- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Ground-based Spectroscopy of the Exoplanet XO-2b Using a Systematic Wavelength Calibration
摘要： Exoplanets orbiting close to their host star are expected to support a large ionosphere, which extends to larger pressures than witnessed in our solar system. These ionospheres can be investigated with ground-based transit observations of the optical signatures of alkali metals, which are the source of the ions. However, most ground-based transit spectra do not systematically resolve the wings of the features and continuum, as needed to constrain the alkali abundances. Here we present new observations and analyses of optical transit spectra that cover the Na doublet in the atmosphere of the exoplanet XO-2b. To assess the consistency of our results, observations were obtained from two separate platforms: Gemini/GMOS and Mayall/KOSMOS. To mitigate the systematic errors, we chose XO-2, because it has a binary companion of the same brightness and stellar type, which provides an ideal reference star to model Earth’s atmospheric effects. We find that interpretation of the data is highly sensitive to time-varying translations along the detector, which change according to wavelength and differ between the target and reference star. It was necessary to employ a time-dependent cross-correlation to align our wavelength bins and correct for atmospheric differential refraction. This approach allows us to resolve the wings of the Na line across five wavelength bins at a resolution of ～1.6 nm and limit the abundance of Na. We obtain consistent results from each telescope with an Na amplitude of 521 ± 161 and 403 ± 186 ppm for GMOS and KOSMOS, respectively. The results are analyzed with a radiative transfer model that includes the effects of ionization. The data are consistent with a clear atmosphere between ～1 and 100 mbar that establishes a lower limit on Na at 0.4 +0.3 -0.2 ppm ([Na/H] = -0.64 +0.6 -0.78), consistent with solar. However, we cannot rule out the presence of clouds at ～10 mbar that allow for higher Na abundances, which would be consistent with the stellar metallicity measured for the host star ([Na/H] = 0.485 ± 0.043).
关键词： planets and satellites: atmospheres,planets and satellites: individual (XO-2b),methods: observational,methods: data analysis,techniques: spectroscopic,methods: analytical
更新于2025-09-19 17:15:36
-
A VERSATILE TECHNIQUE TO ENABLE SUB-MILLI-KELVIN INSTRUMENT STABILITY FOR PRECISE RADIAL VELOCITY MEASUREMENTS: TESTS WITH THE HABITABLE-ZONE PLANET FINDER
摘要： Insufficient instrument thermomechanical stability is one of the many roadblocks for achieving 10 cm s?1 Doppler radial velocity precision, the precision needed to detect Earth-twins orbiting solar-type stars. Highly temperature and pressure stabilized spectrographs allow us to better calibrate out instrumental drifts, thereby helping in distinguishing instrumental noise from astrophysical stellar signals. We present the design and performance of the Environmental Control System (ECS) for the Habitable-zone Planet Finder (HPF), a high-resolution (R = 50,000) fiber-fed near-infrared (NIR) spectrograph for the 10 m Hobby–Eberly Telescope at McDonald Observatory. HPF will operate at 180 K, driven by the choice of an H2RG NIR detector array with a 1.7 μm cutoff. This ECS has demonstrated 0.6 mK rms stability over 15 days at both 180 and 300 K, and maintained high-quality vacuum (<10?7 Torr) over months, during long-term stability tests conducted without a planned passive thermal enclosure surrounding the vacuum chamber. This control scheme is versatile and can be applied as a blueprint to stabilize future NIR and optical high-precision Doppler instruments over a wide temperature range from ～77 K to elevated room temperatures. A similar ECS is being implemented to stabilize NEID, the NASA/NSF NN-EXPLORE spectrograph for the 3.5 m WIYN telescope at Kitt Peak, operating at 300 K. A [full SolidWorks 3D-CAD model] and a comprehensive parts list of the HPF ECS are included with this manuscript to facilitate the adaptation of this versatile environmental control scheme in the broader astronomical community.
关键词： instrumentation: spectrographs,techniques: radial velocities,techniques: spectroscopic
更新于2025-09-10 09:29:36
-
High density fiber postitioner system for massive spectroscopic surveys
摘要： We describe here a novel design of a fast high-density robotized fiber positioner system for massive spectroscopic surveys. The fiber positioners are compact, robust, and they can be coordinated, allowing for a high spatial density. Furthermore, the high absolute accuracy removes the need for a metrology system and reduces the reconfiguration time. First, we present the requirements for such a high-density fiber positioner system and put them in relation with the science goals. Then, we discuss the positioner design that accomplishes these requirements (including mechanical design, local control electronics board, overall communication solution, and observation sequencing). Finally, the performance of the proposed design is measured using 25 mm pitch prototypes of the positioners, through a dedicated novel designed test-bench. The related results show that our prototypes fulfil the requirements particularly in terms of positioning precision (<20 μm rms for one single open loop move) and partially in tilt (<0.15 deg).
关键词： cosmology: observations,telescopes,techniques: spectroscopic,surveys,large-scale structure of Universe,dark energy
更新于2025-09-10 09:29:36
-
Efficient Spectroscopy of Exoplanets at Small Angular Separations with Vortex Fiber Nulling
摘要： Instrumentation designed to characterize potentially habitable planets may combine adaptive optics and high-resolution spectroscopy techniques to achieve the highest possible sensitivity to spectral signs of life. Detecting the weak signal from a planet containing biomarkers will require exquisite control of the optical wavefront to maximize the planet signal and significantly reduce unwanted starlight. We present an optical technique, known as vortex fiber nulling (VFN), that allows polychromatic light from faint planets at extremely small separations from their host stars (～λ/D) to be efficiently routed to a diffraction-limited spectrograph via a single-mode optical fiber, while light from the star is prevented from entering the spectrograph. VFN takes advantage of the spatial selectivity of a single-mode fiber to isolate the light from close-in companions in a small field of view around the star. We provide theoretical performance predictions of a conceptual design and show that VFN may be utilized to characterize planets detected by radial velocity (RV) instruments in the infrared without knowledge of the azimuthal orientation of their orbits. Using a spectral template-matching technique, we calculate an integration time of ～400, ～100, and ～30 hr for Ross 128 b with Keck, the Thirty Meter Telescope, and the Large Ultraviolet/Optical/Infrared Surveyor, respectively.
关键词： techniques: spectroscopic,instrumentation: adaptive optics,instrumentation: high angular resolution
更新于2025-09-10 09:29:36
-
Spatially resolved spectroscopy across stellar surfaces
摘要： Context. High-precision stellar analyses require hydrodynamic modeling to interpret chemical abundances or oscillation modes. Exoplanet atmosphere studies require stellar background spectra to be known along the transit path while detection of Earth analogs require stellar microvariability to be understood. Hydrodynamic 3D models can be computed for widely di?erent stars but have been tested in detail only for the Sun with its resolved surface features. Model predictions include spectral line shapes, asymmetries, and wavelength shifts, and their center-to-limb changes across stellar disks. Aims. We observe high-resolution spectral line pro?les across spatially highly resolved stellar surfaces, which are free from the e?ects of spatial smearing and rotational broadening present in full-disk spectra, enabling comparisons to synthetic pro?les from 3D models. Methods. During exoplanet transits, successive stellar surface portions become hidden and di?erential spectroscopy between various transit phases provides spectra of small surface segments temporarily hidden behind the planet. Planets cover no more than ～1% of any main-sequence star, enabling high spatial resolution but demanding very precise observations. Realistically measurable quantities are identi?ed through simulated observations of synthetic spectral lines. Results. In normal stars, line pro?le ratios between various transit phases may vary by ～0.5%, requiring S /N (cid:38) 5000 for meaningful spectral reconstruction. While not yet realistic for individual spectral lines, this is achievable for cool stars by averaging over numerous lines with similar parameters. Conclusions. For bright host stars of large transiting planets, spatially resolved spectroscopy is currently practical. More observable targets are likely to be found in the near future by ongoing photometric searches.
关键词： line: pro?les,hydrodynamics,stars: atmospheres,planets and satellites: gaseous planets,techniques: spectroscopic,stars: solar-type
更新于2025-09-10 09:29:36
-
On the robustness of analysis techniques for molecular detections using high resolution exoplanet spectroscopy
摘要： High-resolution doppler spectroscopy provides a powerful means for chemical detections in exoplanetary atmospheres. This approach involves monitoring hundreds of molecular lines in the planetary spectrum doppler shifted by the orbital motion of the planet. The molecules are detected by cross-correlating the observed spectrum of the system with a model planetary spectrum. The method has led to molecular detections of H2O, CO, and TiO in hot Jupiters using large ground-based telescopes. Critical to this method, however, is the accurate removal of the stellar and telluric features from the observed spectrum, also known as detrending. Previous molecular detections have relied on specific choices of detrending methods and parameters. However, the robustness of molecular detections across the different choices has not been investigated in detail. We conduct a systematic investigation of the effect of detrending algorithms, parameters, and optimizations on chemical detections using high-resolution spectroscopy. As a case study, we consider the hot Jupiter HD 189733 b. Using multiple methods, we confirm high-significance detections of H2O (4.8σ) and CO (4.7σ). Additionally, we report evidence for HCN at high significance (5.0σ). On the other hand, our results highlight the need for improved metrics and extended observations for robust confirmations of such detections. In particular, we show that detection significances of (cid:38) 4σ can be obtained by optimizing detrending at incorrect locations in the planetary velocity space; such false positives can occur in nearly 30% of cases. We discuss approaches to help distinguish molecular detections from spurious noise.
关键词： planets and satellites: atmospheres – methods: data analysis – techniques: spectroscopic
更新于2025-09-10 09:29:36
-
Near-infrared colors of minor planets recovered from VISTA-VHS survey (MOVIS)
摘要： Context. The Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE) provide information about the surface composition of about 100 000 minor planets. The resulting visible colors and albedos enabled us to group them in several major classes, which are a simplified view of the diversity shown by the few existing spectra. A large set of data in the 0.8?2.5 μm, where wide spectral features are expected, is required to refine and complement the global picture of these small bodies of the solar system. Aims. We aim to obtain the near-infrared colors for a large sample of solar system objects using the observations made during the VISTA-VHS survey. Methods. We performed a serendipitous search in VISTA-VHS observations using a pipeline developed to retrieve and process the data that corresponds to solar system objects (SSo). The resulting photometric data is analyzed using color?color plots and by comparison with the known spectral properties of asteroids. Results. The colors and the magnitudes of the minor planets observed by the VISTA survey are compiled into three catalogs that are available online: the detections catalog (MOVIS-D), the magnitudes catalog (MOVIS-M), and the colors catalog (MOVIS-C). They were built using the third data release of the survey (VISTA VHS-DR3). A total of 39 947 objects were detected, including 52 NEAs, 325 Mars Crossers, 515 Hungaria asteroids, 38 428 main-belt asteroids, 146 Cybele asteroids, 147 Hilda asteroids, 270 Trojans, 13 comets, 12 Kuiper Belt objects and Neptune with its four satellites. The colors found for asteroids with known spectral properties reveal well-defined patterns corresponding to different mineralogies. The distributions of MOVIS-C data in color?color plots shows clusters identified with different taxonomic types. All the diagrams that use (Y ? J) color separate the spectral classes more effectively than the (J ? H) and (H ? Ks) plots used until now: even for large color errors (<0.1), the plots (Y ? J) vs. (Y ? Ks) and (Y ? J) vs. (J ? Ks) provide the separation between S-complex and C-complex. The end members A, D, R, and V-types occupy well-defined regions.
关键词： minor planets,asteroids: general – techniques: photometric – techniques: spectroscopic – methods: statistical
更新于2025-09-09 09:28:46
-
SOPHIE velocimetry of <i>Kepler</i> transit candidates
摘要： The exoplanet KOI-142b (Kepler-88b) shows transit timing variations (TTVs) with a semi-amplitude of ～12 h, which earned it the nickname “king of transit variations”. Only the transit of planet b was detected in the Kepler data with an orbital period of ～10.92 days and a radius of ～0.36 RJup. The TTVs together with the transit duration variations of KOI-142b were analysed recently, ?nding a unique solution for a companion-perturbing planet. An outer non-transiting companion was predicted, KOI-142c, with a mass of 0.626 ± 0.03 MJup and a period of 22.3397+0.0021 ?0.0018 days, which is close to the 2:1 mean-motion resonance with the inner transiting planet. We report an independent con?rmation of KOI-142c using radial velocity observations with the SOPHIE spectrograph at the Observatoire de Haute-Provence. We derive an orbital period of 22.10 ± 0.25 days and a minimum planetary mass of 0.76+0.32 0.16 MJup, both in good agreement with the predictions by previous transit timing analysis. Therefore, this is the ?rst radial velocity con?rmation of a non-transiting planet discovered with TTVs, providing an independent validation of the TTVs technique.
关键词： techniques: spectroscopic,stars: fundamental parameters,stars: individual: Kepler-88,planetary systems,stars: individual: KIC5446285,techniques: radial velocities
更新于2025-09-09 09:28:46
-
The GTC exoplanet transit spectroscopy survey
摘要： Aims. We search for Rayleigh scattering and K and Na absorption signatures from the atmosphere of TrES-3b using ground-based transmission spectroscopy covering the wavelength range from 530 to 950 nm as observed with the OSIRIS instrument at the Gran Telescopio CANARIAS. Methods. Our analysis is based on a Bayesian approach where the light curves covering a set of given passbands are ?tted jointly with PHOENIX-calculated stellar limb darkening pro?les. The analysis is carried out assuming both white and red noise that is temporally correlated, with two approaches (Gaussian processes and divide-by-white) to account for the red noise. Results. An initial analysis reveals a transmission spectrum that shows a strong Rayleigh-like increase in extinction towards the blue end of the spectrum, and enhanced extinction around the K I resonance doublet near 767 nm. However, the signal amplitudes are signi?cantly larger than expected from theoretical considerations. A detailed analysis reveals that the K I-like feature is entirely due to variability in the telluric O2 absorption, but the Rayleigh-like feature remains unexplained.
关键词： techniques: spectroscopic,methods: statistical,techniques: photometric,stars: individual: TrES-3,planets and satellites: atmospheres,planets and satellites: individual: TrES-3b
更新于2025-09-09 09:28:46
-
The Breakthrough Listen Search for Intelligent Life: No Evidence of Claimed Periodic Spectral Modulations in High-resolution Optical Spectra of Nearby Stars
摘要： We report on high-resolution spectra obtained by the Automated Planet Finder and high-resolution optical Levy Spectrometer to search for periodic spectral modulations, such as those reported in Borra & Trottier. In their analysis of 2.5 million spectra from the Sloan Digital Sky Survey, Borra & Trottier report periodic spectral modulations in 234 stars, and suggest that these signals may be evidence of extraterrestrial civilizations. To evaluate this claim, we observed three of the 234 stars with the Automated Planet Finder Telescope and Levy Spectrometer including all stars brighter than a visual magnitude of 14. Fourier analysis of the resultant spectra of these three sources does not reveal any periodic spectral modulations at the reported period, nor at any other period.
关键词： extraterrestrial intelligence,techniques: spectroscopic
更新于2025-09-09 09:28:46