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The existence of multiple subclasses of type Ia supernovae (SNeIa) has been the subject of great debate in the last decade. In this work, we show how machine learning tools facilitate identification of subtypes of SNe Ia. Using Deep Learning for dimensionality reduction, we were capable of performing such identification in a parameter space of significantly lower dimension than its principal component analysis counterpart. This is evidence that the progenitor system and the explosion mechanism can be described with a small number of initial physical parameters. All tools used here are publicly available in the Python package DRACULA (Dimensionality Reduction And Clustering for Unsupervised Learning in Astronomy) and can be found within COINtoolbox (https://github.com/COINtoolbox/DRACULA).
Euclid is the ESA M2 mission and a milestone in the understanding of the geometry of the Universe. In total Euclid will produce up to 26 PB per year of observations. The Science Archive Systems (SAS) belongs to the Euclid Archive System (EAS) that sits in the core of the Euclid Science Ground Segment (SGS). The SAS is being built at the ESAC Science Data Centre (ESDC), which is responsible for the development and operations of the scientific archives for the Astronomy, Planetary and Heliophysics missions of ESA. The SAS is focused on the needs of the scientific community and is intended to provide access to the most valuable scientific metadata from the Euclid mission. In this paper we describe the architectural design of the system, implementation progress and the main challenges from the data management point of view in the building of the SAS.
The history and current status of the cross-disciplinary fields of astrostatistics and astroinformatics are reviewed. Astronomers need a wide range of statistical methods for both data reduction and science analysis. With the proliferation of high-throughput telescopes, efficient large scale computational methods are also becoming essential. However, astronomers receive only weak training in these fields during their formal education. Interest in the fields is rapidly growing with conferences organized by scholarly societies, textbooks and tutorial workshops, and research studies pushing the frontiers of methodology. R, the premier language of statistical computing, can provide an important software environment for the incorporation of advanced statistical and computational methodology into the astronomical community.
Unknown aspects of the initiation, evolution, and associated phenomena of coronal mass ejections (CMEs), together with their capability of perturbing the fragile technological equilibrium on which nowadays society depends, turn them a compelling subject of study. While space weather forecasts are thus far not able to predict when and where in the Sun will the next CME take place, various CME triggering mechanisms have been proposed, without reaching consensus on which is the predominant one. To improve our knowledge in these respects, we investigate a long-duration active region throughout its life, from birth until decay along five solar rotations, in connection with its production of ejective events. We benefit from the wealth of solar remote-sensing data with improved temporal, spatial, and spectral resolution provided by the ground-breaking space missions STEREO, SDO, and SOHO. During the investigated time interval, which covers the months July – November 2010, the STEREO spacecraft were nearly 180 degrees apart, allowing for the uninterrupted tracking of the active region and its ensuing CMEs. The ejective aspect is examined from multi-viewpoint coronagraphic images, while the dynamics of the active region photospheric magnetic field are inspected by means of SDO/HMI data for specific subintervals of interest. The ultimate goal of this work in progress is to identify common patterns in the ejective aspect that can be connected with the active region characteristics.
The study of chemical abundance gradients can provide essential information on the evolution of disk galaxies. Here I briefly review our current observational knowledge concerning the abundances of the ionized gas (H ii regions and planetary nebulae) in nearby galaxies, and how they inform us about the time evolution of metallicity gradients.
X-ray emission from planetary nebulae (PNe) provides unique insight on the formation and evolution of PNe. Past observations and the ongoing Chandra Planetary Nebulae Survey (ChanPlaNS) provide a consensus on the two types of X-ray emission detected from PNe: extended and compact point-like sources. Extended X-ray emission arises from a shocked “hot bubble” plasma that resides within the nebular shell. Cooler than expected hot bubble plasma temperatures spurred a number of potential solutions with one emerging as the likely dominate process. The origin of X-ray emission from compact sources at the location of the central star is less clear. These sources might arise from one or combinations of the following processes: self-shocking stellar winds, spun-up binary companions, and/or accretion, perhaps from mass transfer, PN fallback, or debris disks. In the discovery phase, X-ray studies of PNe have mainly focused on the origin of the various emission processes. New directions incorporate multi-wavelength observations to study the influence of X-ray emission on the rest of the electromagnetic spectrum.
Determining the demographics of the Galactic planetary nebula (PN) population is an important goal to further our understanding of this intriguing phase of stellar evolution. The Galactic population has more than doubled in number over the last 15 years, particularly from narrowband Hα surveys along the plane. In this review I will summarise these results, with emphasis on the time interval since the last IAU Symposium. These primarily optical surveys are not without their limitations and new surveys for PNe in the infrared similarly face a number of challenges. I will discuss the need for multi-wavelength approaches to discovery and analysis. The desire to have accurate volume-limited samples of Galactic PNe at our disposal is emphasised, which will be impacted with new data from the Gaia satellite mission. We need robust surveys of PNe and their central stars, especially volume-limited surveys, in order to clarify and quantify their evolutionary pathways.
We present infrared two color diagrams (2CDs) for a large sample of AGB stars, post-AGB stars, and planetary nebulae (PNe) to study their spectral evolution in infrared bands. We discuss possible evolutionary tracks from AGB stars to PNe on the 2CDs. We use catalogs from the available literature for the sample of AGB stars, post-AGB stars, and PNe in our Galaxy.
Extreme solar-terrestrial events are those in which very energetic solar ejections hit the earth?s magnetosphere, causing intense energization of the earth?s ring current. Statistically, their occurrence is approximately once per Gleissberg solar cycle (70-100yrs). The solar transient occurred on July, 23rd (2012) was potentially one of such extreme events. The associated coronal mass ejection (CME), however, was not ejected towards the earth. Instead, it hit the STEREO A spacecraft, located 120 degrees away from the Sun-Earth line. Estimates of the geoeffectiveness of such a CME point to a scenario of extreme Space Weather conditions. In terms of the ring current energization, as measured by the Disturbance Storm-Time index (Dst), had this CME hit the Earth, it would have caused the strongest geomagnetic storm in space era.
It is widely accepted that binary interactions are responsible for the shaping of planetary nebula. However, these binary interactions and evolutionary channels are poorly understood. Our recent study revealed a newly discovered population of low-luminosity, low-metallicity, likely binaries in the Magellanic Clouds: dusty post-RGB stars. They are likely to have evolved off the RGB via binary interaction. In this paper we present preliminary results of the first radial velocity monitoring of the post-RGB stars in the Small Magellanic Cloud (SMC) and the implications on stellar (binary) evolution. We also investigate their link, if any, to the planetary nebulae systems.
Small-scale kG strong magnetic field elements in the solar photosphere are often identified as so-called magnetic bright points (MBPs). In principle these MBPs represent the cross-section of a vertical, strong, magnetic flux tube which is expanding with height in the solar atmosphere. As these magnetic elements represent possible MHD wave guides, a significant interest has been already paid to them from the viewpoint of observations and simulations. In this work we would like to shed more light on a possible scenario for the creation of such strong magnetic field concentrations. The accepted standard scenario involves the convective collapse process. In this ongoing work we will show indications that this convective collapse process may become triggered by sufficiently strong pressure disturbances. However, it is highly unlikely that p-mode waves can be of such a strength.
We investigate the stellar halo of the nearby elliptical Virgo-cluster galaxy M49 using Planetary Nebulae (PNe). M49 is the second-brightest galaxy of the Virgo cluster and is at the center of the Virgo subcluster B. We present an extended catalogue extracted from a narrow-band survey carried out with Subaru’s Suprime Cam, consisting of 735 PNe down to a limiting magnitude of m5007 = 29.3. This PNe population traces the halo out to 155 kpc from the galaxy’s center, which provides accurate measurement of the luminosity-specific PN-number (α-parameter) in the inner and outer regions of M49’s halo. We are also able to determine the morphological variation of the planetary nebulae luminosity function (PNLF), that may trace different parent stellar populations. This enables us to identify the transition from the PN-scarce, possibly metal-rich, galaxy halo to the PN-rich, metal-poor, outer component.
Wavelet analysis was employed to identify the major frequencies of low-frequency waves present in the Martian magnetosheath. The Morlet wavelet transform was selected and applied to the electron density data, obtained from the Analyzer of Space Plasmas and Energetic Atoms experiment (ASPERA-3), onboard the Mars Express (MEX) spacecraft. We have selected magnetosheath crossings and analyzed electron density data. From a preliminary study of 502 magnetosheath crossings (observed during the year of 2005), we have found 1409 periods between 0.005 and 0.06Hz. The major frequencies observed were in the range 0.005-0.02 Hz with 58.5% of the 1409 frequencies identified.
We study the effects of mergers on non-parametric morphologies of galaxies. We compute the Gini index, M20, asymmetry and concentration statistics for z = 0 galaxies in the Illustris simulation and compare non-parametric morphologies of major mergers, minor merges, close pairs, distant pairs and unperturbed galaxies. We determine the effectiveness of observational methods based on these statistics to select merging galaxies.
The visible surface of the Sun, or photosphere, is defined as the solar radius in the optical spectrum range located at 696,000 km (Cox et al. (Ed. 2015)). However, as the altitude increases, the dominant electromagnetic radiation is emitted at other frequencies. Our aim is to measure the solar radius at frequencies of 212 GHz and 405 GHz through out a solar cycle and, therefore, the altitude where these emissions are generated and that variation along the years. Also we tried to verify the the radius dependence on the solar activity cycle, which can be a good indicator of the changes that occur in the atmosphere structure. For this, we used data obtained by the Submillimetric Solar Telescope (SST) created from daily scans made by SST from 1990 to 2015. From these scans a 2D map of the solar disk was constructed. The solar radius is then determined by adjusting a circumference to the points where the brightness is half of the quiet Sun level, which is set as the most common temperature value in the solar map, i.e., the mode of the temperature distribution. Thus, we determined the solar radius at 212 and 405 GHz and the altitude of the emissions respectively. For 212 GHz, we obtained a radius of 976.5”±8” (707±4 Mm), whereas for 405 GHz, we obtained 975.0”±8” (707±5 Mm). optical spectrum range
Semi-empirical atmospheric modeling is here used to obtain the chromospheric magnetic field distribution versus height in the K2 primary component of the RS CVn binary system HR 7428. The chromospheric magnetic field estimation versus height comes from considering the possibility of not imposing hydrostatic equilibrium in the atmospheric modeling. The stability of the best Non-hydrostatic equilibrium model, implies the presence of and additive (toward the center of the star) pressure, that decrease in strength from the base of the chromosphere toward the outer layers. Interpreting the additive pressure as magnetic pressure and I derive a magnetic field intensity of about 500 Gauss at the base of the chromosphere.
We are building a catalogue of interactively reprocessed observations of evolved stars observed with Herschel. The catalogue will offer not only the PACS and SPIRE spectroscopic data for each observation, but also complementary information from other infrared space observatories. As a first step, we are concentrating our efforts on two main activities: 1) the interactive data-reduction of more than 500 individual spectra obtained with PACS in the 55-210 μm range, available in the Herschel Science Archive; 2) the creation of a catalogue, accesible via a web-based interface and through the Virtual Observatory. Our ultimate goal is to carry out a comprehensive and systematic study of the far infrared properties of low-and intermediate-mass evolved stars using these data and enable science based on Herschel archival data. The objects cover the whole range of possible evolutionary stages in this short-lived phase of stellar evolution, from the AGB to the PN stage, displaying a wide variety of chemical and physical properties.
Python is considered to be a mature programming language, besides of being widely accepted as an engaging option for scientific analysis in multiple areas, as will be presented in this work for the particular case of solar physics research. SunPy is an open-source library based on Python that has been recently developed to furnish software tools to solar data analysis and visualization. In this work we present a graphical user interface (GUI) based on Python and Qt to effectively compute proper motions for the analysis of time series of solar data. This user-friendly computing interface, that is intended to be incorporated to the Sunpy library, uses a local correlation tracking technique and some extra tools that allows the selection of different parameters to calculate, vizualize and analyze vector velocity fields of solar data, i.e. time series of solar filtergrams and magnetograms.
We present high resolution spectroscopy obtained with MIKE-Magellan and MES OAN-SPM of a number of planetary nebulae (PNe) and H ii regions, distributed along the dwarf irregular galaxy NGC 3109 and compare their kinematical behavior with the one of H i data. We aim to determine if there is a kinematical connection among these objects. We also perform a revision of the chemical composition of PNe and H ii regions in this galaxy and discuss it in comparison with stellar evolution models.
We present the results of a long-term search (25 yrs) for radial velocity variability in a sample of seven bright proto-planetary nebulae showing axial symmetry. They all vary in velocity due to periodic pulsations. However, only marginal evidence is found for multi-year variations that might be due to a binary companion.