scholarly journals Spectral obervations of flare stars TZ ARI and ROSS 867

2020 ◽  
pp. 13-20
Author(s):  
G. R. Kostandian ◽  
N. D. Melikian ◽  
R. Sh. Natsvlishvili ◽  
G. M. Paronyan
Keyword(s):  
Measurement Errors ◽  
Emission Lines ◽  
Quiescent State ◽  
Byurakan Astrophysical Observatory ◽  
Strong Change ◽  
Maximum Value ◽  
Flare Stars ◽  
Ev Lac ◽  
Spectral Ranges

The results of spectral observations of flare stars TZ Ari and Ross 867B are presented. Observations have been carried out by the 2.6m telescope of Byurakan Astrophysical Observatory in 1999, 2001 and 2018. The spectral cameras "ByuFOSC" and "SCORPIO" were used during the observations. A strong change of emission lines detected on TZ Ari in 2018, while at the same time the brightness changes of the star in all measured spectral ranges are within the framework of measurement errors. Slight variations of brightness and EWHα are detected in quiescent state of star during the observations in 1999. A strong flare of Ross 867B were observed, with a duration of more than 20min. In this case if EWHα shows strong change, when its maximum value corresponds to the photometric maximum of are, at the same time EWHα shows decrease, similar to that, observed earlier during the flares of stars EV Lac, HU Del, CM Dra and WX UMa.

scholarly journals X-Ray Emission from Flare Stars

1983 ◽  
Vol 71 ◽  
pp. 125-129
Author(s):  
P.C. Agrawal ◽  
A.R. Rao ◽  
B.V. Sreekantan
Keyword(s):  
Emission Lines ◽  
Quiescent State ◽  
X Ray ◽  
Uv Emission ◽  
Chromospheric Emission ◽  
Flare Stars ◽  
Einstein Observatory

Flare stars are a group of mostly dMe stars, which show intense flaring activity in the optical as well as in the radio and X-ray bands. These stars are characterized by the presence of chromospheric emission lines like % and Call H and K which are present even during the quiescent state. The presence of transition regions and coronae have been inferred from the detection of UV emission lines like NV, CIV, SiIV etc. with IUE and X-ray observations made with the Einstein Observatory. We report here X-ray observations of flare stars made with Einstein to measure their coronal X-ray emission during the quiescent state.

scholarly journals Rapid spike flares on AD Leo and EV Lac

1990 ◽  
Vol 137 ◽  
pp. 27-30
Author(s):  
K. P. Panov ◽  
M. S. Ivanova ◽  
A. Antov
Keyword(s):  
Astronomical Observatory ◽  
Monitoring Time ◽  
Flare Stars ◽  
Ev Lac

Photoelectric U - band observations of the flare stars A Leo and EV Lac during the last 9 years obtained at the Bulgarian National Astronomical Observatory revealed 8 rapid spike flares on AD Leo and 9 rapid spike flares on EV Lac which duration is less than 6 seconds. The corresponding total monitoring time is 173.6 hours for AD Leo and 173.3 hours for EV Lac.

scholarly journals Flare-Like Events on the T-Tauri Star RU LUP1

1989 ◽  
Vol 104 (2) ◽  
pp. 139-142 ◽  
Author(s):  
F. Giovannelli ◽  
D. Castaldo ◽  
E. Covino ◽  
A.A. Vittone ◽  
C. Rossi
Keyword(s):  
Tauri Star ◽  
Quiescent State ◽  
Complete Coverage ◽  
Patchy Distribution ◽  
Active Star ◽  
X Ray ◽  
T Tauri ◽  
Observed Behaviour ◽  
Flare Stars

AbstractA long term multifrequency campaign on the T Tauri star RU Lupi has been carried out in the X-Ray, UV optical and IR spectral regions with ASTRON and IUE satellites and ESO 1.5 m+IDS, 1.4 m CAT, 0.5 m UBVRI and 1 m IR telescopes, respectively.We present two flare-like events occurred on April 17, 1984 and June 30, 1986. The first one was detected only in the UV, clue to lack the of simultaneous observations in other spectral regions. The second one was observed in UV, optical and IR regions showing a maximum roughly in the U band A comparison of the whole energy distribution of this event with that of a quiescent state observed on June 27 shows a flux enhancement of (89 ± 2)%. A detailed analysis of UV continuum and lines, namely N V, C I, CII, CIV, Si II and Si IV, shows that ihe surfaces fluxes of RU Lupi are always larger than those observed on typical flare stars and on the Sun by a factor of roughly 2 and 3 orders of magnitude, respectively. This fact allows us to conclude that RU Lupi activity cannot be explained even invoking a complete coverage by solar-like plages. On the contrary a patchy distribution of the emitting regions could explain the observed behaviour of this active star.

scholarly journals Metallicity and Binarity in WC and WO Stars

2003 ◽  
Vol 212 ◽  
pp. 566-567
Author(s):  
Laura Norci ◽  
V. Francesco Polcaro ◽  
Roberto F. Viotti
Keyword(s):  
Statistical Analysis ◽  
Equivalent Width ◽  
Emission Lines ◽  
Physical Conditions ◽  
Maximum Value ◽  
Ionization Effect ◽  
Significant Difference ◽  
Increasing Trend ◽  
The Difference

Median values of the fwhm and equivalent width Wλ of the C iv 581 nm, O v 559 nm and 465 nm emission lines were derived from an extended statistical analysis of WC and WO stars (Norci et al. 2002; see Table 1). We find that the C iv equivalent width shows an increasing trend towards earlier WC subtypes, reaching a maximum value of 95 nm (± 32 %) for the Galactic WC4-6 stars, and decreases by about a factor of three in the hotter WO stars (Figure 1, left). The line appears about twice as strong in the LMC than in the Galactic WC4 stars, and the difference is particularly evident in the non-Galactic WO stars. Such an effect is absent in the O v 559 nm line, which smoothly increases towards WCE and WO stars, with no significant difference between Galactic and non-Galactic WC4 and WO stars. Thus this C anomaly is not an ionization effect; it is, therefore, probably due to a cause that selectively operates on C rather than on O. Different physical conditions in the winds of Galactic and non-Galactic stars, possibly related to the different initial metallicity Z, could be responsible for the anomaly.

scholarly journals UV and optical spectrum variability of T Tau and RY Tau

2012 ◽  
Vol 8 (S292) ◽  
pp. 44-44
Author(s):  
N. Z. Ismailov ◽  
N. Kh. Quliyev ◽  
O. V. Khalilov ◽  
H. N. Adigezalzade
Keyword(s):  
Emission Line ◽  
Brightness Variation ◽  
Emission Lines ◽  
Spectral Energy ◽  
Spectral Radiation ◽  
Line Intensities ◽  
T Tauri ◽  
Spectral Ranges ◽  
T Tau ◽  
Archive Data

AbstractIn this report we have presented results of spectral observations of classical T Tauri type stars T Tau and RY Tau. Observational dates were obtained from following sources: spectrograms of the UV range from the IUE archive data, and spectrograms of the visual range obtained in the 2 m telescope of ShAO of the NAS of Azerbaijan (Ismailov et al. 2010). For both of stars on the Scargle method we have searched a periodicity of variations in equivalent widths of emission lines in the optical and UV ranges. In the RY Tau firstly was detected the periodic variability in MgII λ2800 Å emission doublet intensities with a period of 23 days. The observed period had also revealed with the equivalent widths and displacements of components of Hα and H+Hϵ and K CaII emission.The lines were found to be shifted to short wavelengths as the emission line intensities increased in both UV and optical spectral ranges. The lack of a correlation between the brightness variation and the emission line intensity also suggests that, on the whole, the contribution from the radiation in emission lines for the star RY Tau is insignificant.On the analysis of T Tau we conclude that there is a significant variation of spectral emission lines in the optical and UV on a time scale of about 33 days and that this variations is periodic. Both of stars shows the periodicity also for observed group of such lines as CIV λ1450 Å, HeII λ 1640 Å, SII λ1756 Å (Ismailov et al. 2010, Ismailov et al. 2011).Additionally we have carried out spectral energy distributions of this stars in the range 0.36-100 μm which have indicated the excess of spectral radiation in the IR range of spectrum. These excesses of radiations can be explained by the thermal radiation of still unformed bodies at the circumstellar environment. The periodic variability in the spectrum together with the excess of the spectral radiation may be occurred by protoplanets and/or protostars in these young systems. It is showed that possible, planet formation processes mainly to be completed at the time of the formation of classical T Tauri type stars.

Evaluation of calibrations for limb scattering sensors

2020 ◽  
Author(s):  
Natalya Kramarova ◽  
Pawan Bhartia ◽  
Glen Jaross ◽  
Zhong Chen
Keyword(s):  
Measurement Errors ◽  
Montreal Protocol ◽  
Measuring Instruments ◽  
The Us ◽  
Mean Differences ◽  
Ozone Depleting Substances ◽  
Spectral Ranges ◽  
Stratospheric Composition ◽  
New Generation ◽  
Vertical Ozone

<p>The Ozone Mapping and Profiler Suite represents a new generation of the US ozone measuring instruments aimed to monitor the ozone recovery associated to the reduction in levels of man-made ozone depleting substances regulated by the Montreal protocol. The first OMPS was launched on board of the Suomi NPP satellite in October 2011. The Limb Profiler is a part of the OMPS instrumental suite, and it collects solar radiances scattered from the atmospheric limb in the UV and VIS spectral ranges. The next OMPS Limb Profiler is scheduled to launch in 2022 on board of NASA/NOAA JPSS-2 mission. These limb scattering measurements allow to retrieve vertical ozone profiles from the tropopause up to the mesosphere with a high vertical resolution (~2 km). The expected ozone recovery is almost three times slower than the ozone loss observed in 1980s and 1990s. To detect such small trends in ozone concentration, the instrument calibrations should be extremely accurate. Comparisons of ozone retrievals from OMPS LP with the correlative satellite measurements from Aura MLS and ISS SAGE III revealed that OMPS LP retrievals accurately characterize the vertical ozone distribution in different atmospheric regions which are most sensitive to changes in the stratospheric composition and dynamics. Between 18 and 42 km the mean differences between LP and correlative measurements are within ±10%, except for the northern high latitudes where between 20 and 32 km biases exceed 10% due to the measurement errors. We also found a small positive drift of ~0.5%/yr against MLS with a pattern that is consistent with the ~150-meter drift (over 7 years) in sensor pointing detected by one of our altitude resolving methods. The spatial patterns in the ozone biases and drifts suggest that remaining errors in the LP ozone retrievals are due to errors in altitude registration and instrument calibrations. We present a study where we evaluate calibrations of the OMPS LP by converting ozone differences between OMPS LP and Aura MLS into differences in radiances. Then these radiance differences are compared with the LP measured radiances to determine errors in OMPS LP calibrations. Since the OMPS LP has three slits, some of the errors, like a drift in the altitude registration, should be common across all three slits, but other errors will be unique for each slit, helping to isolate different sources of errors. This approach can be extended to earlier ESA’s limb scattering missions, like SCIAMACHY and OSIRIS, since MLS has long overlap with the ENVISAT and Odin missions.</p>

scholarly journals New Spectral Observations of the Variable Galaxy Kaz 163

2013 ◽  
Vol 9 (S304) ◽  
pp. 39-40
Author(s):  
Emilia L. Karapetyan
Keyword(s):  
Elliptical Galaxy ◽  
Short Wave ◽  
Mean Value ◽  
Emission Lines ◽  
Byurakan Astrophysical Observatory ◽  
X Ray ◽  
Long Wave ◽  
The Galaxy ◽  
The Mean ◽  
Active Processes

AbstractKaz 163 is a close double galaxy. Its southern component S is compact, with a very blue nucleus, in which heated active processes take place. From time to time gas formations are ejected from it, which behave themselves like emission components around the main emission lines Hα and Hβ, around both from their long-wave and short-wave sides. This paper presents the spectral data of new observations, which were carried out with the 2.6m telescope at the Byurakan Astrophysical Observatory in September 2011. During the former observation in October 1981, lines [NII] λλ 6584,6548 were not visible in the spectrum of the component S. In 2001 they were already visible on the spectrum, and on the spectrum obtained in 2011 they already surpassed the intensity of Hα. The magnitude of the component S is also changing: its nucleus is very blue and its U-B = −0m.63. In the soft X-ray spectral range (0.1–2 keV) the flux of the radiation changed by 45% during 55,000 sec, and in the hard one (2–10keV) it changed up to 3.4 times. Photoindices Γ for the soft and hard ranges in the spectrum of galaxy S, unlike other objects, do not so much differ from each other. The mean value for the first interval is approximately 2.5 and is equal −2.0 for the second one. On the histogram of redshifts Kaz 163 corresponds to the first big peak of the distribution. It is concluded that the component S of the galaxy Kaz 163 is a NLS1 galaxy, with the development of their evolution, is in the preliminary stage. Component N is a normal elliptical galaxy with no activity.

scholarly journals Energy Dissipation Mechanisms in Flare Stars

1985 ◽  
Vol 107 ◽  
pp. 245-262
Author(s):  
D. J. Mullan
Keyword(s):  
Solar Flare ◽  
Solar Flares ◽  
Visible Spectrum ◽  
Stellar Disk ◽  
Total Power ◽  
Quiescent State ◽  
Stellar Flare ◽  
Stellar Spectrum ◽  
Flare Stars ◽  
Visible Disk

Flare stars derive their name from intermittent increases in luminosity which have certain characteristics reminiscent of solar flares (e.g. enhanced strengths of emission lines in the stellar spectrum during the outbursts). When a flare star is observed in a filter which transmits, say, the violet part of the visible spectrum, the increase in luminosity during a flare may range from noise level up to perhaps 100 times the quiescent brightness. During a flare, certain spectral features of the quiescent star (e.g. molecular bands) remain visible, indicating that the flare occupies only a fraction of the visible disk. Thus, analagous to a solar flare, a stellar flare is confined to a single active region. However the total power is large enough to affect the integrated light from the stellar disk. In contrast, the largest solar flare (Etot ≈ 1032 ergs) has a rate of energy release (L ≈ 1029 erg/sec) which is so small that a distant observer would record such a flare as a luminosity increase of less than 10−4Lsun. However, even apart from the flares themselves, it has become apparent in recent years that flare stars in their “quiescent state” provide some extreme contrasts with the sun.

scholarly journals Statistics of flares observed for UV Ceti type stars YZ CMi, AD Leo, and EV Lac at the Okayama Observatory

1990 ◽  
Vol 137 ◽  
pp. 43-47
Author(s):  
K. Ishida
Keyword(s):  
Time Resolution ◽  
High Time ◽  
High Time Resolution ◽  
Ceti Type ◽  
Flare Stars ◽  
Ev Lac

Photoelectric monitoring of flare stars YZ CMi, AD Leo, and EV Lac has been done at the Okayama Observatory since early 1970s. This is a simultaneous UBV observations with a high time resolution. Some statistics of the flares of the UV Ceti type stars are presented.

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