Follow-up Photometry in Another Band Helps to Reduce Kepler’s False-positive Rates

2021 ◽  
Vol 162 (6) ◽  
pp. 258
Author(s):  
Mu-Tian Wang ◽  
Hui-Gen Liu ◽  
Jiapeng Zhu ◽  
Ji-Lin Zhou
Keyword(s):  
False Positive ◽  
Binary Systems ◽  
False Positives ◽  
Eclipsing Binaries ◽  
Identification Rate ◽  
Transiting Planets ◽  
Secondary Star ◽  
Band Depth ◽  
Depth Feature

Abstract The Kepler mission’s single-band photometry suffers from astrophysical false positives, most commonly of background eclipsing binaries (BEBs) and companion transiting planets (CTPs). Multicolor photometry can reveal the color-dependent depth feature of false positives and thus exclude them. In this work, we aim to estimate the fraction of false positives that cannot be classified by Kepler alone but can be identified from their color-dependent depth feature if a reference band (z, K s , and Transiting Exoplanet Survey Satellite (TESS)) is adopted in follow-up observation. We construct physics-based blend models to simulate multiband signals of false positives. Nearly 65%–95% of the BEBs and more than 80% of the CTPs that host a Jupiter-sized planet will show detectable depth variations if the reference band can achieve a Kepler-like precision. The K s band is most effective in eliminating BEBs exhibiting features of any depth, while the z and TESS bands are better for identifying giant candidates, and their identification rates are more sensitive to photometric precision. Given the radius distribution of planets transiting the secondary star in binary systems, we derive a formalism to calculate the overall identification rate for CTPs. By comparing the likelihood distribution of the double-band depth ratio for BEB and planet models, we calculate the false-positive probability (FPP) for typical Kepler candidates. Additionally, we show that the FPP calculation helps distinguish the planet candidate’s host star in an unresolved binary system. The framework of the analysis in this paper can be easily adapted to predict the multicolor photometric yield for other transit surveys, especially TESS.

scholarly journals The KELT Follow-up Network and Transit False-positive Catalog: Pre-vetted False Positives for TESS

2018 ◽  
Vol 156 (5) ◽  
pp. 234 ◽  
Author(s):  
Karen A. Collins ◽  
Kevin I. Collins ◽  
Joshua Pepper ◽  
Jonathan Labadie-Bartz ◽  
Keivan G. Stassun ◽  
...  
Keyword(s):  
False Positive ◽  
False Positives

scholarly journals Discovery and characterisation of long-period eclipsing binary stars from Kepler K2 campaigns 1, 2, and 3

2018 ◽  
Vol 616 ◽  
pp. A38 ◽  
Author(s):  
P. F. L. Maxted ◽  
R. J. Hutcheon
Keyword(s):  
Binary Stars ◽  
Binary Systems ◽  
Binary Star ◽  
Eclipsing Binaries ◽  
Star Model ◽  
Eclipsing Binary ◽  
Giant Stars ◽  
Long Period ◽  
Eclipsing Binary Stars

Context. The Kepler K2 mission now makes it possible to find and study a wider variety of eclipsing binary stars than has been possible to-date, particularly long-period systems with narrow eclipses. Aims. Our aim is to characterise eclipsing binary stars observed by the Kepler K2 mission with orbital periods longer than P ≈ 5.5 days. Methods. The ellc binary star model has been used to determine the geometry of eclipsing binary systems in Kepler K2 campaigns 1, 2 and 3. The nature of the stars in each binary is estimated by comparison to stellar evolution tracks in the effective temperature – mean stellar density plane. Results. 43 eclipsing binary systems have been identified and 40 of these are characterised in some detail. The majority of these systems are found to be late-type dwarf and sub-giant stars with masses in the range 0.6–1.4 solar masses. We identify two eclipsing binaries containing red giant stars, including one bright system with total eclipses that is ideal for detailed follow-up observations. The bright B3V-type star HD 142883 is found to be an eclipsing binary in a triple star system. We observe a series of frequencies at large multiples of the orbital frequency in BW Aqr that we tentatively identify as tidally induced pulsations in this well-studied eccentric binary system. We find that the faint eclipsing binary EPIC 201160323 shows rapid apsidal motion. Rotational modulation signals are observed in 13 eclipsing systems, the majority of which are found to rotate non-synchronously with their orbits. Conclusions. The K2 mission is a rich source of data that can be used to find long period eclipsing binary stars. These data combined with follow-up observations can be used to precisely measure the masses and radii of stars for which such fundamental data are currently lacking, e.g., sub-giant stars and slowly-rotating low-mass stars.

Variable Star Identification in the BATC Field of M67

2005 ◽  
Vol 277-279 ◽  
pp. 869-875
Author(s):  
Hwihyun Kim ◽  
Yong Ik Byun
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Variable Star ◽  
Open Cluster ◽  
Open Clusters ◽  
Eclipsing Binaries ◽  
Photometric Variability ◽  
Phase Dispersion ◽  
Star Identification

We present the result of photometric variability investigation for stars in the field of M67. The old open cluster M67, one of the most studied open clusters, shows the sign of significant main-sequence binary population in its color-magnitude diagrams. Identification of eclipsing binaries and follow-up studies will enable us to study the nature of binary population in most direct manner. We used approximately 350 images from the BATC (Beijing-Arizona-Taipei-Connecticut) data archive to examine variability within one square degree field centered on M67. A total of 18 stars were classified to be real variables. Our new discoveries include seven eclipsing binary systems of which two are likely to be W UMa systems. All of these variables were found using the phase dispersion minimization (PDM) method developed by Shin and Byun[11].

scholarly journals SuperWASP dispositions and false positive catalogue

2019 ◽  
Vol 488 (4) ◽  
pp. 4905-4915 ◽  
Author(s):  
N Schanche ◽  
A Collier Cameron ◽  
J M Almenara ◽  
K A Alsubai ◽  
D R Anderson ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
False Positive ◽  
Binary Systems ◽  
Pixel Size ◽  
Eclipsing Binary ◽  
La Palma ◽  
Planetary Transits

ABSTRACT SuperWASP, the Northern hemisphere WASP observatory, has been observing the skies from La Palma since 2004. In that time, more than 50 planets have been discovered with data contributions from SuperWASP. In the process of validating planets, many false-positive candidates have also been identified. The TESS telescope is set to begin observations of the northern sky in 2019. Similar to the WASP survey, the TESS pixel size is relatively large (13 arcsec for WASP and 21 arcsec for TESS), making it susceptible to many blended signals and false detections caused principally by grazing and blended stellar eclipsing binary systems. In order to reduce duplication of effort on targets, we present a catalogue of 1 041 Northern hemisphere SuperWASP targets that have been rejected as planetary transits through follow-up observation.

High False Positive Rate with the Use of CT and FDG-PET in Post-Remission Surveillance for Hodgkin Lymphoma.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2327-2327 ◽  
Author(s):  
Dan Zuckerman ◽  
Ann Lacasce ◽  
Eric Jacobsen ◽  
Tak Takvorian ◽  
Ephraim Hochberg
Keyword(s):  
Hodgkin Lymphoma ◽  
False Positive ◽  
Fdg Pet ◽  
Lung Lesion ◽  
False Positives ◽  
Ct Scans ◽  
Second Malignancy ◽  
Pet Ct ◽  
Relapsed Disease

Abstract The role of radiologic surveillance in the follow-up of patients with Hodgkin lymphoma is poorly defined. There is no consensus in the NCCN guidelines regarding the use of CT scans. The use of FDG-PET is discouraged given anecdotal experience with false positives. We have retrospectively analyzed 45 cases of classical Hodgkin lymphoma treated with curative intent at our institutions between 2003 and 2005. All patients received ABVD and had a negative FDG-PET within 6 weeks of completing therapy. Follow-up with surveillance CT scans and PET/CT scans were obtained at the discretion of the treating clinician at 3–6 month intervals for the first 2–3 years of follow-up and then every 6–12 months for the next 2–3 years (median every 6 months). A false positive was defined as a radiologic finding on CT or PET/CT that resulted in either increased frequency of surveillance or medical intervention that was subsequently proven by pathology to be benign or resolved spontaneously on further imaging within 12 months. Of the 45 patients, 29 were women and 16 were men. The median age was 34 (18–71) and the median duration of follow-up was 41 months (12–57 months). Sixteen patients had advanced stage (III or IV) disease. Forty-one (91%) patients are alive and without disease, three patients (7%) are alive with relapsed disease, and one patient (2%) has died from disease. There were 25 patients (56%) for whom scans did not change management; 6 patients (13%) for whom scans revealed relapsed disease (4) or second malignancy (2); and 14 patients (31%) for whom scans proved to be false positives. All 4 relapses were asymptomatic, occurred within 3 to 9 months of completing therapy, and were identified on both CT and PET(3) or CT alone (1). All 4 patients proceeded to salvage chemotherapy and autologous or allogeneic transplantation; one patient died of disease and three have relapsed following transplantation. The 2 second malignancies, which were high-grade sarcomas, were asymptomatic and identified on both CT and PET. Both patients had received XRT and one sarcoma was within the radiation field. There were 17 false positive results identifed in 14 patients during follow-up. Of the 17 false positives, 8 were identified on CT with a normal PET (5 lung lesions, 1 ovarian cyst, 1 retractile testicle and 1 renal cyst), 6 were identified on PET with a normal CT (2 parotid uptakes, 2 thymic “rebounds,” 1 nodal uptake, and 1 splenic uptake), and 3 were identified on CT and PET (1 lung lesion, 1 splenic and hilar adenopathy, and 1 small bowel lesion). The patient with the FDG-avid lung lesion underwent CT-guided FNA of the lesion and bronchoscopy with BAL, both of which were negative. The patient with FDG-avid splenic and hilar nodal lesions underwent splenectomy and was found to have sarcoidosis, from which she has been asymptomatic. In conclusion, there is a high rate of false positives when using CT and/or PET as post-remission surveillance. There were no instances in which PET identified early relapsed disease or second malignancy without corresponding CT findings. In our series, PET had no clinical utility in the surveillance of patients with Hodgkin’s lymphoma in remission.

scholarly journals The quest for stable circumbinary companions to post-common envelope sdB eclipsing binaries

2018 ◽  
Vol 611 ◽  
pp. A48 ◽  
Author(s):  
D. Pulley ◽  
G. Faillace ◽  
D. Smith ◽  
A. Watkins ◽  
S. von Harrach
Keyword(s):  
Binary Systems ◽  
Conclusive Evidence ◽  
Eclipsing Binaries ◽  
Low Mass Stars ◽  
Common Envelope ◽  
Secondary Star ◽  
Complex Processes ◽  
Period Variations ◽  
Low Mass ◽  
Worldwide Network

Context. Period variations have been detected in a number of eclipsing close compact binary subdwarf B stars (sdBs) and these have often been interpreted as being caused by circumbinary massive planets or brown dwarfs. According to canonical binary models, the majority of sdB systems are produced from low mass stars with degenerate cores where helium is ignited in flashes. Various evolutionary scenarios have been proposed for these stars, but a definite mechanism remains to be established. Equally puzzling is the formation of these putative circumbinary objects which must have formed from the remaining post-common envelope circumbinary disk or survived its evolution.Aim. In this paper we review the eclipse time variations (ETVs) exhibited by seven such systems (EC 10246-2707, HS 0705+6700, HS 2231+2441, J08205+0008, NSVS 07826147, NSVS 14256825, and NY Vir) and explore whether there is conclusive evidence that the ETVs observed over the last two decades can reliably predict the presence of one or more circumbinary bodies.Methods. We report 246 new observations of the seven sdB systems made between 2013 September and 2017 July using a worldwide network of telescopes. We combined our new data with previously published measurements to analyse the ETVs of these systems.Results. Our data show that period variations cannot be modelled simply on the basis of circumbinary objects. This implies that more complex processes may be taking place in these systems. These difficulties are compounded by the secondary star not being spectroscopically visible. From ETVs, it has historically been suggested that five of the seven binary systems reported here had circumbinary objects. Based on our recent observations and analysis, only three systems remain serious contenders. We find agreement with other observers that at least a decade of observations is required to establish reliable ephemerides. With longer observational baselines it is quite conceivable that the data will support the circumbinary object hypothesis of these binary systems. Also, we generally agree with other observers that higher values of (O–C) residuals are found with secondary companions of spectral type M5/6 (or possibly earlier as a result of an Applegate type mechanism).

scholarly journals News From The Erebos Project

2017 ◽  
Vol 26 (1) ◽  
Author(s):  
Veronika Schaffenroth ◽  
Brad Barlow ◽  
Stephan Geier ◽  
Maja Vučković ◽  
Dave Kilkenny ◽  
...  
Keyword(s):  
Binary Systems ◽  
Brown Dwarfs ◽  
Eclipsing Binaries ◽  
Current Status ◽  
Red Giants ◽  
Large Program ◽  
Low Mass ◽  
Orbital Periods ◽  
Red Giant

AbstractPlanets and brown dwarfs in close orbits will interact with their host stars, as soon as the stars evolve to become red giants. However, the outcome of those interactions is still unclear. Recently, several brown dwarfs have been discovered orbiting hot subdwarf stars at very short orbital periods of 0.065 - 0.096 d. More than 8% of the close hot subdwarf binaries might have sub-stellar companions. This shows that such companions can significantly affect late stellar evolution and that sdB binaries are ideal objects to study this influence. Thirty-eight new eclipsing sdB binary systems with cool low-mass companions and periods from 0.05 to 0.5 d were discovered based on their light curves by the OGLE project. In the recently published catalog of eclipsing binaries in the Galactic bulge, we discovered 75 more systems. We want to use this unique and homogeneously selected sample to derive the mass distribution of the companions, constrain the fraction of sub-stellar companions and determine the minimum mass needed to strip off the red-giant envelope. We are especially interested in testing models that predict hot Jupiter planets as possible companions. Therefore, we started the EREBOS (Eclipsing Reflection Effect Binaries from the OGLE Survey) project, which aims at analyzing those new HW Vir systems based on a spectroscopic and photometric follow up. For this we were granted an ESO Large Program for ESO-VLT/FORS2. Here we give an update on the the current status of the project and present some preliminary results.

Improving diagnosis of acute appendicitis with atypical findings by Tc-99m HMPAO leukocyte scan

2002 ◽  
Vol 41 (01) ◽  
pp. 37-41 ◽  
Author(s):  
S. Shung-Shung ◽  
S. Yu-Chien ◽  
Y. Mei-Due ◽  
W. Hwei-Chung ◽  
A. Kao
Keyword(s):  
Acute Appendicitis ◽  
False Positive ◽  
False Positive Rate ◽  
Accurate Method ◽  
Clinical Findings ◽  
Pathological Findings ◽  
Lower Quadrant ◽  
Predictive Values ◽  
Positive Rate

Summary Aim: Even with careful observation, the overall false-positive rate of laparotomy remains 10-15% when acute appendicitis was suspected. Therefore, the clinical efficacy of Tc-99m HMPAO labeled leukocyte (TC-WBC) scan for the diagnosis of acute appendicitis in patients presenting with atypical clinical findings is assessed. Patients and Methods: Eighty patients presenting with acute abdominal pain and possible acute appendicitis but atypical findings were included in this study. After intravenous injection of TC-WBC, serial anterior abdominal/pelvic images at 30, 60, 120 and 240 min with 800k counts were obtained with a gamma camera. Any abnormal localization of radioactivity in the right lower quadrant of the abdomen, equal to or greater than bone marrow activity, was considered as a positive scan. Results: 36 out of 49 patients showing positive TC-WBC scans received appendectomy. They all proved to have positive pathological findings. Five positive TC-WBC were not related to acute appendicitis, because of other pathological lesions. Eight patients were not operated and clinical follow-up after one month revealed no acute abdominal condition. Three of 31 patients with negative TC-WBC scans received appendectomy. They also presented positive pathological findings. The remaining 28 patients did not receive operations and revealed no evidence of appendicitis after at least one month of follow-up. The overall sensitivity, specificity, accuracy, positive and negative predictive values for TC-WBC scan to diagnose acute appendicitis were 92, 78, 86, 82, and 90%, respectively. Conclusion: TC-WBC scan provides a rapid and highly accurate method for the diagnosis of acute appendicitis in patients with equivocal clinical examination. It proved useful in reducing the false-positive rate of laparotomy and shortens the time necessary for clinical observation.

scholarly journals SuperWASP variable stars: classifying light curves using citizen science

2021 ◽  
Vol 502 (1) ◽  
pp. 1299-1311
Author(s):  
Heidi B Thiemann ◽  
Andrew J Norton ◽  
Hugh J Dickinson ◽  
Adam McMaster ◽  
Ulrich C Kolb
Keyword(s):  
Variable Stars ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Data Set ◽  
Resultant Data ◽  
Sky Survey ◽  
Short Period ◽  
Contact Binaries ◽  
Analysis Of Results

ABSTRACT We present the first analysis of results from the SuperWASP variable stars Zooniverse project, which is aiming to classify 1.6 million phase-folded light curves of candidate stellar variables observed by the SuperWASP all sky survey with periods detected in the SuperWASP periodicity catalogue. The resultant data set currently contains >1 million classifications corresponding to >500 000 object–period combinations, provided by citizen–scientist volunteers. Volunteer-classified light curves have ∼89 per cent accuracy for detached and semidetached eclipsing binaries, but only ∼9 per cent accuracy for rotationally modulated variables, based on known objects. We demonstrate that this Zooniverse project will be valuable for both population studies of individual variable types and the identification of stellar variables for follow-up. We present preliminary findings on various unique and extreme variables in this analysis, including long-period contact binaries and binaries near the short-period cut-off, and we identify 301 previously unknown binaries and pulsators. We are now in the process of developing a web portal to enable other researchers to access the outputs of the SuperWASP variable stars project.

scholarly journals Train Fast While Reducing False Positives: Improving Animal Classification Performance Using Convolutional Neural Networks

Geomatics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 34-49
Author(s):  
Mael Moreni ◽  
Jerome Theau ◽  
Samuel Foucher
Keyword(s):  
False Positive ◽  
Classification Performance ◽  
Large Datasets ◽  
False Positives ◽  
Fine Tuning ◽  
Training Time ◽  
In The Wild ◽  
Test Sets ◽  
High Level ◽  
Time Decrease

The combination of unmanned aerial vehicles (UAV) with deep learning models has the capacity to replace manned aircrafts for wildlife surveys. However, the scarcity of animals in the wild often leads to highly unbalanced, large datasets for which even a good detection method can return a large amount of false detections. Our objectives in this paper were to design a training method that would reduce training time, decrease the number of false positives and alleviate the fine-tuning effort of an image classifier in a context of animal surveys. We acquired two highly unbalanced datasets of deer images with a UAV and trained a Resnet-18 classifier using hard-negative mining and a series of recent techniques. Our method achieved sub-decimal false positive rates on two test sets (1 false positive per 19,162 and 213,312 negatives respectively), while training on small but relevant fractions of the data. The resulting training times were therefore significantly shorter than they would have been using the whole datasets. This high level of efficiency was achieved with little tuning effort and using simple techniques. We believe this parsimonious approach to dealing with highly unbalanced, large datasets could be particularly useful to projects with either limited resources or extremely large datasets.

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