benchmark companions: ultracool dwarfs that are companions to stars have their primary star name in the “has_higher_mass_companion” column and their angular separation in the “sep_companion” column. An additional table with data for the host stars is in preparation. (See Zhang et al. 2020 for the properties of L6-T6 companions and their primary stars, and Deacon et al. 2014 for properties of stars with wide (>100 AU) ultracool companions.)
44	* Young moving group members: use the “age_category” column to select members of the various YMGs, based on our homogenous analysis of membership (see description below). Note that the "literature_flag" column also contains literature claims of objects' YMG memberships, which may or may not agree with our analysis. (In cases where a literature result has been superseded, either by more recent literature results or our membership analysis, the obsolete info is not explicitly listed but rather documented as a Note to the cell.)
45	* Young and/or low-gravity objects: the “youth_evidence” column is a general flag for any objects <=300 Myr old. It includes tags for “lowg” (determined from the object’s spectrum) and also cases where youth comes from other methods (dynamical cooling ages, association with a young star or moving group, from lithium absorption, etc.). The "age_category" column contains the specific age assignment. The “grav_opt” and “grav_ir” columns contain specific gravity classifications (VL-G, gamma, etc.).
46	* Volume-limited sample (e.g. for CMD plots): the “Best24_vollim_sample” column indicates if the object is included in the Best et al. (2024) 25 pc sample of L, T, and Y dwarfs. For making plots summarizing the properties of ultracool dwarfs, we recommend using this sample because it is far less biased than simply plotting everything with a parallax.
47	* Imaged exoplanets: The “exoplanet” column gives our judgment on whether companions belong to this category, based on how their estimated masses compare to the IAU-established 13 Jupiter-mass dividing line.
48	Note that for constructing custom subsets, it's easy to download all the data using the File-->Download pulldown menu.
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50	Why are there 2 variants of the Main tab?
51	Starting with v2.0, UltracoolSheet includes two variants of the Main tab. Main contains only objects for which the UltracoolSheet data is complete, i.e., all the data columns have been filled in for every object. Main - In Progress contains everything in Main plus additional objects for which the UltracoolSheet data is incomplete (i.e., some cells are blank). We anticipate the Main tab will be sufficient for most purposes, but users who want to work with the very largest list of objects should examine the Main - In Progress tab.
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53	What’s missing/incomplete?
54	These tables were derived from multiple sources as part of research over the years by the creators of this spreadsheet. For the initial public release in 2020 (v1.0), we prioritized vetting the objects already in our master list over adding objects discovered after 2015-04-15. In the current release (v2.0), we have attempted to increase the completeness significantly by adding objects discovered up to the release date (2024 February). Despite these efforts, both the object list and associated data are surely incomplete, e.g., for aspects that were not essential to our research or for recent publications with small samples of objects and/or data. The most notable deficiencies are:
55	* Late-M dwarfs: we have aimed to be complete all nearby (< 25 pc) late-M dwarfs, as well as late-M dwarfs of any distance that are the primary in a binary system (i.e., all ultracool + ultracool binaries). The UCS includes the objects in the 25 pc volume-limited sample of Bardalez Gagliuffi et al. (2019) for M7-L5 dwarfs. For additional objects not included in the UCS, the Gaia papers on the solar neighborhood (e.g., Reylé et al. 2021) and the big list of late-M dwarfs compiled by Jonathan Gagné several years ago would be valuable.
56	* Objects beyond 100 pc: some are here (e.g. imaged companions), but this is not the full ultracool census of star-forming regions nor the Pleiades.
57	* Ultracool dwarfs found purely with photometric techniques, but lacking spectra: some are here (e.g., all imaged exoplanets, the coldest late-T and Y dwarf candidates from WISE data), but many are not (e.g., the full set of ultracool candidates from the 74k+ objects in Kiman et al. 2019).
58	* Directly-imaged brown dwarf companions: many are here, some are not.
59	* SDSS photometry is not included. Note that Pan-STARRS photometry is current for all available objects.
60	* VISTA photometry is included for only a handful of objects, as we have not done a bulk query of this photometry. UKIDSS photometry is current for DR11+ and UHS DR2.
61	* Radial velocities: we include RVs in SIMBAD (900+ values), Gaia DR3, and for some other objects, but we have not otherwise comprehensively searched the literature.
62	* Measurements that are not fundamentally astrometric or photometric in nature (other than age), e.g., rotation periods, vsini, effective temperatures from model atmosphere fitting, etc.
63	* In cases of multiple measurements in the literature for the same property, we usually chose the highest S/N one. For measurements without S/N information (e.g. spectral types), we made a judgment call. Alternative/obsolete measurements were not preserved, though significant discrepancies for qualitative quantities (YMG membership or SpT) are sometimes retained in the Notes of the corresponding cells (as indicated by the black triangle in the upper right corner of a cell) or in the note column.
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65	QUESTIONS, COMMENTS, SUGGESTIONS, or CONTRIBUTIONS?
66	We plan to continue additions and updates as time permits. We welcome input from the community.
67	Please send them to ultracool.sheet@gmail.com (especially contributions!).
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69
70	CITATION
71	When using data from these tables, please cite the individual papers from which the data comes. Citations are included for all the data in the tables, and the References text below explains how to translate our citation codes into ADS bibcodes, Papers citekeys, and publication titles. Note that cells in ref_* columns may contain more than one reference (separated by semi-colons).
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73	All data from Gaia DR3 should cite Gaia Collaboration et al. (2016, A&A, 595, 1) and Gaia Collaboration et al. (2023, A&A, 674, 1).
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75	The UltracoolSheet itself can be cited by its Zenodo DOI: 10.5281/zenodo.4169084
76	Data with a "UCS_24" or "usyn24" reference should also cite this Zenodo DOI. (This refers to unpublished analysis and synthetic photometry, respectively.)
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78	For research that benefits from this compilation, please include the following acknowledgment:
79	“This work has benefitted from The UltracoolSheet at http://bit.ly/UltracoolSheet, maintained by Will Best, Trent Dupuy, Michael Liu, Aniket Sanghi, Rob Siverd, and Zhoujian Zhang, and developed from compilations by Dupuy & Liu (2012, ApJS, 201, 19), Dupuy & Kraus (2013, Science, 341, 1492), Deacon et al. (2014, ApJ, 792, 119), Liu et al. (2016, ApJ, 833, 96), Best et al. (2018, ApJS, 234, 1), Best et al. (2021, AJ, 161, 42), Sanghi et al. (2023, ApJ, 959, 63), and Schneider et al. (2023, AJ, 166, 103).
80	and here is a version with the ADS bibcodes:
81	"This work has benefited from The UltracoolSheet at http://bit.ly/UltracoolSheet, maintained by Will Best, Trent Dupuy, Michael Liu, Aniket Sanghi, Rob Siverd, and Zhoujian Zhang, and developed from compilations by \citet{2012ApJS..201...19D, 2013Sci...341.1492D, 2014ApJ...792..119D, 2016ApJ...833...96L, 2018ApJS..234....1B, 2021AJ....161...42B, 2023ApJ...959...63S, 2023AJ....166..103S}."
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83
84	FORMATTING
85	rules for binaries, etc.		The general rule is that all multiple systems that require high-resolution imaging to resolve, and where the brightest component is an ultracool dwarf, have their integrated-light properties listed in the Main tab and resolved information in the Binaries/Triples+ tabs. For example, 2M1207b itself does not directly appear in the Main tab. By this rule 2M1207b is a binary companion of the ultracool dwarf 2M1207A, so its properties appear in the Binaries tab.
86	column naming rules		[what the column is][append "err" if this is the uncertainty]_[type of measurement, e.g., epoch or J2000]_[where it's from]_["formula" if the column is computed]
87			no whitespace, (), [], -, etc.; also try to keep column names valid for common coding languages (Python, IDL, etc.)
88	other rules		Cells should not have formulas unless the entire column is computed by the same formula.
89			Text cells should not use commas (to avoid potential problems with exported CSV files).
90			Reference cells with more than one reference should separate the references with semicolons.
91			Cells with no data should contain "null" (text) or "NaN" numbers. Blank cells indicate in-progress data entry.
92			The only column that is duplicated between any tabs is the first one (name). [Exception: *_formula columns may appear across multiple tabs, e.g., by VLOOKUP( ).]
93			Text color should be set to either black or white, with conditional formatting used for grays and all other hues
94	cross-tab rules		The first column in every tab shall be "name" and is an exact copy of the name listed in the Main tab. There may be other columns in the tab that use information from the Main tab by using vlookup formulas.
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96
97	COLUMN DESCRIPTIONS
98	Main	(unit)	individual ultracool dwarfs, one seeing-limited object per row	which columns does a given ref_* refer to?
99	name		Unique object name (normally taken from the object's first publication)
100	UCS_done		Indicates whether an object has all UltracoolSheet columns filled in with available data. “yes” means the object does, and thus appears in both the Main and Main - In Progess tabs. “no” means the object has incomplete data and only appears in the Main - In Progess tab.