scholarly journals Mode Switching in Red Semiregular Variable Stars?

1995 ◽  
Vol 155 ◽  
pp. 405-406
Author(s):  
J. Gál ◽  
K. Szatmáry
Keyword(s):  
Variable Stars ◽  
Point Of View ◽  
Mode Switching ◽  
Radial Pulsation ◽  
Light Curve Analysis ◽  
Time Intervals ◽  
Frequency Spectra ◽  
The Mean ◽  
Semiregular Variable

AbstractLight curve analysis of the carbon variable RY Dra and the oxygen-rich variables TX Dra and AF Cyg is summarised. In each case, two shorter periods were found (which may be connected with the radial pulsation of the stars) and also a long term variation in the mean brightness. In the case of RY Dra, the amplitudes of the shorter periods both decreased while the amplitude of the long secondary variation was found to be increasing. The light curves and frequency spectra of TX Dra and AF Cyg can be interpreted as a result of mode switching. These stars pulsate with two different periods and there are time intervals when the longer period disappears and the shorter one remains dominant, and it lasts for many cycles. We concluded that the double and multi-periodic red semiregular variables may be very important from both theoretical and observational point of view, because, based on the ratio of the periods, we can identify the pulsational modes in these variables.

Annual hazard rates of recurrence for breast cancer after primary therapy.

1996 ◽  
Vol 14 (10) ◽  
pp. 2738-2746 ◽  
Author(s):  
T Saphner ◽  
D C Tormey ◽  
R Gray
Keyword(s):  
Breast Cancer ◽  
Eastern Cooperative Oncology Group ◽  
Entire Group ◽  
Hazard Rates ◽  
Primary Therapy ◽  
Time Intervals ◽  
Differentiating Agents ◽  
The Mean ◽  
Lower Hazard

PURPOSE To determine if the long-term increase of recurrence for breast cancer is stable or slowly decreasing, or if it ever reaches zero; and to determine the effect of prognostic factors on the hazard of recurrence. METHODS All patients entered onto the seven completed and unblinded Eastern Cooperative Oncology Group (ECOG) coordinated studies of postoperative adjuvant therapy for breast cancer were analyzed in terms of annual hazard of recurrence of breast cancer. RESULTS For the entire group, the peak hazard of recurrence occurred in the interval of 1 to 2 years. The hazard decreased consistently in the interval of 2 to 5 years. Beyond 5 years, the hazard of recurrence decreased very, very slowly through year 12. The average hazard of recurrence between years 5 and 12 for the entire population was 4.3% per year. The pattern of a peak hazard of recurrence during the first 5 years with a slowly decreasing hazard of recurrence beyond 5 years was also observed to varying degrees in most subsets. Higher risk subsets such as patients with more than three nodes positive had a higher hazard of recurrence at all time intervals, while lower risk subsets such as patients with negative nodes had a lower hazard of recurrence in all time periods. CONCLUSION Patients 5 years postsurgery for breast cancer appear to have a very slowly decreasing hazard of recurrence. The mean hazard of recurrence between years 5 to 12 postsurgery is 4.3% per year. This group of patients may be well suited for trials evaluating cytostatic drugs or differentiating agents.

Photometry of Variable Stars, and System Transformability Over Long Time Intervals

2003 ◽  
Vol 12 (4) ◽  
Author(s):  
C. Sterken
Keyword(s):  
Fundamental Problem ◽  
Variable Stars ◽  
Time Intervals ◽  
Multi Wavelength ◽  
Long Time ◽  
Photometric Monitoring ◽  
Made In

AbstractThe fundamental problem of long-term photometric monitoring of variable stars and of multi-wavelength photometric campaigns is the problem of bringing the data to a common standard. Such homogenization can be achieved only when the measurements are made in photometric systems that are truly transformable. This fundamental problem is of a technical nature, and photometric observers, sometimes, are not aware of the problems. This frequently leads to over-interpretation of the data.

scholarly journals Evaluation of long-term sagittal lip changes using Burstone line: Pilot Study

2021 ◽  
Vol 7 (2) ◽  
pp. 32-37
Author(s):  
Rachel Sathekge ◽  
Colin Lesar
Keyword(s):  
Soft Tissue ◽  
Upper Lip ◽  
Short Term ◽  
Time Intervals ◽  
Lower Lip ◽  
Linear Distance ◽  
Long Term Follow Up ◽  
The Mean

Objective Lip position has become one of the most important soft tissue analyses as it influences the occlusion, tooth stability and facial aesthetic. Hence, the objective of this study was to compare the short-term and long-term sagittal lip positions/changes using the Burstone line (B-line).   Methods The sample consisted of 18 Caucasoid females only (14 extractions, 4 non-extractions) who were successfully treated with edgewise appliances. All the patients were evaluated before treatment (T1),at the end of active treatment (T2), and at a long-term follow-up observation (T3). The mean age at commencement was 13.2 years with the range of 10.5-19 years. The linear distance between the tip of the lips and the B-line were measured.   Results T1-T2 time intervals showed the upper lip underwent a mean change of 1.272 mm relative to the B-line (-32.8%) which was statistically significant. The lower lip showed a mean change of 1.549 mm (-22.2%), but these changes were not statistically significant. Lip protrusion relative to the B-line continued to reduce during the long term follow up period. The upper lip showed slight changes (-9.2%), whereas the lower lip demonstrated greater change (-53.8%).   Conclusion Using B-line, the sagittal soft tissue lip positions were more retrusive on the long-term follow-up records for both extraction and non-extraction cases, their values were not very different from the normal values of the untreated cases. Although the differences were not statistically significant,  upper lips were retrusive post treatment from T1-T2, while were statistically significant the lower lips were retrusive from T1-T2.

scholarly journals The relevance of glacier melt in the water cycle of the Alps: the example of Austria

2011 ◽  
Vol 15 (6) ◽  
pp. 2039-2048 ◽  
Author(s):  
G. R. Koboltschnig ◽  
W. Schöner
Keyword(s):  
River Runoff ◽  
Water Cycle ◽  
Point Of View ◽  
Statistical Interpretation ◽  
Study Region ◽  
Ice Melt ◽  
Glacier Melt ◽  
Precipitation Increase ◽  
The Mean

Abstract. This paper quantifies the contribution of glacier melt to river runoff from compilation and statistical interpretation of data from available studies based on observations or glacio- hydrological modelling for the region of Austria (Austrian Salzach and Inn river basin). A logarithmic fit between the glacier melt contribution and the relative glacierized area was found not only for the long-term mean glacier contributions but also for the glacier melt contribution during the extreme hot an dry summer of 2003. Interestingly, the mean contributions of glacier melt to river runoff do not exceed 15 % for both river catchments and are uncorrelated to glacierization for glacierization values >10 %. This finding, however, has to be seen in the light of the general precipitation increase with altitude for the study region which levels out the increase of absolute melt with glacierization thus resulting in the rather constant value of glacier melt contribution. In order to qualitatively proof this finding another approach has been applied by calculating the quotient qA03 of the mean monthly August runoff in 2003 and the long-term mean August runoff for 38 gauging stations in Austria. The extreme summer 2003 was worth to be analysed as from the meteorological and glaciological point of view an extraordinary situation was observed. During June and July nearly the entire snow-cover melted and during August mainly bare ice melt of glaciers contributed to runoff. The qA03 quotients were calculated between 0.32 for a non-glacierized and 2.0 for a highly glacierized catchment. Using the results of this study the mean and maximum possible glacier melt contribution of catchments can be estimated based on the relative glacierized area. It can also be shown that the found correlation of glacierized area and glacier melt contribution is applicable for the Drau basin where yet no results of modelled glacier melt contributions are available.

scholarly journals 30 Years of Multifrequency Quasar Variability: A Personal Journey

Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 69
Author(s):  
James R. Webb
Keyword(s):  
Gamma Rays ◽  
Point Of View ◽  
Light Curves ◽  
X Rays ◽  
Optical Monitoring ◽  
Frequency Spectra ◽  
History Of ◽  
Quasar Variability ◽  
Term Monitoring

I outline the history of and progress in observing and understanding quasar multi-frequency and multi-messenger variability from the point of view of someone who has been working in the field for over 30 years. I will present some important references for the evolution from optical monitoring to multi-frequency cooperative programs that revealed the true multi-frequency/multi-timescale nature of variability in these objects. Quasar observations began with separate radio and optical monitoring programs; then the optical and radio observations w ere combined. This was followed by expanding the analyses to include far IR, UV, X-rays, and finally adding gamma rays. This progression yielded simultaneous multi-frequency spectra of these objects and light curves over 15 decades in frequency. The future is adding particle (neutrino) and gravitational waves to the picture. I also present long-term (50 years) optical light curves, and discuss optical variability at all timescales from minutes to tens of years in some selected objects for which we have reliable long-term monitoring observations.

scholarly journals Aperiodic Ordered Sequences and Multiperiodicity in Semiregular Variable Stars

2002 ◽  
Vol 185 ◽  
pp. 568-569
Author(s):  
Juan García Escudero
Keyword(s):  
Light Curve ◽  
Variable Stars ◽  
Curve Analysis ◽  
Lindenmayer Systems ◽  
Light Curve Analysis ◽  
Fibonacci Sequences ◽  
Semiregular Variable Stars ◽  
Semiregular Variable

AbstractThe use of aperiodic ordered sequences described by Lindenmayer systems in the study of the strings of periods for multiperiodic semiregular variables is proposed. Fibonacci sequences play a central role in the light curve analysis of UW Herculis.

scholarly journals Period-Gravity Relation for Semiregular Variable Stars

2002 ◽  
Vol 185 ◽  
pp. 566-567
Author(s):  
K. Szatmáry ◽  
L.L. Kiss
Keyword(s):  
Variable Stars ◽  
Radial Pulsation ◽  
Giant Stars ◽  
Pulsating Variable Stars ◽  
Stellar Pulsation ◽  
Short Period ◽  
Red Giant ◽  
Rotating Star ◽  
Semiregular Variable Stars ◽  
Semiregular Variable

Red giant stars located on the AGB are intrinsically variable, which is usually associated with stellar pulsation. The complex light variation of semiregular variables (SRVs) has many alternative explanations. Besides the pulsation, other contributors to variability cannot be solidly excluded, such as time-dependent surface inhomogeneities, ellipsoidal deformation due to the presence of a close companion, or spots on a rotating star. The identification of ultra-short period M-giants with periods of a few days raised the possibility of very high-order overtone pulsation of these stars. Thus, it is very important to draw various constraints on the stellar pulsation in semiregular variables and to separate other physical causes. Here we present new empirical evidence for radial pulsation in SRVs through studying their period-gravity relation, following the ideas outlined by Fernie (1995, F95). F95 studied a log P versus log g relation for various types of radially pulsating variable stars. He found a well-defined linear relation, which might serve to test whether the pulsation is radial or nonradial and, in the former case, fundamental or overtone. The main goal of our study is to extend the relation into the domain of SRVs.

Observation of possible mode switching in three semiregular variable stars

1991 ◽  
Vol 101 ◽  
pp. 1043 ◽  
Author(s):  
R. R., Jr. Cadmus ◽  
L. A. Willson ◽  
C. Sneden ◽  
J. A. Mattei
Keyword(s):  
Variable Stars ◽  
Mode Switching ◽  
Semiregular Variable Stars ◽  
Semiregular Variable

scholarly journals OH masers in semiregular variables: Insights from long-term monitoring

2002 ◽  
Vol 206 ◽  
pp. 323-326
Author(s):  
Leszek Błaszkiewicz ◽  
Marian Szymczak ◽  
Sandra Etoka ◽  
A.M. Le Squeren
Keyword(s):  
Circumstellar Matter ◽  
Variable Stars ◽  
Radial Velocities ◽  
Spectral Features ◽  
Long Term Monitoring ◽  
Peak Emission ◽  
Term Monitoring ◽  
Semiregular Variable Stars ◽  
Semiregular Variable

Drifts in radial velocities of OH maser features of the three semiregular variable stars R Crt, RT Vir and W Hya have been analyzed. The radial velocities of the extreme blue- and red-shifted features drifted by about 0.2 kms−1 to 1 km s−1 on time-scales of few months to several years. In the case of W Hya a blending effect of spectral features can account for those drifts. In the two other sources the velocity drifts are likely to be intrinsic to the clumps for which the velocities of peak emission vary due to appearance or disappearance of maser emission in the regions where circumstellar matter is still accelerated.

Long-term photometric observations in the field of the star formation region NGC7129

2017 ◽  
Vol 13 (S336) ◽  
pp. 287-288
Author(s):  
Evgeni Semkov ◽  
Stoyanka Peneva ◽  
Sunay Ibryamov ◽  
Asen Mutafov
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Variable Stars ◽  
Time Intervals ◽  
Star Formation Region ◽  
Formation Region ◽  
Photometric Observations ◽  
Pms Stars ◽  
Short Time

AbstractWe present results from long-term optical photometric observations of the Pre-Main Sequence (PMS) stars, located in the star formation region around the bright nebula NGC 7129. Using the long-term light curves and spectroscopic data, we tried to classify the PMS objects in the field and to define the reasons for the observed brightness variations. Our main goal is to explore the known PMS stars and discover new, young, variable stars. The new variable PMS star 2MASS J21403576+6635000 exhibits unusual brightness variations for very short time intervals (few minutes or hours) with comparatively large amplitudes (ΔI = 2.65 mag).

Sign in / Sign up

Export Citation Format

Share Document