| 1. |
- Bonfanti, A., et al.
(författare)
-
Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley ★,★★
- 2024
-
Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 682
-
Tidskriftsartikel (refereegranskat)abstract
- TOI-732 is an M dwarf hosting two transiting planets that are located on the two opposite sides of the radius valley. Inferring a reliable demographics for this type of systems is key to understanding their formation and evolution mechanisms. Aims. By doubling the number of available space-based observations and increasing the number of radial velocity (RV) measurements, we aim at refining the parameters of TOI-732 b and c. We also use the results to study the slope of the radius valley and the density valley for a well-characterised sample of M-dwarf exoplanets. Methods. We performed a global Markov chain Monte Carlo analysis by jointly modelling ground-based light curves and CHEOPS and TESS observations, along with RV time series both taken from the literature and obtained with the MAROON-X spectrograph. The slopes of the M-dwarf valleys were quantified via a support vector machine (SVM) procedure. Results. TOI-732 b is an ultrashort-period planet (P = 0.76837931−+000000004200000039 days) with a radius Rb = 1.325+−00057058 R☉, a mass Mb = 2.46 ± 0.19 M☉, and thus a mean density ρb = 5.8+−1008 g cm−3, while the outer planet at P = 12.252284 ± 0.000013 days has Rc = 2.39+−001011 R☉, Mc = 8.04+−005048 M☉, and thus ρc = 3.24+−005543 g cm−3. Even with respect to the most recently reported values, this work yields uncertainties on the transit depths and on the RV semi-amplitudes that are smaller up to a factor of ∼1.6 and ∼2.4 for TOI-732 b and c, respectively. Our calculations for the interior structure and the location of the planets in the mass-radius diagram lead us to classify TOI-732 b as a super-Earth and TOI-732 c as a mini-Neptune. Following the SVM approach, we quantified d log Rp,valley/d log P = −0.065+−00024013, which is flatter than for Sun-like stars. In line with former analyses, we note that the radius valley for M-dwarf planets is more densely populated, and we further quantify the slope of the density valley as d log ρ̂valley/d log P = −0.02+−001204. Conclusions. Compared to FGK stars, the weaker dependence of the position of the radius valley on the orbital period might indicate that the formation shapes the radius valley around M dwarfs more strongly than the evolution mechanisms.
|
|
| 2. |
- Chaturvedi, P., et al.
(författare)
-
TOI-1468: A system of two transiting planets, a super-Earth and a mini-Neptune, on opposite sides of the radius valley
- 2022
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
-
Tidskriftsartikel (refereegranskat)abstract
- We report the discovery and characterization of two small transiting planets orbiting the bright M3.0V star TOI-1468 (LSPM J0106+1913), whose transit signals were detected in the photometric time series in three sectors of the TESS mission. We confirm the planetary nature of both of them using precise radial velocity measurements from the CARMENES and MAROON-X spectrographs, and supplement them with ground-based transit photometry. A joint analysis of all these data reveals that the shorter-period planet, TOI-1468 b (P-b = 1.88 d), has a planetary mass of M-b = 3.21 +/- 0.24M(circle plus) and a radius of R-b = 1.280(-0.039)(+0.038) R-circle plus, resulting in a density of rho(b) = 8.39(-0.92)(+1.05) g cm(-3), which is consistent with a mostly rocky composition. For the outer planet, TOI-1468 c (P-c = 15.53 d), we derive a mass of M-c = 6.64(-0.68)(+0.67) M-circle plus,aradius of R-c = 2.06 +/- 0.04 R-circle plus, and a bulk density of rho(c) = 2.00(-0.19)(+0.21) g cm(-3), which corresponds to a rocky core composition with a H/He gas envelope. These planets are located on opposite sides of the radius valley, making our system an interesting discovery as there are only a handful of other systems with the same properties. This discovery can further help determine a more precise location of the radius valley for small planets around M dwarfs and, therefore, shed more light on planet formation and evolution scenarios.
|
|
| 3. |
- Lebzelter, T., et al.
(författare)
-
CRIRES-POP A library of high resolution spectra in the near-infrared
- 2012
-
Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 539
-
Tidskriftsartikel (refereegranskat)abstract
- Context. New instrumental capabilities and the wealth of astrophysical information extractable from the near-infrared wavelength region have led to a growing interest in the field of high resolution spectroscopy at 1-5 mu m. Aims. We aim to provide a library of observed high-resolution and high signal-to-noise-ratio near-infrared spectra of stars of various types throughout the Hertzsprung-Russell diagram. This is needed for the exploration of spectral features in this wavelength range and for comparison of reference targets with observations and models. Methods. High quality spectra were obtained using the CRIRES near-infrared spectrograph at ESO's VLT covering the range from 0.97 mu m to 5.3 mu m at high spectral resolution. Accurate wavelength calibration and correction for telluric lines were performed by fitting synthetic transmission spectra for the Earth's atmosphere to each spectrum individually. Results. We describe the observational strategy and the current status and content of the library which includes 13 objects. The first examples of finally reduced spectra are presented. This publication will serve as a reference paper to introduce the library to the community and explore the extensive amount of material.
|
|
| 4. |
|
|
| 5. |
- Nicholls, Christine P, et al.
(författare)
-
CRIRES-POP : a library of high resolution spectra in the near-infrared II. Data reduction and the spectrum of the K giant 10 Leonis
- 2017
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 598
-
Tidskriftsartikel (refereegranskat)abstract
- Context. High resolution stellar spectral atlases are valuable resources to astronomy. They are rare in the 1 − 5 μm region for historical reasons, but once available, high resolution atlases in this part of the spectrum will aid the study of a wide range of astrophysical phenomena. Aims. The aim of the CRIRES-POP project is to produce a high resolution near-infrared spectral library of stars across the H-R diagram. The aim of this paper is to present the fully reduced spectrum of the K giant 10 Leo that will form the basis of the first atlas within the CRIRES-POP library, to provide a full description of the data reduction processes involved, and to provide an update on the CRIRES-POP project. Methods. All CRIRES-POP targets were observed with almost 200 different observational settings of CRIRES on the ESO Very Large Telescope, resulting in a basically complete coverage of its spectral range as accessible from the ground. We reduced the spectra of 10 Leo with the CRIRES pipeline, corrected the wavelength solution and removed telluric absorption with Molecfit, then resampled the spectra to a common wavelength scale, shifted them to rest wavelengths, flux normalised, and median combined them into one final data product. Results. We present the fully reduced, high resolution, near-infrared spectrum of 10 Leo. This is also the first complete spectrum from the CRIRES instrument. The spectrum is available online. Conclusions. The first CRIRES-POP spectrum has exceeded our quality expectations and will form the centre of a state-of-the-art stellar atlas. This first CRIRES-POP atlas will soon be available, and further atlases will follow. All CRIRES-POP data products will be freely and publicly available online.
|
|
| 6. |
- Seifahrt, A., et al.
(författare)
-
Observation and modelling of dusty, low gravity L, and M dwarfs
- 2009
-
Ingår i: COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. - : AIP. - 9780735406278 ; , s. 283-290
-
Konferensbidrag (refereegranskat)abstract
- Observational facilities allow now the detection of optical and IR spectra of young M- and L-dwarfs. This enables empirical comparisons with old M- and L- dwarfs, and detailed studies in comparison with synthetic spectra. While classical stellar atmosphere physics seems perfectly appropriate for old M-dwarfs, more physical and chemical processes, cloud formation in particular, needs to be modelled in the substellar regime to allow a detailed spectral interpretation. Not much is known so far about the details of the inset of cloud formation at the spectral transition region between M and L dwarfs. Furthermore there is observational evidence for diversity in the dust properties of objects having the same spectral type. Do we understand these differences? The question is also how young M- and L-dwarfs need to be classified, which stellar parameter do they have and whether degenerations in the stellar parameter space due to the changing atmosphere physics are present, like in the L-T transition region. The Splinter was driven by these questions which we will use to encourage interactions between observation and theory. Given the recent advances, both in observations and spectral modelling, an intensive discussion between observers and theoreticians will create new synergies in our field.
|
|
| 7. |
- Shulyak, D., et al.
(författare)
-
Magnetic Fields of M-Dwarfs from the Molecular and Atomic Diagnostics
- 2011
-
Ingår i: Magnetic Stars. ; , s. 280-290
-
Konferensbidrag (refereegranskat)abstract
- Strong surface magnetic fields are frequently found in the spectra of M-dwarfs, with the mean intensities on the order of a few thousand Gauss - three orders of magnitude higher than the mean surface magnetic field of the Sun. The appearance of such fields in both partially and fully convective M-dwarfs provides strong constraints on the theoretical models of stellar magnetism. The accurate estimates of the magnetic field intensity and geometry in these cool objects, however, is strongly limited to our ability to simulate the Zeeman effect in molecular lines. Here we present the first quantitative results of modelling and analysis of the magnetic fields in selected M-dwarfs in FeH Wing-Ford F\^4Δ-X\^4Δ transitions and some strong atomic lines from polarised radiative transfer.
|
|
| 8. |
- Shulyak, D., et al.
(författare)
-
Modelling the molecular Zeeman-effect in M-dwarfs : methods and first results
- 2010
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 523, s. A37-
-
Tidskriftsartikel (refereegranskat)abstract
- Aims. We present first quantitative results of the surface magnetic field measurements in selected M-dwarfs based on detailed spectra synthesis conducted simultaneously in atomic and molecular lines of the FeH Wing-Ford F-4 Delta - X-4 Delta transitions. Methods. A modified version of the Molecular Zeeman Library (MZL) was used to compute Lande g-factors for FeH lines in different Hund's cases. Magnetic spectra synthesis was performed with the SYNMAST code. Results. We show that the implementation of different Hund's case for FeH states depending on their quantum numbers allows us to achieve a good fit to the majority of lines in a sunspot spectrum in an automatic regime. Strong magnetic fields are confirmed via the modelling of atomic and FeH lines for three M-dwarfs YZ CMi, EV Lac, and AD Leo, but their mean intensities are found to be systematically lower than previously reported. A much weaker field (1.7-2 kG against 2.7 kG) is required to fit FeH lines in the spectra of GJ 1224. Conclusions. Our method allows us to measure average magnetic fields in very low-mass stars from polarized radiative transfer. The obtained results indicate that the fields reported in earlier works were probably overestimated by about 15-30%. Higher quality observations are needed for more definite results.
|
|
| 9. |
- Shulyak, D., et al.
(författare)
-
Rotation, magnetism and metallicity of M dwarf systems
- 2011
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 418:4, s. 2548-2557
-
Tidskriftsartikel (refereegranskat)abstract
- Close M dwarf binaries and higher multiples allow the investigation of rotational evolution and mean magnetic flux unbiased from scatter in inclination angle and age since the orientation of the spin axis of the components is most likely parallel and the individual systems are coeval. Systems composed of an early-type (M0.0-M4.0) and a late-type (M4.0-M8.0) component offer the possibility to study differences in rotation and magnetism between partially and fully convective stars. We have selected 10 of the closest dM systems to determine the rotation velocities and the mean magnetic field strengths based on spectroscopic analysis of FeH lines of Wing-Ford transitions at 1 μm observed with Very Large Telescope/CRIRES. We also studied the quality of our spectroscopic model regarding atmospheric parameters including metallicity. A modified version of the Molecular Zeeman Library (MZL) was used to compute Landég-factors for FeH lines. Magnetic spectral synthesis was performed with the SYNMAST code. We confirmed previously reported findings that less massive M dwarfs are braked less effectively than objects of earlier types. Strong surface magnetic fields were detected in primaries of four systems (GJ 852, GJ 234, LP 717-36 and GJ 3322), and in the secondary of the triple system GJ 852. We also confirm strong 2-kG magnetic field in the primary of the triple system GJ 2005. No fields could be accurately determined in rapidly rotating stars with \upsi sin i \gt 10 km s$^-1$. For slowly and moderately rotating stars, we find the surface magnetic field strength to increase with the rotational velocity \upsi sin i which is consistent with other results from studying field stars. Based on observations made with European Southern Observatory (ESO) Telescopes at the Paranal Observatories under programme ID 81.D-0189.
|
|
| 10. |
- Prinoth, B., et al.
(författare)
-
An atlas of resolved spectral features in the transmission spectrum of WASP-189 b with MAROON-X
- 2024
-
Ingår i: Astronomy and Astrophysics. - 0004-6361. ; 685
-
Tidskriftsartikel (refereegranskat)abstract
- Exoplanets in the ultra-hot Jupiter regime provide an excellent laboratory for testing the impact of stellar irradiation on the dynamics and chemical composition of gas giant atmospheres. In this study, we observed two transits of the ultra-hot Jupiter WASP-189 b with MAROON-X/Gemini-North to probe its high-altitude atmospheric layers, using strong absorption lines. We derived posterior probability distributions for the planetary and stellar parameters by calculating the stellar spectrum behind the planet at every orbital phase during the transit. This was used to correct the Rossiter- McLaughlin imprint on the transmission spectra. Using differential transmission spectroscopy, we detect strong absorption lines of Ca+, Ba+, Na, Hα, Mg, Fe, and Fe+, providing an unprecedented and detailed view of the atmospheric chemical composition. Ca+ absorption is particularly well suited for analysis through time-resolved narrow-band spectroscopy, owing to its transition lines formed in high-altitude layers. The spectral absorption lines show no significant blueshifts that would indicate high-altitude day-to-night winds, and further analysis is needed to investigate the implications for atmospheric dynamics. These high signal-to-noise observations provide a benchmark data set for testing high-resolution retrievals and the assumptions of atmospheric models. We also simulate observations of WASP-189 b with ANDES/ELT, and show that ANDES will be highly sensitive to the individual absorption lines of a myriad of elements and molecules, including TiO and CO.
|
|
