scholarly journals Detection of a repeated transit signature in the light curve of the enigma star KIC 8462852: A possible 928-day period

2017 ◽  
Vol 608 ◽  
pp. A132 ◽  
Author(s):  
F. Kiefer ◽  
A. Lecavelier des Étangs ◽  
A. Vidal-Madjar ◽  
G. Hébrard ◽  
V. Bourrier ◽  
...  
Keyword(s):  
Light Curve ◽  
Production Rate ◽  
A Priori ◽  
Ring System ◽  
Striking Similarity ◽  
Dust Production ◽  
High Quality ◽  
Bad Weather ◽  
Absorption Features

As revealed by its peculiar Kepler light curve, the enigmatic star KIC 8462852 undergoes short and deep flux dimmings at a priori unrelated epochs. This star presents nonetheless all other characteristics of a quiet 1 Gyr old F3V star. These dimmings resemble the absorption features expected for the transit of dust cometary tails. The exocomet scenario is therefore most commonly advocated. We reanalysed the Kepler data and extracted a new high-quality light curve to allow for the search of shallow signatures of single or a few exocomets. We discovered that among the 22 flux dimming events that we identified, two events present a striking similarity. These events occurred 928.25 days apart and lasted for 4.4 days with a drop in the star brightness by 1000 ppm. We show that the light curve of these events is well explained by the occultation of the star by a giant ring system or by the transit of a string of half a dozen exocomets with a typical dust production rate of 105–106 kg s-1. Assuming that these two similar events are related to the transit of the same object, we derive a period of 928.25 days. The following transit was expected in March 2017 but bad weather prohibited us from detecting it from ground-based spectroscopy. We predict that the next event will occur between 3−8 October 2019.

Modelling gas and dust around carbon stars in the Large Magellanic Cloud

2018 ◽  
Vol 14 (S343) ◽  
pp. 504-505
Author(s):  
Sundar Srinivasan ◽  
I.-K. Chen ◽  
P. Scicluna ◽  
J. Cami ◽  
F. Kemper
Keyword(s):  
Production Rate ◽  
Strong Correlation ◽  
Column Density ◽  
Preliminary Investigation ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Carbon Stars ◽  
Molecular Absorption ◽  
Dust Production ◽  
Absorption Features

AbstractIn order to investigate the effect of dust production on the molecular absorption, we model the dust continuum and the 7.5 and 13.7 μm acetylene absorption features in the Spitzer IRS spectra of 148 carbon stars in the Large Magellanic Cloud (LMC). Our preliminary investigation does not find a strong correlation between the dust-production rate and the column density of acetylene for the LMC sample. However, we will construct more models at high optical depths and probe a larger range of dust properties for more robust results.

scholarly journals 523676 (2013 UL10): the first active red centaur

2018 ◽  
Vol 620 ◽  
pp. A93 ◽  
Author(s):  
E. Mazzotta Epifani ◽  
E. Dotto ◽  
S. Ieva ◽  
D. Perna ◽  
P. Palumbo ◽  
...  
Keyword(s):  
Production Rate ◽  
Canary Islands ◽  
Colour Index ◽  
Nucleus Size ◽  
Dust Production ◽  
La Palma ◽  
Upper Limit ◽  
Nucleus Surface ◽  
Perihelion Passage

Aims. We present observations of 523676 (2013 UL10), a centaur orbiting between Jupiter and Uranus that is dynamically similar to the few tens of active centaurs that are currently known. Methods. We analysed visible BVR images of the centaur obtained at the Telescopio Nazionale Galileo (La Palma, Canary Islands, Spain) to investigate the weak comet-like activity and to derive information on the nucleus surface colours and size. Results. Centaur 523676 (2013 UL10) is the only centaur known so far that has both comet-like activity and red surface colours: its nucleus has a colour index [B – R] = 1.88 ± 0.11. The nucleus R magnitude (R = 20.93 ± 0.09) allowed us to derive an upper limit for its nucleus size of D ≤ 10 km. We estimated its dust production rate to be Qd ~ 10 kg s−1 at 6.2 au (just after its perihelion passage), resulting in a timescale for the surface blanketing process τB of approximately tens of years, which is very short with respect to typical dynamical lifetime inside the group. Future monitoring of 523676 (2013 UL10) is needed to further constrain the blanketing model for active centaurs and its timescale.

scholarly journals Narrow-band photometry of Long Period Comets with TRAPPIST telescopes in 2019-2020

2020 ◽  
Author(s):  
Youssef Moulane ◽  
Emmanuel Jehin ◽  
Francisco José Pozuelos ◽  
Jean Manfroid ◽  
Zouhair Benkhaldoun ◽  
...  
Keyword(s):  
Solar System ◽  
Production Rate ◽  
Heliocentric Distance ◽  
Narrow Band ◽  
Maximum Activity ◽  
The Sun ◽  
Water Production ◽  
Dust Production ◽  
Long Period ◽  
Water Production Rate

<p>Long Period Comets (LPCs) have orbital periods longer than 200 years, perturbed from their resting place in the Oort cloud. Such gravitational influences may send these icy bodies on a path towards the center of the Solar system in highly elliptical orbits. In this work, we present the activity and composition evolution of several LPCs observed with both TRAPPIST telescopes (TS and TN) during the period of 2019-2020. These comets include: C/2017 T2 (PANSTARRS), C/2018 Y1 (Iwamoto), C/2018 W2 (Africano), and disintegrated comet C/2019 Y4 (ATLAS). We monitored the OH, NH, CN, C<sub>2</sub> and C<sub>3</sub> production rates evolution and their chemical mixing ratios with respect to their distances to the Sun as well as the dust production rate proxy (A(0)fp) during the journey of these comets into the inner Solar system.</p> <p><strong>C/2017 T2 (PANSTARRS)</strong> is a very bright comet which was discovered on October 2, 2017 when it was 9.20 au from the Sun. We started observing this comet with TS at the beginning of August 2019 when it was at 3.70 au. The comet made the closest approach to the Earth on December 28, 2019 at a distance of 1.52 au and it passed the perihelion on May 4, 2020 at 1.61 au. The water production rate of the comet reached a maximum of (4,27±0,12)10<sup>28 </sup>molecules/s and its dust production rate (A(0)fp(RC)) also reached the peak of 5110±25 cm on January 26, 2020, when the comet was at 2.08 au from the Sun (-100 days pre-perihelion). At the time of writing, we still monitoring the activity of the comet with TN at heliocentric distance of 1.70 au. Our observations show that C/2017 T2 is a normal LPC.</p> <p><strong>C/2018 Y1 (Iwamoto)</strong> is a nearly parabolic comet with a retrograde orbit discovered on December 18, 2018 by Japanese amateur astronomer Masayuki Iwamoto. We monitored the activity and composition of Iwamoto with both TN and TS telescopes from January to March 2019. The comet reached its maximum activity on January 29, 2019 when it was at 1.29 au from the Sun (-8 days pre-perihelion) with Q(H<sub>2</sub>O)=(1,68±0,05)10<sup>28 </sup>molecules/s and A(0)fp(RC)= 92±5 cm. These measurements show that it was a dust-poor comet compared to the typical LPCs.</p> <p><strong>C/2018 W2 (Africano) </strong>was discovered on November 27, 2018 at Mount Lemmon Survey with a visual magnitude of 20. The comet reached its perihelion on September 6, 2019 when it was at 1.45 au from the Sun. We monitored the comet from July 2019 (r<sub>h</sub>=1.71 au) to January 2020 (r<sub>h</sub>=2.18 au) with both TN and TS telescopes. The comet reached its maximum activity on September 21, 15 days post-perihelion (r<sub>h</sub>=1.47 au) with Q(H<sub>2</sub>O)=(0,40±0,03)10<sup>28 </sup>molecules/s.</p> <p><strong>C/2019 Y4 (ATLAS)</strong> is a comet with a nearly parabolic orbit discovered on December 18, 2019 by the ATLAS survey. We started to follow its activity and composition with broad- and narrow-band filters with the TN telescope on February 22, 2019 when it was at 1.32 au from the Sun until May 3, 2020 when the comet was at a heliocentric distance of 0.90 au inbound. The comet activity reached a maximum on March 22 (r<sub>h</sub>=1.65 au) 70 days before perihelion. At that time, the water-production rate reached (1,53±0,04)10<sup>28 </sup>molecules/s and the A(0)fp reached (1096±14) cm in the red filter. After that, the comet began to fade and disintegrated into several fragments.</p>

scholarly journals Observations of Type Ia Supernovae and Challenges for Cosmology

2005 ◽  
Vol 192 ◽  
pp. 525-533
Author(s):  
Weidong Li ◽  
Alexei V. Filippenko
Keyword(s):  
Dark Energy ◽  
Light Curve ◽  
Rise Time ◽  
Accelerating Universe ◽  
Type Ia Supernovae ◽  
Hubble Diagram ◽  
High Quality ◽  
Type Ia ◽  
Secondary Parameter ◽  
Ia Supernovae

SummaryObservations of Type Ia supernovae (SNe Ia) reveal correlations between their luminosities and light-curve shapes, and between their spectral sequence and photometric sequence. Assuming SNe Ia do not evolve at different redshifts, the Hubble diagram of SNe Ia may indicate an accelerating Universe, the signature of a cosmological constant or other forms of dark energy. Several studies raise concerns about the evolution of SNe Ia (e.g., the peculiarity rate, the rise time, and the color of SNe Ia at different redshifts), but all these studies suffer from the difficulties of obtaining high-quality spectroscopy and photometry for SNe Ia at high redshifts. There are also some troubling cases of SNe Ia that provide counter examples to the observed correlations, suggesting that a secondary parameter is necessary to describe the whole SN Ia family. Understanding SNe Ia both observationally and theoretically will be the key to boosting confidence in the SN Ia cosmological results.

scholarly journals Estimating the dust production rate of carbon stars in the Small Magellanic Cloud

2017 ◽  
Vol 473 (4) ◽  
pp. 5492-5513 ◽  
Author(s):  
Ambra Nanni ◽  
Paola Marigo ◽  
Léo Girardi ◽  
Stefano Rubele ◽  
Alessandro Bressan ◽  
...  
Keyword(s):  
Production Rate ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Carbon Stars ◽  
Dust Production

A model of dust production in the Neptune ring system

1990 ◽  
Vol 17 (10) ◽  
pp. 1741-1744 ◽  
Author(s):  
Joshua E. Colwell ◽  
Larry W. Esposito
Keyword(s):  
Ring System ◽  
Dust Production

scholarly journals Improved Single Haze Removal using Weighted Filter and Gaussian-Laplacian

2020 ◽  
Vol 8 (2) ◽  
pp. 26-31
Author(s):  
Ajeeta Singh Bhadoria ◽  
Vandana Vikas Thakre
Keyword(s):  
Median Filter ◽  
Depth Map ◽  
Vital Role ◽  
Computer Applications ◽  
Color Channel ◽  
High Quality ◽  
Haze Removal ◽  
Imaging Model ◽  
Laplacian Filter ◽  
Bad Weather

Generally computer applications use digital images. Digital image plays a vital role in the analysis and explanation of data, which is in the digital form. Images and videos of outside scenes are generally affected by the bad weather environment such as haze, fog, mist etc. It will result in bad visibility of the scene caused by the lack of quality. This paper exhibits a study about various image defogging techniques to eject the haze from the fog images caught in true world to recuperate a fast and enhanced nature of fog free images. In this paper, we propose a simple but effective the weighted median (WM) filter was first presented as an overview of the standard median filter, where a nonnegative integer weight is assigned to each position in the filter window image .Gaussian and laplacian pyramids are applying Gaussian and laplacian filter in an image in cascade order with different kernel sizes of gaussian and laplacian filter .The dark channel prior is a type of statistics of the haze-free outdoor images. It is based on a key observation - most local patches in haze-free outdoor images contain some pixels which have very low intensities in at least one-color channel. Using this prior with the haze imaging model, we can directly estimate the thickness of the haze and recover a high-quality haze-free image. Results on a variety of outdoor haze images demonstrate the power of the proposed prior. Moreover, a high-quality depth map can also be obtained as a by-product of haze removal and Calculate the PSNR and MSE of three sample images.

Patient-Reported Outcomes in Sinonasal and Skull Base Malignancy: An Assessment of Study Quality and Clinical Relevance

2020 ◽  
Vol 34 (6) ◽  
pp. 822-829
Author(s):  
Kody G. Bolk ◽  
Kelly A. Roth ◽  
Arun Sharma ◽  
Dana L. Crosby
Keyword(s):  
Quality Of Life ◽  
Skull Base ◽  
Patient Reported Outcomes ◽  
A Priori ◽  
High Quality ◽  
Exclusion Criteria ◽  
Future Studies ◽  
Patient Reported ◽  
Specific Symptoms

Background Sinonasal and skull base malignancies can cause significant adverse effects on functional status and survival. Objective The goal of this study was to systematically review the published literature of patient-reported outcomes pertaining to treatment of sinonasal and skull base malignancy. Methods A systematic literature search of Medline was conducted with PubMed to identify studies that assessed patient-reported outcomes in patients with sinonasal or skull base malignancy. Patient-reported outcomes studies with at least 10 patients published in English from January 2000 to April 2017 were included. Criteria from International Society for Quality of Life guidelines and criteria unique to sinonasal and skull base malignancies were used to calculate a composite score for each article. Studies with the top 33% of scores were categorized as high quality articles. Results Twenty-two articles met inclusion/exclusion criteria. Three studies (14%) reported a priori hypothesis. Eleven (50%) assessed specific quality of life domains and 10 studies (45%) performed statistical analysis on these domains. Specific symptoms were assessed in up to 32% of studies. Eight studies were characterized as high quality; these studies had higher sample sizes and more often assessed patient-reported outcomes prior to treatment compared to low quality studies. Conclusions The goal of the current study was to evaluate the quality of the current patient-reported outcomes literature on sinonasal and skull base malignancies. Areas of improvement for future studies include analysis of individual domains and disease-specific symptoms, reporting a priori hypotheses, and collecting preoperative and longitudinal patient-reported outcomes data.

scholarly journals Comet Kohoutek: Ground and Airborne High Resolution Tilting Filter IR Photometry

1976 ◽  
Vol 25 (Part1) ◽  
pp. 357-360
Author(s):  
C. Barbieri ◽  
C. B. Cosmovici ◽  
S. Drapatz ◽  
K. W. Michel ◽  
T Nishimura ◽  
...  
Keyword(s):  
High Resolution ◽  
Production Rate ◽  
Near Infrared ◽  
Gas Production ◽  
Volatile Components ◽  
The Sun ◽  
Dust Production ◽  
Production Rates ◽  
Fabry Perot ◽  
Vibration Rotation

AbstractBecause of Comet Kohoutek's anticipated large gas production, which seemed to offer a unique chance to reveal parent molecules, two Fabry-Perot Tilting Filter Photometers were designed with the purpose to detect and study the behaviour of CH4 and its photolysis product H2 The importance of these two molecules is well known and their detection would have given valuable indications about the structure of the nucleus, its thermal history and conditions of formation.Similar to CH4, H2 has no dipole moment and cannot be detected by radioastronomy. The most obvious way for measuring H2 in extended cometary comae is certainly on the basis of fluorescence from the Lyman bands around 1000Å, there are, however, vibrational quadrupole transitions within the overtone bands of the ground electronic state which give rise to emissions in the near infrared, accessible by means of ground based telescopes. Three of the stronger lines are: λ = 0.8748 μ; 0.8560 μ and 0.8497 μ. Methane is more readily detectable in the infrared, since it has strong fundamental (1-0) infrared vibration rotation bands at 3.3 μ (ν3).In order to measure both the CH4 concentration and its rotational temperature, a. very high resolution (~3.7A) high throughput instrument was designed which could isolate several individual vibration-rotation lines in the v3 band, namely the P2, P3 and P9 lines. The instrument consisting of a Fabry-Periot Tilting Filter Photometer with InSb detector interfaced with the 30 cm f/30 Dahl-Kirkham Telescope is described in detail elsewhere.( l). The observations were made in January from the NASA Convair 990 (Galileo II) at an altitude of 13 km, where atmospheric methane absorption can be minimized but not avoided. Doppler shift of cometary and atmospheric lines with respect to one another by at least a few A caused by the orbiting velocity of the comet would be sufficient to allow for high transmission measurements. Though long integration time measurements with Lock-In- Amplifier technique have been carried out, no signals from the CH4-rotational lines of the comet coma could be detected. Using the planet Venus as a calibration source for the photon flux and as a result of delicate laboratory measnrements an upper limit ofcould be derived. This value is several orders of magnitude less than the original predictions for Kohoutek during close approach. Therefore, one could conclude that volatile components like CH4 boiled off the comet well before perihelion, at large (~4 AU) distances from the sun and were responsible for the high brightness of the comet at that time. Such a fractionation is only possible if the nucleus was composed of relatively loose, porous ice, rather than compact ice. This hypothesis was strongly supported by the second experiment for search of H2 in the near infrared at the 182 cm telescope of Asiago. Also in this case a Fabry-Perot tilting filter photometer was designed to match with the f/9 optics of the telescope. The instrument (2) consists in a high resolution (~0.7A) tilting filter system with photon counting technique which allows phase-sensitive background subtraction. On the basis of the best data achieved between January 10 and 15 the occurrence of H2-lines with an intensity larger than 2% of the continuum could be excluded, viz. the flux averaged over the field of view was less than 4.105 photons/cm2 sec sr A. Since the pre- and post-perihelion measurements were not affected by molecular fluorescence, they represent only the light scattering flux from dust particles. The data display that the comet's dust coma was definitely brighter during approach than during recession from the sun. However, the quantity of more fundamental interest is the difference in dust production rates, and a derivation of the mass-production rate of dust could be derived. The study shows that both the dust and gas production rate differ greatly in the pre-perihelion period as compared to the post-perihelion period, as conjectured previously for "virgin" comets. (Dust production rate/gas production rate: pre-perihelion 0.1, post-perihelion 1). The pronounced asymmetry in the production rates strongly suggests that fractionation and dust entrainment effects have to be considered in brightness predictions of young comets, the nucleus of which will generally consist of a multi-component mixture of parent molecules.

INTEGRATION OF MASS OPEN ONLINE COURSES IN THE EDUCATIONAL PROCESS OF A PEDAGOGICAL UNIVERSITY

2020 ◽  
Vol 88 (3) ◽  
pp. 111-123
Author(s):  
Ilia V. Kudinov ◽  
◽  
Gulnara F. Kudinova ◽  
Keyword(s):  
Higher Education ◽  
Online Courses ◽  
Human Life ◽  
A Priori ◽  
Learning Technologies ◽  
Educational Process ◽  
Modern World ◽  
High Quality ◽  
Higher Education System

The relevance of the problem stated in the article is due to the fact that the role and functions of higher education institutions is fundamentally changing nowadays. It happens thanks to breakthrough IT solutions in various areas of human life, the development of online learning technologies, and the increased need for fast and highly specialized education. This is primarily due to the demands of the time – the transformation of the modern world economy towards digitalization. The purpose of the work was to obtain objective information about the effectiveness of the use of innovative forms in the educational process of higher education. The implementation of the priority project in the field of education "Modern digital educational environment in the Russian Federation" allowed us to deploy a national Internet platform with the possibility of integrating mass open online courses (MOOCs) into the educational process. This approach has opened up new opportunities for universities to implement online educational programs and use Internet technologies to form individual educational trajectories of students. A priori, the high quality of moocs was declared and, as a result, the high quality of students educational results. However, there were no separate studies on the quality of students' competence formation. The article considers models for organizing the educational process in higher education using mass open online courses, describes the experience of the Bashkir state pedagogical University named after M. Akmulla as a specialized pedagogical university, considers private methods for online and offline training in the higher education system, and presents experimental data on the introduction of online lectures as an element of MOOCs in the educational process of a pedagogical university. The authors as well studied the students' opinions about new forms of education.

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