English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present a precise characterization of the TOI-561 planetary systemobtained by combining previously published data with TESS and CHEOPSphotometry, and a new set of $62$ HARPS-N radial velocities (RVs). Our jointanalysis confirms the presence of four transiting planets, namely TOI-561 b ($P= 0.45$ d, $R = 1.42$ R$_\oplus$, $M = 2.0$ M$_\oplus$), c ($P = 10.78$ d, $R =2.91$ R$_\oplus$, $M = 5.4$ M$_\oplus$), d ($P = 25.7$ d, $R = 2.82$R$_\oplus$, $M = 13.2$ M$_\oplus$) and e ($P = 77$ d, $R = 2.55$ R$_\oplus$, $M= 12.6$ M$_\oplus$). Moreover, we identify an additional, long-period signal($>450$ d) in the RVs, which could be due to either an external planetarycompanion or to stellar magnetic activity. The precise masses and radiiobtained for the four planets allowed us to conduct interior structure andatmospheric escape modelling. TOI-561 b is confirmed to be the lowest density($\rho_{\rm b} = 3.8 \pm 0.5$ g cm$^{-3}$) ultra-short period (USP) planetknown to date, and the low metallicity of the host star makes it consistentwith the general bulk density-stellar metallicity trend. According to ourinterior structure modelling, planet b has basically no gas envelope, and itcould host a certain amount of water. In contrast, TOI-561 c, d, and e likelyretained an H/He envelope, in addition to a possibly large water layer. Theinferred planetary compositions suggest different atmospheric evolutionarypaths, with planets b and c having experienced significant gas loss, andplanets d and e showing an atmospheric content consistent with the originalone. The uniqueness of the USP planet, the presence of the long-period planetTOI-561 e, and the complex architecture make this system an appealing targetfor follow-up studies.

Investigating the architecture and internal structure of the TOI-561 system planets with CHEOPS, HARPS-N and TESS