scholarly journals CHEOPS precision phase curve of the Super-Earth 55 Cancri e

2021 ◽  
Vol 653 ◽  
pp. A173
Author(s):  
B. M. Morris ◽  
L. Delrez ◽  
A. Brandeker ◽  
A. C. Cameron ◽  
A. E. Simon ◽  
...  
Keyword(s):  
Optical Filter ◽  
Phase Variation ◽  
Optical Observations ◽  
Phase Curve ◽  
Time Varying ◽  
Optical Telescope ◽  
Circumstellar Material ◽  
Effective Aperture ◽  
Phase Variations ◽  
Photometric Monitoring

Context. 55 Cnc e is a transiting super-Earth (radius 1.88 R⊕ and mass 8 M⊕) orbiting a G8V host star on a 17-h orbit. Spitzer observations of the planet’s phase curve at 4.5 μm revealed a time-varying occultation depth, and MOST optical observations are consistent with a time-varying phase curve amplitude and phase offset of maximum light. Both broadband and high-resolution spectroscopic analyses are consistent with either a high mean molecular weight atmosphere or no atmosphere for planet e. A long-term photometric monitoring campaign on an independent optical telescope is needed to probe the variability in this system. Aims. We seek to measure the phase variations of 55 Cnc e with a broadband optical filter with the 30 cm effective aperture space telescope CHEOPS and explore how the precision photometry narrows down the range of possible scenarios. Methods. We observed 55 Cnc for 1.6 orbital phases in March of 2020. We designed a phase curve detrending toolkit for CHEOPS photometry which allowed us to study the underlying flux variations in the 55 Cnc system. Results. We detected a phase variation with a full-amplitude of 72 ± 7 ppm, but did not detect a significant secondary eclipse of the planet. The shape of the phase variation resembles that of a piecewise-Lambertian; however, the non-detection of the planetary secondary eclipse, and the large amplitude of the variations exclude reflection from the planetary surface as a possible origin of the observed phase variations. They are also likely incompatible with magnetospheric interactions between the star and planet, but may imply that circumplanetary or circumstellar material modulate the flux of the system. Conclusions. This year, further precision photometry of 55 Cnc from CHEOPS will measure variations in the phase curve amplitude and shape over time.

Progress cargo spacecraft observed with the AZT-33IK optical telescope

2016 ◽  
Vol 2 (3) ◽  
pp. 17-23 ◽  
Author(s):  
Евгений Клунко ◽  
Evgeny Klunko ◽  
Максим Еселевич ◽  
Maxim Eselevich ◽  
Владимир Тергоев ◽  
...  
Keyword(s):  
Object Tracking ◽  
Measuring Equipment ◽  
Outer Space ◽  
Measurement Techniques ◽  
Solar Observatory ◽  
Space Experiment ◽  
Optical Observations ◽  
Optical Telescope ◽  
Physical Conditions ◽  
Optical Phenomena

In this paper, we describe a telescope and measuring equipment used for optical observations of Progress cargo spacecraft (PCS), which were made during Radar–Progress space experiment sessions. We also describe object tracking and measurement techniques. The observations were made with the optical telescope AZT-33IK at Sayan Solar Observatory of ISTP SB RAS. During many of the sessions, we registered optical phenomena that occurred in regions of space surrounding PCS and appeared due to the work of PCS onboard engines. The data we obtained can be used to independently control the geometry of the experiment and to analyze physical conditions in outer space.

The effect of phase variations and cross-shear on vortical structures in a plane mixing layer

1994 ◽  
Vol 276 ◽  
pp. 21-59 ◽  
Author(s):  
Kris J. Nygaard ◽  
Ari Glezer
Keyword(s):  
Shear Layer ◽  
Phase Distribution ◽  
Surface Film ◽  
Transverse Velocity ◽  
Excitation Frequency ◽  
Phase Variation ◽  
Two Dimensional ◽  
Oblique Waves ◽  
Phase Variations ◽  
Secondary Vortices

The evolution of spanwise phase variations of nominally two-dimensional instability modes in a plane shear layer is studied in a closed-return water facility using time-harmonic excitation having spanwise-non-uniform phase or frequency distributions. The excitation waveform is synthesized by a linear array of 32 surface film heaters flush-mounted on the flow partition. A span wise-linear phase distribution leads to the excitation of oblique waves and to the rollup of oblique primary vortices. When the prescribed phase distribution is piecewise-constant and spanwise-periodic, the flow is excited with a linear combination of a two-dimensional wavetrain and pairs of equal and opposite oblique waves, the amplitudes of which depend on the magnitude of the phase variation ΔΦ. As a result of the excitation, the primary vortices undergo spanwise-non-uniform rollup and develop spanwise-periodic deformations that induce cross-shear and secondary vortices in the braid region. The amplitude of the deformations of the primary vortices and the shape and strength of the secondary vortices depend on the magnitude of ΔΦ. When ΔΦ is small, the secondary vortices are counter-rotating vortex pairs. As ΔΦ increases, cross-shear induced by oblique segments of the primary vortices in the braid region results in the formation of single secondary vortex strands. The flow is not receptive to spanwise phase variations with wavelengths shorter than the streamwise wavelength of the Kelvin–Helmholtz instability. When the phase variation is ΔΦ = ϕ, the flow is excited with pairs of oblique waves only and undergoes a double rollup, resulting in the formation of spanwise-deformed vortices at twice the excitation frequency. Measurements of the streamwise velocity component show that the excitation leads to a substantial increase in the cross-stream spreading of the shear layer and that distortions of transverse velocity profiles are accompanied by an increase in the high-frequency content of velocity power spectra. Detailed schlieren visualizations shed light on the nature of ‘vortex dislocations’ previously observed by other investigators. Complex spanwise-non-uniform pairing interactions between the spanwise vortices are forced farther downstream by spanwise-amplitude or phase variations of subharmonic excitation wavetrains.

Experimental determination of electric-field-induced differences in structure-factor phases of the order of 2%

1999 ◽  
Vol 55 (6) ◽  
pp. 1034-1037 ◽  
Author(s):  
J. Stahn ◽  
A. Pucher ◽  
U. Pietsch ◽  
J. Zellner ◽  
E. Weckert
Keyword(s):  
Electric Field ◽  
Structure Factor ◽  
Phase Variation ◽  
Bonded Materials ◽  
Charge Model ◽  
Covalently Bonded ◽  
Phase Variations ◽  
Bond Charge ◽  
Semi Empirical

In order to understand the induced electron-density response of covalently bonded materials to an externally applied electric field, the change of structure-factor phases of several weak reflections of GaAs has been measured by three-beam interferences. Using a modulation technique, phase variations of the order of 1° for a field strength of 1 kV mm−1 were determined. Although the statistics of these first experiments are rather poor, the experiment verifies qualitatively the predictions of a semi-empirical bond-charge model. The measured phase variation is the smallest value determined up to now.

scholarly journals AT 2019abn: multi-wavelength observations over the first 200 days

2020 ◽  
Vol 637 ◽  
pp. A20 ◽  
Author(s):  
S. C. Williams ◽  
D. Jones ◽  
P. Pessev ◽  
S. Geier ◽  
R. L. M. Corradi ◽  
...  
Keyword(s):  
Light Curve ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Absolute Magnitude ◽  
Low Velocity ◽  
Optical Telescope ◽  
Circumstellar Material ◽  
Medium Resolution ◽  
Multi Wavelength ◽  
Optical Light Curve

Context. AT 2019abn was discovered in the nearby M51 galaxy by the Zwicky Transient Facility at more than two magnitudes and around three weeks prior to its optical peak. Aims. We aim to conduct a detailed photometric and spectroscopic follow-up campaign for AT 2019abn, with early discovery allowing for significant pre-maximum observations of an intermediate luminosity red transient (ILRT) for the first time. Methods. This work is based on the analysis of u′BVr′i′z′H photometry and low-resolution spectroscopy using the Liverpool Telescope, medium-resolution spectroscopy with the Gran Telescopio Canarias (GTC), and near-infrared imaging with the GTC and the Nordic Optical Telescope. Results. We present the most detailed optical light curve of an ILRT to date, with multi-band photometry starting around three weeks before peak brightness. The transient peaked at an observed absolute magnitude of Mr′ = −13.1, although it is subject to significant reddening from dust in M51, implying an intrinsic Mr′ ∼ −15.2. The initial light curve showed a linear, achromatic rise in magnitude before becoming bluer at peak. After peak brightness, the transient gradually cooled. This is reflected in our spectra, which at later times show absorption from such species as Fe I, Ni I and Li I. A spectrum taken around peak brightness shows narrow, low-velocity absorption lines, which we interpret as likely to originate from pre-existing circumstellar material. Conclusions. We conclude that while there are some peculiarities, such as the radius evolution, AT 2019abn fits in well overall with the ILRT class of objects and is the most luminous member of the class seen to date.

scholarly journals Phase Variations of the Mycoplasma penetrans Main Surface Lipoprotein Increase Antigenic Diversity

1999 ◽  
Vol 67 (4) ◽  
pp. 1569-1578 ◽  
Author(s):  
Olivier Neyrolles ◽  
Isabelle Chambaud ◽  
Stéphane Ferris ◽  
Marie-Christine Prevost ◽  
Tsuguo Sasaki ◽  
...  
Keyword(s):  
Point Mutations ◽  
Phase Variation ◽  
Antigen Expression ◽  
Polyclonal Antiserum ◽  
Humoral Immune ◽  
Immunodeficiency Virus ◽  
Surface Antigen Expression ◽  
Major Antigen ◽  
Phase Variations ◽  
Triton X

ABSTRACT Mycoplasma penetrans is a recently identified mycoplasma, isolated from urine samples collected from human immunodeficiency virus (HIV)-infected patients. Its presence is significantly associated with HIV infection. The major antigen recognized during natural and experimental infections is an abundant P35 lipoprotein which, upon extraction, segregates in the Triton X-114 detergent phase and is the basis of M. penetrans-specific serological assays. We report here that the P35 antigen undergoes spontaneous and reversible phase variation at high frequency, leading to heterogeneous populations of mycoplasmas, even when derived from a clonal lineage. This variation was found to be determined at the transcription level, and although this property is not unique among the members of the class Mollicutes, the mechanism by which it occurs in M. penetrans differs from those previously described for other Mycoplasma species. Indeed, the P35 phase variation was due neither to a p35 gene rearrangement nor to point mutations within the gene itself or its promoter. The P35 phase variation in the different variants obtained was concomitant with modifications in the pattern of other expressed lipoproteins, probably due to regulated expression of selected members of a gene family which was found to potentially encode similar lipoproteins. M. penetrans variants could be selected on the basis of their lack of colony immunoreactivity with a polyclonal antiserum against a Triton X-114 extract, strongly suggesting that the mechanisms involved in altering surface antigen expression might allow evasion of the humoral immune response of the infected host.

scholarly journals Characterising phase variations in MALDI-TOF data and correcting them by peak alignment

2005 ◽  
Vol 1 ◽  
pp. 117693510500100 ◽  
Author(s):  
Simon M Lin ◽  
Richard P Haney ◽  
Michael J Campa ◽  
Michael C Fitzgerald ◽  
Edward F Patz
Keyword(s):  
Data Analysis ◽  
Phase Variation ◽  
Principal Component ◽  
Microarray Data Analysis ◽  
Alignment Algorithm ◽  
Data Set ◽  
Peak Alignment ◽  
Maldi Tof ◽  
Biological Interest ◽  
Phase Variations

The use of MALDI-TOF mass spectrometry as a means of analyzing the proteome has been evaluated extensively in recent years. One of the limitations of this technique that has impeded the development of robust data analysis algorithms is the variability in the location of protein ion signals along the x-axis. We studied technical variations of MALDI-TOF measurements in the context of proteomics profiling. By acquiring a benchmark data set with five replicates, we estimated 76% to 85% of the total variance is due to phase variation. We devised a lobster plot, so named because of the resemblance to a lobster claw, to help detect the phase variation in replicates. We also investigated a peak alignment algorithm to remove the phase variation. This operation is analogous to the normalization step in microarray data analysis. Only after this critical step can features of biological interest be clearly revealed. With the help of principal component analysis, we demonstrated that after peak alignment, the differences among replicates are reduced. We compared this approach to peak alignment with a model-based calibration approach in which there was known information about peaks in common among all spectra. Finally, we examined the potential value at each point in an analysis pipeline of having a set of methods available that includes parametric, semiparametric and nonparametric methods; among such methods are those that benefit from the use of prior information.

scholarly journals Phase Variation Measurement in Mach–Zehnder Interferometric Switch

2021 ◽  
Vol 21 (6) ◽  
pp. 180-184
Author(s):  
Sichen Fan ◽  
Jun Ruan ◽  
Dandan Liu ◽  
Xinliang Wang ◽  
Fan Yang ◽  
...  
Keyword(s):  
Extinction Ratio ◽  
Phase Fluctuation ◽  
Phase Variation ◽  
Transient Effects ◽  
Rf Switch ◽  
Phase Fluctuations ◽  
Phase Variations ◽  
Ramsey Type ◽  
Lock In ◽  
Better Than

Abstract Phase variations of the interrogation field lead to frequency shifts in Ramsey-type atomic clocks. This paper reports the development of a 300 MHz Mach–Zehnder (MZ) switch that effectively suppresses phase-transient effects. Similar to MZ interferometers, this radio-frequency (RF) MZ switch comprises two arms that are power- and phase-matched with each other. By inserting a PIN diode RF switch in one arm, the other arm remains undisturbed, freeing it of the phase transient. Trigger phase fluctuation measurements are implemented by using a lock-in amplifier to extract the in-phase and quadrature (I/Q) demodulation data. The results show that the extinction ratio of the RF MZ switch phase fluctuations is <5 μrad, which is significantly lower than that of a PIN (50 μrad). When applied to a cesium fountain clock, the RF MZ switch produces a frequency shift better than 1.73 × 10−16.

scholarly journals Optical observations of comet 67P/Churyumov-Gerasimenko with the Nordic Optical Telescope

2015 ◽  
Vol 583 ◽  
pp. A10 ◽  
Author(s):  
B. Zaprudin ◽  
H. J. Lehto ◽  
K. Nilsson ◽  
T. Pursimo ◽  
A. Somero ◽  
...  
Keyword(s):  
Optical Observations ◽  
Optical Telescope ◽  
Comet 67P

scholarly journals Reference Phase Stabilizer for Distributed Underwater Sonar Systems

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4279
Author(s):  
Lijie Yang ◽  
Ruirui Dang ◽  
Chunyi Song ◽  
Zhiwei Xu
Keyword(s):  
Clock Synchronization ◽  
Phase Error ◽  
Phase Variation ◽  
Phase Shifters ◽  
Sensor Nodes ◽  
Detection Accuracy ◽  
Sonar Systems ◽  
Phase Variations ◽  
The Impact ◽  
Central Station

An optical fiber is a promising approach for data and clock transmission in distributed underwater sonar systems. However, synchronization is a critical challenge in distributed sonar systems, which mandates accurate clock synchronization down to a sub degree. Potential phase misalignment is caused by fiber length variations. In this paper, we propose a fiber-based phase stabilizer method to achieve accurate clock synchronization among sensor nodes. We use fiber-based feedback loop between sensor nodes and central station unit to monitor phase variations. Subsequently, we leverage phase shifters symmetrically arranged on the forward lane and feedback lane to compensate real-time phase variation and maintain high-precision synchronization. Besides, an ambiguity eliminator circuit is designed to remove the clock’s cyclic ambiguity. Both analysis and experimental results suggest that the proposed phase stabilizer can achieve 10 MHz reference clock synchronization within 0.4 degree. We also analyze the impact of the reference clock’s phase error on the system range detection accuracy, which indicates that the proposed phase stabilizer can greatly improve detection accuracy of sonar systems.

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