Pontifical Catholic University of Chile

www.uc.cl
Santiago, Chile

The Pontifical Catholic University of Chile is one of the six Catholic Universities existing in the Chilean university system and one of the two Pontifical Universities in the country, along with the Pontifical Catholic University of Valparaíso. It is also one of Chile's oldest universities and one of the most recognized educational institutions in Latin America. It ranks 1st in South America by QS ranking. Wikipedia.

SEARCH FILTERS
Time filter
Source Type

News Article | May 22, 2017
Site: phys.org

Tidal tails are thin, elongated regions of stars and interstellar gas extending into space. They are formed as a result of gravitational interactions between galaxies and star clusters. Studying tidal tails offers clues on the tides experienced by the cluster and its internal dynamics. Such studies can also reveal essential information about the evolution of a cluster and could shed new light on the lumpiness of dark matter distribution in a galaxy. To date, only a handful of clusters with tidal tails have been detected in the Milky Way galaxy. Seeking more examples of such clusters, a team of researchers led by Camila Navarrete of the Pontifical Catholic University of Chile searched for the presence of stellar tails around globular clusters located within the footprint of the Pan-STARRS1 (PS1) 3Pi survey. The survey offers multi-band, multi-epoch, precise photometry across much of the sky. By analyzing the data provided by the first telescope of the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) program, located on Haleakala, Maui, Hawaii, the team found that a globular cluster, designated NGC 7492, has the features they were looking for. Located some 86,000 light years away from the Earth, NGC 7492 is a sparse outer-halo galactic globular cluster discovered by William Herschel in 1786. The presence of extra-tidal stellar material was suggested by previous studies and has been recently confirmed by Navarrete's team. "We report the discovery of tidal tails around the galactic globular cluster NGC 7492, based on the Data Release 1 of the Pan-STARRS 1 survey," the astronomers wrote in the paper. According to the study, NGC 7492 exhibits two tidal tails on either side of the cluster. These features extend in the north-south direction over approximately 3.5 degrees, which corresponds to about 4,900 light years in projected length. The authors noted that the newly detected structure resembles the characteristic "S-shaped" tidal feature found around other disrupting globular clusters, like Pal 5 and NGC 5466. Pan-STARRS observations also revealed the positions of Blue Horizontal Branch (BHB) candidate stars in the cluster. The team found that despite their overall low number density, BHBs appear to follow NGC 7492's Northern tail, connecting its uppermost tip with the cluster itself. However, there is an observable lack of the BHB candidates on the other side of the cluster. "This perhaps is not surprising, given the low number of BHB stars expected in a given stellar population. While the spatial distribution of the possible BHB candidates is suggestive, deeper wide imaging is required to confirm (and perhaps extend) the discovery presented here," the team concluded. Explore further: Two of Milky Way's globular clusters found to have halo stars More information: The discovery of tidal tails around the globular cluster NGC 7492 with Pan-STARRS1, arXiv:1705.04324 [astro-ph.GA] arxiv.org/abs/1705.04324 Abstract We report the discovery of tidal tails around the Galactic globular cluster NGC 7492, based on the Data Release 1 of the Pan-STARRS 1 survey. The tails were detected with a version of the matched filter technique applied to the (g−r,r) and (g−i,i) color-magnitude diagrams. Tidal tails emerging from the cluster extend at least ∼3.5 degrees in the North-East to South-East direction, equivalent to ∼1.5 kpc in projected length.


Court F.A.,Pontifical Catholic University of Chile | Court F.A.,Neurounion Biomedical Foundation | Coleman M.P.,Babraham Institute
Trends in Neurosciences | Year: 2012

Axonal degeneration is a major contributor to neuronal dysfunction in many neurological conditions and has additional roles in development. It can be triggered by divergent stimuli including mechanical, metabolic, infectious, toxic, hereditary and inflammatory stresses. Axonal mitochondria are an important convergence point as regulators of bioenergetic metabolism, reactive oxygen species (ROS), Ca 2+ homeostasis and protease activation. The challenges likely to render axonal mitochondria more vulnerable than their cellular counterparts are reviewed, including axonal transport, replenishing nuclear-encoded proteins and maintenance of quality control, fusion and fission in locations remote from the cell body. The potential for mitochondria to act as a decision node in axon loss is considered, highlighting the need to understand the biology of axonal mitochondria and their contributions to degenerative mechanisms for novel therapeutic strategies. © 2012 Elsevier Ltd.


News Article | February 23, 2017
Site: www.eurekalert.org

Glowing nebula found at the heart of a huge "rotocluster' of early galaxies appears to be part of the cosmic web of filaments connecting galaxies, but what's lighting it up? Astronomers have found an enormous, glowing blob of gas in the distant universe, with no obvious source of power for the light it is emitting. Called an "enormous Lyman-alpha nebula" (ELAN), it is the brightest and among the largest of these rare objects, only a handful of which have been observed. ELANs are huge blobs of gas surrounding and extending between galaxies in the intergalactic medium. They are thought to be parts of the network of filaments connecting galaxies in a vast cosmic web. Previously discovered ELANs are likely illuminated by the intense radiation from quasars, but it's not clear what is causing the hydrogen gas in the newly discovered nebula to emit Lyman-alpha radiation (a characteristic wavelength of light absorbed and emitted by hydrogen atoms). The newly discovered nebula was found at a distance of 10 billion light years in the middle of a region with an extraordinary concentration of galaxies. Researchers found this massive overdensity of early galaxies, called a "protocluster," through a novel survey project led by Zheng Cai, a Hubble Postdoctoral Fellow at UC Santa Cruz. "Our survey was not trying to find nebulae. We're looking for the most overdense environments in the early universe, the big cities where there are lots of galaxies," said Cai. "We found this enormous nebula in the middle of the protocluster, near the peak density." Cai is first author of a paper on the discovery accepted for publication in the Astrophysical Journal and available online at arxiv.org/abs/1609.04021. His survey project is called Mapping the Most Massive Overdensities Through Hydrogen (MAMMOTH), and the newly discovered ELAN is known as MAMMOTH-1. Coauthor J. Xavier Prochaska, professor of astronomy and astrophysics at UC Santa Cruz, said previously discovered ELANs have been detected in quasar surveys. In those cases, the intense radiation from a quasar illuminated hydrogen gas in the nebula, causing it to emit Lyman-alpha radiation. Prochaska's team discovered the first ELAN, dubbed the "Slug Nebula," in 2014. MAMMOTH-1 is the first one not associated with a visible quasar, he said. "It's extremely bright, and it's probably larger than the Slug Nebula, but there's nothing else visible except the faint smudge of a galaxy. So it's a terrifically energetic phenomenon without an obvious power source," Prochaska said. Equally impressive is the enormous protocluster in which it resides, he said. Protoclusters are the precursors to galaxy clusters, which consist of hundreds to thousands of galaxies bound together by gravity. Because protoclusters are spread out over a much larger area of the sky, they are much harder to find than galaxy clusters. The protocluster hosting the MAMMOTH-1 nebula is massive, with an unusually high concentration of galaxies in an area about 50 million light years across. Because it is so far away (10 billion light years), astronomers are in effect looking back in time to see the protocluster as it was 10 billion years ago, or about 3 billion years after the big bang, during the peak epoch of galaxy formation. After evolving for 10 billion more years, this protocluster would today be a mature galaxy cluster perhaps only one million light years across, having collapsed down to a much smaller area, Prochaska said. The standard cosmological model of structure formation in the universe predicts that galaxies are embedded in a cosmic web of matter, most of which is invisible dark matter. The gas that collapses to form galaxies and stars traces the distribution of dark matter and extends beyond the galaxies along the filaments of the cosmic web. The MAMMOTH-1 nebula appears to have a filamentary structure that aligns with the galaxy distribution in the large-scale structure of the protocluster, supporting the idea that ELANs are illuminated segments of the cosmic web, Cai said. "From the distribution of galaxies we can infer where the filaments of the cosmic web are, and the nebula is perfectly aligned with that structure," he said. Cai and his coauthors considered several possible mechanisms that could be powering the Lyman-alpha emission from the nebula. The most likely explanations involve radiation or outflows from an active galactic nucleus (AGN) that is strongly obscured by dust so that only a faint source can be seen associated with the nebula. An AGN is powered by a supermassive black hole actively feeding on gas in the center of a galaxy, and it is usually an extremely bright source of light (quasars being the most luminous AGNs in visible light). The intense radiation from an AGN can ionize the gas around it (called photoionization), and this may be one mechanism at work in MAMMOTH-1. When ionized hydrogen in the nebula recombines it would emit Lyman-alpha radiation. Another possible mechanism powering the Lyman-alpha emissions is shock heating by a powerful outflow of gas from the AGN. The researchers described several lines of evidence supporting the existence of a hidden AGN energizing the nebula, including the dynamics of the gas and emissions from other elements besides hydrogen, notably helium and carbon. "It has all the hallmarks of an AGN, but we don't see anything in our optical images. I expect there's a quasar that is so obscured by dust that most of its light is hidden," Prochaska said. In addition to Cai and Prochaska at UC Santa Cruz, the team includes coauthors at Steward Observatory, University of Arizona; Korea Astronomy and Space Institute; Mount Stromlo Observatory, Australia; Pontifical Catholic University of Chile; Institute for Astronomy, ETH Zurich; California Institute of Technology; Kavli Institute for Astronomy and Astrophysics, Peking University; and National Astronomical Observatory of Japan. This research was supported by the National Science Foundation and NASA.


News Article | February 24, 2017
Site: spaceref.com

Astronomers have found an enormous, glowing blob of gas in the distant universe, with no obvious source of power for the light it is emitting. Called an "enormous Lyman-alpha nebula" (ELAN), it is the brightest and among the largest of these rare objects, only a handful of which have been observed. ELANs are huge blobs of gas surrounding and extending between galaxies in the intergalactic medium. They are thought to be parts of the network of filaments connecting galaxies in a vast cosmic web. Previously discovered ELANs are likely illuminated by the intense radiation from quasars, but it's not clear what is causing the hydrogen gas in the newly discovered nebula to emit Lyman-alpha radiation (a characteristic wavelength of light absorbed and emitted by hydrogen atoms). The newly discovered nebula was found at a distance of 10 billion light-years in the middle of a region with an extraordinary concentration of galaxies. Researchers found this massive overdensity of early galaxies, called a "protocluster," through a novel survey project led by Zheng Cai, a Hubble Postdoctoral Fellow at UC Santa Cruz. "Our survey was not trying to find nebulae. We're looking for the most overdense environments in the early universe, the big cities where there are lots of galaxies," said Cai. "We found this enormous nebula in the middle of the protocluster, near the peak density." Cai is first author of a paper on the discovery accepted for publication in the Astrophysical Journal and available online. His survey project is called Mapping the Most Massive Overdensities Through Hydrogen (MAMMOTH), and the newly discovered ELAN is known as MAMMOTH-1. Coauthor J. Xavier Prochaska, professor of astronomy and astrophysics at UC Santa Cruz, said previously discovered ELANs have been detected in quasar surveys. In those cases, the intense radiation from a quasar illuminated hydrogen gas in the nebula, causing it to emit Lyman-alpha radiation. Prochaska's team discovered the first ELAN, dubbed the "Slug Nebula," in 2014. MAMMOTH-1 is the first one not associated with a visible quasar, he said. "It's extremely bright, and it's probably larger than the Slug Nebula, but there's nothing else visible except the faint smudge of a galaxy. So it's a terrifically energetic phenomenon without an obvious power source," Prochaska said. Equally impressive is the enormous protocluster in which it resides, he said. Protoclusters are the precursors to galaxy clusters, which consist of hundreds to thousands of galaxies bound together by gravity. Because protoclusters are spread out over a much larger area of the sky, they are much harder to find than galaxy clusters. The protocluster hosting the MAMMOTH-1 nebula is massive, with an unusually high concentration of galaxies in an area about 50 million light-years across. Because it is so far away (10 billion light-years), astronomers are in effect looking back in time to see the protocluster as it was 10 billion years ago, or about 3 billion years after the big bang, during the peak epoch of galaxy formation. After evolving for 10 billion more years, this protocluster would today be a mature galaxy cluster perhaps only one million light-years across, having collapsed down to a much smaller area, Prochaska said. The standard cosmological model of structure formation in the universe predicts that galaxies are embedded in a cosmic web of matter, most of which is invisible dark matter. The gas that collapses to form galaxies and stars traces the distribution of dark matter and extends beyond the galaxies along the filaments of the cosmic web. The MAMMOTH-1 nebula appears to have a filamentary structure that aligns with the galaxy distribution in the large-scale structure of the protocluster, supporting the idea that ELANs are illuminated segments of the cosmic web, Cai said. "From the distribution of galaxies we can infer where the filaments of the cosmic web are, and the nebula is perfectly aligned with that structure," he said. Cai and his coauthors considered several possible mechanisms that could be powering the Lyman-alpha emission from the nebula. The most likely explanations involve radiation or outflows from an active galactic nucleus (AGN) that is strongly obscured by dust so that only a faint source can be seen associated with the nebula. An AGN is powered by a supermassive black hole actively feeding on gas in the center of a galaxy, and it is usually an extremely bright source of light (quasars being the most luminous AGNs in visible light). The intense radiation from an AGN can ionize the gas around it (called photoionization), and this may be one mechanism at work in MAMMOTH-1. When ionized hydrogen in the nebula recombines it would emit Lyman-alpha radiation. Another possible mechanism powering the Lyman-alpha emissions is shock heating by a powerful outflow of gas from the AGN. The researchers described several lines of evidence supporting the existence of a hidden AGN energizing the nebula, including the dynamics of the gas and emissions from other elements besides hydrogen, notably helium and carbon. "It has all the hallmarks of an AGN, but we don't see anything in our optical images. I expect there's a quasar that is so obscured by dust that most of its light is hidden," Prochaska said. * "Discovery of an Enormous Ly-alpha Nebula in a Massive Galaxy Overdensity at z = 2.3," Zheng Cai et al., 2017, to appear in the Astrophysical Journal [http://apj.aas.org, preprint: https://arxiv.org/abs/1609.04021]. * "MApping the Most Massive Overdensities Through Hydrogen (MAMMOTH) I: Methodology," Zheng Cai et al., 2016 Dec. 20, Astrophysical Journal [http://iopscience.iop.org/article/10.3847/1538-4357/833/2/135 , preprint: https://arxiv.org/abs/1512.06859]. In addition to Cai and Prochaska at UC Santa Cruz, the team includes coauthors at Steward Observatory, University of Arizona; Korea Astronomy and Space Institute; Mount Stromlo Observatory, Australia; Pontifical Catholic University of Chile; Institute for Astronomy, ETH Zurich; California Institute of Technology; Kavli Institute for Astronomy and Astrophysics, Peking University; and National Astronomical Observatory of Japan. This research was supported by the National Science Foundation and NASA. Please follow SpaceRef on Twitter and Like us on Facebook.


News Article | March 18, 2016
Site: www.techtimes.com

Five new Jupiter-like exoplanets have been discovered last month, and now astronomers identify four more that are orbiting stars bigger than our sun. The new exoplanets' sizes range between 2.4 and 5.5 times the size of Jupiter. They can take two to four years to orbit their stars. The scientists first found the new giant exoplanets in the data collected by several telescopes in Chile. Using a telescope in Australia, they verified the facts and confirmed the existence of four new exoplanets orbiting four massive stars namely HIP8541, HIP74890, HIP84056 and HIP95124. The discovery adds to the growing trend that stars rich in metal are more likely to host planets. The research was published on March 11. The research team was led by Matias Jones from the Pontifical Catholic University of Chile. The discovery was first made during the EXoPlanets aRound Evolved StarS (EXPRESS) radial velocity program. They used two telescopes in Chile's Atacama Desert - La Silla Observatory's 2.2-meter telescope and the Cerro Tololo Inter-American Observatory's 1.5-meter telescope. To confirm the initial findings, they used Australia's 3.9-meter Anglo-Australian telescope. The researchers initially monitored a sample pool of 166 bright massive stars that can be viewed from the southern hemisphere. They found signal variations in the velocities of the four stars mentioned above. According to the researchers, these could be the effect of the presence of orbiting planets. "These velocities show periodic signals, with semi-amplitudes between 50 to 100 ms-1, which are likely caused by the doppler shift induced by orbiting companions," wrote the researchers. The researchers conducted several tests to determine the presence of an inherent indicator in the giant stars. These standard tests included photometric variability, chromospheric emission and line bisector analysis. They found no link between inherent indicators and the observed velocities of the four stars. The researchers found that massive planets are mostly detected orbiting start that are rich in metal. The discovery adds information on the link between occurrence rate of exoplanets and stellar properties. "In addition to these planet discoveries, we present a detailed analysis of the mass-metallicity correlations of the planet-hosting and non-planet-hosting stars in our sample, along with studying the fraction of multiple-planet systems observed in giant stars," they wrote in the paper.


News Article | March 15, 2016
Site: phys.org

The team, led by Matias Jones of the Pontifical Catholic University of Chile, made the discovery during observations under the EXPRESS (EXoPlanets aRound Evolved StarS) radial velocity program. They used two telescopes located in the Atacama desert in Chile: the 1.5 m telescope at the Cerro Tololo Inter-American Observatory and the 2.2 m telescope at La Silla observatory. Complementary observations were conducted at the 3.9 m Anglo-Australian telescope in Australia. Using spectrographs mounted on these telescopes, the researchers were monitoring a sample of 166 bright giant stars that are observable from the southern hemisphere. They took several spectra for each of the stars in the sample thanks to these instruments. The observation campaign lasted from 2009 to 2015. The astronomers have computed a series of precision radial velocities of four giant stars: HIP8541, HIP74890, HIP84056 and HIP95124. According to them, these velocities show periodic signal variations. The team concluded that the most probable explanation of the periodic radial velocity signals observed in these stars must be the presence of planetary companions. "These velocities show periodic signals, with semi-amplitudes between approximately 50 to 100 ms−1, which are likely caused by the doppler shift induced by orbiting companions. We performed standard tests (chromospheric emission, line bisector analysis and photometric variability) aimed at studying whether these radial velocity signals have an intrinsic stellar origin. We found no correlation between the stellar intrinsic indicator with the observed velocities," the paper reads. HIP8541b is the most massive of the newly found quartet of planets. With a mass of about 5.5 Jupiter masses, this exoplanet also has a much longer orbital period than the other three worlds, equal to 1,560 days. Its parent star is slightly more massive than the sun and has a radius of nearly eight solar radii. HIP74890b and HIP84056b are very similar in terms of mass and orbital period. The mass of HIP74890b is estimated to be 2.4 Jupiter masses, what is about 92 percent of the mass of HIP84056b. The more massive planet of this comparable duo has an orbital period lasting nearly 819 days – about three fewer days than the other planet. Their host stars are also of similar mass and size, about 1.7 the mass of the sun, with a radius of 5.03 (HIP 84056) and 5.77 (HIP 74890) solar radii. Among the exoplanets described in the paper, the one with the shortest orbital period (562 days), is designated HIP95124b. It has a mass of 2.9 Jupiter masses and orbits a star nearly two times more massive than the sun, with a radius of 5.12 solar radii. The discovery of these planets also yielded interesting results about correlations between the stellar properties and the occurrence rate of planets. The researchers have found that giant planets are preferentially detected around metal-rich stars. "We also present a statistical analysis of the mass-metallicity correlations of the planet-hosting stars in our sample. (…) We show that the fraction of giant planets increases with the stellar mass in the range between 1 to 2.1 solar masses, despite the fact that planets are more easily detected around less massive stars," the scientists noted. The team concluded that the high fraction of multiple systems observed in giant stars is a natural consequence of the planet formation mechanism around intermediate-mass stars. More information: Four new planets around giant stars and the mass-metallicity correlation of planet-hosting stars, arXiv:1603.03738 [astro-ph.EP] arxiv.org/abs/1603.03738 Abstract CONTEXT. Exoplanet searches have demonstrated that giant planets are preferentially found around metal-rich stars and that their fraction increases with the stellar mass. AIMS. During the past six years, we have conducted a radial velocity follow-up program of 166 giant stars, to detect substellar companions, and characterizing their orbital properties. Using this information, we aim to study the role of the stellar evolution in the orbital parameters of the companions, and to unveil possible correlations between the stellar properties and the occurrence rate of giant planets. METHODS. Using FEROS and CHIRON spectra, we have computed precision radial velocities and we have derived atmospheric and physical parameters for all of our targets. Additionally, velocities computed from UCLES spectra are presented here. By studying the periodic radial velocity signals, we have detected the presence of several substellar companions. RESULTS. We present four new planetary systems around the giant stars HIP8541, HIP74890, HIP84056 and HIP95124. Additionally, we find that giant planets are more frequent around metal-rich stars, reaching a peak in the detection of f = 16.7+15.5−5.9% around stars with [Fe/H] ∼ 0.35 dex. Similarly, we observe a positive correlation of the planet occurrence rate with the stellar mass, between M⋆ ∼ 1.0 -2.1 M⊙, with a maximum of f = 13.0+10.1−4.2%, at M⋆ = 2.1 M⊙. CONCLUSIONS. We conclude that giant planets are preferentially formed around metal-rich stars. Also, we conclude that they are more efficiently formed around more massive stars, in the mass range of M⋆ ∼ 1.0 - 2.1 M⊙. These observational results confirm previous findings for solar-type and post-MS hosting stars, and provide further support to the core-accretion formation model.


News Article | November 29, 2016
Site: phys.org

EPIC 220504338b was first spotted by K2 as a planetary candidate during the spacecraft's Campaign 8 in mid-2016. To confirm it as a planet, a team of researchers led by Nestor Espinoza of the Pontifical Catholic University of Chile conducted follow-up observations using ESO's Fibre-fed, Extended Range, Échelle Spectrograph (FEROS) at La Silla Observatory in Chile. FEROS observational campaign was carried out in August and November 2016. FEROS is a bench-mounted, high-resolution, environmentally controlled, astronomical Échelle spectrograph with high efficiency, large wavelength range and high resolution. The instrument enables conducting a large variety of stellar and extra-galactic spectroscopic observation programs requiring high spectral stability high-resolution. Recent FEROS spectroscopic observations allowed the team to perform radial velocity measurements that confirmed EPIC 220504338b is a dense "hot Jupiter" transiting a solar analogue as well as provided initial stellar parameters of its host star. "In this work, we have presented the discovery of EPIC 220504338b, a new hot Jupiter orbiting a metal-rich solar analogue discovered using photometry from Campaign 8 of the K2 mission and follow-up radial velocities using the FEROS spectrograph," the scientists wrote in the paper. The so-called "hot Jupiters" like EPIC 220504338b are gas giant planets, similar in characteristics to the solar system's biggest planet, with orbital periods of less than 10 days. They have high surface temperatures, as they orbit their parent stars very closely. According to the research, EPIC 220504338b is about 10 percent smaller than Jupiter and approximately 30 percent more massive. The exoworld orbits its 6-billion-year-old sun-like parent star every 5.8 days. Notably, with a density of nearly 2.1 gr/cm3 and an equilibrium temperature of about 1,160 K, the planet is one of the densest "hot Jupiters" below two Jupiter masses known to date. The researchers explain the newly discovered planet's mass and radius by the amount of heavy elements in the planet, which should be on the order of at least 110 Earth masses. "The mass and radius of EPIC 220504338b could be explained in terms of the amount of heavy elements in the planet. (...) Based on its mass and radius, we estimate that EPIC 220504338b should have a heavy element content on the order of about 110 Earth masses or greater," the paper reads. The team also derived fundamental parameters of the host star EPIC 220504338. The observations indicate that this star has a mass to that of the sun, with a radius of about 1.05 solar radii. It is also approximately 23 percent more dense than the sun. However, EPIC 220504338 shows a high metallicity, which significantly deviates from the sun. Therefore, this star was classified as a slightly metal-rich solar analogue. Abstract We present the discovery of EPIC 220504338b, a dense hot-Jupiter discovered using photometry from Campaign 8 of the Kepler-2 (K2) mission and high-resolution spectroscopic follow up obtained with the FEROS spectrograph. The planet orbits a V=13.68 solar analogue in a P=5.81771+0.00004−0.00004 day orbit, has a radius of 0.91+0.10−0.07RJ and a mass of 1.28+0.11−0.12MJ. With a density of 2.08+0.66−0.57 gr/cm3, the planet is among the densest systems known having masses below 2 MJ and Teq>1000, and is just above the temperature limit at which inflation mechanisms are believed to start being important. Based on its mass and radius, we estimate that EPIC 220504338b should have a heavy element content on the order of ∼ 110 M⊕ or greater.


News Article | March 10, 2016
Site: phys.org

The so-called "hot Jupiters" are gas giant planets, similar in characteristics to the solar system's biggest planet, with orbital periods of less than 10 days. They have high surface temperatures as they orbit their parent stars very closely—between 0.015 and 0.5 AU—while Jupiter orbits the sun at 5.2 AU. To date, about 250 transiting "hot Jupiters" have been found, mostly by ground-based photometric surveys. Now, the researchers have made use of a space-borne telescope to detect new, interesting hot giant exoworlds. K2 is a repurposed mission of the Kepler spacecraft to perform high-precision photometry of selected fields in the ecliptic, following the failure of two reaction wheels in 2013. Due to this malfunction, observations are currently conducted only within the orbital plane of the spacecraft, which approximates to the ecliptic. However, despite these difficulties, K2 has managed to detect 234 planetary candidates in the first year of the mission. The researchers, led by Rafael Brahm of the Pontifical Catholic University of Chile, have analyzed the photometric data of K2's two observation campaigns and discovered that the stars EPIC210957318 and EPIC212110888 show significant periodic signals every four and three days, respectively. "Both of these systems were selected as strong Jovian planetary candidates based on their transit properties (depths, shapes and durations), and due to the lack of evident out of transit variations," the paper reads. Next, the researchers acquired high-resolution spectra of the two candidates, with three different stabilized spectrographs mounted on telescopes at the La Silla Observatory in Chile. These instruments were helpful in measuring the radial velocity variation of the stellar hosts produced by the gravitational pull of orbiting planets. According to the paper, the smaller planet of the newly discovered duo, named EPIC210957318b, orbits its parent sun-like star, located about 970 light years from the Earth, every 4.1 days. The mass of this exoplanet is between the Saturn and Jupiter masses (approximately 0.65 Jupiter masses) and its radius is slightly larger than the one of the solar system's largest planets. The temperatures on this planet range from 584 to 939 degrees Celsius. EPIC212110888b is more massive and larger than Jupiter. Having a mass of about 1.63 Jupiter masses, this planet orbits its host star every three days and is even hotter than EPIC210957318b, with temperatures spanning from 932 to 1,430 degrees Celsius. The star, slightly more massive than sun, lies some 1,270 light years away from our planet. Both planets have similar densities, close to half of Jupiter's. The scientists noted that the physical and orbital properties of both of these extrasolar systems are typical of the population of known hot Jupiters. They also concluded that these two exoplanets are interesting candidates for follow-up studies. "The low density of EPIC210957318b combined with the relatively small radius of its host star implies a scale height of 340 km and a transmission spectroscopic signal of 744 ppm (assuming an H dominated atmosphere and a signal of five scale-heights), which means that this system is a good target to be observed via transmission spectroscopy to characterize its atmosphere," they wrote. Explore further: Detection of two new exoplanets with Kepler, SOPHIE and HARPS-N More information: An independent discovery of two hot Jupiters from the K2 mission, arXiv:1603.01721 [astro-ph.EP] arxiv.org/abs/1603.01721 Abstract We report the discovery of two hot Jupiters using photometry from Campaigns 4 and 5 of the two-wheeled Kepler (K2) mission. EPIC210957318b has a mass of 0.65±0.14MJ, a radius of 1.070±0.018RJ and transits its G dwarf (Teff=5675±50 K), slightly metal rich ([Fe/H]=+0.06±0.04 dex) host star in a 4.1 days circular orbit. EPIC212110888b has a mass of 1.63±0.12MJ, a radius of 1.38±0.014RJ and has an orbital period of 3.0 days in which it orbits a late F dwarf (Teff=6149±55 K) solar metallicity star. Both planets were validated probabilistically and confirmed via precision radial velocity (RV) measurements. They have physical and orbital properties similar to the ones of the already uncovered population of hot Jupiters and are well-suited candidates for further orbital and atmospheric characterization via detailed follow-up observations.


Quiroga T.,Pontifical Catholic University of Chile
Hematology / the Education Program of the American Society of Hematology. American Society of Hematology. Education Program | Year: 2012

Congenital mild bleeding disorders (MBDs) are very prevalent and are the source of frequent diagnostic problems. Most MBDs are categorized as disorders of primary hemostasis (ie, type 1 VWD and platelet function disorders), but mild or moderate deficiencies of clotting factors and some rare hyperfibrinolytic disorders are also included. These patients have abnormal bleeding from the skin and mucous membranes, menorrhagia, and disproportionate hemorrhages after trauma, invasive procedures, and surgery. This review addresses the main problems that physicians and hemostasis laboratories confront with the diagnosis of these patients, including: discerning normal/appropriate from pathological bleeding, the role and yield of screening tests, the lack of distinctive bleeding pattern among the different diseases, the inherent difficulties in the diagnosis of type 1 VWD and the most common platelet functional disorders, improvements in assays to measure platelet aggregation and secretion, and the evidence that most of the patients with MBDs end up without a definite diagnosis after exhaustive and repeated laboratory testing. Much research is needed to determine the pathogenesis of bleeding in MBD patients. Better standardization of current laboratory assays, progress in the knowledge of fibrinolytic mechanisms and their laboratory evaluation, and new understanding of the factors contributing to platelet-vessel wall interaction, along with the corresponding development of laboratory tools, should improve our capacity to diagnose a greater proportion of patients with MBDs.


News Article | February 3, 2016
Site: www.sciencenews.org

When it comes to big balls of rock, exoplanet BD+20594b might have all other known worlds beat. At roughly half the diameter of Neptune, BD+20594b is 100 percent rock, researchers suggest online January 28 at arXiv.org. The planet seems to defy recent calculations that indicate a planet this large should be gassy (SN: 8/22/15, p. 32). BD+20594b sits about 500 light-years away in the constellation Taurus. The planet is about 16 times as massive as Earth but just a little over twice as wide, making its density about 8 grams per cubic centimeter, Néstor Espinoza, an astrophysicist at the Pontifical Catholic University of Chile in Santiago, and colleagues report. Earth’s density, by comparison, is 5.5 grams per cubic centimeter. The new rocky planet was discovered in 2015 with the Kepler space telescope, which looks for the silhouettes of planets passing in front of their stars. BD+20594b is comparable to Kepler 10c, a rocky “mega Earth” reported in 2014 (SN: 7/12/14, p. 10) to be 2.4 times as wide as Earth with a hefty mass (equal to about 17 Earths). Recent measurements indicate, however, that Kepler 10c isn’t quite as “mega” or as rocky as thought — only 14 times as massive as Earth — which means that the planet is probably encased in shell of gas or water. Editor’s note: This story was updated February 17, 2016, to correct the name of the constellation in which BD+20594b resides.

Loading Pontifical Catholic University of Chile collaborators
Loading Pontifical Catholic University of Chile collaborators