The Fe~ { } K \alpha line , an important physical diagnostic in the X-ray spectra of active galaxies ( AGNs ) and quasars , has been notoriously difficult to measure in the high-luminosity , radio-loud quasar 3C 273 ( z = 0.158 ) .
On the few occasions that it has been detected its intrinsic width has been thought to be narrow ( FWHM < 10 , 000 km s ^ { -1 } ) with an equivalent width ( EW ) of a few tens of eV .
This was consistent with the general trend that as one goes from low to high luminosity AGNs the Fe~ { } K \alpha line goes from being strong ( { EW } \sim 200 - 300 eV ) and broad ( FWHM \sim 10 ^ { 5 } km/s ) to being weak and narrow , or absent altogether .
Here we present the results of new ASCA and RXTE observations , together with archival ASCA data , and show for the first time that the Fe~ { } K \alpha line in 3C 273 is as broad as that seen in Seyfert 1 galaxies .
The line is resolved in two of the observations , with a mean Gaussian width of 0.8 \pm 0.3 keV , corresponding to a FWHM of \sim 0.3 \pm 0.1 c .
The smallest and largest equivalent width measured is 43 _ { -34 } ^ { +34 } eV and 133 ^ { +52 } _ { -53 } eV respectively ( quasar frame ) .
The Compton-reflection continuum is less than 10 % of that expected from a centrally illuminated semi-infinite , face-on , Compton-thick disk , confirming previous studies that Compton reflection is negligible in 3C 273 .
The largest values of the Fe~ { } K \alpha line EW are under-predicted if the line originates in the disk , unless a time lag longer than several days between line and continuum and/or an over-abundance of Fe is invoked .
We can not unambiguously constrain the disk inclination angle .
About 60 ^ { \circ } is preferred for a cold disk , while a face-on disk is allowed if the ionization state of Fe is H-like .