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Three Thousand Motion-Confirmed L and T Dwarf Candidates from the Backyard Worlds:~Planet 9 Citizen Science Project

Adam C. Schneider, Marc J. Kuchner, Jacqueline K. Faherty, Aaron M. Meisner, J. Davy Kirkpatrick, Adam J. Burgasser, Daniella Bardalez Gagliuffi, Thomas P. Bickle, Dan Caselden, Sarah L. Casewell, Jonathan Gagné, Easton J. Honaker, Frank Kiwy, Federico Marocco, Austin Rothermich, Nikolaj Stevnbak Andersen, Lizzeth Ruiz Arroyo, Bruce Baller, Paul Beaulieu, John Bell, Martin Bilsing, Troy K. Bohling, Guillaume Colin, Giovanni Colombo, Sam Deen, Alexandru Dereveanco, Kevin Dixon, Hugo A. Durantini Luca, Deiby Flores, Christoph Frank, Christopher Fulvi, Michael Gallmann, Jean Marc Gantier, Konstantin Glebov, Léopold Gramaize, Leslie K. Hamlet, Ken Hinckley, Kevin Jablonski, Peter A. Jałowiczor, Martin Kabatnik, Peter Kasprowitz, K Ly, David W. Martin, Naoufel Marzak, Alexander McColgan, Neil J. McEwan, Marianne N. Michaels, William Pendrill, Stéphane Perlin, Ben Pumphrey, James Rabe, Henry Raway, Walter Ruben Robledo, David Roser, Animesh Roy, Arttu Sainio, Vincent Schindler, Manfred Schonau, Jörg Schümann, Karl Selg-Mann, Andrea Serio, David Sirbescu-Stanley, Patrick Smith, Andres Stenner, Christine Sunjoto, Christopher Tanner, Melina Thévenot, Vinod Thakur, Mayahuel Torres Guerrero, Maurizio Ventura, Nikita V. Voloshin, Jim Walla, Zbigniew Wȩdracki, Bailey Weyandt, Breck Wilhite, Spartacus Zitouni

Abstract

The Backyard Worlds: Planet 9 citizen science project uses data from the Wide-field Infrared Survey Explorer to detect infrared objects with significant motion. In this work, we present the majority of the L and T dwarf candidates discovered through this effort. For each candidate, we provide proper motion measurements as well as optical, near-infrared, and mid-infrared photometry (when available), photometric spectral types and distance estimates. Three thousand and six new motion-confirmed discoveries are presented in this work, 2,357 with L-type photometric spectral types and 649 with T-type photometric spectral types. We also present an additional 80 objects as likely L or T dwarfs based on available photometry, but for which a significant motion measurement could not be obtained. We identify 28 objects in this sample as new comoving companions to higher-mass stars, and an additional 9 sources that are candidate binary systems made up of two ultracool dwarfs of L-type or later. Follow-up spectroscopic observations will be necessary to confirm spectral types and further characterize the sources discovered through this project. This work presents the largest single sample of motion-confirmed L and T dwarf discoveries to date, which would more than double the number of known L and T dwarfs, if confirmed. We wish to sincerely thank our citizen scientist collaborators for their monumental efforts that have directly impacted this project's success.

Three Thousand Motion-Confirmed L and T Dwarf Candidates from the Backyard Worlds:~Planet 9 Citizen Science Project

Abstract

The Backyard Worlds: Planet 9 citizen science project uses data from the Wide-field Infrared Survey Explorer to detect infrared objects with significant motion. In this work, we present the majority of the L and T dwarf candidates discovered through this effort. For each candidate, we provide proper motion measurements as well as optical, near-infrared, and mid-infrared photometry (when available), photometric spectral types and distance estimates. Three thousand and six new motion-confirmed discoveries are presented in this work, 2,357 with L-type photometric spectral types and 649 with T-type photometric spectral types. We also present an additional 80 objects as likely L or T dwarfs based on available photometry, but for which a significant motion measurement could not be obtained. We identify 28 objects in this sample as new comoving companions to higher-mass stars, and an additional 9 sources that are candidate binary systems made up of two ultracool dwarfs of L-type or later. Follow-up spectroscopic observations will be necessary to confirm spectral types and further characterize the sources discovered through this project. This work presents the largest single sample of motion-confirmed L and T dwarf discoveries to date, which would more than double the number of known L and T dwarfs, if confirmed. We wish to sincerely thank our citizen scientist collaborators for their monumental efforts that have directly impacted this project's success.

Paper Structure

This paper contains 21 sections, 5 figures.

Table of Contents

  1. Introduction
  2. Candidate Selection
  3. Sample Properties
  4. Proper Motions
  5. Spectral Type Estimates
  6. Distances
  7. Notes on Particular Populations of Interest
  8. Wide Companions
  9. LP 704$-$77 and CWISE J001822.14--135823.1
  10. CD--42 565AB and CWISE J013745.05--420956.8
  11. PM J02155--2437 and CWISE J021530.62--243612.1
  12. UCAC4 297--003544 and CWISE J033205.98--304234.6
  13. G 160--45 and CWISE J040633.62--170849.6
  14. StKM 1--570AB and CWISE J053409.85+651953.1
  15. ATO J119.4548+55.4544, Gaia DR3 1080989465348498816, and CWISE J075748.41+552712.1
  16. ...and 6 more sections

Figures (5)

  • Figure 1: Histogram of spectral type estimates for the BYW sample. The orange histogram shows the additional objects that are likely new L or T dwarf discoveries but for which significant motion could not be confirmed.
  • Figure 2: Colors as a function of estimated spectral type for this sample (gray symbols) compared to median colors from the sample of schneider2023 (blue diamonds). Newly discovered objects generally follow the trends of known objects, with outliers typically due to unusual colors or blending in WISE images.
  • Figure 3: Histogram of $J$-band (blue) and W2 (orange) distance estimates for the motion-confirmed BYW sample.
  • Figure 4: Left: Proper motions components of newly identified systems, with primaries represented by blue diamonds and candidate companions plotted as red circles. Lines connect the components of each system. Right: Comparison of primary distance measurements versus photometric distance estimates of candidate companions, where the dashed black line represents equivalent distances. Median values are plotted for photometric distances, with error bars representing the entire range of estimated distances. Most distance estimates are consistent with measured primary distances, with some discrepancies for the most distant pairs, likely due to uncertain spectral type estimates and/or larger distance uncertainties.
  • Figure 5: WISE, near-infrared, and optical images of all ultracool wide binary candidates. Optical images either come from Pan-STARRS (PS1; chambers2016) or DECam images obtained through the Astro Data Lab image cutout service fitzpatrick2014nikutta2020. Primaries are marked with light blue lines while candidate ultracool companions are marked with red lines in all images where the components are resolved. Neither component of the CWISE J132836.50+635527.7AB system is detected in any available near-infrared imaging. North is up and East is left in all images.