Context : The Transiting Exoplanet Survey Satellite ( TESS ) is observing bright known planet-host stars across almost the entire sky .
These stars have been subject to extensive ground-based observations , providing a large number of radial velocity ( RV ) measurements .

Aims : In this work we use the new TESS photometric observations to characterize the star \lambda ^ { 2 } Fornacis , and following this to update the parameters of the orbiting planet \lambda ^ { 2 } For b .

Methods : We measure the p-mode oscillation frequencies in \lambda ^ { 2 } For , and in combination with non-seismic parameters estimate the stellar fundamental properties using stellar models .
Using the revised stellar properties and a time series of archival RV data from the UCLES , HIRES and HARPS instruments spanning almost 20 years , we refit the orbit of \lambda ^ { 2 } For b and search the RV residuals for remaining variability .

Results : We find that \lambda ^ { 2 } For has a mass of 1.16 \pm 0.03 M _ { \odot } and a radius of 1.63 \pm 0.04 R _ { \odot } , with an age of 6.3 \pm 0.9 Gyr .
This and the updated RV measurements suggest a mass of \lambda ^ { 2 } For b of 16.8 ^ { +1.2 } _ { -1.3 } M _ { \oplus } , which is \sim 5 M _ { \oplus } less than literature estimates .
We also detect a periodicity at 33 days in the RV measurements , which is likely due to the rotation of the host star .

Conclusions : While previous literature estimates of the properties of \lambda ^ { 2 } are ambiguous , the asteroseismic measurements place the star firmly at the early stage of its subgiant evolutionary phase .
Typically only short time series of photometric data are available from TESS , but by using asteroseismology it is still possible to provide tight constraints on the properties of bright stars that until now have only been observed from the ground .
This prompts a reexamination of archival RV data from the past few decades to update the characteristics of the planet hosting systems observed by TESS for which asteroseismology is possible .