scholarly journals A Study of the Short-Period Cepheid EU Tauri

1985 ◽  
Vol 82 ◽  
pp. 98-99
Author(s):  
W. P. Gieren
Keyword(s):  
Light Curve ◽  
Velocity Curve ◽  
Radial Velocities ◽  
Correlation Technique ◽  
Fourier Decomposition ◽  
Classical Cepheid ◽  
Photometric Observations ◽  
Short Period ◽  
Johnson System ◽  
Better Than

EU Tauri is a classical Cepheid with one of the shortest period known. A Fourier decomposition study of its V light curve by Simon S Lee (1981) revealed a peculiar position in phase-period diagrams, very similar to the star SU Cas which is probably an overtone pulsator (Gieren, 1982). This suggested the possibility that EU Tau might be another galactic overtone pulsator. In order to investigate this question, some 100 new photometric observations of this star on the UBVRI (Johnson) system were obtained with the #2 0.9m telescope of KPNO. Simultaneously, 43 CCD spectra of the star were secured on the Coudé feed telescope of KPNO which were measured for radial velocities using a correlation technique. These velocities have an internal accuracy of better than 0.5 km/s and define a complete velocity curve of EU Tau.

scholarly journals Kinematics of Short-Period Mira Variables - A Progress Report

1989 ◽  
Vol 106 ◽  
pp. 56-56
Author(s):  
J. Hron
Keyword(s):  
Stellar Populations ◽  
Progress Report ◽  
Radial Velocities ◽  
Correlation Technique ◽  
Echelle Spectrograph ◽  
Mira Variables ◽  
Short Period ◽  
First Results ◽  
Visual Magnitude

First results of an observing program recently started at the Figl Observatory for Astrophysics, Austria, are presented. Radial velocities derived by a correlation technique from the TiO bandheads near 7050 Å will be used to identify the stellar populations present among the short period (P ≤ 200d) Mira variables. From the first observations with the Reticon-equipped Echelle Spectrograph of the FOA (resolution 0.3 Å at 7000 Å) we conclude that for Mira stars with a limiting visual magnitude of about 10m velocities can be determined with an external accuracy of 6 km/s.

scholarly journals Observations and light curve solutions of the eclipsing binaries KR Lyn, CSS J110212+244412, NSVS 4917488 and NSVS 7336024

2018 ◽  
pp. 21-27 ◽  
Author(s):  
D. Kjurkchieva ◽  
V.A. Popov ◽  
J. Eneva ◽  
N. Petrov
Keyword(s):  
Light Curve ◽  
Eclipsing Binaries ◽  
Type Star ◽  
Eclipsing Stars ◽  
Photometric Observations ◽  
Short Period

We present photometric observations in Sloan filters g?, i? of the short-period eclipsing stars KR Lyn, CSS J110212+244412, NSVS 4917488 and NSVS 7336024. The light curve solutions revealed that all targets are overcontact binaries whose components are G and K stars. Their temperature differences do not exceed 300 K but they differ considerably in size and mass. NSVS 4917488 and NSVS 7336024 reveal total eclipses and their parameters can be considered as well-determined. We found that KR Lyn, NSVS 4917488 and NSVS 7336024 are of W-subtype while CSS J110212+244412 is A-subtype W UMa-type star.

scholarly journals Observations and light curve solutions of the eclipsing binaries USNO-B1.0 1395-0370184 and USNO-B1.0 1395-0370731

2016 ◽  
pp. 27-32 ◽  
Author(s):  
D. Kjurkchieva ◽  
V.A. Popov ◽  
D. Vasileva ◽  
N. Petrov
Keyword(s):  
Light Curve ◽  
Eclipsing Binaries ◽  
Eclipsing Stars ◽  
System P ◽  
Photometric Observations ◽  
Short Period ◽  
Orbital Periods ◽  
Period System

We present follow-up photometric observations in Sloan filters g', i' of the newly discovered eclipsing stars USNO-B1.0 1395-0370184 and USNO-B1.0 1395-0370731. Our data revealed that their orbital periods are considerably bigger than the previous values. This result changed the classification of USNO-B1.0 1395-0370184 from ultrashort-period binary (P=0.197 d) to short-period system (P=0.251 d). The light curve solutions of our observations revealed that USNOB1.0 1395-0370184 and USNO-B1.0 1395-0370731 are overcontact binaries in which components are K dwarfs, close in masses and radii. The light curve distortions were reproduced by cool spots with angular radius of around 20?.

scholarly journals An unusually low density ultra-short period super-Earth and three mini-Neptunes around the old star TOI-561

2020 ◽  
Author(s):  
G Lacedelli ◽  
L Malavolta ◽  
L Borsato ◽  
G Piotto ◽  
D Nardiello ◽  
...  
Keyword(s):  
Transit Time ◽  
Time Variation ◽  
Planetary System ◽  
Radial Velocities ◽  
Low Density ◽  
Outer Planets ◽  
Short Period ◽  
The Stability

Abstract Based on HARPS-N radial velocities (RVs) and TESS photometry, we present a full characterisation of the planetary system orbiting the late G dwarf After the identification of three transiting candidates by TESS, we discovered two additional external planets from RV analysis. RVs cannot confirm the outer TESS transiting candidate, which would also make the system dynamically unstable. We demonstrate that the two transits initially associated with this candidate are instead due to single transits of the two planets discovered using RVs. The four planets orbiting TOI-561 include an ultra-short period (USP) super-Earth (TOI-561 b) with period Pb = 0.45 d, mass Mb = 1.59 ± 0.36 M⊕ and radius Rb = 1.42 ± 0.07 R⊕, and three mini-Neptunes: TOI-561 c, with Pc = 10.78 d, Mc = 5.40 ± 0.98 M⊕, Rc = 2.88 ± 0.09 R⊕; TOI-561 d, with Pd = 25.6 d, Md = 11.9 ± 1.3 M⊕, Rd = 2.53 ± 0.13 R⊕; and TOI-561 e, with Pe = 77.2 d, Me = 16.0 ± 2.3 M⊕, Re = 2.67 ± 0.11 R⊕. Having a density of 3.0 ± 0.8 g cm−3, TOI-561 b is the lowest density USP planet known to date. Our N-body simulations confirm the stability of the system and predict a strong, anti-correlated, long-term transit time variation signal between planets d and e. The unusual density of the inner super-Earth and the dynamical interactions between the outer planets make TOI-561 an interesting follow-up target.

Phenylbenzopyrone of flavonoids as a potential scaffold to prevent SARS-CoV-2 replication by inhibiting its MPRO main protease

2021 ◽  
Vol 22 ◽  
Author(s):  
Angamba Meetei Potshangbam ◽  
Potshangbam Nongdam ◽  
A. Kiran Kumar ◽  
R.S. Rathore
Keyword(s):  
Antiviral Drugs ◽  
Dynamics Simulation ◽  
Compound Libraries ◽  
Main Protease ◽  
Enterovirus A71 ◽  
Short Period ◽  
Novel Coronavirus ◽  
Effective Drugs ◽  
Drug Leads ◽  
Better Than

Background: In December 2019, an outbreak of a pneumonia-like illness, Coronavirusdisease-2019 (COVID-19), originating from Wuhan, China was linked to novel coronavirus, now termed SARS-CoV-2. Unfortunately, no effective drugs or vaccines have been reported yet. The main protease (MPRO) remains the most validated pharmacological target for the design and discovery of inhibitors. Objective: The purpose of the study was to find a prospective natural scaffold as an inhibitor for MPRO main protease in SARS-CoV-2 and compare it with repurposed antiviral drugs lopinavir and nelflinavir. Methods: Natural compound libraries were screened for potential scaffold against MPRO main protease. Molecular dynamics simulation, MM-GBSA and principle component analyses of enzyme-ligand complexes were carried out with the top-ranking hits and compared with the repurposed antiviral drugs lopinavir and nelfinavir. Results: The structure-based virtual screening indicated phenylbenzopyrone of flavonoids as one of the top-ranking scaffolds that have the potential to inhibit the main protease with O-glycosidic form performing better than corresponding aglyconic form. Simulation studies indicated that glycosidic form of flavonoid as more suitable inhibitor with compounds rutin, procyanidin B6, baicalin and galloylquercetin, demonstrating high affinity and stability, and rutin emerging as one of the best candidate compound. Interestingly, rutin was reported to have inhibitory activity against similar protease (3Cprotease of enterovirus A71) as well as implicated in lung fibrosis. Conclusion: The present study displaying flavonoids, possessing a potential scaffold for inhibiting main protease activity for all betacoronavirus is an attempt to provide new and safe drug leads within a reasonably short period.

Early Blue Excess from the Type Ia Supernova 2017cbv

2017 ◽  
Vol 14 (S339) ◽  
pp. 47-49
Author(s):  
G. Hosseinzadeh
Keyword(s):  
Light Curve ◽  
Standard Type ◽  
Circumstellar Material ◽  
Type Ia Supernova ◽  
Unusual Distribution ◽  
Photometric Observations ◽  
Type Ia ◽  
Optical Light Curve ◽  
Ia Supernovae

AbstractThis paper presented very early, high-cadence photometric observations of the nearby Type Ia SN 2017cbv. The light-curve is unique in that during the first five days of observations it has a blue bump in the U, B, and g bands which is clearly resolved by virtue of our photometric cadence of 5.7 hr during that time span. We modelled the light-curve as the combination of an early shock of the supernova ejecta against a non-degenerate companion star plus a standard Type Ia supernova component. Our best-fit model suggested the presence of a subgiant star 56 R⊙ from the exploding white dwarf, although that number is highly model-dependent. While the model matches the optical light-curve well, it over-predicts the flux expected in the ultraviolet bands. That may indicate that the shock is not a blackbody, perhaps because of line blanketing in the UV. Alternatively, it could point to another physical explanation for the optical blue bump, such as interaction with circumstellar material or an unusual distribution of the element Ni. Early optical spectra of SN 2017cbv show strong carbon absorption as far as day –13 with respect to maximum light, suggesting that the progenitor system contained a significant amount of unburnt material. These results for SN 2017cbv illustrate the power of early discovery and intense follow-up of nearby supernovæ for resolving standing questions about the progenitor systems and explosion mechanisms of Type Ia supernovæ.

scholarly journals Accurate Fourier Decomposition of Cepheid Radial Velocity Curves

2000 ◽  
Vol 176 ◽  
pp. 233-234 ◽  
Author(s):  
P. Moskalik ◽  
T. Krzyt ◽  
N. A. Gorynya ◽  
N. N. Samus
Keyword(s):  
Radial Velocity ◽  
Light Curves ◽  
Fourier Decomposition ◽  
Hydrodynamical Models ◽  
Classical Cepheid

AbstractThe shapes of light curves and of radial velocity curves are two main predictions of the hydrodynamical models of Cepheids. Of the two, the velocity curves are more robust numerically and therefore, more suitable for comparison with the observations. In this report, we present accurate Fourier parameters for an extensive set of classical Cepheid velocity curves. Published radiative models reproduce the observations very well, with only small discrepancies present. We estimate the center of the ω2 = 2ω0 resonance to occur at Pr = 9.947 ± 0.051 day

scholarly journals Adaptation of Docobo’s Method for the Calculation of Orbits of Spectroscopic-Interferometric Binaries with Mixed Data

1992 ◽  
Vol 135 ◽  
pp. 220-222
Author(s):  
J.A. Docobo ◽  
J.F. Ling ◽  
C. Prieto
Keyword(s):  
Observational Data ◽  
Radial Velocities ◽  
Polar Coordinates ◽  
Mixed Data ◽  
Short Period ◽  
Visual Binaries

AbstractBased on Docobo’s method for the calculation of orbits of visual binaries, an algorithm is presented for the calculation of short-period orbits when observational data comprise radial velocities and polar coordinates. The method is applied to some examples.

Detection of an Extremely Active State of AM Canum Venaticorum

1985 ◽  
Vol 87 ◽  
pp. 397-403
Author(s):  
K.R. Narayanan Kutty ◽  
T.M.K. Marar ◽  
V.N. Padmini ◽  
S. Seetha ◽  
K. Kasturirangan ◽  
...  
Keyword(s):  
White Light ◽  
Cataclysmic Variables ◽  
Active State ◽  
Photometric Observations ◽  
Short Period

Abstract:We report fast photometric observations on AM CANUM VENATICORUM (AM CVn) the ultra short period, hydrogen deficient variable. We have detected on 24th February, 1985 an intense flare of (Δm)peak≈0.34 in white light lasting over 200s. Following this flare we observe an enhanced double humped structure lasting for 1051s which is the dominant periodicity exhibited by AM CVn. We have also detected the 525s and 1051s periods. In addition, we report flickerings, lasting typically 1-2 minutes, that are characteristic of cataclysmic variables.

Radial Velocities for the Pulsating Subdwarf B Star PG 1605+072

2002 ◽  
Vol 185 ◽  
pp. 376-377
Author(s):  
V.M. Woolf ◽  
C.S. Jeffery ◽  
D.L. Pollacco
Keyword(s):  
Radial Velocity ◽  
Line Shape ◽  
High Speed ◽  
Radial Velocities ◽  
Peak Amplitude ◽  
Amplitude Ratios ◽  
Time Line ◽  
Photometric Observations ◽  
Velocity Variations ◽  
Over Time

AbstractWe have performed high-speed spectroscopy of the pulsating subdwarf B star PG 1605+072. Its radial velocity variations have frequencies similar to those reported from photometric observations. Peak amplitude ratios are different, probably as a result of power shifting between modes over time. Line-shape variations have also been detected.

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