scholarly journals Multicolour photometry for exoplanet candidate validation

2019 ◽  
Vol 630 ◽  
pp. A89 ◽  
Author(s):  
H. Parviainen ◽  
B. Tingley ◽  
H. J. Deeg ◽  
E. Palle ◽  
R. Alonso ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Radius Ratio ◽  
Alternative Methods ◽  
Contamination Level ◽  
Light Sources ◽  
Rotating Stars ◽  
True Nature ◽  
Stellar Radius ◽  
Astrophysical Source

Context. The TESS and PLATO missions are expected to find vast numbers of new transiting planet candidates. However, only a fraction of these candidates will be legitimate planets, and the candidate validation will require a significant amount of follow-up resources. Radial velocity (RV) follow-up study can be carried out only for the most promising candidates around bright, slowly rotating, stars. Thus, before devoting RV resources to candidates, they need to be vetted using cheaper methods, and, in the cases for which an RV confirmation is not feasible, the candidate’s true nature needs to be determined based on these alternative methods alone. Aims. We study the applicability of multicolour transit photometry in the validation of transiting planet candidates when the candidate signal arises from a real astrophysical source (transiting planet, eclipsing binary, etc.), and not from an instrumental artefact. Particularly, we aim to answer how securely we can estimate the true uncontaminated star-planet radius ratio when the light curve may contain contamination from unresolved light sources inside the photometry aperture when combining multicolour transit observations with a physics-based contamination model in a Bayesian parameter estimation setting. More generally, we study how the contamination level, colour differences between the planet host and contaminant stars, transit signal-to-noise ratio, and available prior information affect the contamination and true radius ratio estimates. Methods. The study is based on simulations and ground-based multicolour transit observations. The contamination analyses were carried out with a contamination model integrated into the PYTRANSIT v2 transit modelling package, and the observations were carried out with the MuSCAT2 multicolour imager installed in the 1.5 m Telescopio Carlos Sanchez in the Teide Observatory, in Tenerife. Results. We show that multicolour transit photometry can be used to estimate the amount of flux contamination and the true radius ratio. Combining the true radius ratio with an estimate for the stellar radius yields the true absolute radius of the transiting object, which is a valuable quantity in statistical candidate validation, and enough in itself to validate a candidate whose radius falls below the theoretical lower limit for a brown dwarf.

scholarly journals MuSCAT2 multicolour validation of TESS candidates: an ultra-short-period substellar object around an M dwarf

2020 ◽  
Vol 633 ◽  
pp. A28 ◽  
Author(s):  
H. Parviainen ◽  
E. Palle ◽  
M. R. Zapatero-Osorio ◽  
P. Montanes Rodriguez ◽  
F. Murgas ◽  
...  
Keyword(s):  
Radius Ratio ◽  
Light Curves ◽  
Reliable Estimate ◽  
Brown Dwarf ◽  
Colour Difference ◽  
Stellar Radius ◽  
Short Period ◽  
Transit Model ◽  
M Dwarf

Context. We report the discovery of TOI 263.01 (TIC 120916706), a transiting substellar object (R = 0.87 RJup) orbiting a faint M3.5 V dwarf (V = 18.97) on a 0.56 d orbit. Aims. We setout to determine the nature of the Transiting Exoplanet Survey Satellite (TESS) planet candidate TOI 263.01 using ground-based multicolour transit photometry. The host star is faint, which makes radial-velocity confirmation challenging, but the large transit depth makes the candidate suitable for validation through multicolour photometry. Methods. Our analysis combines three transits observed simultaneously in r′, i′, and zs bands usingthe MuSCAT2 multicolour imager, three LCOGT-observed transit light curves in g′, r′, and i′ bands, a TESS light curve from Sector 3, and a low-resolution spectrum for stellar characterisation observed with the ALFOSC spectrograph. We modelled the light curves with PYTRANSIT using a transit model that includes a physics-based light contamination component, allowing us to estimate the contamination from unresolved sources from the multicolour photometry. Using this information we were able to derive the true planet–star radius ratio marginalised over the contamination allowed by the photometry.Combining this with the stellar radius, we were able to make a reliable estimate of the absolute radius of the object. Results. The ground-based photometry strongly excludes contamination from unresolved sources with a significant colour difference to TOI 263. Furthermore, contamination from sources of the same stellar type as the host is constrained to levels where the true radius ratio posterior has a median of 0.217 and a 99 percentile of0.286. The median and maximum radius ratios correspond to absolute planet radii of 0.87 and 1.41 RJup, respectively,which confirms the substellar nature of the planet candidate. The object is either a giant planetor a brown dwarf (BD) located deep inside the so-called “brown dwarf desert”. Both possibilities offer a challenge to current planet/BD formation models and make TOI 263.01 an object that merits in-depth follow-up studies.

scholarly journals Velody 2—Resilient High-Capacity MIDI Steganography for Organ and Harpsichord Music

2020 ◽  
Vol 11 (1) ◽  
pp. 39
Author(s):  
Eric Järpe ◽  
Mattias Weckstén
Keyword(s):  
Mean Absolute Error ◽  
Signal To Noise Ratio ◽  
High Capacity ◽  
Absolute Error ◽  
Music Technology ◽  
Alternative Methods ◽  
File Size ◽  
User Friendly ◽  
Different Levels ◽  
Better Than

A new method for musical steganography for the MIDI format is presented. The MIDI standard is a user-friendly music technology protocol that is frequently deployed by composers of different levels of ambition. There is to the author’s knowledge no fully implemented and rigorously specified, publicly available method for MIDI steganography. The goal of this study, however, is to investigate how a novel MIDI steganography algorithm can be implemented by manipulation of the velocity attribute subject to restrictions of capacity and security. Many of today’s MIDI steganography methods—less rigorously described in the literature—fail to be resilient to steganalysis. Traces (such as artefacts in the MIDI code which would not occur by the mere generation of MIDI music: MIDI file size inflation, radical changes in mean absolute error or peak signal-to-noise ratio of certain kinds of MIDI events or even audible effects in the stego MIDI file) that could catch the eye of a scrutinizing steganalyst are side-effects of many current methods described in the literature. This steganalysis resilience is an imperative property of the steganography method. However, by restricting the carrier MIDI files to classical organ and harpsichord pieces, the problem of velocities following the mood of the music can be avoided. The proposed method, called Velody 2, is found to be on par with or better than the cutting edge alternative methods regarding capacity and inflation while still possessing a better resilience against steganalysis. An audibility test was conducted to check that there are no signs of audible traces in the stego MIDI files.

scholarly journals Search for dormant black holes in ellipsoidal variables III. The OGLE BULGE short-period sample

2021 ◽  
Author(s):  
Roy Gomel ◽  
Simchon Faigler ◽  
Tsevi Mazeh ◽  
Michał Pawlak
Keyword(s):  
Main Sequence ◽  
Compact Object ◽  
Close Binaries ◽  
Periodic Modulation ◽  
Mass Ratio ◽  
True Nature ◽  
The Third ◽  
Short Period ◽  
Actual Mass

Abstract This is the third of a series of papers that presents an algorithm to search for close binaries with massive, possibly compact, unseen secondaries. The detection of such a binary is based on identifying a star that displays a large ellipsoidal periodic modulation, induced by tidal interaction with its companion. In the second paper of the series we presented a simple approach to derive a robust modified minimum mass ratio (mMMR), based on the observed ellipsoidal amplitude, without knowing the primary mass and radius, assuming the primary fills its Roche lobe. The newly defined mMMR is always smaller than the actual mass ratio. Therefore, a binary with an mMMR larger than unity is a good candidate for having a massive secondary, which might be a black hole or a neutron star. This paper considers 10,956 OGLE short-period ellipsoidals observed towards the Galactic Bulge. We re-analyse their modulation and identify 136 main-sequence systems with mMMR significantly larger than unity as candidates for having compact-object secondaries, assuming their observed periodic modulations reflect indeed the ellipsoidal effect. Obviously, one needs follow-up observations to find out the true nature of these companions.

scholarly journals Recent Results on Abundance Determinations

1993 ◽  
Vol 138 ◽  
pp. 27-41
Author(s):  
Saul J. Adelman
Keyword(s):  
Signal To Noise Ratio ◽  
Model Atmosphere ◽  
Bulletin Board ◽  
High Signal ◽  
Rotating Stars ◽  
Signal To Noise ◽  
Peculiar Stars ◽  
Noise Data ◽  
Noise Ratio ◽  
Moving Groups

AbstractI review abundance determinations of normal B5-F4 and peculiar stars published since 1984. Several analyses performed with photographic spectrograms indicate interesting stars which should be analyzed with high signal-to-noise data. Studies of stars of known ages which belong to clusters, associations, and moving groups should led to the most direct confrontations with theory. The increase in signal-to-noise ratio provided by electronic detectors with respect to photographic plates should allow accurate analyses of moderating rotating stars. High resolution, high signal-to-noise ratio studies have revealed crucial information about the line profiles of Sirius, Vega, and other A stars. It would aid comparison of analyses if we could agree on a standard set of gf-values and line damping constants. A computer bulletin board would be a useful means to provide and maintain such data as well as model atmosphere codes.

Long-term Outcomes of Clip Coupler Implantation in Patients with Unilateral Congenital Aural Atresia

2020 ◽  
Vol 129 (12) ◽  
pp. 1221-1228
Author(s):  
Chunli Zhao ◽  
Jinsong Yang ◽  
Yujie Liu ◽  
Mengdie Gao ◽  
Peiwei Chen ◽  
...  
Keyword(s):  
Speech Intelligibility ◽  
Signal To Noise Ratio ◽  
Bone Conduction ◽  
Free Field ◽  
Short Term ◽  
Aural Atresia ◽  
Long Term Follow Up ◽  
Congenital Aural Atresia

Objective: To evaluate the long-term safety and efficacy of the Clip coupler attached to the stapes head in patients with unilateral congenital aural atresia (CAA). Methods: This single-center retrospective study included 16 Mandarin-speaking patients who had unilateral microtia accompanied by CAA. All patients were divided into two groups: the short-term follow-up group (n = 9) and the long-term follow-up group (n = 7). The floating mass transducer of the Vibrant Soundbridge (VSB) was positioned in the stapes head by the Clip coupler. The safety of the VSB was investigated by comparing preoperative and postoperative bone-conduction (BC) thresholds as well as by complications. The effectiveness was evaluated by functional gain (FG), word recognition score (WRS), speech reception threshold (SRT) and signal-to-noise ratio (SNR). Results: Pre- and post-operative BC thresholds were no different in all patients. And no complications developed. VSB-aided thresholds in the free-field had improved significantly in both short- and long-term follow-up groups. The improvements of WRS were observed in two groups. The monosyllabic VSB-aided WRS in the long-term follow-up group was significantly higher than that in the short-term follow-up group. When speech was from the impaired ear and noise presented to the side of normal ear (SVSBNCL), lower SNRs were found in two groups after VSB implantation. However, there was no statistical difference in aided SNR between the two groups at SVSBNCL status. Conclusions: Our results show that the FMT connected to the stapes head is a secure and useful device for patients with unilateral CHL/MHL, not only in terms of improved hearing thresholds, but also improved speech intelligibility in quiet and noisy environments.

Evaluation of a tertiary and district general hospital menopause service

2020 ◽  
pp. 205336912094762
Author(s):  
Kristyn M Manley ◽  
T Hillard ◽  
D Holloway ◽  
D Bruce ◽  
J Rymer
Keyword(s):  
Primary Care ◽  
Hormone Replacement ◽  
Treatment Options ◽  
Treatment Resistance ◽  
District General Hospital ◽  
Behavioural Therapy ◽  
Alternative Methods ◽  
Require Time ◽  
Co Morbidity

Objective Requests for management of menopausal symptoms and hormone replacement are increasing in the UK. Referrals to specialist clinics have to be balanced with increasing recommendations within the NHS to improve efficiency and patient care. Study design Retrospective evaluation of clinic records over two months at a district general (Poole Hospital) and tertiary (Guy’s Hospital) menopause service. Data on referral origin, reason for referral, interval from referral to review and outcome were collected and compared between trusts. Main outcome measures To evaluate and compare referrals and outcomes in a tertiary and district general menopause service and provide recommendations for improving efficiency. Results Most referrals are from primary care but up to 25% are from other specialties. Half of the appointments are new referrals and 95% of women attend. Of the new referrals, 50% have multiple medical comorbidities, 25% a personal or family history of cancer and 25% treatment resistance; 30% have premature ovarian insufficiency. At Guy’s Hospital, 30% are reviewed more than 18 weeks after referral, at Poole Hospital this is 6%. Treatment resistance is reported in half of the women reviewed at follow-up. Conclusions Menopause services review a complex patient population and the majority of referred women have more than one co-morbidity; they require time, specialist knowledge of current treatment options and a multidisciplinary approach. The main barrier to service efficiency is capacity, particularly in population dense areas; cognitive behavioural therapy and non-hormonal methods appear under-utilised in primary care, as do alternative methods of follow-up within the clinics such as telephone and patient-initiated appointments.

scholarly journals SLE clinical trials: impact of missing data on estimating treatment effects

2019 ◽  
Vol 6 (1) ◽  
pp. e000348 ◽  
Author(s):  
Mimi Kim ◽  
Joan T Merrill ◽  
Cuiling Wang ◽  
Shankar Viswanathan ◽  
Ken Kalunian ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Missing Data ◽  
Multiple Imputation ◽  
Treatment Effects ◽  
Standard Of Care ◽  
Response Rates ◽  
Alternative Methods ◽  
Loss To Follow Up ◽  
Collective Data

ObjectiveA common problem in clinical trials is missing data due to participant dropout and loss to follow-up, an issue which continues to receive considerable attention in the clinical research community. Our objective was to examine and compare current and alternative methods for handling missing data in SLE trials with a particular focus on multiple imputation, a flexible technique that has been applied in different disease settings but not to address missing data in the primary outcome of an SLE trial.MethodsData on 279 patients with SLE randomised to standard of care (SoC) and also receiving mycophenolate mofetil (MMF), azathioprine or methotrexate were obtained from the Lupus Foundation of America-Collective Data Analysis Initiative Database. Complete case analysis (CC), last observation carried forward (LOCF), non-responder imputation (NRI) and multiple imputation (MI) were applied to handle missing data in an analysis to assess differences in SLE Responder Index-5 (SRI-5) response rates at 52 weeks between patients on SoC treated with MMF versus other immunosuppressants (non-MMF).ResultsThe rates of missing data were 32% in the MMF and 23% in the non-MMF groups. As expected, the NRI missing data approach yielded the lowest estimated response rates. The smallest and least significant estimates of differences between groups were observed with LOCF, and precision was lowest with the CC method. Estimated between-group differences were magnified with the MI approach, and imputing SRI-5 directly versus deriving SRI-5 after separately imputing its individual components yielded similar results.ConclusionThe potential advantages of applying MI to address missing data in an SLE trial include reduced bias when estimating treatment effects, and measures of precision that properly reflect uncertainty in the imputations. However, results can vary depending on the imputation model used, and the underlying assumptions should be plausible. Sensitivity analysis should be conducted to demonstrate robustness of results, especially when missing data proportions are high.

Twelve cases of glottic carcinoma in situ treated by radiotheraphy: an observation on clinical course versus response

1993 ◽  
Vol 107 (11) ◽  
pp. 1014-1016 ◽  
Author(s):  
J. P. Brooks ◽  
D. W. Morgan ◽  
J. Glaholm
Keyword(s):  
Carcinoma In Situ ◽  
Clinical Course ◽  
Alternative Methods ◽  
Glottic Carcinoma ◽  
Methods Of Treatment ◽  
Disease Free ◽  
Long Term Studies

AbstractCarcinoma in Situ (CIS) of the glottis is an uncommon and poorly understood condition with few, large, long- term studies. Twelve cases are presented which were treated with radiotherapy. At three-year follow-up all the patients are disease free and in 83 per cent the mucosa has returned to normal. The alternative methods of treatment are discussed.

CT follow-up in patients with neuroendocrine tumors (NETs): combined radiation and contrast dose reduction

2017 ◽  
Vol 59 (5) ◽  
pp. 517-526 ◽  
Author(s):  
G Böning ◽  
JF Kahn ◽  
D Kaul ◽  
R Rotzinger ◽  
P Freyhardt ◽  
...  
Keyword(s):  
Image Quality ◽  
Contrast Agent ◽  
Dose Reduction ◽  
Neuroendocrine Tumors ◽  
Signal To Noise Ratio ◽  
Low Grade ◽  
Diagnostic Confidence ◽  
Reduction Techniques ◽  
Applied Dose

Background Frequent computed tomography (CT) follow-ups involve significant radiation related risks for patients with low-grade neuroendocrine tumors (NETs). Contrast agent (CA) application is essential for diagnostic evidence and has additional risks especially in patients with limited renal function. Purpose To investigate if a combination of dose and contrast agent (CA) reduction affects image quality and diagnostic evidence in neuroendocrine tumor (NET) patients. Material and Methods A total of 51 NET patients were enrolled in the study and 153 CT scans were analyzed. Patients underwent a baseline CT scan (A = 120 kVp, filtered back projection [FBP]) and two follow-up CTs (B = 120 kVp, adaptive statistical iterative reconstruction [ASIR] 40%; C1 = 100 kVp, ASIR 40%; C2 = 100 kVp, ASIR 60%; the latter two protocols were applied with a 30% reduction in CA volume). We evaluated image quality and applied dose. Results In C1/2, the combination of low kV (100 kVp) with ASIR 40%/60% reduced the mean applied dose significantly by 28% compared to B and by 57% compared to A. Signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR) of tumor to liver/muscle were significantly increased by using C1/2 compared to B and A. With respect to subjective image quality, a slight loss of diagnostic confidence in C1 could be counterbalanced by the higher ASIR blending in C2. Conclusion Combined dose reduction techniques can be used to reduce radiation dose and CA volume without sacrificing image quality and diagnostic confidence in staging CT of NET patients.

scholarly journals Design and performance of a three-wavelength LED-based total scatter and backscatter integrating nephelometer

2010 ◽  
Vol 3 (6) ◽  
pp. 4835-4864 ◽  
Author(s):  
T. Müller ◽  
M. Laborde ◽  
G. Kassell ◽  
A. Wiedensohler
Keyword(s):  
Signal To Noise Ratio ◽  
Ambient Air ◽  
Light Sources ◽  
Light Emitting ◽  
Sensitivity Functions ◽  
A Value ◽  
Commercial Instrument ◽  
And Performance ◽  
Comparison Measurements

Abstract. Integrating nephelometers are instruments that directly measure a value close to the light scattering coefficient of airborne particles. Different models of nephelometers have been used for decades for monitoring and research applications. Now, a series of nephelometers (Ecotech models M9003, Aurora 1000 and Aurora 3000) with newly designed light sources based on light emitting diodes are available. This article reports on the design of these integrating nephelometers and a comparison of the Aurora 3000 to another commercial instrument (TSI model 3563) that uses an incandescent lamp. Both instruments are three-wavelength, total and backscatter integrating nephelometers. We present a characterization of the new light source design of the Aurora 3000 and provide parameterizations for its angular sensitivity functions. These parameterizations facilitate to correct for measurement artefacts using Mie-theory. Comparison measurements against the TSI 3563 with laboratory generated white particles and ambient air are shown and discussed. Both instruments agree well within the calibration uncertainties and detection limit for total scattering with differences less than 5%. Differences for backscattering are higher by up to 11%. Highest differences were found for the longest wavelengths, where the signal to noise ratio is lowest. Differences at the blue and green wavelengths are less than 4% and 3%, respectively, for both total and backscattering.

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