Examinando por Autor "Wong, K. H."

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Acceso Abierto
Detection of Reduced Sulfur on Vera Rubin Ridge by Quadratic Discriminant Analysis of Volatiles Observed During Evolved Gas Analysis.
(American Geophysical Union: Advancing Earth and Space Science, 2020-06-10) Wong, K. H.; Lewis, J.; Knudson, C. A.; Millan, M.; McAdam, A. C.; Eigenbrode, J. L.; Andrejkovičová, S.; Gómez, F.; Navarro González, R.; House, C. H.; Universidad Nacional Autónoma de México (UNAM); Navarro González, R. [0000-0002-6078-7621]; Knudson, C. A. [0000-0003-3875-2200]; Andrejkovicova, S. [0000-0001-8429-6926]; Gómez, F. [0000-0001-9977-7060]; McAdam, A. [0000-0001-9120-2991]; House, C. [0000-0002-4926-4985]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The Mars Science Laboratory mission investigated Vera Rubin ridge, which bears spectral indications of elevated amounts of hematite and has been hypothesized as having a complex diagenetic history. Martian samples, including three drilled samples from the ridge, were analyzed by the Sample Analysis at Mars instrument suite via evolved gas analysis‐mass spectrometry (EGA‐MS). Here, we report new EGA‐MS data from Martian samples and describe laboratory analogue experiments. Analyses of laboratory analogues help determine the presence of reduced sulfur in Martian solid samples, which could have supported potential microbial life. We used evolved carbonyl sulfide (COS) and carbon disulfide (CS2) to identify Martian samples likely to contain reduced sulfur by applying a quadratic discriminant analysis. While we report results for 24 Martian samples, we focus on Vera Rubin ridge samples and select others for comparison. Our results suggest the presence of reduced sulfur in the Jura member of Vera Rubin ridge, which can support various diagenetic history models, including, as discussed in this work, diagenetic alteration initiated by a mildly reducing, sulfite‐containing groundwater.
Acceso Abierto
Precise radial velocities of giant stars XV. Mysterious nearly periodic radial velocity variations in the eccentric binary ε Cygni
(EDP Sciences, 2021-03-29) Heeren, P.; Reffert, S.; Trifonov, T.; Wong, K. H.; Hoi Lee, M.; Lillo Box, J.; Quirrenbach, A.; Arentoft, T.; Albrecht, S.; Grundahl, F.; Fredslund Andersen, M.; Antoci, V.; Pallé, P. L.; Agencia Estatal de Investigación (AEI); Danish National Research Foundation; Danish Council for Independent Research; Heeren, P. [0000-0002-3662-9930]; Reffert, S. [0000-0002-0460-8289]; Trifonov, T. [0000-0002-0236-775X]; Hoi Lee, M. [0000-0003-1930-5683]; Lillo Box, J. [0000-0003-3742-1987]; Albrecht, S. [0000-0003-1762-8235]; Fredslund Andersen, M. [0000-0002-9194-8520]; Pallé, P. L. [0000-0003-3803-4823]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. Using the Hamilton Échelle Spectrograph at Lick Observatory, we have obtained precise radial velocities (RVs) of a sample of 373 G- and K-giant stars over more than 12 yr, leading to the discovery of several single and multiple planetary systems. The RVs of the long-period (~53 yr) spectroscopic binary ε Cyg (HIP 102488) are found to exhibit additional regular variations with a much shorter period (~291 days). Aims. We intend to improve the orbital solution of the ε Cyg system and attempt to identify the cause of the nearly periodic shorter period variations, which might be due to an additional substellar companion. Methods. We used precise RV measurements of the K-giant star ε Cyg from Lick Observatory, in combination with a large set of RVs collected more recently with the SONG telescope, as well as archival data sets. We fit Keplerian and fully dynamical N-body models to the RVs in order to explore the properties of a previously known spectroscopic stellar companion and to investigate whether there is an additional planetary companion in the system. To search for long-term stable regions in the parameter space around the orbit of this putative planet, we ran a stability analysis using an N-body code. Furthermore, we explored the possibility of co-orbital bodies to the planet with a demodulation technique. We tested the hypothesis of ε Cyg being a hierarchical stellar triple by using a modified version of the N-body code. Alternative causes for the observed RV variations, such as stellar spots and oscillations, were examined by analyzing photometric data of the system and by comparing its properties to known variable stars with long secondary periods and heartbeat stars from the literature. Results. Our Keplerian model characterizes the orbit of the spectroscopic binary to higher precision than achieved previously, resulting in a semi-major axis of a = 15.8 AU, an eccentricity of e = 0.93, and a minimum mass of the secondary of msini = 0.265 M⊙. Additional short-period RV variations closely resemble the signal of a Jupiter-mass planet orbiting the evolved primary component with a period of 291 d, but the period and amplitude of the putative orbit change strongly over time. Furthermore, in our stability analysis of the system, no stable orbits could be found in a large region around the best fit. Both of these findings deem a planetary cause of the RV variations unlikely. Most of the investigated alternative scenarios also fail to explain the observed variability convincingly. Due to its very eccentric binary orbit, it seems possible, however, that ε Cyg could be an extreme example of a heartbeat system.
Acceso Abierto
The CARMENES search for exoplanets around M dwarfs: Dynamical characterization of the multiple planet system GJ 1148 and prospects of habitable exomoons around GJ 1148 b
(EDP Sciences, 2020-06-03) Trifonov, T.; Lee, M. H.; Kürster, M.; Henning, T.; Grishin, E.; Stock, S.; Tjoa, J.; Caballero, J. A.; Wong, K. H.; Bauer, F. F.; Quirrenbach, A.; Zechmeister, M.; Ribas, I.; Reffert, S.; Reiners, A.; Amado, P. J.; Kossakowski, D.; Azzaro, M.; Béjar, V. J. S.; Cortés Contreras, M.; Dreizler, S.; Hatzes, A. P.; Jeffers, S. V.; Kaminski, A.; Lafarga, M.; Montes, D.; Morales, J. C.; Pavlov, A.; Rodríguez López, C.; Schmitt, H. M. M.; Barnes, R.; Solano, Enrique; Deutsche Forschungsgemeinschaft (DFG); Ministerio de Economía y Competitividad (MINECO); Junta de Andalucía; European Research Council (ERC); Agencia Estatal de Investigación (AEI); Trifonov, T. https://orcid.org/0000-0002-0236-775X; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFÍSICA DE CANARIAS (IAC), SEV-2015-0548; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709
Context. GJ 1148 is an M-dwarf star hosting a planetary system composed of two Saturn-mass planets in eccentric orbits with periods of 41.38 and 532.02 days. Aims. We reanalyze the orbital configuration and dynamics of the GJ 1148 multi-planetary system based on new precise radial velocity measurements taken with CARMENES. Methods. We combined new and archival precise Doppler measurements from CARMENES with those available from HIRES for GJ 1148 and modeled these data with a self-consistent dynamical model. We studied the orbital dynamics of the system using the secular theory and direct N-body integrations. The prospects of potentially habitable moons around GJ 1148 b were examined. Results. The refined dynamical analyses show that the GJ 1148 system is long-term stable in a large phase-space of orbital parameters with an orbital configuration suggesting apsidal alignment, but not in any particular high-order mean-motion resonant commensurability. GJ 1148 b orbits inside the optimistic habitable zone (HZ). We find only a narrow stability region around the planet where exomoons can exist. However, in this stable region exomoons exhibit quick orbital decay due to tidal interaction with the planet. Conclusions. The GJ 1148 planetary system is a very rare M-dwarf planetary system consisting of a pair of gas giants, the inner of which resides in the HZ. We conclude that habitable exomoons around GJ 1148 b are very unlikely to exist. © 2020 T. Trifonov et al.