Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA planetary system around the nearby M dwarf GJ 667C with at least one super-Earth in its habitable zone
137
0
0.0
(
0
)
Added by
Guillem Anglada-Escude
Publication date
2012
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We re-analyze 4 years of HARPS spectra of the nearby M1.5 dwarf GJ 667C available through the ESO public archive. The new radial velocity (RV) measurements were obtained using a new data analysis technique that derives the Doppler measurement and other instrumental effects using a least-squares approach. Combining these new 143 measurements with 41 additional RVs from the Magellan/PFS and Keck/HIRES spectrometers, reveals 3 additional signals beyond the previously reported 7.2-day candidate, with periods of 28 days, 75 days, and a secular trend consistent with the presence of a gas giant (Period sim 10 years). The 28-day signal implies a planet candidate with a minimum mass of 4.5 Mearth orbiting well within the canonical definition of the stars liquid water habitable zone, this is, the region around the star at which an Earth-like planet could sustain liquid water on its surface. Still, the ultimate water supporting capability of this candidate depends on properties that are unknown such as its albedo, atmospheric composition and interior dynamics. The 75-day signal is less certain, being significantly affected by aliasing interactions among a potential 91-day signal, and the likely rotation period of the star at 105 days detected in two activity indices. GJ 667C is the common proper motion companion to the GJ 667AB binary, which is metal poor compared to the Sun. The presence of a super-Earth in the habitable zone of a metal poor M dwarf in a triple star system, supports the evidence that such worlds should be ubiquitous in the Galaxy.
rate research
Read More
We report the detection of GJ 832c, a super-Earth orbiting near the inner edge of the habitable zone of GJ 832, an M dwarf previously known to host a Jupiter analog in a nearly-circular 9.4-year orbit. The combination of precise radial-velocity measurements from three telescopes reveals the presence of a planet with a period of 35.68+/-0.03 days and minimum mass (m sin i) of 5.4+/-1.0 Earth masses. GJ 832c moves on a low-eccentricity orbit (e=0.18+/-0.13) towards the inner edge of the habitable zone. However, given the large mass of the planet, it seems likely that it would possess a massive atmosphere, which may well render the planet inhospitable. Indeed, it is perhaps more likely that GJ 832c is a super-Venus, featuring significant greenhouse forcing. With an outer giant planet and an interior, potentially rocky planet, the GJ 832 planetary system can be thought of as a miniature version of our own Solar system.
The meter-per-second precision achieved by today velocimeters enables the search for 1-10 M_Earth planets in the habitable zone of cool stars. This paper reports on the detection of 3 planets orbiting GJ163 (HIP19394), a M3 dwarf monitored by our ESO/HARPS search for planets. We made use of the HARPS spectrograph to collect 150 radial velocities of GJ163 over a period of 8 years. We searched the RV time series for coherent signals and found 5 distinct periodic variabilities. We investigated the stellar activity and casted doubts on the planetary interpretation for 2 signals. Before more data can be acquired we concluded that at least 3 planets are orbiting GJ163. They have orbital periods of P_b=8.632+-0.002, P_c=25.63+-0.03 and P_d=604+-8 days and minimum masses msini = 10.6+-0.6, 6.8+-0.9, and 29+-3 M_Earth, respectively. We hold our interpretations for the 2 additional signals with periods P_(e)=19.4 and P_(f)=108 days. The inner pair presents an orbital period ratio of 2.97, but a dynamical analysis of the system shows that it lays outside the 3:1 mean motion resonance. GJ163c, in particular, is a super-Earth with an equilibrium temperature of T_eq = (302+-10) (1-A)^(1/4) K and may lie in the so called habitable zone for albedo values (A=0.34-0.89) moderately higher than that of Earth (A_Earth=0.2-0.3).
We report the detection of a transiting Earth-size planet around GJ 357, a nearby M2.5V star, using data from the Transiting Exoplanet Survey Satellite (TESS). GJ 357 b (TOI-562.01) is a transiting, hot, Earth-sized planet (Teq=525+-11 K) with a radius of Rb=1.217+-0.084 Re and an orbital period of Pb=3.93 d. Precise stellar radial velocities from CARMENES and PFS, as well as archival data from HIRES, UVES, and HARPS also display a 3.93-day periodicity, confirming the planetary nature and leading to a planetary mass of Mb=1.84+-0.31 Me. In addition to the radial velocity signal for GJ 357 b, more periodicities are present in the data indicating the presence of two further planets in the system: GJ 357 c, with a minimum mass of Mc=3.40+-0.46 Me in a 9.12 d orbit, and GJ 357 d, with a minimum mass of Md=6.1+-1.0 Me in a 55.7 d orbit inside the habitable zone. The host is relatively inactive and exhibits a photometric rotation period of Prot=78+-2 d. GJ 357 b is to date the second closest transiting planet to the Sun, making it a prime target for further investigations such as transmission spectroscopy. Therefore, GJ 357 b represents one of the best terrestrial planets suitable for atmospheric characterization with the upcoming JWST and ground-based ELTs.
We present an analysis of the significantly expanded HARPS 2011 radial velocity data set for GJ 581 that was presented by Forveille et al. (2011). Our analysis reaches substantially different conclusions regarding the evidence for a Super-Earth-mass planet in the stars Habitable Zone. We were able to reproduce their reported chi_{ u}^2 and RMS values only after removing some outliers from their models and refitting the trimmed down RV set. A suite of 4000 N-body simulations of their Keplerian model all resulted in unstable systems and revealed that their reported 3.6sigma detection of e=0.32 for the eccentricity of GJ 581e is manifestly incompatible with the systems dynamical stability. Furthermore, their Keplerian model, when integrated only over the time baseline of the observations, significantly increases the chi_{ u}^2 and demonstrates the need for including non-Keplerian orbital precession when modeling this system. We find that a four-planet model with all of the planets on circular or nearly circular orbits provides both an excellent self-consistent fit to their RV data and also results in a very stable configuration. The periodogram of the residuals to a 4-planet all-circular-orbit model reveals significant peaks that suggest one or more additional planets in this system. We conclude that the present 240-point HARPS data set, when analyzed in its entirety, and modeled with fully self-consistent stable orbits, by and of itself does offer significant support for a fifth signal in the data with a period near 32 days. This signal has a False Alarm Probability of <4% and is consistent with a planet of minimum mass of 2.2 Earth-masses, orbiting squarely in the stars Habitable Zone at 0.13 AU, where liquid water on planetary surfaces is a distinct possibility
The K2.5 dwarf HD 40307 has been reported to host three super-Earths. The system lacks massive planets and is therefore a potential candidate for having additional low-mass planetary companions. We re-derive Doppler measurements from public HARPS spectra of HD 40307 to confirm the significance of the reported signals using independent data analysis methods. We also investigate these measurements for additional low-amplitude signals. We used Bayesian analysis of our radial velocities to estimate the probability densities of different model parameters. We also estimated the relative probabilities of models with differing numbers of Keplerian signals and verified their significance using periodogram analyses. We investigated the relation of the detected signals with the chromospheric emission of the star. As previously reported for other objects, we found that radial velocity signals correlated with the S-index are strongly wavelength dependent. We identify two additional clear signals with periods of 34 and 51 days, both corresponding to planet candidates with minimum masses a few times that of the Earth. An additional sixth candidate is initially found at a period of 320 days. However, this signal correlates strongly with the chromospheric emission from the star and is also strongly wavelength dependent. When analysing the red half of the spectra only, the five putative planetary signals are recovered together with a very significant periodicity at about 200 days. This signal has a similar amplitude as the other new signals reported in the current work and corresponds to a planet candidate with M sin i = 7 Me (HD 40307 g). ...
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
