A Study of Diverse Hot Jupiter Atmospheres

The discovery of over 5000 planets outside the solar system has evermore changed our view of the universe and the tale of other worlds beyond Earth is no longer folklore. In 1989, David Latham found the first planetary candidate HD 114762b (Latham et al., 1989) using the radial velocity technique which was later used to discover 51 Pegasi b as the first exoplanet orbiting a solar-type star by Didier Queloz and Michel Mayor (Mayor and Queloz, 1995). Then back to December 1999, the first transiting exoplanet HD 209458b lightcurve was measured by David Charbonneau (Charbonneau et al., 2002). The gold rush of exoplanet discovery and characterization today is probably beyond the wildest dreams of the early pioneers.From the early days of discovering hot Jupiters, we are now able to study their atmospheres in detail. This thesis focuses on the study of hot Jupiter atmospheres. Hot Jupiters are rare outcomes of planet formation and their origin remains a mystery (Dawson and Johnson, 2018). The study of their atmospheres can help us to understand their formation and evolution history and also develop techniques for future remote sensing of potentially habitable transiting exoplanets in the search for life beyond earth. Just like our solar system with every planet being special and different, the same is true for hot Jupiters. I will first go into detailed studies of 4 individual hot Jupiters (WASP-76b, WASP-74b, HAT-P-41b, and KELT-20b) and then connect them to more broad population-level statistical studies. These four hot Jupiters all have dayside temperatures exceeding 2000K with an inflated radius and a very short (<10 days) orbital period. However, they exhibit different atmospheric features and properties. The relatively cooler ones like WASP-74b and HAT-P-41b show mostly blackbody-like dayside emission spectra which indicate isothermal temperature-pressure profiles. The largely featureless transmission spectrum from WASP-74b is likely caused by clouds condensing in the terminator region. On the other hand, the hotter WASP-76b dayside shows CO emission features with evidence for water thermal dissociation. Combined with heavy metal absorption features seen in the NUV part of the transmission spectrum, gaseous metals are likely causing thermal inversion in the upper atmosphere. KELT-20b shows the strongest water and CO emission features on the dayside despite a similar dayside temperature compared to WASP-76b. The unique A-type host star of KELT-20b is likely the difference-maker. The intense short-wavelength UV/NUV radiation from the A star gets preferentially absorbed in the upper atmospheres by the gaseous metals which heats up the corresponding layers and drives stronger thermal inversion. The dayside emission spectra of these four planets are then compared to all other hot Jupiters with temperatures ranging from ∼1500K to over 4000K. These four planets sit in a key transitional parameter space where we see dayside emission spectra from cooler planets mostly have water absorption features and hotter planets are mostly blackbody-like. This trend shows the cooler (3000K) ones are affected by thermal dissociation of water and rising continuum opacity of H−. Only in this in-between temperature range combined with strong inversion from gaseous metal absorbers and strong UV radiation, we could see prominent water emission features.I also did a population-level statistical study of all observed transmission spectra focused on the 1.4 μm water band. Each spectrum was fitted to determine the water feature strength which is then normalized by the planetary atmospheric scale height. I found a statistically significant trend of stronger water absorption features as a function of planet equilibrium temperature. This trend can be explained by the presence of aerosols which condense more easily under cooler conditions. Although this study was conducted back in 2017 before my other publications, the trend still holds and provides a valuable statistical comparison study framework for exoplanet atmospheres

QTLs and candidate genes analyses for fruit size under domestication and differentiation in melon (Cucumis melo L.) based on high resolution maps

Background: Melon is a very important horticultural crop produced worldwide with high phenotypic diversity. Fruit size is among the most important domestication and differentiation traits in melon. The molecular mechanisms of fruit size in melon are largely unknown. Results: Two high-density genetic maps were constructed by whole-genome resequencing with two F2 segregating populations (WAP and MAP) derived from two crosses (cultivated agrestis × wild agrestis and cultivated melo × cultivated agrestis). We obtained 1,871,671 and 1,976,589 high quality SNPs that show differences between parents in WAP and MAP. A total of 5138 and 5839 recombination events generated 954 bins in WAP and 1027 bins in MAP with the average size of 321.3 Kb and 301.4 Kb respectively. All bins were mapped onto 12 linkage groups in WAP and MAP. The total lengths of two linkage maps were 904.4 cM (WAP) and 874.5 cM (MAP), covering 86.6% and 87.4% of the melon genome. Two loci for fruit size were identified on chromosome 11 in WAP and chromosome 5 in MAP, respectively. An auxin response factor and a YABBY transcription factor were inferred to be the candidate genes for both loci. Conclusion: The high-resolution genetic maps and QTLs analyses for fruit size described here will provide a better understanding the genetic basis of domestication and differentiation, and provide a valuable tool for map-based cloning and molecular marker assisted breeding.info:eu-repo/semantics/publishedVersio

The Hubble PanCET Program:Emission Spectrum of Hot Jupiter HAT-P-41b

We present the most complete emission spectrum for inflated hot Jupiter HAT-P-41b combining new HST WFC/G141 spectrum from the Hubble Panchromatic Comparative Exoplanet Treasury (PanCET) program with archival Spitzer eclipse observations. We found a near blackbody-like emission spectrum which is best fitted with an isothermal temperature-pressure (TP) profile that agrees well with the dayside heat redistribution scenario assuming zero Bond albedo. The non-inverted TP profile is consistent with the non-detection of NUV/optical absorbers in the transit spectra. We do not find any evidence for significant H$^-$ opacity nor a metal-rich atmosphere. HAT-P-41b is an ideal target that sits in the transitioning parameter space between hot and ultra-hot Jupiters, and future JWST observations will help us to better constrain the thermal structure and chemical composition.Comment: Accepted for publication in A

Recent Progress in Phage Therapy to Modulate Multidrug-Resistant Acinetobacter baumannii, Including in Human and Poultry

Acinetobacter baumannii is a multidrug-resistant and invasive pathogen associated with the etiopathology of both an increasing number of nosocomial infections and is of relevance to poultry production systems. Multidrug-resistant Acinetobacter baumannii has been reported in connection to severe challenges to clinical treatment, mostly due to an increased rate of resistance to carbapenems. Amid the possible strategies aiming to reduce the insurgence of antimicrobial resistance, phage therapy has gained particular importance for the treatment of bacterial infections. This review summarizes the different phage-therapy approaches currently in use for multiple-drug resistant Acinetobacter baumannii, including single phage therapy, phage cocktails, phage&ndash;antibiotic combination therapy, phage-derived enzymes active on Acinetobacter baumannii and some novel technologies based on phage interventions. Although phage therapy represents a potential treatment solution for multidrug-resistant Acinetobacter baumannii, further research is needed to unravel some unanswered questions, especially in regard to its in vivo applications, before possible routine clinical use

Ferroptosis: a new regulatory mechanism in neuropathic pain

Neuropathic pain (NP) is pain caused by damage to the somatosensory system. It is a common progressive neurodegenerative disease that usually presents with clinical features such as spontaneous pain, touch-evoked pain, nociceptive hyperalgesia, and sensory abnormalities. Due to the complexity of the mechanism, NP often persists. In addition to the traditionally recognized mechanisms of peripheral nerve damage and central sensitization, excessive iron accumulation, oxidative stress, neuronal inflammation, and lipid peroxidation damage are distinctive features of NP in pathophysiology. However, the mechanisms linking these pathological features to NP are not fully understood. The complexity of the pathogenesis of NP greatly limits the development of therapeutic approaches for NP. Ferroptosis is a novel form of cell death discovered in recent years, in which cell death is usually accompanied by massive iron accumulation and lipid peroxidation. Ferroptosis-inducing factors can affect glutathione peroxidase directly or indirectly through different pathways, leading to decreased antioxidant capacity and accumulation of lipid reactive oxygen species (ROS) in cells, ultimately leading to oxidative cell death. It has been shown that ferroptosis is closely related to the pathophysiological process of many neurological disorders such as NP. Possible mechanisms involved are changes in intracellular iron ion levels, alteration of glutamate excitability, and the onset of oxidative stress. However, the functional changes and specific molecular mechanisms of ferroptosis during this process still need to be further explored. How to intervene in the development of NP by regulating cellular ferroptosis has become a hot issue in etiological research and treatment. In this review, we systematically summarize the recent progress of ferroptosis research in NP, to provide a reference for further understanding of its pathogenesis and propose new targets for treatment

The Hubble PanCET program: Transit and Eclipse Spectroscopy of the Hot-Jupiter WASP-74b

Planets are like children with each one being unique and special. A better understanding of their collective properties requires a deeper understanding of each planet. Here we add the transit and eclipse spectra of hot-Jupiter WASP-74b into the ever growing data set of exoplanet atmosphere spectral library. With six transits and three eclipses using the Hubble Space Telescope and Spitzer Space Telescope (Spitzer), we present the most complete and precise atmospheric spectra of WASP-74b. We found no evidence for TiO/VO nor super-Rayleigh scattering reported in previous studies. The transit shows a muted water feature with strong Rayleigh scattering extending into the infrared. The eclipse shows a featureless blackbody-like WFC3/G141 spectrum and a weak methane absorption feature in the Spitzer 3.6 μm band. Future James Webb Space Telescope follow-up observations are needed to confirm these results

Toward Exoplanet Transit Spectroscopy Using JWST/MIRI\u27s Medium Resolution Spectrometer

The Mid-Infrared Instrument (MIRI)\u27s Medium Resolution Spectrometer (the MRS) on JWST has potentially important advantages for transit and eclipse spectroscopy of exoplanets, including lack of saturation for bright host stars, wavelength span to longward of 20 microns, and JWST\u27s highest spectral resolving power. We here test the performance of the MRS for time series spectroscopy by observing the secondary eclipse of the bright stellar eclipsing binary R Canis Majoris. Our observations push the MRS into saturation at the shortest wavelength, more than for any currently known exoplanet system. We find strong charge migration between pixels that we mitigate using a custom data analysis pipeline. Our data analysis recovers much of the spatial charge migration by combining detector pixels at the group level, via weighting by the point spread function. We achieve nearly photon-limited performance in time series data at wavelengths longward of 5.2 microns. In 2017, Snellen et al. suggested that the MRS could be used to detect carbon dioxide absorption from the atmosphere of the temperate planet orbiting Proxima Centauri. We infer that the relative spectral response of the MRS versus wavelength is sufficiently stable to make that detection feasible. As regards the secondary eclipse of this Algol-type binary, we measure the eclipse depth by summing our spectra over the wavelengths in four channels, and also measuring the eclipse depth as observed by TESS. Those eclipse depths require a temperature for the secondary star that is significantly hotter than previous observations in the optical to near-IR, probably due to irradiation by the primary star. At full spectral resolution of the MRS, we find atomic hydrogen recombination emission lines in the secondary star, from principal quantum levels n = 7, 8, 10, and 14.Accepted for PASP. 23 pages, 14 figures, 4 table

A carbon-rich atmosphere on a windy pulsar planet

A handful of enigmatic Jupiter-mass objects have been discovered orbiting pulsars. One such object, PSR J2322-2650b, uniquely resembles a hot Jupiter exoplanet due to its minimum density of 1.8 g/cm-3 and its ~1900 K equilibrium temperature. We use JWST to observe its emission spectrum across an entire orbit. In stark contrast to every known exoplanet orbiting a main-sequence star, we find an atmosphere rich in molecular carbon (C3, C2) with strong westward winds. Our observations open up a new exoplanetary chemical regime (ultra-high C/O and C/N ratios of &gt;100 and &gt;10,000 respectively) and dynamical regime (ultra-fast rotation with external irradiation) to observational study. The extreme carbon enrichment poses a severe challenge to the current understanding of "black widow" companions, which were expected to consist of a wider range of elements due to their origins as stripped stellar cores