000007470 001__ 7470
000007470 005__ 20250204104853.0
000007470 0247_ $$2DOI$$a10.1051/0004-6361/202452352
000007470 037__ $$aSCART-2025-0101
000007470 100__ $$aDeshmukh, K.  
000007470 245__ $$aInvestigating 39 Galactic Wolf-Rayet stars with VLTI/GRAVITY: Uncovering a long-period binary desert
000007470 260__ $$c2024
000007470 520__ $$aContext. Wolf-Rayet stars (WRs) represent one of the final evolutionary stages of massive stars and are thought to be the immediate progenitors of stellar-mass black holes. Their multiplicity characteristics form an important anchor point in single and binary population models for predicting gravitational-wave progenitors. Recent spectroscopic campaigns have suggested incompatible multiplicity fractions and period distributions for N- and C-rich Galactic WRs (WNs and WCs) at both short and long orbital periods, in contradiction with evolutionary model predictions. Aims. In this work, we employed long-baseline infrared interferometry to investigate the multiplicity of WRs at long periods and explored the nature of their companions. We present a magnitude-limited (K < 9; V < 14) survey of 39 Galactic WRs, including 11 WN, 15 WC, and 13 H-rich WN (WNh) stars. Methods. We used the K-band instrument GRAVITY at the Very Large Telescope Interferometer (VLTI) in Chile. The sensitivity of GRAVITY at spatial scales of ∼1 to 200 milliarcseconds and flux contrast of 1% allowed an exploration of periods in the range 102 ‑ 105 d and companions down to ∼5 M⊙. We carried out a companion search for all our targets, with the aim of either finding wide companions or calculating detection limits. We also explored the rich GRAVITY dataset beyond a multiplicity search to look for other interesting properties of the WR sample. Results. We detected wide companions with VLTI/GRAVITY for only four stars in our sample: WR 48, WR 89, WR 93, and WR 115. Combining our results with spectroscopic studies, we arrived at observed multiplicity fractions of fobsWN = 0.55 ± 0.15, fobsWC = 0.40 ± 0.13, and fobsWNh = 0.23 ± 0.12. The multiplicity fractions and period distributions of WNs and WCs are consistent in our sample. For single WRs, we placed upper limits on the mass of potential companions down to ∼5 M⊙ for WNs and WCs, and ∼7 M⊙ for WNh stars. In addition, we also found other features in the GRAVITY dataset, such as (i) a diffuse extended component contributing significantly to the K-band flux in over half the WR sample; (ii) five known spectroscopic binaries resolved in differential phase data, which constitutes an alternative detection method for close binaries; and (iii) spatially resolved winds in four stars: WR 16, WR 31a, WR 78, and WR 110. Conclusions. Our survey reveals a lack of intermediate- (a few hundred days) and long- (a few years to decades) period WR systems. The 200d peak in the period distributions of WR+OB and BH+OB binaries predicted by Case B mass-transfer binary evolution models is not seen in our data. The rich companionship of their O-type progenitors in this separation range suggests that the WR progenitor stars expand and interact with their companions, most likely through unstable mass transfer, resulting in either a short-period system or a merger.
000007470 594__ $$aNO
000007470 700__ $$aSana, H.  
000007470 700__ $$aMérand, A.  
000007470 700__ $$aBordier, E.  
000007470 700__ $$aLanger, N.  
000007470 700__ $$aBodensteiner, J. 
000007470 700__ $$aDsilva, K.  
000007470 700__ $$aFrost, A. J. 
000007470 700__ $$aGosset, E. 
000007470 700__ $$aLe Bouquin, J. -B. 
000007470 700__ $$aLefever, R. R.  
000007470 700__ $$aMahy, L.  
000007470 700__ $$aPatrick, L. R.  
000007470 700__ $$aReggiani, M. 
000007470 700__ $$aSander, A. A. C.  
000007470 700__ $$aShenar, T.  
000007470 700__ $$aTramper, F.  
000007470 700__ $$aVillaseñor, J. I.  
000007470 700__ $$aWaisberg, I.
000007470 773__ $$c21$$nA109$$pAstronomy & Astrophysics$$v692$$y2024
000007470 8560_ $$flaurent.mahy@ksb-orb.be
000007470 8564_ $$s22912621$$uhttp://publi2-as.oma.be/record/7470/files/Deshmukh_AA_2024.pdf
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000007470 905__ $$apublished in
000007470 980__ $$aREFERD