Abstract
We present the results of a further investigation of the planetarysystem HD 109833, whose central star is a young, active solaranalog, presumably a member of the Lower Centaurus Cruxassociation (age: \(27\pm 3\) Myr). Using digitized photographicplates from the Digital Access to a Sky Century@Harvard project(providing data on HD 109833 spanning a 100 year observationperiod) we made an additional attempt to study possible activitycycles of the star. Taking into account all uncertainties, itshould be noted that the derived estimates of the activity cycleperiod \(P_{\textrm{cycl}}\) (including the earlier value obtainedfrom ASAS-3 data, \(P_{\textrm{cycl}}=5.3\) years) are on the edgeof statistical reliability. Based on measurements of thechromospheric activity index \(\log R^{\prime}_{HK}\) forHD 109833 from the updated HARP SRV database and its empiricalrelation with \(\log F_{\textrm{XUV}}\) , we estimated the XUVphoton flux to be \(2.0\times 10^{29}\) erg s \({}^{-1}\) . Theexoplanets HD 109833 b and c are located in the overlappingregion of two distinct populations on the ‘‘mass–radius’’diagram: rocky planets and planets rich in volatile compounds. Wepresent calculations of atmospheric mass loss rates \(\dot{M}\) forHD 109833 b and c based on both the energy-limited escape model(EL) and the hydrodynamic approximation model (HA), usingdifferent planetary mass estimates. We also provide the ratios ofmass loss rates \(\dot{M}\) obtained from EL and HA models (Ratio),and the values of the Jeans parameter \(\Lambda\) . It is suggestedthat the HA model significantly underestimates \(\dot{M}\) in thecase of rocky planets, rendering this model inapplicable for suchhigh values of \(\Lambda\) . Our results are in reasonable agreementwith those of Foster et al. (2022), which describe the generalbehavior of \(\dot{M}\) , and fall within the observed spread of thisparameter.
