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Winds of massive stars have density inhomogeneities (clumping) that mayaffect the formation of spectral lines in different ways, depending on theirformation region. Most of previous and current spectroscopic analyses have beenperformed in the optical or ultraviolet domain. However, massive stars areoften hidden behind dense clouds rendering near-infrared observationsnecessary. Our objective is to investigate whether a spectroscopic analysisusing either optical or infrared observations results in the same stellarparameters with comparable accuracy, and whether clumping affects them indifferent ways. We analyzed optical and near-infrared observations of a set ofmassive O stars with spectral types O4-O9.5 and all luminosity classes. Weobtain similar stellar parameters in the optical and the infrared, althoughwith larger uncertainties in the near-infrared, both with and without clumping,albeit with some individual deviating cases. We find that the inclusion ofclumping improves the fit to H$_\alpha$ or HeII 4686 in the optical forsupergiants, as well as that of Br$_\gamma$ in the near-infrared, but itsometimes worsens the fit to HeII 2.18$\mu$m. Globally, there are nosignificant differences when using the clumping laws tested in this work. Theinfrared can be used for spectroscopic analyses, giving similar parameters asfrom the optical, though with larger uncertainties. The best fits to differentlines are obtained with different (linear) clumping laws, indicating that thewind structure may be more complex than adopted in the present work. Noclumping law results in a better global fit, or improves the consistencybetween optical and infrared stellar parameters. Our work shows that theoptical and infrared lines are not sufficient to break the dichotomy betweenthe mass-loss rate and clumping factor.

To clump or not to clump The impact of wind inhomogeneities on the optical and NIR spectroscopic analysis of massive OB stars