Short Term Variations in the Spectrum of the T Tauri Star DI Cep

1979 ◽  
Vol 46 ◽  
pp. 369-370
Author(s):  
R. Mundt ◽  
U. Bastian
Keyword(s):  
Time Scales ◽  
Time Resolution ◽  
Equivalent Width ◽  
Tauri Star ◽  
Emission Lines ◽  
Short Term ◽  
Spectroscopic Observations ◽  
T Tauri ◽  
Time Variations ◽  
Short Time

AbstractExtended spectroscopic observations of the T Tauri star DI Cep with a time resolution of 10 to 15 minutes have been carried out. On 2 of 6 observing nights the star showed significant variations of the strengths of its emission lines on time scales down to the time resolution of the observations. The most drastic event is shown in Figure 1. The equivalent width of the Hα line increased by a factor of 7 within two hours. Even faster variations, but of smaller amplitude, were observed in the strengths of the Hβ and Till 82 (λ 4572 Å) lines on another night. Obviously strong short time variations are not always present in DI Cep, as in 4 nights no significant variations could be detected.

scholarly journals Actvity on T Tauri Stars

1995 ◽  
Vol 151 ◽  
pp. 221-222
Author(s):  
Erik Gullbring ◽  
Gösia F. Gahm ◽  
Heinz Barwig ◽  
Peicheng Chen
Keyword(s):  
Time Scales ◽  
High Speed ◽  
T Tauri Stars ◽  
Young Stars ◽  
Tauri Star ◽  
Emission Lines ◽  
Base Line ◽  
Short Term ◽  
T Tauri ◽  
Short Term Variability

We have made a detailed investigation of the short-term variability of the classical T Tauri star BP Tauri in UBVRI. Data were collected from the Wendelstein Observatory in 1991, 1992 and 1993 with time resolutions down to 1 sec. The 0.8m telescope was equipped with a fiber-fed fifteen channel high-speed photometer (Barwig et al. 1987). Observations (in UBV) were also collected in China at the Yunnan and Shanghai Observatories to get a long base line in time. To search for differences in the properties between the brightness variations of classical T Tauri stars (CTTS) and T Tauri stars with weak emission lines (WTTS) we performed simultaneous photometry (in the UBV and Strömgren systems) and spectroscopy of 6 young stars during two observing periods at ESO La Silla. The study concerned mainly short-term variability on time-scales of minutes to a few hours. The sample contained two CTTS, SY Ori and VW Cha; three WTTS, San 1, SZ Cha and ADA 481 and one post-T Tauri candidate, HD 70309B.

scholarly journals Optical Short-Time Variations in GK Persei during the 1983 Outburst

1987 ◽  
Vol 93 ◽  
pp. 485-485
Author(s):  
H. Steinle ◽  
W. Pietsck
Keyword(s):  
Accretion Disk ◽  
Time Resolution ◽  
X Rays ◽  
X Ray ◽  
Time Variations ◽  
Short Time ◽  
First Time ◽  
Calar Alto

AbstractDuring the August 1983 outburst of the old nova GK Persei observations with EXOSAT showed for the first time a 351 second periodicity in X-rays.Our fast photometry (U(B)V with 25 sec time resolution) was made at the end of the outburst in the nights of September 29 , and October 1–3 , using the 2.2 meter telescope at Calar Alto (Spain).Optical variations up to 10% in U and 4% in V with periodicities in the range 350 to 360 seconds were found, lasting only for few cycles.A comparison with the extrapolated prediction of the X-ray maxima did not show a coincidence, but rather an anticoincidence in several cases. This supports a model of reprocessed X-rays at the inner edge of an accretion disk.

scholarly journals Short-Term Radio-X-Ray Correlations of Cygnus X-1

2004 ◽  
Vol 194 ◽  
pp. 202-202
Author(s):  
T. Gleissner ◽  
J. Wihns ◽  
G. G. Pooley ◽  
M. A. Nowak ◽  
K. Pottschmidt ◽  
...  
Keyword(s):  
White Noise ◽  
Correlation Coefficient ◽  
Time Scales ◽  
Cross Correlation ◽  
Short Term ◽  
X Ray ◽  
Noise Statistics ◽  
Short Time

We analyze simultaneous radio-X-ray data of Cygnus X-l from the Ryle telescope (RT) and RXTE over more than 4 a. We show that apparent correlations on short time scales in the lightcurves of Cyg X-l are probably the coincidental outcome of white noise statistics.As a measure of correlation between radio and X-ray emission, we calculate the maximum cross-correlation coefficient, ccf, of simultaneous radio and X-ray lightcurves, which are rebinned to a resolution of 32 s and smoothed. Every single X-ray lightcurve segment is cross-correlated with the corresponding radio lightcurve, up to a maximum shift Δt = ±10 h.

scholarly journals A survey for variable young stars with small telescopes: II – mapping a protoplanetary disc with stable structures at 0.15 au

2020 ◽  
Vol 493 (1) ◽  
pp. 184-198 ◽  
Author(s):  
Jack J Evitts ◽  
Dirk Froebrich ◽  
Aleks Scholz ◽  
Jochen Eislöffel ◽  
Justyn Campbell-White ◽  
...  
Keyword(s):  
Time Scales ◽  
Broad Band ◽  
T Tauri ◽  
Low Levels ◽  
Short Time ◽  
Citizen Science Project ◽  
The Hill ◽  
Colour Terms ◽  
High Cadence

ABSTRACT The HOYS citizen science project conducts long-term, multifilter, high-cadence monitoring of large YSO samples with a wide variety of professional and amateur telescopes. We present the analysis of the light curve of V1490 Cyg in the Pelican Nebula. We show that colour terms in the diverse photometric data can be calibrated out to achieve a median photometric accuracy of 0.02 mag in broad-band filters, allowing detailed investigations into a variety of variability amplitudes over time-scales from hours to several years. Using Gaia DR2, we estimate the distance to the Pelican Nebula to be 870 $^{+70}_{-55}$ pc. V1490 Cyg is a quasi-periodic dipper with a period of 31.447 ± 0.011 d. The obscuring dust has homogeneous properties, and grains larger than those typical in the ISM. Larger variability on short time-scales is observed in U and Rc−H α, with U amplitudes reaching 3 mag on time-scales of hours, indicating that the source is accreting. The H α equivalent width and NIR/MIR colours place V1490 Cyg between CTTS/WTTS and transition disc objects. The material responsible for the dipping is located in a warped inner disc, about 0.15 au from the star. This mass reservoir can be filled and emptied on time-scales shorter than the period at a rate of up to 10−10 M⊙ yr−1, consistent with low levels of accretion in other T Tauri stars. Most likely, the warp at this separation from the star is induced by a protoplanet in the inner accretion disc. However, we cannot fully rule out the possibility of an AA Tau-like warp, or occultations by the Hill sphere around a forming planet.

scholarly journals Pulsations in 66 Oph: Multiperiodicity in He I 6678

2000 ◽  
Vol 175 ◽  
pp. 256-259 ◽  
Author(s):  
M. Floquet ◽  
C. Neiner ◽  
D. Briot ◽  
J. Chauville ◽  
A.M. Hubert ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Line Profile ◽  
Equivalent Width ◽  
Phase Distribution ◽  
Line Profiles ◽  
Short Term ◽  
Spectroscopic Observations

Abstract66 Oph has shown recurrent short-lived outbursts nicely detected from ground-based and space (Hipparcos) photometry.Spectroscopic observations of He I 6678 and Hα lines were performed in June 1997 and June 1998. Search for short-term periodicities was done in He I 6678 line profiles as in equivalent width EW, radial velocity of the line centroid, and V and R components. At least two frequencies were present: ν = 4.0 c/d and ν = 2.2 c/d. The phase distribution of these frequencies over the line profile corresponds in the nrp frame to g-modes with ℓ ~ 3 − 4 and ℓ = 2 respectively.

scholarly journals Short term changes in methanol emission and pectin methylesterase activity are not directly affected by light in <i>Lycopersicon esculentum</i>

2011 ◽  
Vol 8 (4) ◽  
pp. 1023-1030 ◽  
Author(s):  
P. Y. Oikawa ◽  
L. Li ◽  
M. P. Timko ◽  
J. E. Mak ◽  
M. T. Lerdau
Keyword(s):  
Time Scales ◽  
Pectin Methylesterase ◽  
Light Activation ◽  
Short Term ◽  
Substrate Limitation ◽  
Emission Models ◽  
Seasonal Time Scale ◽  
Short Time ◽  
Cell Wall Expansion

Abstract. Plants are an important source of atmospheric methanol (MeOH), the second most abundant organic gas after methane. Factors regulating phytogenic MeOH production are not well constrained in current MeOH emission models. Previous studies have indicated that light may have a direct influence on MeOH production. As light is known to regulate cell wall expansion, it was predicted that light would stimulate MeOH production through the pectin methylesterase (PME) pathway. MeOH emissions normalized for stomatal conductance (gs) did not, however, increase with light over short time scales (20–30 min). After experimentally controlling for gs and temperature, no light activation of PME activity or MeOH emission was observed. The results clearly demonstrate that light does not directly influence short-term changes in MeOH production and emission. Our data suggest that substrate limitation may be important in regulating MeOH production over short time scales. Future investigation of the long-term impacts of light on MeOH production may increase understanding of MeOH emission dynamics at the seasonal time scale.

scholarly journals Permitted Iron Emission Lines in the Classical T Tauri Star DR Tauri

1998 ◽  
Vol 499 (2) ◽  
pp. 828-852 ◽  
Author(s):  
Georgina Beristain ◽  
Suzan Edwards ◽  
John Kwan
Keyword(s):  
Tauri Star ◽  
Emission Lines ◽  
T Tauri

scholarly journals Photometric variability of the T Tauri star TW Hya on time-scales of hours to years★

2008 ◽  
Vol 391 (4) ◽  
pp. 1913-1924 ◽  
Author(s):  
Slavek M. Rucinski ◽  
Jaymie M. Matthews ◽  
Rainer Kuschnig ◽  
Grzegorz Pojmański ◽  
Jason Rowe ◽  
...  
Keyword(s):  
Time Scales ◽  
Tauri Star ◽  
Photometric Variability ◽  
T Tauri

scholarly journals Optimization of supercooling effect in nanoscaled thermoelectric layers

2016 ◽  
Vol 7 (2) ◽  
pp. 98-110 ◽  
Author(s):  
Iván Rivera ◽  
Aldo Figueroa ◽  
Federico Vázquez
Keyword(s):  
Time Evolution ◽  
Time Scales ◽  
Spectral Methods ◽  
Constitutive Equations ◽  
Electric Pulse ◽  
Length Scale ◽  
Short Term ◽  
Nonlocal Effects ◽  
Spectral Convergence ◽  
Short Time

Abstract In this paper we address the problem of optimization of the so called supercooling effect in thermoelectric nanoscaled layers. The effect arises when a short term electric pulse is applied to the layer. The analysis is based on constitutive equations of the Maxwell-Cattaneo type describing the time evolution of dissipative flows with the thermal and electric conductivities depending on the width of the layer. This introduces memory and nonlocal effects and consequently a wave-like behaviour of system’s temperature. We study the effects of the shape of the electric pulse on the maximum diminishing of temperature by applying pulses of the form ta with a a power going from 0 to 10. Pulses with a a fractionary number perform better for nanoscaled devices whereas those with a bigger than unity do it for microscaled ones. We also find that the supercooling effect is improved by a factor of 6.6 over long length scale devices in the best performances and that the elapsed supercooling time for the nanoscaled devices equals the best of the microscaled ones. We use the spectral methods of solution which assure a well representation of wave behaviour of heat and electric charge in short time scales given their spectral convergence.

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