scholarly journals Photometry of Type II Cepheids. I. The Long-Period Stars

2004 ◽  
Vol 128 (4) ◽  
pp. 1748-1760 ◽  
Author(s):  
Edward G. Schmidt ◽  
Dale Johnston ◽  
Shawn Langan ◽  
Kevin M. Lee
Keyword(s):  
Type Ii ◽  
Long Period

scholarly journals Spectra of Type II Cepheids

1975 ◽  
Vol 67 ◽  
pp. 555-555
Author(s):  
T. Lloyd Evans
Keyword(s):  
Globular Clusters ◽  
Line Strength ◽  
Type Ii ◽  
Long Period ◽  
Molecular Features ◽  
Metallic Line ◽  
Short Period ◽  
The Galaxy ◽  
Metal Abundance ◽  
Central Bulge

Spectra of over 100 stars classed as type II Cepheids of short period (BL Her-type) or long period (W Vir-type) or RV Tauri stars have been obtained. A range of metallic line strength and hence presumably metal abundance is present at all periods, those having weak lines being found especially in the globular clusters and the central bulge of the Galaxy. Stars which have enhanced Carbon molecular features (CH, CN and sometimes C2) occur at all periods but are probably distributed differently in space from the other stars.

scholarly journals Long-Period InAs/GaSb Type-II Superlattices for Terahertz Application

2014 ◽  
Vol 05 (17) ◽  
pp. 1880-1888
Author(s):  
Longlong Li ◽  
Jun Ni ◽  
Wen Xu
Keyword(s):  
Type Ii ◽  
Long Period ◽  
Type Ii Superlattices

scholarly journals Evolutionary and pulsation properties of Type II Cepheids

2020 ◽  
Vol 644 ◽  
pp. A96
Author(s):  
G. Bono ◽  
V. F. Braga ◽  
G. Fiorentino ◽  
M. Salaris ◽  
A. Pietrinferni ◽  
...  
Keyword(s):  
Variable Stars ◽  
Asymptotic Giant Branch ◽  
Type Ii ◽  
Agb Stars ◽  
Instability Strip ◽  
Low Mass Stars ◽  
Long Period ◽  
Short Period ◽  
The Galaxy ◽  
Modal Mass

We discuss the observed pulsation properties of Type II Cepheids (TIICs) in the Galaxy and in the Magellanic Clouds. We found that period (P) distributions, luminosity amplitudes, and population ratios of the three different sub-groups (BL Herculis [BLH, P < 5 days], W Virginis [WV, 5 ≤ P < 20 days], RV Tauri [RVT, P > 20 days]) are quite similar in different stellar systems, suggesting a common evolutionary channel and a mild dependence on both metallicity and environment. We present a homogeneous theoretical framework based on horizontal branch (HB) evolutionary models, showing that TIICs are mainly old (t ≥ 10 Gyr) low-mass stars. The BLH stars (BLHs) are predicted to be post-early asymptotic giant branch (PEAGB) stars (double shell burning) on the verge of reaching their AGB track (first crossing of the instability strip), while WV stars (WVs) are a mix of PEAGB and post-AGB stars (hydrogen shell burning) moving from the cool to the hot side (second crossing) of the Hertzsprung-Russell Diagram. This suggests that they are a single group of variable stars. The RVT stars (RVTs) are predicted to be a mix of post-AGB stars along their second crossing (short-period tail) and thermally pulsing AGB stars (long-period tail) evolving towards their white dwarf cooling sequence. We also present several sets of synthetic HB models by assuming a bi-modal mass distribution along the HB. Theory suggests, in agreement with observations, that TIIC pulsation properties marginally depend on metallicity. Predicted period distributions and population ratios for BLHs agree quite well with observations, while those for WVs and RVTs are almost a factor of two smaller and higher than observed, respectively. Moreover, the predicted period distributions for WVs peak at periods shorter than observed, while those for RVTs display a long-period tail not supported by observations. We investigate several avenues to explain these differences, but more detailed calculations are required to address these discrepancies.

scholarly journals The Spectra of Type II Cepheids. III. The Hα Line and Helium Emission in Long-Period Stars

2004 ◽  
Vol 128 (6) ◽  
pp. 2988-2996 ◽  
Author(s):  
Edward G. Schmidt ◽  
Dale Johnston ◽  
Kevin M. Lee ◽  
Shawn Langan ◽  
Peter R. Newman ◽  
...  
Keyword(s):  
Type Ii ◽  
Long Period ◽  
Helium Emission

scholarly journals Retention of Long-period Gas Giant Planets: Type II Migration Revisited

2020 ◽  
Vol 900 (1) ◽  
pp. 44 ◽  
Author(s):  
Yi-Xian Chen ◽  
Xiaojia Zhang ◽  
Ya-Ping Li ◽  
Hui Li ◽  
Douglas N. C. Lin
Keyword(s):  
Giant Planets ◽  
Type Ii ◽  
Long Period ◽  
Gas Giant

scholarly journals Spectral Characteristics of Square-Wave-Modulated Type II Long-Period Fiber Gratings Inscribed by a Femtosecond Laser

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 3278
Author(s):  
Xiaofan Zhao ◽  
Hongye Li ◽  
Binyu Rao ◽  
Meng Wang ◽  
Baiyi Wu ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Duty Cycle ◽  
Spectral Characteristics ◽  
Great Influence ◽  
Higher Order ◽  
Type Ii ◽  
Fiber Gratings ◽  
Square Wave ◽  
Long Period ◽  
Long Period Fiber Gratings

We study here the spectral characteristics of square-wave-modulated type II long-period fiber gratings (LPFGs) inscribed by a femtosecond laser. Both theoretical and experimental results indicate that higher-order harmonics refractive index (RI) modulation commonly exists together with the fundamental harmonic RI modulation in such LPFGs, and the duty cycle of a square wave has a great influence on the number and amplitudes of higher-order harmonics. A linear increase in the duty cycle in a series of square wave pulses will induce another LPFG with a minor difference in periods, which is useful for expanding the bandwidth of LPFGs. We also propose a method to reduce insertion loss by fabricating type II LPFGs without higher-order harmonic resonances. This work intensifies our comprehension of type II fiber gratings with which novel optical fiber sensors can be fabricated.

On nearly-commensurable periods in the restricted problem of three bodies, with calculations of the long-period variations in the interior 2:1 case

1966 ◽  
Vol 25 ◽  
pp. 197-222 ◽  
Author(s):  
P. J. Message
Keyword(s):  
Periodic Solution ◽  
Periodic Solutions ◽  
Large Amplitude ◽  
Restricted Problem ◽  
Small Amplitude ◽  
Minor Planets ◽  
Long Period ◽  
Numerical Integrations ◽  
Period Variations ◽  
The Mean

An analytical discussion of that case of motion in the restricted problem, in which the mean motions of the infinitesimal, and smaller-massed, bodies about the larger one are nearly in the ratio of two small integers displays the existence of a series of periodic solutions which, for commensurabilities of the typep+ 1:p, includes solutions of Poincaré'sdeuxième sortewhen the commensurability is very close, and of thepremière sortewhen it is less close. A linear treatment of the long-period variations of the elements, valid for motions in which the elements remain close to a particular periodic solution of this type, shows the continuity of near-commensurable motion with other motion, and some of the properties of long-period librations of small amplitude.To extend the investigation to other types of motion near commensurability, numerical integrations of the equations for the long-period variations of the elements were carried out for the 2:1 interior case (of which the planet 108 “Hecuba” is an example) to survey those motions in which the eccentricity takes values less than 0·1. An investigation of the effect of the large amplitude perturbations near commensurability on a distribution of minor planets, which is originally uniform over mean motion, shows a “draining off” effect from the vicinity of exact commensurability of a magnitude large enough to account for the observed gap in the distribution at the 2:1 commensurability.

Type II Solar Radio Bursts over Solar Cycle 21

1994 ◽  
Vol 144 ◽  
pp. 283-284
Author(s):  
G. Maris ◽  
E. Tifrea
Keyword(s):  
Solar Radio ◽  
Interplanetary Space ◽  
Impulsive Phase ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Strong Energy ◽  
Mass Ejection ◽  
Geophysical Effect ◽  
Radio Event

The type II solar radio bursts produced by a shock wave passing through the solar corona are one of the most frequently studied solar activity phenomena. The scientific interest in this type of phenomenon is due to the fact that the presence of this radio event in a solar flare is an almost certain indicator of a future geophysical effect. The origin of the shock waves which produce these bursts is not at all simple; besides the shocks which are generated as a result of a strong energy release during the impulsive phase of a flare, there are also the shocks generated by a coronal mass ejection or the shocks which appear in the interplanetary space due to the supplementary acceleration of the solar particles.

Discussion following the presentation by F. Deubner

1977 ◽  
Vol 36 ◽  
pp. 69-74
Keyword(s):  
List Type ◽  
The Sun ◽  
Type Number ◽  
Harmonic Motion ◽  
Locally Excited ◽  
Long Period ◽  
Coherent Wave ◽  
Short Period ◽  
Global Modes

The discussion was separated into 3 different topics according to the separation made by the reviewer between the different periods of waves observed in the sun :1) global modes (long period oscillations) with predominantly radial harmonic motion.2) modes with large coherent - wave systems but not necessarily global excitation (300 s oscillation).3) locally excited - short period waves.

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