2 X-ray data (XMM-Newton)

NGC 4698 is an Sab spiral galaxy located in the Virgo cluster (d=16.8 Mpc). It hosts an active nucleus, classified as a Seyfert 1.9 by Ho et al. (1997). The galaxy was observed on 16 December 2001 using the European Photon Imaging Camera (EPIC) on board the XMM-Newton satellite. EPIC is composed of two instruments: the PN-CCD camera (Strüder et al. 2001) and two MOS-CCD detectors (Turner et al. 2001). The effective exposure time was 9.2 ks.

We find only one ULX apparently associated with NGC 4698 (Foschini et al. 2002), located $73\hbox{$^{\prime\prime}$ }$ from the optical nucleus of the galaxy, at $\rm\alpha = 12^h48^m25.9^s$ and $\delta = +08^{\circ}30\hbox{$^\prime$ }20\hbox{$^{\prime\prime}$ }$ (J2000). The point source centroid is measured to precision of better than  $0\hbox{$.\!\!^{\prime\prime}$ }1$, and the absolute pointing uncertainty is < $4\hbox{$^{\prime\prime}$ }$ (Jansen et al. 2001). We detected 198 photons with MOS1, in a circle of radius  $30\hbox{$^{\prime\prime}$ }$, 249with MOS2, and 414 with PN. These statistics are sufficient to perform spectral fitting with simple models. The ones we use are the power law (PL), black body (BB), bremsstrahlung (BR), and the multicolor black body disk (MCD, diskbb in Xspec) by Mitsuda et al. (1984). Fluxes were corrected according to the energy encircled fraction (Ghizzardi 2001).

For the processing, screening, and analysis of the data we used the standard tools in the XMM-SAS software (v. 5.2) and HEAsoft Xspec (v. 11.0.1). Correction for vignetting has not been applied because the source is close to the center of the field of view (< $2\hbox{$^\prime$ }$) and most of the detected photons have energies less than 5 keV (see Lumb 2002).

The best fit (Fig. 3) is found using the power-law model with $\Gamma = 2.0\pm 0.2$ ( $\chi^2=18.3$, $\nu=24$), giving a flux of $8.6\times 10^{-14}$ erg cm^-2 s^-1. If the source is located in NGC 4698, for which we assume a distance of 16.8 Mpc, the corresponding luminosity, assuming isotropic emission, is $\sim$ $3\times 10^{39}$ erg s^-1. For z = 0.43, as discussed below, the luminosity becomes $3.9\times 10^{43}$ erg s^-1. Additional information on the fits using the other models is given in Table 1.