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We report the discovery of the faint (V=21.7) quasar QSO03027-0010 at z=2.808in the vicinity of Q0302-003, one of the few quasars observed with STIS tostudy intergalactic HeII absorption. Together with another newly discovered QSOat z=2.29, there are now 6 QSOs known near the line of sight towards Q0302-003,of which 4 are located within the redshift region 2.76<=z<=3.28 covered by theSTIS spectrum. We correlated the opacity variations in the HI and HeII Lymanforest spectra with the locations of known quasars. There is no significantproximity effect in the HI Lyman alpha forest for any of the QSOs, except forthe well-known line of sight effect for Q0302-003 itself. By comparing theabsorption properties in HI and HeII, we estimated the fluctuating hardness ofthe extragalactic UV radiation field along this line of sight. We find thatclose to each foreground quasar, the ionizing background is considerably harderthan on average. In particular, our newly discovered QSO03027-0010 shows such ahardness increase despite being associated with an overdensity in the HI Lymanforest. We argue that the spectral hardness is a sensitive physical measure toreveal the influence of QSOs onto the UV background even over scales of severalMpc, and that it breaks the density degeneracy hampering the traditionaltransverse proximity effect analysis. We infer from our sample that there is noneed for significantly anisotropic UV radiation from the QSOs. From thetransverse proximity effect detected in the sample we obtain minimum quasarlifetimes in the range ~10-30 Myr.Comment: 15 pages, 9 figures, accepted by A&A, problems with paper size fixe

Quasars near the line of sight towards Q 0302-003 and the transverse proximity effect