We report on the discovery and characterization of three planets orbiting the F8 star HD 28109, which sits comfortably in TESS ’s continuous viewing zone. The two outer planets have periods of 56 . ...0067 ±0 . 0003 d and 84 . 2597 + 0 . 0010 −0 . 0008 d, which implies a period ratio very close to that of the first-order 3:2 mean motion resonance, exciting transit timing variations (TTVs) of up to 60 min. These two planets were first identified by TESS , and we identified a third planet in the TESS photometry with a period of 22 . 8911 ±0 . 0004 d. We confirm the planetary nature of all three planetary candidates using ground-based photometry from Hazelwood , ASTEP , and LCO , including a full detection of the ∼9 h transit of HD 28109 c from Antarctica. The radii of the three planets are R b = 2 . 199 + 0 . 098 −0 . 10 R ⊕, R c = 4 . 23 ±0 . 11 R ⊕, and R d = 3 . 25 ±0 . 11 R ⊕; we characterize their masses using TTVs and precise radial velocities from ESPRESSO and HARPS, and find them to be M b = 18 . 5 + 9 . 1 −7 . 6 M ⊕, M c = 7 . 9 + 4 . 2 −3 . 0 M ⊕, and M d = 5 . 7 + 2 . 7 −2 . 1 M ⊕, making planet b a dense, massive planet while c and d are both underdense. We also demonstrate that the two outer planets are ripe for atmospheric characterization using transmission spectroscopy, especially given their position in the CVZ of James Webb Space Telescope . The data obtained to date are consistent with resonant (librating) and non-resonant (circulating) solutions; additional observations will show whether the pair is actually locked in resonance or just near-resonant.
The aim of the LUCAS program is to observe chlorophyll and atmospheric molecules in the Earthshine spectrum in order to prepare the detection of life in terrestrial extrasolar planets to be ...discovered. Actually, observations from Antarctica offer a unique possibility to study the variations of Earthshine spectrum during Earth rotation while various parts of Earth are facing the Moon. Special instrumentation for the LUCAS program was designed and put in the Concordia station in the Dome C. Observations are in progress.
We report on the discovery and characterisation of three planets orbiting the F8 star HD~28109, which sits comfortably in \tess's continuous viewing zone. The two outer planets have periods of \(\rm ...56.0067 \pm 0.0003~days\) and \(\rm 84.2597_{-0.0008}^{+0.0010}~days\), which implies a period ratio very close to that of the first-order 3:2 mean motion resonance, exciting transit timing variations (TTVs) of up to \(\rm 60\,mins\). These two planets were first identified by \tess, and we identified a third planet in the \textcolor{black}{\tess photometry} with a period of \(\rm 22.8911 \pm 0.0004~days\). We confirm the planetary nature of all three planetary candidates using ground-based photometry from Hazelwood, ASTEP and LCO, including a full detection of the \(\rm \sim9\,h\) transit of HD~28109 c from Antarctica. The radii of the three planets are \textcolor{black}{\(\rm R_b=2.199_{-0.10}^{+0.098} ~R_{\oplus}\), \(\rm R_c=4.23\pm0.11~ R_{\oplus}\) and \(\rm R_d=3.25\pm0.11 ~R_{\oplus}\)}; we characterise their masses using TTVs and precise radial velocities from ESPRESSO and HARPS, and find them to be \(\rm M_b=18.5_{-7.6}^{+9.1}~M_{\oplus}\), \(\rm M_c=7.9_{-3.0}^{+4.2}~M_{\oplus}\) and \(\rm M_d=5.7_{-2.1}^{+2.7}~M_{\oplus}\), making planet b a dense, massive planet while c and d are both under-dense. We also demonstrate that the two outer planets are ripe for atmospheric characterisation using transmission spectroscopy, especially given their position in the CVZ of JWST. The data obtained to date are consistent with resonant (librating) and non-resonant (circulating) solutions; additional observations will show whether the pair is actually locked in resonance or just near-resonant.
The search for life in extraterrestrial planets is to be tested first with the only planet known to shelter life. If the planet Earth is used as an example to search for a signature of life, the ...vegetation is one of its possible detectable signature, using the Vegetation Red Edge due to chlorophyll in the near infrared (0.725 μm). We focus on the test of the detectability of vegetation in the spectrum of Earth seen as a simple dot, using the reflection of the global Earth on the lunar surface, i.e., Earthshine. On the Antartic, the Earthshine can be seen during several hours in a day (not possible at our latitudes) and so variations due to different parts of Earth, that is to say oceans and continents facing the Moon could be detected.
The full scientific potential of the VLTI with its second generation instruments MATISSE and GRAVITY require fringe tracking up to magnitudes K>14 with the UTs and K>10 with the ATs. The GRAVITY ...fringe tracker (FT) will be limited to K~10.5 with UTs and K~7.5 with ATs, for fundamental conceptual reasons: the flux of each telescope is distributed among 3 cophasing pairs and then among 5 spectral channels for coherencing. To overcome this limit we propose a new FT concept, called Hierarchical Fringe Tracker (HFT) that cophase pairs of apertures with all the flux from two apertures and only one spectral channel. When the pair is cophased, most of the flux is transmitted as if it was produced by an unique single mode beam and then used to cophase pairs of pairs and then pairs of groups. At the deeper level, the flux is used in an optimized dispersed fringe device for coherencing. On the VLTI such a system allows a gain of about 3 magnitudes over the GRAVITY FT. On interferometers with more apertures such as CHARA (6 telescopes) or a future Planet Formation Imager (12 to 20 telescopes), the HFT would be even more decisive, as its performance does not decrease with the number of apertures. It would allow building a PFI reaching a coherent magnitude H~10 with 16 apertures with diameters smaller than 2 m. We present the HFT concept, the first steps of its feasibility demonstration from computer simulations and the optical design of a 4 telescopes HFT prototype.
Multi-aperture interferometry at Concordia Fossat, Eric; Vakili, Farrokh; Aristidi, Eric ...
Proceedings of the International Astronomical Union,
08/2006, Letnik:
2, Številka:
14
Journal Article
Recenzirano
Odprti dostop
The next generation (post-VLTI) of multi-telescope interferometric arrays operated in optical/infrared wavelengths should be kilometric, from 1 to 10 km. The Concordia station offers a unique ...opportunity to set such an interferometer in the best atmospheric conditions presently known on Earth.
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