SPECTROSCOPIC ANALYSIS OF OB STARS IN THE CARINA NEBULA Simone Daﬂon 1, Wilton Santos 1,2, João Victor Sales Silva 1, and the Gaia-ESO Survey Team 1Observatório Nacional 2UESC Introduction Massive OB stars are luminous and young objects, being easily observed and located close to their place of birth, allowing the mapping of the present-day abundances of the Galaxy. OB stars are generally found in OB associations, one of them is Car OB, a large, very active star-forming region in the Carina- Sagittarius spiral arm. Its stellar population is split into several open clusters associated with the Carina Nebula. In this work, we present a detailed spectroscopic study for a sample of OB stars located in 8 open clusters in the Carina Nebula: Trumpler 14, Trumpler 15, Trumpler 16E/W, Collinder 228, Collinder 232, Bochum 11 and NGC 3293. Data This study is based on high-resolution spectra obtained with the FLAMES/GIRAFFE spectrograph coupled to the UT2 VLT 8 m telescope, in the context of the Gaia-ESO Public Spectroscopic Survey. The GIRAFFE conﬁgurations are optimized to detect important features in the spectra of early-type stars such as Hγ line, an important log g-indicator and some important lines for Teff diagnosis, as for example, C iii, O ii, Si iii, and Si iv lines. Projected rotational velocity We obtained the projected rotation velocity V sin i for a sample of 330 OB stars, probable members of 8 open clusters in the Carina Nebula, based on a calibration for the widths of two He i lines, at λ 4388 and 4471Å[2]. The V sin i distribution for the full sample represented by the blue histogram (Fig 1) is consistent with typical V sin i distributions for open clusters while the V sin i distributions for ﬁeld OB stars tend to peak at lower V sin i. Fig 2 presents the violin distributions for the 5 clusters of our sample with more than 40 studied stars: the average V sin i for individual clusters varies between 126±77 km s−1, for Collinder 228, and 180±84 km s−1, for NGC 3293. Stellar Parameters and Abundances We use a semi-automatic routine based on non-NLTE model atmospheres and synthetic spectra (TLUSTY/SYNPLOT) [1, 3] to perform a self-consistent analysis and determine the atmospheric parameters Teff, log g, V sin i, microturbulence and macroturbulence, as well as abundances of Silicon, Oxygen, Carbon and Nitrogen, for a subsample of 65 sharp-lined stars. The eﬀective temperature has been deﬁned from the ionization balance between Si ii, Si iii, and Si iv (Fig 3), while log g has been derived from the ﬁts of H wings (Fig 4). Results The stars in our sample are mainly on the main sequence, with Teff between 14,000 and 33,000 K and log g between 3.00 and 4.50 (Fig 5). In Fig 6 we present the violin distributions for the abundances of studied species. The average abundances of C, N, and O are consistent with the solar value while being slightly subsolar for Si. Our results suggest that the Carina Nebula is chemically homogeneous to within ∼ 0.10 dex and the average abundances of O and Si are consistent with its radial position in the Galactic disk (Fig 7), as expected by [1]. References [1]G. A. Bragança, S. Daﬂon, and et al. A&A, 625:A120, 2019. [2]S. Daﬂon, K. Cunha, F. X. de Araújo, S. Wolﬀ, and N. Przybilla. The Astronomical Journal, 134:1570–1578, 2007. [3]I. Hubeny and T. Lanz. arXiv:1706.01859, 2017. Acknowledgements W.S acknowledges ﬁnancial support from CAPES and FAPERJ for Ph.D. fellowships. S.D. acknowledges CNPq/MCTI for grant 306859/2022-0.