XMM-Newton observation of Mrk 110

Context. We report on the first XMM-Newton observation of the bright narrow-line Seyfert 1 galaxy Mrk 110. Aims. Our analysis is aimed to study the properties of the X-ray spectrum of Mrk 110 and compare them with those inferred from optical spectroscopy. Methods. We make use of detailed timing and spectral analysis as well as high resolution X-ray spectroscopy with the XMM-Newton gratings. Results. We find a narrow Fe K fluorescent line, a broad component (FWHM similar or equal to 16 500 km s(-1)) of the O VII triplet, either due to infall motions or gravitational redshift effects in the vicinity of the central black hole, a Comptonized accretion disk layer, and a strong starburst component. Conclusions. We found that Mrk 110 has a complex X-ray spectrum, exhibiting relatively strong broadening of the O VII emission line, probably associated with X-ray emission from the Broad Line Region (BLR), which might be correlated with the optical gravitationally redshifted, asymmetric line profiles. Spectral fits including a Gaussian line or a discline give the same statistical significance. If the broad redshifted soft X-ray components are due to gravitational redshift effects, the distance of the line-emitting regions ranges between about 0.2 and 1 light day with respect to the central black hole. In addition, the EPIC pn spectrum shows a double power-law and a strong starburst component. One power-law component exhibits a photon index slope of 1.40(1.38)(1.50), while the second is much steeper with a power law slope of 2.50(2.48)(2.63). The second power-law is most probably due to thermal Comptonization of a hot electron layer above the accretion disk. Mrk 110 is another example of extragalactic sources showing Comptonization effects in the accretion disc and its properties are very similar to the narrow-line Seyfert 1 Galaxy Ton S 180.