OGLE-2018-BLG-1185b : A Low-Mass Microlensing Planet Orbiting a Low-Mass Dwarf (Planetary Science)

A team of international astronomers reported on the analysis of planetary microlensing event OGLE-2018-BLG-1185, which was observed by a large number of ground-based telescopes and by the Spitzer Space Telescope. They discovered a low-mass planet OGLE-2018-BLG-1185b around the star. The ground-based light curve indicates a low planet-host star mass ratio of q = (6.9 ± 0.2) × 10¯5, which is near the peak of the wide-orbit exoplanet mass-ratio distribution. Their study recently appeared on Journal ArXiv.

The most common method for measuring the microlens parallax has been via the effects of the motion of the observer, which is called the “orbital parallax effect.” In order to detect the orbital parallax, the ratio of tE (typically tE is ∼ 30 days) to Earth’s orbital period (365 days) should be significant. Thus, we only measure the orbital parallax effect for microlensing events with long durations and/or with relatively nearby lens systems, yielding mass measurements in less than half of published microlensing planetary systems.

The most effective method for routinely obtaining a microlens parallax measurement is via the “satellite parallax effect”, which is caused by the separation between two observers. Because the typical Einstein radius projected onto the observer plane, ˜rE, is about 10 au, the satellite parallax effect can be measured for a wide range of microlenses provided the separation between Earth and the satellite is about 1 au (as was the case for Spitzer).

Now, astronomers estimated the masses of the host star, OGLE-2018-BLG-1185 and planet, OGLE-2018-BLG-1185b with a Bayesian analysis using the measured angular Einstein radius under the assumption that stars of all masses have an equal probability to host this planet. The flux variation observed by Spitzer was marginal, but still places a constraint on the microlens parallax. Imposing a conservative constraint that this flux variation should be ∆fSpz < 4 instrumental flux units indicated a host mass (star) (Mhost) of 0.37 M and a planet mass (Mp) of 8.4 M located at 7.4 Kpc.

A Bayesian analysis including the full parallax constraint from Spitzer suggested, smaller host star and planet masses of Mhost = 0.091 M and mp = 2.1 M, respectively, that is either in the disk at DL ∼ 5 kpc or in the bulge at DL ∼ 7.5 kpc.

Figure 1. The mass distribution of the detected exoplanets as of 2021 February 25 from http://exoplanetarchive.ipac.caltech.edu. The purple stars indicate OGLE-2018-BLG-1185. The pink circles show the microlens planets without mass measurements, and the red circles show the microlens planets with mass measurements from ground-based orbital parallax effects and/or the detection of the lens flux by the high resolution follow-up observations. The red squares represent the microlens planets with mass measurements from satellite parallax effects by Spitzer. The blue, yellow, and black dots indicate planets found by the transit, direct imaging, and radial velocity methods, respectively. © Kondo et al.

They also compared the Bayesian estimates from the conservative Spitzer flux constraint and the full Spitzer parallax measurement of the host and planet mass for OGLE-2018-BLG-1185 to those of other planetary systems (as shown in Fig 1 above) . The pink circles shows the microlens planets without mass measurements, and the red circles shows the microlens planets with mass measurements from ground-based orbital parallax effects and/or the detection of the lens flux by high resolution follow-up observations. The red squares represent microlens planets with mass measurements from the satellite parallax effect observed by Spitzer. It indicates that if the Spitzer parallax is correct, this is one of the lowest mass planets discovered by microlensing.

“If the Spitzer parallax is correct, this is one of the lowest mass planets discovered by microlensing.”

— told Kondo, lead author of the study

Astronomers concluded that future high-resolution imaging observations with HST or ELTs could distinguish between these two scenarios and help to reveal the planetary system properties in more detail.

Reference: Iona Kondo, Jennifer C. Yee, David P. Bennett, Takahiro Sumi, Naoki Koshimoto, Ian A. Bond, Andrew Gould, Andrzej Udalski, Yossi Shvartzvald, Youn Kil Jung, Weicheng Zang, Valerio Bozza, Etienne Bachelet, Markus P.G. Hundertmark, Nicholas J. Rattenbury, F. Abe, R. Barry, A. Bhattacharya, M. Donachie, A. Fukui, H. Fujii, Y. Hirao, S. Ishitani Silva, Y. Itow, R. Kirikawa, M. C. A. Li, Y. Matsubara, S. Miyazaki, Y. Muraki, G. Olmschenk, C. Ranc, Y. Satoh, H. Shoji, D. Suzuki, Y. Tanaka, P. J. Tristram, T. Yamawaki, A. Yonehara, P. Mróz, R. Poleski, J. Skowron, M. K. Szymański, I. Soszyński, S. Kozłowski, P. Pietrukowicz K. Ulaczyk, K. A. Rybicki, P. Iwanek, M. Wrona, M. D. Albrow, S.-J. Chung, C. Han, K.-H. Hwang, H.-W. Kim, I.-G. Shin, S.-M. Cha, D.-J. Kim, S.-L. Kim, C.-U. Lee, D.-J. Lee, Y. Lee, B.-G. Park, R. W. Pogge, Y.-H. Ryu, C. A. Beichman, G. Bryden, S. Calchi Novati, S. Carey, B. S. Gaudi, C. B. Henderson, W. Zhu, D. Maoz, M. T. Penny, M. Dominik, U. G. Jørgensen, P. Longa-Pe{~{ n}}a, N. Peixinho, S. Sajadian, J. Skottfelt, C. Snodgrass, J. Tregloan-Reed, M. J. Burgdorf, J. Campbell-White, S. Dib, Y. I. Fujii, T. C. Hinse, E. Khalouei, S. Rahvar, M. Rabus, J. Southworth, Y. Tsapras, R. A. Street, D. M. Bramich, A. Cassan, K. Horne, J. Wambsganss, S. Mao, A. Saha, “OGLE-2018-BLG-1185b : A Low-Mass Microlensing Planet Orbiting a Low-Mass Dwarf”, ArXiv, pp. 1-30, 2021. https://arxiv.org/abs/2104.02157

Copyright of this article totally belongs to our author S. Aman. One is allowed to reuse it only by giving proper credit either to him or to us

Why Primordial Non-Gaussianity is Very Small? (Quantum Physics / Maths)

Inflation in the early universe has been a part of standard cosmology not only to solve the horizon, flatness, and monopole problems, but also to account for the origin of large-scale structures. Inflation is well described by a homogeneous scalar field dubbed as inflaton φ in quasi de-Sitter (dS) space. Properties of the inflaton, such as the forms of its kinetic and potential terms as well as its coupling to gravity are yet to be clarified both from theoretical and observational viewpoints. Quantum fluctuations of scalar field and gravitational field generated during inflation serve as probes of its physics that can be tested by observations of cosmic microwave background (CMB) and large-scale structures..

The simplest class of inflation models is the potential driven canonical slow-roll inflation where the kinetic term of the inflaton has the canonical form and its potential energy drives inflation. In this model, fluctuations can be expressed approximately as a massless free scalar field in dS space minimally-coupled to gravity. As a result, its linear perturbation calculation predicts a nearly scale-invariant spectrum with highly Gaussian distribution, in good agreement with observations. In these canonical models, deviations from the scale-invariant Gaussian distribution are controlled by the slow-roll parameters. Observationally, exact scale-invariant power spectrum has already been ruled out with more than two-σ confidence level with the red-tilted spectral index n_s < 1, but the primordial non-Gaussianity characterized by the bispectrum has not been detected so far, and only constraints on the non-linearity parameter “f_NL” of various types have been obtained so far.

Primordial non-Gaussianity is a potentially powerful discriminant of the physical mechanisms that generated the cosmological fluctuations observed today.”

In this situation, a number of extended inflation models has been proposed so far which can realize sizable non-Gaussianity while reproducing the observed red-tilted spectrum. Theoretically, the simplest local type non-Gaussianity may be produced by curvaton or modulated reheating scenarios, both of which require another fluctuating field in addition to the inflaton. Since there is no observational evidence requiring multiple fluctuating fields during inflation, we do not consider such models but stick to the single-field inflation models, whose non-Gaussian signature is mostly the equilateral one. To realize sizable non-Gaussianity in single field models, some models modify the kinetic terms as in k- or G-inflation, ghost condensate, Dirac-Born Infeld, and other models extend the gravitational sector, or both. In these non-canonical models, enhanced non-Gaussianity may be realized due to the smallness of sound speed during inflation and still consistent with the observation. Hence primordial non-Gaussianity serves as a good probe of new physics these extended models are based.

In the language of quantum field theory (QFT), power spectrum of perturbation corresponds to the vacuum expectation value (VEV) of the fluctuation two-point functions. The lowest order of non-Gaussianity is the VEV of the fluctuation three-point functions. Technically, the non-Gaussianity exists because of higher order interaction terms and it is evaluated by in-in perturbation theory with two-point function as the input to the calculation. However, such interaction terms also generate higher-order corrections to the two-point function which are called “loop corrections” in QFT terminology. Such correction must be analyzed carefully to ensure its smallness compared with the tree-level amplitude, or the result of calculations based on the linear perturbation theory, on which most cosmologists rely to set the initial condition of the post-inflationary universe, would lose its significance.

Now, Kristiano and Yokoyama calculated one-loop corrections to the power spectrum in generic single-field inflation, arising from the three-body interactions of perturbations which also generate primordial non-Gaussianity, using soft effective field theory.

The effective field theory (EFT) for soft limit of scalar field in dS space was proposed by Cohen and Green. Kristiano and Yokoyama applied their framework to inflation, because the fluctuations in inflation can be approximated as a scalar field in dS space. In particular, they used the EFT power counting method to classify interaction terms based on their significance on super-horizon scale. Then, they calculated the loop correction to the power spectrum by using the standard in-in perturbation theory.

They found that spectral index plays a role of a regulator of the divergence. Because of it, the loop correction is enhanced by an inverse factor of 1 − n_s which is a small positive number according to the latest observation. As a result in order for the loop correction to be small enough to warrant the validity of the standard perturbation theory, the amplitude of equilateral non-Gaussianity must be much smaller than the current observational bound.

“Due to the enhancement inversely proportional to the observed red-tilt of the spectral index of curvature perturbation, the correction turns out to be much larger than previously anticipated. As a result, the primordial non-Gaussianity must be much smaller than the current observational bound in order to warrant the validity of cosmological perturbation theory.”

— told Kristiano, first author of the study

Reference: J. Kristiano, Jun’ichi Yokoyama, “Why Primordial Non-Gaussianity is Very Small?”, ArXiv, pp. 1-7, 2021. https://arxiv.org/abs/2104.01953

Copyright of this article totally belongs to our author S. Aman. One is allowed to reuse it only by giving proper credit either to him or to us

Antifungal And Antidepressant Drugs May Help Protect Against COVID-19 (Medicine)

New research published in the British Journal of Pharmacology indicates that two currently available medications–an antifungal drug and an antidepressant–can effectively inhibit the virus that causes COVID-19 in laboratory cells.

Investigators found that the antifungal itraconazole and the antidepressant fluoxetine each blocked the production of infectious SARS-CoV-2 virus in cell culture lab tests. When either drug was used in combination with the antiviral drug remdesiver, the combination showed synergistic effects and inhibited the production of SARS-CoV-2 by more than 90%.

“Preventive vaccination and therapeutic medicines against COVID-19 are both required to effectively combat pandemics caused by emerging zoonotic viruses such as SARS-CoV-2,” said senior author Ursula Rescher, PhD, of the University of Muenster, in Germany.

Reference: Schloer, S, Brunotte, L, Mecate‐Zambrano, A, et al. Drug synergy of combinatory treatment with remdesivir and the repurposed drugs fluoxetine and itraconazole effectively impairs SARS‐CoV‐2 infection in vitro. Br J Pharmacol. 2021; 1– 12. https://doi.org/10.1111/bph.15418

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New Insights On Cause Of Anaphylaxis Following COVID-19 Vaccination (Medicine)

On the first day of the UK campaign for COVID-19 vaccination, there were reports of two cases of anaphylaxis–a severe, potentially life-threatening allergic reaction–within minutes of administration of the Pfizer/BioNTech mRNA vaccine. Subsequently further cases of suspected anaphylaxis to the Pfizer vaccine were reported. A new report published in Clinical & Experimental Allergy reveals that an allergy to the ingredient polyethylene glycol (PEG) is a cause of anaphylaxis to the vaccine. However, this is in the context of millions of doses safely administered.

The authors note that very few people are allergic to PEG, and they provide a guide to identifying those who are at risk. “This preliminary report confirms PEG as a cause of anaphylaxis to the Pfizer/BioNTech vaccine, for the first time,” they wrote. “COVID-19 vaccine anaphylaxis and PEG allergy are both rare, so proof of PEG as the cause in one case of vaccine anaphylaxis is important. However, it is important to emphasise that PEG allergy is rare and that COVID-19 vaccines remain safe.”

URL Upon Publication: https://onlinelibrary.wiley.com/doi/10.1111/cea.13874

Reference: Sellaturay, P., Nasser, S., Islam, S., Gurugama, P. and Ewan, P. (2021), Polyethylene glycol (PEG) is a cause of anaphylaxis to the Pfizer/BioNTech mRNA COVID‐19 vaccine. Clin Exp Allergy. Accepted Author Manuscript. https://doi.org/10.1111/cea.13874

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New Findings On How Diabetes Impacts Bone Health (Medicine)

In addition to causing blood sugar imbalances, type 1 diabetes can contribute to nerve damage and sensory abnormalities–a condition call neuropathy–and has been linked to a higher risk of bone fractures. A new study published in the Journal of Bone and Mineral Research has examined the effects of type 1 diabetes and diabetic neuropathy on the skeleton.

Investigators found that type 1 diabetes and diabetic neuropathy have various impacts on bone structure, but these effects do not fully explain the higher fracture risk in patients with type 1 diabetes.

The results suggest that the increase in the risk of fractures in type 1 diabetes is multifactorial, with both skeletal and non-skeletal features involved.

“It is important to investigate what leads to an increased risk of fractures in type 1 diabetes. Our results suggest that in addition to bone features, balance and muscle strength also play a role,” said lead author Tatiane Vilaca, MD, PhD, of the University of Sheffield, in the U.K. “These findings could help improve approaches to fracture prevention.”

Reference: Vilaca, T., Paggiosi, M., Walsh, J.S., Selvarajah, D. and Eastell, R. (2021), The Effects of Type 1 Diabetes and Diabetic Peripheral Neuropathy on the Musculoskeletal System: A Case–Control Study. J Bone Miner Res. https://doi.org/10.1002/jbmr.4271 https://asbmr.onlinelibrary.wiley.com/doi/full/10.1002/jbmr.4271

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Fossil Discovery Deepens Snakefly Mystery (Paleontology)

Ancient Predatory Insects Discovered In Region Once Thought Uninhabitable

Fossil discoveries often help answer long-standing questions about how our modern world came to be. However, sometimes they only deepen the mystery—as a recent discovery of four new species of ancient insects in British Columbia and Washington state is proving.

The fossil species, recently discovered by paleontologists Bruce Archibald of Simon Fraser University and Vladimir Makarkin of the Russian Academy of Sciences, are from a group of insects known as snakeflies, now shown to have lived in the region some 50 million years ago. The findings, published in Zootaxa, raise more questions about the evolutionary history of the distinctly elongated insects and why they live where they do today.

Snakeflies are slender, predatory insects that are native to the Northern Hemisphere and noticeably absent from tropical regions. Scientists have traditionally believed that they require cold winters to trigger development into adults, restricting them almost exclusively to regions that experience winter frost days or colder. However, the fossil sites where the ancient species were found experienced a climate that doesn’t fit with this explanation.

“The average yearly climate was moderate like Vancouver or Seattle today, but importantly, with very mild winters of few or no frost days,” says Archibald. “We can see this by the presence of frost intolerant plants like palms living in these forests along with more northerly plants like spruce.”

The fossil sites where the ancient species were discovered span 1,000 kilometers of an ancient upland from Driftwood Canyon in northwest B.C. to the McAbee fossil site in southern B.C., and all the way to the city of Republic in northern Washington.

According to Archibald, the paleontologists found species of two families of snakeflies in these fossil sites, both of which had previously been thought to require cold winters to survive. Each family appears to have independently adapted to cold winters after these fossil species lived.

“Now we know that earlier in their evolutionary history, snakeflies were living in climates with very mild winters and so the question becomes why didn’t they keep their ability to live in such regions? Why aren’t snakeflies found in the tropics today?”  

Pervious fossil insect discoveries in these sites have shown connections with Europe, Pacific coastal Russia, and even Australia.

Archibald emphasizes that understanding how life adapts to climate by looking deep into the past helps explain why species are distributed across the globe today, and can perhaps help foresee how further change in climate may affect that pattern.

“Such discoveries are coming out of these fossil sites all the time,” says Archibald. “They’re an important part of our heritage.”

Link to photos: http://at.sfu.ca/agvGKO

Featured image: Modern snakefly pictured above Fifty-two-million-year-old fossil snakefly from Driftwood Canyon in British Columbia. Fossil image copyright Zootaxa.

Reference: Bruce Archibald, Vladimir Makarkin, “Early Eocene snakeflies (Raphidioptera) of western North America from the Okanagan Highlands and Green River Formation”, Zootaxa, 4905(1), 2021. DOI: https://doi.org/10.11646/zootaxa.4951.1.2 link: https://www.biotaxa.org/Zootaxa/article/view/zootaxa.4951.1.2

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Key Brain Molecule May Play Role in Many Brain Disorders (Neuroscience)

UNC-Chapel Hill scientists discovered microRNA-29 is an important cellular switch controlling late-stage brain development, a foundational discovery that will help researchers explore new therapeutic approaches for neurodevelopmental conditions.

A team led by scientists at the UNC School of Medicine identified a molecule called microRNA-29 as a powerful controller of brain maturation in mammals. Deleting microRNA-29 in mice caused problems very similar to those seen in autism, epilepsy, and other neurodevelopmental conditions.

The results, published in Cell Reports, illuminate an important process in the normal maturation of the brain and point to the possibility that disrupting this process could contribute to multiple human brain diseases.

Mohanish Deshmukh, PhD

“We think abnormalities in microRNA-29 activity are likely to be a common theme in neurodevelopmental disorders and even in ordinary behavioral differences in individuals,” said senior author Mohanish Deshmukh, PhD, professor in the UNC Department of Cell Biology & Physiology and member of the UNC Neuroscience Center. “Our work suggests that boosting levels of miR-29, perhaps even by delivering it directly, could lead to a therapeutic strategy for neurodevelopmental disorders such as autism.”

miR-29 and brain maturation

MicroRNAs are short stretches of ribonucleic acid inside cells that regulate gene expression. Each microRNA, or miR, can bind directly to an RNA transcript from certain other genes, preventing it from being translated into a protein. MiRNAs thus effectively serve as inhibitors of gene activity, and the typical microRNA regulates multiple genes in this way so that genetic information is not overexpressed. These essential regulators have been intensively researched only in the past two decades. Therefore, much remains to be discovered about their roles in health and disease.

Deshmukh and colleagues set out to find microRNAs involved in the maturation of the brain after birth, a phase that in humans includes approximately the first 20 years of life. When the scientists looked for microRNAs with more activity in the adult mouse brain than the young mouse brain, one set of miRNA stuck way out from the rest. Levels of the miR-29 family were 50 to 70 times higher in the adult mouse brains than in young mouse brains.

The researchers examined a mouse model in which the genes for the miR-29 family were deleted just in the brain. They observed that although the mice were born normally, they soon developed a mix of problems, including repetitive behaviors, hyperactivity, and other abnormalities typically seen in mouse models of autism and other neurodevelopmental disorders. Many developed severe epileptic seizures.

To get a sense of what caused these abnormalities, the researchers examined gene activity in the brains of the mice, comparing it to activity in mouse brains that had miR-29. As expected, many genes were much more active when miR-29 was no longer there to block their activity. But the scientists unexpectedly found a large set of genes – associated with brain cells – that were less active in miR-29’s absence.

A mysterious methylator

With key assistance from co-author Michael Greenberg, PhD, a professor of neuroscience at Harvard University, the researchers eventually found the explanation for this mysterious reduction in gene activity.

One of the target genes that miR-29 normally blocks is a gene that encodes for an enzyme called DNMT3A. This enzyme places special chemical modifications called CH-methylations onto DNA, to silence genes in the vicinity. In mice brains, the activity of the gene for DNMT3A normally rises at birth and then sharply declines several weeks later. The scientists found that miR-29, which blocks DNMT3A, is what normally forces this sharp decline.

Thus, in the mice whose brains lack miR-29, DNMT3A is not suppressed and the CH-methylation process continues abnormally – and many brain cell genes that should become active continue to be suppressed instead. Some of these genes, and the gene for DNMT3A itself, have been found to be missing or mutated in individuals with neurodevelopmental disorders such as autism, epilepsy, and schizophrenia.

To confirm DNMT3A’s role, the scientists created a unique mouse model that prevents miR-29 from suppressing DNMT3A, but leaves miR-29’s other targets untouched. They showed that this unleashing of DNMT3A on its own results in many of the same problems such as seizures and early death, as seen in the mice without miR-29.

The findings highlight and clarify what seems likely to be a crucial process in shaping the brain late in its development: the switching-off of DNMT3A to free up many genes that are meant to be more active in the adult brain.

“These results are the first to identify miR-29 as an essential regulator of CH methylation, and to show why restricting CH methylation to a critical period is important for normal brain maturation,” Deshmukh said.

Deshmukh and colleagues are now following up by studying in more detail how the lack of miR-29 in different sets of brain cells might give rise to such disorders, and more generally they are studying how miR-29’s activity is regulated in childhood to fine-tune brain functions, thereby giving humans the traits that make them unique individuals.

The Cell Reports paper was co-first authored by Vijay Swahari, Ayumi Nakamura, and Emilie Hollville. Other authors include Hume Stroud, Jeremy Simon, Travis Ptacek, Matthew Beck, Cornelius Flowers, Jiami Guo, Charlotte Plestant, Jie Liang, Lisa Kurtz, Matt Kanke, Scott Hammond, You-Wen He, E.S. Anton, Praveen Sethupathy, Sheryl Moy, and Michael Greenberg.

The research was supported by the National Institutes of Health (GM118331, AG055304, U54HD079124, P30NS045892) and the Damon Runyon Cancer Research Foundation (DRG-2194-14).

Featured image: Right, miRNA29-deficient mice showing a marked increase in the important enzyme DNMT3A (bright light blue). Credit: Deshmukh Lab

Reference: Vijay Swahari et al., “MicroRNA-29 is an essential regulator of brain maturation through regulation of CH methylation”, Cell, 35(1), 2021. DOI: https://doi.org/10.1016/j.celrep.2021.108946

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