ABSORBING GAS AROUND THE WASP-12 PLANETARY SYSTEM

作者：Fossati L^*; Ayres T R; Haswell C A; Bohlender D; Kochukhov O; Floeer L

来源：Astrophysical Journal Letters, 2013, 766(2): L20.

DOI：10.1088/2041-8205/766/2/L20

• ISM: clouds
• planets and satellites: individual (WASP-12)
• planet-star interactions
• stars: individual (WASP-12)

Near-UV observations of the planet host star WASP-12 uncovered the apparent absence of the normally conspicuous core emission of the Mg II h and k resonance lines. This anomaly could be due either to (1) a lack of stellar activity, which would be unprecedented for a solar-like star of the imputed age of WASP-12 or (2) extrinsic absorption, from the intervening interstellar medium (ISM) or from material within the WASP-12 system itself, presumably ablated from the extreme hot Jupiter WASP-12 b. HIRES archival spectra of the Ca II H and K lines of WASP-12 show broad depressions in the line cores, deeper than those of other inactive and similarly distant stars and similar to WASP-12%26apos;s Mg II h and k line profiles. We took high-resolution ESPaDOnS and FIES spectra of three early-type stars within 20%26apos; of WASP-12 and at similar distances, which show the ISM column is insufficient to produce the broad Ca II depression observed in WASP-12. The EBHIS H I column density map supports and strengthens this conclusion. Extrinsic absorption by material local to the WASP-12 system is therefore the most likely cause of the line core anomalies. Gas escaping from the heavily irradiated planet could form a stable and thick circumstellar disk/cloud. The anomalously low stellar activity index (logR%26apos;(HK)) of WASP-12 is evidently a direct consequence of the extra core absorption, so similar HK index deficiencies might signal the presence of translucent circumstellar gas around other stars hosting evaporating planets.

• 出版日期2013-4-1