[en] Massive stars have a major dynamical as well as chemical impact on their environment in their host galaxy. Despite their importance, many details of their life and evolution remain poorly constrained. Observational determinations of their physical parameters are therefore required to better constrain evolutionary models. In particular, the mass and the mass-loss rate—two key parameters—are known to be more reliably determined through the study of binary stars. In this context, the binary system WR25 (= HD 93162) whose dominant spectral type is that of a nitrogen sequence Wolf-Rayet star, is of particular interest. It exhibits the highest known hydrogen content among the Milky Way Wolf-Rayet stars, as well as additional absorption lines. It is therefore most probably an object still on the main-sequence or close to leaving it. We acquired new high-resolution spectra of this extremely interesting object. Following a detailed analysis, we present an improved version of the SB1 orbital solution for the motion of the WN component. We confirm the detection of the previously reported probable O companion and definitively prove that it is indeed gravitationally bound to the WN star. A first SB2 solution is presented, and a mass-ratio WN/O of 2.02 ± 0.36 (1σ) is derived. Following a spectral disentangling procedure, we identify the companion as an O5(f+) star belonging to either the main-sequence (V) or giant (III) luminosity classes. The spectral type of the companion, together with the above-mentioned mass ratio, points to a very massive primary WN star of at least 55 M(Formula presented). This confirms that WR 25 belongs to the family of very massive WNLh objects, a very poorly populated class in the Milky Way. We demonstrate that the absorption component in the P-Cygni profile of the He ii 24859+Hß line of WR 25 is mainly due to the O-type companion, and we propose to adopt a WN6ha spectral type for the WN component of the system. On the basis of the extracted disentangled spectra, we derive approximate physical parameters through a detailed CMFGEN analysis, given the difficulty in constraining both the extinction towards WR 25 and the definitive brightness ratio between the components. Finally, we propose the presence of a third component contributing to the spectrum of WR 25.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Gosset, Eric ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE) ; Honorary Research Director F.R.S.-FNRS, Belgium
Gamen, Roberto ; Instituto de Astrofísica de La Plata, CONICET-UNLP, La Plata, Argentina ; Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, La Plata, Argentina
Mahy, Laurent ; Royal Observatory of Belgium, Brussels, Belgium
Morrell, Nidia ; Las Campanas Observatory, Carnegie Observatories, La Serena, Chile
Sana, Hugues ; Institute of Astronomy, KU Leuven, Leuven, Belgium
Barbá, Rodolfo H. ; Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, La Plata, Argentina ; Departamento de Física y Astronomía, Universidad de la Serena, La Serena, Chile
Language :
English
Title :
A Detailed Spectroscopic Study of the WN6ha + O5 Colliding-wind Binary WR 25
Publication date :
June 2026
Journal title :
Bulletin de la Société Royale des Sciences de Liège
ISSN :
0037-9565
eISSN :
1783-5720
Publisher :
Societe Royale des Sciences de Liege
Volume :
95
Issue :
1
Pages :
24 - 122
Peer reviewed :
Peer reviewed
Funding text :
The authors are thankful to the two anonymous referees who contributed to the improvement of the paper. This work is based on data collected at the European Southern Observatory (La Silla, Chile) and at the Las Campanas Observatory (Chile), including one observation at the Magellan II (Clay) 6.5-m Telescope. The raw data were processed using the midas and iraf reduction packages. This study used iraf versions 2.13, 2.14, 2.15 and 2.16, which were developed at the National Optical Astronomy Observatories (NOAO, now integrated into the National Optical-Infrared Astronomy Research Laboratory, NOIRLab). These facilities, as well as NSF NOIRLab, are operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the U.S. National Science Foundation (NSF). The first author would like to acknowledge discussions with Pascal Quinet about atomic transitions and related databases. He is also greatly indebted to Alain Detal and Francine M\u00E9len for various forms of support related to computing. The Belgian Fund for Scientific Research\u2014F.R.S.-FNRS has provided financial support that was essential for this project.
Abbott, B. P., Abbott, R., Abbott, T. D., Abernathy, M. R., Acernese, F., Ackley, K., Adams, C., Adams, T., Addesso, P., Adhikari, R. X., Adya, V. B., and 1001 more (LIGO Scientific Collaboration and Virgo Collaboration) (2016) Observation of gravitational waves from a binary black hole merger. PhRvL, 116(6), 061102. https://doi.org/10.1103/PhysRevLett.116. 061102.
Anders, E. and Grevesse, N. (1989) Abundances of the elements: Meteoritic and solar. GeCoA, 53(1), 197-214. https://doi.org/10.1016/0016-7037(89)90286-X.
Arora, B., Pandey, J. C., and De Becker, M. (2019) Long-term soft and hard X-ray investigation of the colliding wind WN+O binary WR 25. MNRAS, 487(2), 2624-2638. https://doi.org/10. 1093/mnras/stz1447.
Bailer-Jones, C. A. L., Rybizki, J., Fouesneau, M., Demleitner, M., and Andrae, R. (2021) Estimating distances from parallaxes. V. Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3. AJ, 161(3), 147. https://doi.org/10.3847/1538-3881/ abd806.
Balona, L. and Crampton, D. (1974) The Hy-absolute magnitude calibration. MNRAS, 166, 203-217. https://doi.org/10.1093/mnras/166.1.203.
Banyard, G., Sana, H., Mahy, L., Bodensteiner, J., Villaseñor, J. I., and Evans, C. J. (2022) The observed multiplicity properties of B-type stars in the Galactic young open cluster NGC 6231. A&A, 658, A69. https://doi.org/10. 105 1/0004-6361/202141037.
Barbá, R. H., Gamen, R., Arias, J. I., and Morrell, N. I. (2017) OWN survey: a spectroscopic monitoring of Southern Galactic O and WN-type stars. In The Lives and Death-Throes of Massive Stars, edited by Eldridge, J. J., Bray, J. C., McClelland, L. A. S., and Xiao, L., IAU Symposium, volume 329, pages 89-96. https://doi.org/10.1017/S1743921317003258.
Barbá, R. H., Gamen, R. C., Martín-Ravelo, P., Arias, J. I., and Morrell, N. I. (2022) The winking eye of a very massive star: WR 21a revealed as an eclipsing binary by TESS. MNRAS, 516(1), 1149-1157. https://doi.org/10.1093/mnras/stac2173.
Blomme, R., Rauw, G., Volpi, D., Nazé, Y., and Abdul-Masih, M. (2024) The colliding-wind binary HD 168112. A&A, 687, A106. https://doi.org/10.1051/0004-6361/202450227.
Brott, I., de Mink, S. E., Cantiello, M., Langer, N., de Koter, A., Evans, C. J., Hunter, I., Trundle, C., and Vink, J. S. (2011) Rotating massive main-sequence stars. I. Grids of evolutionary models and isochrones. A&A, 530, A115. https://doi.org/10.1051/0004-6361/201016113.
Cananzi, K., Augarde, R., and Lequeux, J. (1993) An atlas of Balmer lines (Hd and Hy). A&AS, 101, 599-619. https://ui.adsabs.harvard.edu/abs/1993A&AS..101..599C.
Carrasco, J. M., Evans, D. W., Montegriffo, P., Jordi, C., van Leeuwen, F., Riello, M., Voss, H., De Angeli, F., Busso, G., Fabricius, C., and 17 more (2016) Gaia Data Release 1. Principles of the photometric calibration ofthe G band. A&A, 595, A7. https://doi.org/10. 105 1/0004-6361/ 201629235.
Cherepashchuk, A. M. (1976) Detectability of Wolf-Rayet binaries from X-rays. SvAL, 2(4), 138-139. https://ui.adsabs.harvard.edu/abs/1976SvAL 2..138C.
Conti, P. S. (1973a) Spectroscopic studies of O-type stars. II. Comparison with non-LTE models. ApJ, 179, 161-179. https://doi.org/10.1086/151856.
Conti, P. S. (1973b) Spectroscopic studies of O-type stars. III. The effective-temperature scale. ApJ, 179, 181-188. https://doi.org/10.1086/151857.
Conti, P. S. and Alschuler, W. R. (1971) Spectroscopic studies of O-Type stars. I. Classification and absolute magnitudes. ApJ, 170, 325-344. https://doi.org/10.1086/151218.
Conti, P. S., Leep, E. M., and Lorre, J. J. (1977) Spectroscopic studies of O-type stars. VIII. Radial velocities and the К-term. ApJ, 214(3), 759-772. https://doi.org/10.1086/155305.
Crowther, P. A., Rate, G., and Bestenlehner, J. M. (2023) Line luminosities of Galactic and Magellanic Cloud Wolf-Rayet stars. MNRAS, 521(1), 585-612. https://doi.org/10.1093/ mnras/stad418.
Crowther, P. A., Smith, L. J., Hillier, D. J., and Schmutz, W. (1995) Fundamental parameters of Wolf-Rayet stars. III. The evolutionary status of WNL stars. A&A, 293, 427-445. https: //ui.adsabs.harvard.edu/abs/1995A&A…293..427C.
Crowther, P. A. and Walborn, N. R. (2011) Spectral classification of O2-3.5 If4/WN5-7 stars. MNRAS, 416(2), 1311-1323. https://doi.org/10.1111/j.1365-2966.2011.19129.x.
Ducati, J. R. (2002) Catalogue of stellar photometry in Johnson's 11-colorsystem (2002). VizieR Online Data Catalog, Cat. II/237. https://cdsarc.cds.unistra.fr/viz-bin/cat/II/237.
Dunstall, P. R., Dufton, P. L., Sana, H., Evans, C. J., Howarth, I. D., Simón-Díaz, S., de Mink, S. E., Langer, N., Maíz Apellániz, J., and Taylor, W. D. (2015) The VLT-FLAMES Tarantula Survey. XXII. Multiplicity properties of the B-type stars. A&A, 580, A93. https://doi.org/10. 105 1/0004-6361/201526192.
Fabry, M., Hawcroft, C., Frost, A. J., Mahy, L., Marchant, P., Le Bouquin, J.-B., and Sana, H. (2021) Resolving the dynamical mass tension of the massive binary 9 Sagittarii. A&A, 651, A119. https://doi.org/10.1051/0004-6361/202140452.
Feinstein, A. (1969) The OB stars in Carina-Centaurus. MNRAS, 143(3), 273-287. https: //doi.org/10.1093/mnras/143.3.273.
Feinstein, A. (1982) Faint stars in the open cluster Trumpler 16. AJ, 87(7), 1012-1021. https: //doi.org/10.1086/113183.
Fitzpatrick, E. L. (1999) Correcting for the effects of interstellar extinction. PASP, 111(755), 63-75. https://doi.org/10.1086/316293.
Frost, A. J., Sana, H., Mahy, L., Wade, G., Barron, J., Le Bouquin, J.-B., Mérand, A., Schneider, F. R. N., Shenar, T., Barbá, R. H., Bowman, D. M., Fabry, M., Farhang, A., Marchant, P., Morrell, N. I., and Smoker, J. V. (2024) A magnetic massive star has experienced a stellar merger. Sci, 384, 214-217. https://doi.org/10.1126/science.adg7700.
Gaia Collaboration: Brown, A. G. A., Vallenari, A., Prusti, T., de Brujne, J. H. J., Babusiaux, C., Biermann, M., Creevey, O. L., Evans, D. W., Eyer, L., Hutton, A., and 415 more (2021) Gaia Early Data Release 3. Summary of the contents and survey properties. A&A, 649, A1. https://doi.org/10.1051/0004-6361/202039657.
Gaia Collaboration: Prusti, T., de Brujne, J. H. J., Brown, A. G. A., Vallenari, A., Babusiaux, C., Bailer-Jones, C. A. L., Bastian, U., Biermann, M., Evans, D. W., Eyer, L., and 615 more (2016) The Gaia mission. A&A, 595, A1. https://doi.org/10.1051/0004-6361/201629272.
Gaia Collaboration: Vallenari, A., Brown, A. G. A., Prusti, T., de Brujne, J. H. J., Arenou, F., Babusiaux, C., Biermann, M., Creevey, O. L., Ducourant, C., Evans, D. W., and 445 more (2023) Gaia Data Release 3. Summary of the content and survey properties. A&A, 674, A1. https://doi.org/10.1051/0004-6361/202243940.
Gamen, R., Gosset, E., Morrell, N., Niemela, V., Sana, H., Nazé, Y., Rauw, G., Barbá, R., and Solivella, G. (2006) The first orbital solution for the massive colliding-wind binary HD 93162 ieWR 25). A&A, 460(3), 777-782. https://doi.org/10.1051/0004-6361:20065618.
Gamen, R., Gosset, E., Morrell, N. I., Niemela, V. S., Sana, H., Nazé, Y., Rauw, G., Barbá, R. H., and Solivella, G. R. (2008) The first orbital solution for the massive colliding-wind binary HD 93162 (=WR 25). In Massive Stars: Fundamental Parameters and Circumstellar Interactions, edited by Benaglia, P., Bosch, G., and Cappa, C., RMxAC, volume 33, pages 91-93. https://astronomia.unam.mx/journals/rmxac/article/view/2008rmxac..33…91g.
Gamen, R. C., Fernández-Lajús, E., Niemela, V. S., and Barbá, R. H. (2009) The massive Wolf-Rayet binary LSS 1964 (=WR 29). II. The v light curve. A&A, 506(3), 1269-1275. https://doi.org/10.1051/0004-6361/2008101 12.
Gosset, E., Damerdji, Y., Morel, T., Delchambre, L., Halbwachs, J. L., Sadowski, G., Pourbaix, D., Sozzetti, A., Panuzzo, P., and Arenou, F. (2025) Gaia Data Release 3: Spectroscopic binary-star orbital solutions: The SB1 processing chain. A&A, 693, A124. https://doi.org/10. 105 1/0004-6361/202450600.
Gosset, E., Gamen, R., Mahy, L., Morrell, N., Sana, H., and Barba, R. (2023) New progresses on the spectroscopic orbital solution for the colliding-wind binary WR 25. Oral communication at the colloquium 'The Wolf-Rayet phenomenon in the Universe' held in Morelia (Mexico), June 19-23, 2023 (available at https://hdl.handle.net/2268/334901).
Gosset, E. and Nazé, Y. (2016) The X-ray light curve of the massive colliding wind Wolf-Rayet + O binary WR 21a. A&A, 590, A113. https://doi.org/10.1051/0004-6361/201527051.
Gosset, E., Rauw, G., Manfroid, J., Vreux, J.-M., and Sterken, C. (1994) Photometric monitoring of Wolf-Rayet stars: Strömgren uvby and narrow-band photometry. In The Impact of LongTerm Monitoring on Variable Star Research: Astrophysics, Instrumentation, Data Handling, Archiving, edited by Sterken, C. and de Groot, M., NATO Advanced Study Institute (ASI) Series C, volume 436, pages 101-116. Kluwer Academic Publishers, Dordrecht (NL). https: //doi.org/10. 1007/978-94-01 1- 1 164-5_9.
Gosset, E., Royer, P., Rauw, G., Manfroid, J., and Vreux, J. M. (2001) A first detailed study of the colliding wind WR+O binary WR 30a. MNRAS, 327(2), 435-451. https://doi.org/10. 1046/j.1365-8711.2001.04755.x.
Grevesse, N., Asplund, M., Sauval, A. J., and Scott, P. (2010) The chemical composition of the Sun. Ap&SS, 328(1-2), 179-183. https://doi.org/10.1007/s10509-010-0288-z.
Hadrava, P. (1995) Orbital elements of multiple spectroscopic stars. A&AS, 114, 393-396. https://ui.adsabs.harvard.edu/abs/1995A&AS..114..393H.
Hamann, W.-R., Gräfener, G., and Liermann, A. (2006) The Galactic WN stars. Spectral analyses with line-blanketed model atmospheres versus stellar evolution models with and without rotation. A&A, 457(3), 1015-1031. https://doi.org/10.1051/0004-6361:20065052.
Hamann, W. R., Gräfener, G., Liermann, A., Hainich, R., Sander, A. A. C., Shenar, T., Ramachandran, V., Todt, H., and Oskinova, L. M. (2019) The Galactic WN stars re-visited: Impact of Gaia distances on fundamental stellar parameters. A&A, 625, A57. https://doi.org/10.1051/0004-6361/201834850.
Hamann, W. R., Koesterke, L., and Wessolowski, U. (1993) Spectral analyses of the galactic Wolf-Rayet stars: a comprehensive study of the WN class. A&A, 274, 397-414. https: //ui.adsabs.harvard.edu/abs/1993A&A…274..397H.
Hawcroft, C., Sana, H., Mahy, L., Sundqvist, J. O., de Koter, A., Crowther, P. A., Bestenlehner, J. M., Brands, S. A., David-Uraz, A., Decin, L., and 19 others (2024) X-shooting ULLYSES: Massive stars at low metallicity. III. Terminal wind speeds of ULLYSES massive stars. A&A, 688, A105. https://doi.org/10. 1051/0004-6361/202245588.
Heap, S. R., Lanz, T., and Hubeny, I. (2006) Fundamental properties of O-Type stars. ApJ, 638(1), 409-432. https://doi.org/10.1086/498635.
Heck, A., Manfroid, J., and Mersch, G. (1985) On period determination methods. A&AS, 59, 63-72. https://ui.adsabs.harvard.edu/abs/1985A&AS…59…63H.
Hillier, D. J. and Miller, D. L. (1998) The treatment of non-LTE line blanketing in spherically expanding outflows. ApJ, 496(1), 407-427. https://doi.org/10.1086/305350.
Ilijic, S. (2004) Thoughts about disentangling in wavelength and in Fourier-space. In Spectroscopically and Spatially Resolving the Components of the Close Binary Stars, edited by Hilditch, R. W., Hensberge, H., and Pavlovski, K., Astronomical Society of the Pacific Conference Series, volume 318, pages 107-110. https://www.aspbooks.org/a/volumes/article_ details/?paper_id=140.
Indebetouw, R., Mathis, J. S., Babler, B. L., Meade, M. R., Watson, C., Whitney, B. A., Wolff, M. J., Wolfire, M. G., Cohen, M., Bania, T. M., Benjamin, R. A., Clemens, D. P., Dickey, J. M., Jackson, J. M., Kobulnicky, H. A., Marston, A. P., Mercer, E. P., Stauffer, J. R., Stolovy, S. R., and Churchwell, E. (2005) The wavelength dependence of interstellar extinction from 1.25 to 8.0 μm using GLIMPSE data. ApJ, 619(2), 931-938. https://doi.org/10.1086/426679.
Kaufer, A., Stahl, O., Tubbesing, S., N⊘rregaard, P., Avila, G., Francois, P., Pasquini, L., and Pizzella, A. (1999) Commissioning FEROS, the new high-resolution spectrograph at La Silla. Msngr, 95, 8-12. https://www.eso.org/sci/publications/messenger/archive/no. 95-mar99/messenger-no95-8- 12.pdf.
Li, S., Frank, A., and Blackman, E. G. (2014) Triggered star formation and its consequences. MNRAS, 444(3), 2884-2892. https://doi.org/10.1093/mnras/stu1571.
Lucy, L. B. and Sweeney, M. A. (1971) Spectroscopic binaries with circular orbits. AJ, 76(6), 544-556. https://doi.org/10.1086/111159.
Luo, D., McCray, R., and Mac Low, M.-M. (1990) X-rays from colliding stellar winds. ApJ, 362(1), 267-273. https://doi.org/10.1086/169263.
Mahy, L., Damerdji, Y., Gosset, E., Nitschelm, C., Eenens, P., Sana, H., and Klotz, A. (2017) A modern study of HD 166734: a massive supergiant system. A&A, 607, A96. https: //doi.org/10. 105 1/0004-6361/201730674.
Mahy, L., Gosset, E., Manfroid, J., Nitschelm, C., Hervé, A., Semaan, T., Sana, H., Le Bouquin, J. B., and Toonen, S. (2018) The triple system HD 150136: From periastron passage to actual masses. A&A, 616, A75. https://doi.org/10.1051/0004-6361/201832810.
Mahy, L., Hutsemékers, D., Royer, P., and Waelkens, C. (2016) Tracing back the evolution ofthe candidate LBV HD 168625. A&A, 594, A94. https://doi.org/10.1051/0004-6361/201628584.
Mahy, L., Lanthermann, C., Hutsemékers, D., Kluska, J., Lobel, A., Manick, R., Miszalski, B., Reggiani, M., Sana, H., and Gosset, E. (2022a) Multiplicity of Galactic luminous blue variable stars. A&A, 657, A4. https://doi.org/10.1051/0004-6361/202040062.
Mahy, L., Sana, H., Shenar, T., Sen, K., Langer, N., Marchant, P., Abdul-Masih, M., Banyard, G., Bodensteiner, J., Bowman, D. M., Dsilva, K., Fabry, M., Hawcroft, C., Janssens, S., Van Reeth, T., and Eldridge, C. (2022b) Identifying quiescent compact objects in massive Galactic single-lined spectroscopic binaries. A&A, 664, A159. https://doi.org/10.1051/ 0004-6361/202243147.
Maíz Apellániz, J., Sota, A., Arias, J. I., Barbá, R. H., Walborn, N. R., Simón-Díaz, S., Negueruela, I., Marco, A., Leão, J. R. S., Herrero, A., Gamen, R. C., and Alfaro, E. J. (2016) The Galactic O-Star Spectroscopic Survey (GOSSS). III. 142 additional O-type systems. ApJS, 224(1), 4. https://doi.org/10.3847/0067-0049/224/1/4.
Martins, F. (2018) Quantitative spectral classification of Galactic O stars. A&A, 616, A135. https://doi.org/10.1051/0004-6361/201833050.
Martins, F. and Plez, B. (2006) UBVJHK synthetic photometry of Galactic O stars. A&A, 457(2), 637-644. https://doi.org/10.1051/0004-6361:20065753.
Martins, F., Schaerer, D., and Hillier, D. J. (2005) A new calibration of stellar parameters of Galactic O stars. A&A, 436(3), 1049-1065. https://doi.org/10.1051/0004-6361:20042386.
Massey, Ph. and Conti, P. S. (1983) Wolf-Rayet stars in the LMC: how faint are the faintest? ApJ, 264, 126-133. https://doi.org/10.1086/160579.
Massey, Ph. and Johnson, J. (1993) Massive stars near eta Carinae: The stellar content of Tr 14 and Tr 16. AJ, 105(3), 980-1001,1225-1233. https://doi.org/10.1086/116487.
Mathys, G. (1988) The upper main sequence of OB associations. I. Spectral types and lines of C and N of southern single-lined O stars. A&AS, 76(3), 427-444. https://ui.adsabs.harvard. edu/abs/1988A&AS…76..427M.
Mokiem, M. R., de Koter, A., Evans, C. J., Puls, J., Smartt, S. J., Crowther, P. A., Herrero, A., Langer, N., Lennon, D. J., Najarro, F., Villamariz, M. R., and Yoon, S.-C. (2006) The VLT-FLAMES survey ofmassive stars: mass loss and rotation ofearly-type stars in the SMC. A&A, 456(3), 1131-1151. https://doi.org/10.1051/0004-6361:20064995.
Niemela, V. S., Gamen, R. C., Barbá, R. H., Fernández Lajús, E., Benaglia, P., Solivella, G. R., Reig, P., and Coe, M. J. (2008) The very massive X-ray bright binary system Wack2134 (=WR 21a). MNRAS, 389(3), 1447-1452. https://doi.org/10.1 1 1 1/j. 1365-2966.2008.13684. x.
Nishiyama, S., Tamura, M., Hatano, H., Kato, D., Tanabé, T., Sugitani, K., and Nagata, T. (2009) Interstellar extinction law toward the Galactic center III: J, H, Ks bands in the 2MASS and the MKO systems, and 3.6, 4.5, 5.8, 8.0μm in the Spitzer/IRAC system. ApJ, 696(2), 1407-1417. https://doi.org/10. 1088/0004-637X/696/2/1407.
Pandey, J. C., Pandey, S. B., and Karmakar, S. (2014) Phase-resolved XMM-Newton and Swift observations of WR 25. ApJ, 788(1), 84. https://doi.org/10.1088/0004-637X/788/1/84.
Pantaleoni González, M., Maíz Apellániz, J., Barbá, R. H., Reed, B. C., Berlanas, S. R., Parras Rico, A., and Bodaghee, A. (2025) The Alma catalogue of OB stars - III. a crossmatch with Gaia DR3 and an extension based on new spectral classifications. MNRAS, 543(1), 63-82. https://doi.org/10.1093/mnras/staf1409.
Parkin, E. R. and Gosset, E. (2011) Investigating the X-ray emission from the massive WR+O binary WR 22 using 3D hydrodynamical models. A&A, 530, A119. https://doi.org/10.1051/ 0004-6361/201016125.
Pollock, A. M. T. and Corcoran, M. F. (2006) Evidence for colliding winds in WR 25 from XMM-Newton observations of X-ray variability. A&A, 445(3), 1093-1097. https://doi.org/ 10.1051/0004-6361:20053496.
Pradhan, P., Huenemoerder, D. P., Ignace, R., Pollock, A. M. T., and Nichols, J. S. (2021) The colliding winds of WR 25 in high-resolution X-rays. ApJ, 915(2), 114. https://doi.org/10. 3847/1538-4357/ac02c4.
Press, W. H., Teukolsky, S. A., Vetterling, W. T., and Flannery, B. P. (2007) Numerical Recipes: The Art of Scientific Computing. Cambridge University Press, 3rd edition.
Prilutskii, O. F. and Usov, V. V. (1976) X rays from Wolf-Rayet binaries. SvA, 20(1), 2-4. https://ui.adsabs.harvard.edu/abs/1976SvA 20 2P.
Pritchard, J. (2005) FEROS-II User Manual. http://www.eso.org/sci/facilities/lasilla/ instruments/feros/doc/manual/P77/FEROSII-UserManual-77.0.pdf.
Puls, J., Vink, J. S., and Najarro, F. (2008) Mass loss from hot massive stars. A&ARv, 16(3-4), 209-325. https://doi.org/10. 1007/s00159-008-0015-8.
Putkuri, C., Gamen, R., Morrell, N. I., Maíz Apellániz, J., Arias, J. I., Simón-Díaz, S., Ferrero, G. A., Rodríguez, C. N., Sota, A., Benvenuto, O. G., and Barbá, R. H. (2023) The spectroscopic orbit of HD 168112 A, B in NGC 6604: another massive binary target for interferometry. MNRAS, 525(4), 6084-6096. https://doi.org/10.1093/mnras/stad2657.
Rauw, G., Crowther, P. A., De Becker, M., Gosset, E., Nazé, Y., Sana, H., van der Hucht, K. A., Vreux, J. M., and Williams, P. M. (2005) The spectrum of the very massive binary system WR 20a (WN6ha + WN6ha): Fundamental parameters and wind interactions. A&A, 432(3), 985-998. https://doi.org/10.1051/0004-6361:20042136.
Rauw, G., Vreux, J.-M., Gosset, E., Hutsemékers, D., and Magain, P. (1995) WR22 as a core hydrogen-burning Wolf-Rayet star. In Stellar Evolution: What Should Be Done?, edited by Noels, A., Fraipont-Caro, D., Gabriel, M., Grevesse, N., and Demarque, P., Liege International Astrophysical Colloquia, volume 32, pages 463-467. https://hdl.handle.net/2268/15913.
Rauw, G., Vreux, J. M., Gosset, E., Hutsemékers, D., Magain, P., and Rochowicz, K. (1996) WR 22: the most massive Wolf-Rayet star ever weighed. A&A, 306, 771-782. https: //ui.adsabs.harvard.edu/abs/1996A&A…306..771R.
Renson, P. (1978) Méthode de recherche des périodes des étoiles variables [Method for finding the periods of variable stars]. A&A, 63, 125-129. https://ui.adsabs.harvard.edu/abs/1978A& A 63..125R. In French, with a summary in English.
Repolust, T., Puls, J., and Herrero, A. (2004) Stellar and wind parameters of Galactic O-stars. The influence of line-blocking/blanketing. A&A, 415, 349-376. https://doi.org/10.1051/ 0004-6361:20034594.
Sana, H. (2009) The nature of the line profile variability in the spectrum of the massive binary HD 152219. A&A, 501(1), 291-295. https://doi.org/10.1051/0004-6361/200810271.
Sana, H., de Koter, A., de Mink, S. E., Dunstall, P. R., Evans, C. J., Hénault-Brunet, V., Maíz Apellániz, J., Ramírez-Agudelo, O. H., Taylor, W. D., Walborn, N. R., Clark, J. S., Crowther, P. A., Herrero, A., Gieles, M., Langer, N., Lennon, D. J., and Vink, J. S. (2013) The VLT-FLAMES Tarantula Survey. VIII. Multiplicity properties of the O-type star population. A&A, 550, A107. https://doi.org/10.1051/0004-6361/201219621.
Sana, H., de Mink, S. E., de Koter, A., Langer, N., Evans, C. J., Gieles, M., Gosset, E., Izzard, R. G., Le Bouquin, J. B., and Schneider, F. R. N. (2012) Binary interaction dominates the evolution of massive stars. Sci, 337, 444-446. https://doi.org/10.1126/science.1223344.
Sana, H., Gosset, E., and Rauw, G. (2006) The OB binary HD 152219: a detached, double-lined, eclipsing system. MNRAS, 371(1), 67-80. https://doi.org/10.1 1 1 1/j.1365-2966.2006.10654.x.
Sana, H., Le Bouquin, J. B., Lacour, S., Berger, J. P., Duvert, G., Gauchet, L., Norris, B., Olofsson, J., Pickel, D., Zins, G., Absil, O., de Koter, A., Kratter, K., Schnurr, O., and Zinnecker, H. (2014) Southern massive stars at high angular resolution: Observational campaign and companion detection. ApJS, 215(1), 15. https://doi.org/10.1088/0067-0049/215/1/15.
Sana, H., Shenar, T., Bodensteiner, J., Britavskiy, N., Langer, N., Lennon, D. J., Mahy, L., Mandel, I., de Mink, S. E., Patrick, L. R., and 66 more (2025) A high fraction of close massive binary stars at low metallicity. NatAs, 9, 1337-1346. https://doi.org/10.1038/ s41550-025-02610-x.
Schweickhardt, J., Schmutz, W., Stahl, O., Szeifert, Th., and Wolf, B. (1999) Revised mass determination of the super massive Wolf-Rayet star WR 22. A&A, 347, 127-136. https: //ui.adsabs.harvard.edu/abs/1999A&A…347..127S.
Seward, F. D. and Chlebowski, T. (1982) X-ray emission from the Carina Nebula and the associated early stars. ApJ, 256, 530-542. https://doi.org/10.1086/159929.
Seward, F. D., Forman, W. R., Giacconi, R., Griffiths, R. E., Harnden, J., F. R., Jones, C., and Pye, J. P. (1979) X-rays from Eta Carinae and the surrounding nebula. ApJL, 234(1), L55-L58. https://doi.org/10.1086/183108.
Shenar, T., Sana, H., Mahy, L., Maíz Apellániz, J., Crowther, P. A., Gromadzki, M., Herrero, A., Langer, N., Marchant, P., Schneider, F. R. N., Sen, K., Soszyński, I., and Toonen, S. (2022) The Tarantula Massive Binary Monitoring. VI. Characterisation of hidden companions in 51 single-lined O-type binaries: A flat mass-ratio distribution and black-hole binary candidates. A&A, 665, A148. https://doi.org/10.1051/0004-6361/202244245.
Simón-Díaz, S. and Herrero, A. (2014) The IACOB project: I. Rotational velocities in northern Galactic O- and early B-type stars revisited. The impact of other sources of line-broadening. A&A, 562, A135. https://doi.org/10.1051/0004-6361/201322758.
Smith, L. F. (1968) A revised spectral classification system and a new catalogue for galactic Wolf-Rayet stars. MNRAS, 138(1), 109-121. https://doi.org/10.1093/mnras/138.1.109.
Smith, L. F., Shara, M. M., and Moffat, A. F. J. (1996) A three-dimensional classification for WN stars. MNRAS, 281(1), 163-191. https://doi.org/10.1093/mnras/281.1.163.
Sota, A., Maíz Apellániz, J., Morrell, N. I., Barbá, R. H., Walborn, N. R., Gamen, R. C., Arias, J. I., and Alfaro, E. J. (2014) The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright southern stars. ApJS, 211(1), 10. https://doi.org/10.1088/0067-0049/21 1/1/10.
Sota, A., Maíz Apellániz, J., Walborn, N. R., Alfaro, E. J., Barbá, R. H., Morrell, N. I., Gamen, R. C., and Arias, J. I. (2011) The Galactic O-Star spectroscopic survey. I. Classification system and bright northern stars in the blue-violet at R ~ 2500. ApJS, 193(2), 24. https: //doi.org/10. 1088/0067-0049/193/2/24.
Stevens, I. R., Blondin, J. M., and Pollock, A. M. T. (1992) Colliding winds from early-type stars in binary systems. ApJ, 386(1), 265-287. https://doi.org/10.1086/171013.
Tramper, F., Sana, H., Fitzsimons, N. E., de Koter, A., Kaper, L., Mahy, L., and Moffat, A. (2016) The mass of the very massive binary WR21a. MNRAS, 455(2), 1275-1281. https://doi.org/10.1093/mnras/stv2373.
Tsang, B. T. H. and Milosavljević, M. (2018) Radiation pressure in super star cluster formation. MNRAS, 478(3), 4142-4161. https://doi.org/10.1093/mnras/sty1217.
van der Hucht, K. A. (1996) Past and present classification of hot massive stars. In Wolf-Rayet Stars in the Framework of Stellar Evolution, edited by Vreux, J.-M., Detal, A., Fraipont-Caro, D., Gosset, E., and Rauw, G., Liege International Astrophysical Colloquia, volume 33, pages 1-22. https://ui.adsabs.harvard.edu/abs/1996LIACo..33 1V.
van der Hucht, K. A. (2001) The VIIth catalogue of galactic Wolf-Rayet stars. NewAR, 45(3), 135-232. https://doi.org/10.1016/S1387-6473(00)00112-3.
van Hoof, P. A. M. (2018) Recent development of the Atomic Line List. Galax, 6(2), 63. https://doi.org/10.3390/galaxies6020063.
Villaseñor, J. I., Sana, H., Mahy, L., Shenar, T., Bodensteiner, J., Britavskiy, N., Lennon, D. J., Moe, M., Patrick, L. R., Pawlak, M., and 23 more (2025) Binarity at LOw Metallicity (BLOeM): Enhanced multiplicity of early B-type dwarfs and giants at Z = 0.2ZO. A&A, 698, A41. https://doi.org/10.1051/0004-6361/202453166.
Vink, J. S., de Koter, A., and Lamers, H. J. G. L. M. (2000) New theoretical mass-loss rates of O and B stars. A&A, 362, 295-309. https://doi.org/10.48550/arXiv.astro-ph/0008 1 83.
Vink, J. S., de Koter, A., and Lamers, H. J. G. L. M. (2001) Mass-loss predictions for O and B stars as a function of metallicity. A&A, 369, 574-588. https://doi.org/10.1051/0004-6361: 20010127.
Walborn, N. (2001) Selective emission lines in O-type spectra. In Eta Carinae and Other Mysterious Stars: The Hidden Opportunities of Emission Spectroscopy, edited by Gull, T. R., Johannson, S., and Davidson, K., Astronomical Society of the Pacific Conference Series, volume 242, pages 217-228. https://www.aspbooks.org/a/volumes/article_details/?paper_ id=22980.
Walborn, N. R. (1971) Some spectroscopic characteristics of the OB stars: an investigation of the space distribution of certain OB stars and the reference frame of the classification. ApJS, 23, 257-282. https://doi.org/10.1086/190239.
Walborn, N. R. and Fitzpatrick, E. L. (1990) Contemporary optical spectral classification of the OB stars: A digital atlas. PASP, 102, 379. https://doi.org/10.1086/132646.
Werner, K. and Rauch, T. (2001) Identification of the 4486, 4504 Å emission lines in O-type spectra. In Eta Carinae and Other Mysterious Stars: The Hidden Opportunities of Emission Spectroscopy, edited by Gull, T. R., Johannson, S., and Davidson, K., Astronomical Society of the Pacific Conference Series, volume 242, pages 229-232. https://www.aspbooks.org/a/ volumes/article_details/?paper_id=22981.
Zacharias, N., Finch, C. T., Girard, T. M., Henden, A., Bartlett, J. L., Monet, D. G., and Zacharias, M. I. (2013) The fourth US Naval Observatory CCD Astrograph Catalog (UCAC4). AJ, 145(2), 44. https://doi.org/10.1088/0004-6256/145/2/44.
