NGTS-EB-8: A Double-lined Eclipsing M+M Binary Discovered by Citizen Scientists
Abstract We report the identification and characterization of a new binary system composed of two near-equal mass M-dwarfs. The binary NGTS-EB-8 was identified as a planet candidate in data from the Next Generation Transit Survey (NGTS) by citizen scientists participating in the Planet Hunters NGTS project. High-resolution spectroscopic observations reveal the system to be a double-lined binary. By modeling the photometric and radial velocity observations, we determine an orbital period of 4.2 days and the masses and radii of both stars to be <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>A</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.25</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.004</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.005</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> M ⊙ , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>B</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.20</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.004</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.005</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> M ⊙ , and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>A</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.25</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.005</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.004</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> R ⊙ , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>B</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.23</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.005</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.006</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> R ⊙ , respectively. We detect Balmer line emission from at least one of the stars but no significant flare activity. We note that both components lie in the fully convective regime of low-mass stars (≲0.35 M ⊙ ); therefore, they can be a valuable test for stellar evolutionary models. We demonstrate that the photometric observations, speckle imaging, and initial radial velocity measurements were unable to identify the true nature of this system and highlight that high-resolution spectroscopic observations are crucial in determining whether systems such as this are in fact binaries.
Authors
- Laura Trouille (ORCID: https://orcid.org/0000-0002-1113-4122)
- J. McCormac (ORCID: https://orcid.org/0000-0003-1631-4170)
- M. R. Burleigh (ORCID: https://orcid.org/0000-0003-0684-7803)
- Maximilian N. Günther (ORCID: https://orcid.org/0000-0002-3164-9086)
- Truman O. Woodruff
- R. G. West (ORCID: https://orcid.org/0000-0001-6604-5533)
- Megan E. Schwamb (ORCID: https://orcid.org/0000-0003-4365-1455)
- Jorge Fernández Fernández (ORCID: https://orcid.org/0000-0002-1416-2188)
- B. Baller (ORCID: https://orcid.org/0000-0001-8731-9281)
- Ernst de Mooij (ORCID: https://orcid.org/0000-0001-6391-9266)
- Daniel Bayliss (ORCID: https://orcid.org/0000-0001-6023-1335)
- L. Fortson (ORCID: https://orcid.org/0000-0002-1067-8558)
- Michael Hanke (ORCID: https://orcid.org/0000-0002-8427-2155)
- Alicia Kendall (ORCID: https://orcid.org/0009-0006-0719-9229)
- S. L. Casewell (ORCID: https://orcid.org/0000-0003-2478-0120)
- Samuel Gill (ORCID: https://orcid.org/0000-0002-4259-0155)
- J. S. Jenkins (ORCID: https://orcid.org/0000-0003-2733-8725)
- Elisabeth Baeten (ORCID: https://orcid.org/0000-0003-2556-3152)
- Alex Strickland
- Carine Steiner (ORCID: https://orcid.org/0000-0001-5983-6767)
- K. Hobbs (ORCID: https://orcid.org/0009-0004-4519-5080)
- Chris Pearson (ORCID: https://orcid.org/0000-0001-6139-649X)
- Pete Hermes
- Ivan A. Terentev (ORCID: https://orcid.org/0000-0002-0654-4442)
- P. J. Wheatley (ORCID: https://orcid.org/0000-0003-1452-2240)
- Sean O'Brien (ORCID: https://orcid.org/0000-0001-7367-1188)
- Arttu Sainio (ORCID: https://orcid.org/0000-0003-4864-5484)
- Chris Lintott (ORCID: https://orcid.org/0000-0001-5578-359X)
- Faith Hawthorn (ORCID: https://orcid.org/0000-0002-8675-182X)
- C. A. Watson (ORCID: https://orcid.org/0000-0002-9718-3266)
- Edward M. Bryant (ORCID: https://orcid.org/0000-0001-7904-4441)
- Louise D. Nielsen (ORCID: https://orcid.org/0000-0002-5254-2499)
- Virgilio Gonano
- A. R. Hildebrand (ORCID: https://orcid.org/0000-0001-9926-2059)
- Suman Saha (ORCID: https://orcid.org/0000-0001-8018-0264)
- Kim L. O’Neill (ORCID: https://orcid.org/0000-0002-8747-6217)
- Graham Mitchell
- Leilah K. McCarthy (ORCID: https://orcid.org/0000-0003-3585-4754)
- Toby Rodel (ORCID: https://orcid.org/0009-0009-2175-7284)
- Ioannis Apergis (ORCID: https://orcid.org/0009-0004-7473-4573)
- S. M. Lim (ORCID: https://orcid.org/0009-0008-0576-556X)
- Christopher Tanner
- Sebastián A. Freigeiro
- Juergen Saeftel
- Ernest Jude P. Tiu
- Deniz Rüzgar Apaydın
- Jeff Carabott
- Nolan Reket
- Sergey Y. Tumanov
- Pia Vahlenkamp
- Femke de Vroome
- John S. Langley
- Marius Constantin Agafitei
- Sallyann Chesson
- Paweł Wantuch
- Marciniak Urszula
- Jeanne Riethmiller
Institutions
- Queen's University Belfast (GB)
- University of Minnesota (US)
- Adler Planetarium (US)
- University of Leicester (GB)
- University of Warwick (GB)
- University of Oxford (GB)
- Chinese Academy of Science South America Center for Astronomy (CL)
- Public Citizen (US)
- European Space Research and Technology Centre (NL)
- University College London (GB)
- Ludwig-Maximilians-Universität München (DE)
- Universidad Diego Portales (CL)
Publication Details
- Journal
- The Astronomical Journal
- Published
- 2025-11-11
- DOI
- https://doi.org/10.3847/1538-3881/ae0e0d
- Primary Topic
- Stellar, planetary, and galactic studies
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- National Science Foundation
- National Aeronautics and Space Administration
- Institute of Museum and Library Services
- Alfred P. Sloan Foundation
- California Institute of Technology
- Australian National Data Service
- National Computational Infrastructure
- Astronomy Australia Limited
- Space Telescope Science Institute
- UK Research and Innovation
- NASA Exoplanet Science Institute
- Australian Government
- European Space Agency
- University of Warwick
- Queen's University Belfast
- Australian National University
- Monash University
- Swinburne University of Technology
- Curtin University of Technology
- Queen's University
- Nuclear Safety and Security Commission
- Korea Astronomy and Space Science Institute
- European Southern Observatory
- Ministério da Ciência, Tecnologia, Inovações e Comunicações
- Agencia Nacional de Investigación y Desarrollo
- Ames Research Center
- Jet Propulsion Laboratory
- Goddard Space Flight Center
- University of California, Los Angeles
- Science Mission Directorate
- Science and Technology Facilities Council
- Australian Astronomical Optics-Macquarie
- Agencia Estatal de Investigación
- National Cancer Institute