Temperature analysis of solar prominences by multi-wavelength observations

2020 ◽  
Vol 72 (5) ◽  
Author(s):  
Sanetaka Okada ◽  
Kiyoshi Ichimoto ◽  
Aki Machida ◽  
Satomi Tokuda ◽  
Yuwei Huang ◽  
...  
Keyword(s):  
Spectral Lines ◽  
Emission Lines ◽  
Kinetic Temperature ◽  
Slab Model ◽  
Thermal Velocity ◽  
Radiative Balance ◽  
Gaussian Profile ◽  
Solar Prominences ◽  
Multi Wavelength ◽  
The Difference

Abstract The aim of this paper is to determine the kinetic temperature of solar prominences from widths of emission lines with a careful evaluation of its validity, and to investigate the spatial distribution of the non-thermal velocity and the kinetic temperature in prominences. Spectroscopic observations of prominences were carried out using the Domeless Solar Telescope at the Hida observatory in four emission lines, i.e., H$\alpha$$656.3\:$nm, H$\beta$$486.1\:$nm, Ca$^{+}$IR $854.2\:$nm, and Ca$^{+}$K $393.4\:$nm. We found systematic differences in temperature and its spatial distributions in prominences obtained from different pairs of spectral lines. The reason for the difference is that the intrinsic widths of emission lines determined by a single-slab model are different for optically thick and thin lines, and can be attributed to the assumption of a Gaussian profile of the non-thermal broadening in the single-slab model. With numerical experiments, we found that the observed differences among line pairs can be reproduced by a multi-slab model, in which each slab has different non-thermal broadening and line-of-sight velocity. The most accurate evaluation of the temperature is obtained with the pair of H$\beta$ and Ca$^{+}$IR in our selection. Based on these results, we found the typical kinetic temperature of prominences to be 8000–$12000\:$K, which is significantly higher than the temperature determined by radiative balance and suggests the presence of mechanical heating in prominences. Also suggested is the presence of positive spatial correlation between non-thermal velocity and temperature. We revisit past observational results on the prominence temperature and discuss the reason for discrepancies among them.

Measurement of Dysprosium Stark Width and the Electron Impact Width Parameter

2018 ◽  
Vol 73 (2) ◽  
pp. 203-213 ◽  
Author(s):  
Jhonatha R. dos Santos ◽  
Jonas Jakutis Neto ◽  
N. Rodrigues ◽  
M.G. Destro ◽  
José W. Neri ◽  
...  
Keyword(s):  
Electron Density ◽  
Impact Parameter ◽  
Plasma Temperature ◽  
Spectral Lines ◽  
Emission Lines ◽  
Spectroscopic Methods ◽  
Species Concentration ◽  
The Impact ◽  
Stark Width

In this work, we suggest a methodology to determine the impact parameter for neutral dysprosium emission lines from the characterization of the plasma generated by laser ablation in a sealed chamber filled with argon. The procedure is a combination of known consistent spectroscopic methods for plasma temperature determination, electron density, and species concentration. With an electron density of 3.1 × 1018 cm–3 and temperature close to 104 K, we estimated the impact electron parameter for nine spectral lines of the neutral dysprosium atom. The gaps in the impact parameter data in the literature, mainly for heavy elements, stress the importance of the proposed method.

scholarly journals Statistical Features of the Quiet Sun in EUV

2001 ◽  
Vol 203 ◽  
pp. 416-418
Author(s):  
A. Pauluhn ◽  
S. K. Solanki ◽  
I. Rüedi ◽  
E. Landi ◽  
U. Schühle
Keyword(s):  
Lognormal Distribution ◽  
Distribution Functions ◽  
Spectral Lines ◽  
Emission Lines ◽  
Statistical Features ◽  
Frequency Distributions ◽  
Quiet Sun ◽  
Euv Emission ◽  
The Past ◽  
Radiance Distribution

Frequency distributions of the intensities of EUV emission lines in the quiet Sun have in the past usually been modelled using two Gaussians. Here we test this and other distribution functions against observed distributions with exceptional statistics. The data were obtained in a number of spectral lines observed with CDS and SUMER. We show that the frequency distribution of the radiance is best modelled by a lognormal distribution. The fact that the radiance distribution of the quiet Sun including the network and the intranetwork is better reproduced by a single lognormal distribution function than by two Gaussians suggests that the same heating processes are acting in both types of features.

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 Molecular environs and triggered star formation around the large Galactic infrared bubble N 24

2019 ◽  
Vol 487 (2) ◽  
pp. 1517-1528 ◽  
Author(s):  
Xu Li ◽  
Jarken Esimbek ◽  
Jianjun Zhou ◽  
W A Baan ◽  
Weiguang Ji ◽  
...  
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Young Stellar Objects ◽  
Collapse Mechanism ◽  
Kinetic Temperature ◽  
H Ii Regions ◽  
Dark Cloud ◽  
Stellar Objects ◽  
Multi Wavelength ◽  
Mass Size

Abstract A multi-wavelength analysis of the large Galactic infrared bubble N 24 is presented in this paper in order to investigate the molecular and star-formation environment around expanding H ii regions. Using archival data from Herschel and ATLASGAL, the distribution and physical properties of the dust over the entire bubble are studied. Using the Clumpfind2d algorithm, 23 dense clumps are identified, with sizes and masses in the range 0.65–1.73 pc and 600–16 300 M⊙, respectively. To analyse the molecular environment in N 24, observations of NH3 (1,1) and (2,2) were carried out using the Nanshan 26-m radio telescope. Analysis of the kinetic temperature and gravitational stability of these clumps suggests gravitational collapse in several of them. The mass–size distributions of the clumps and the presence of massive young protostars indicate that the shell of N 24 is a region of ongoing massive-star formation. The compatibility of the dynamical and fragmentation timescales and the overabundance of young stellar objects and clumps on the rim suggest that the ‘collect-and-collapse’ mechanism is in play at the boundary of the bubble, but the existence of the infrared dark cloud at the edge of bubble indicates that a ‘radiation-driven implosion’ mechanism may also have played a role there.

scholarly journals Short and Medium Term Variability of Emission Lines in Selected Southern be Stars

1999 ◽  
Vol 169 ◽  
pp. 36-39
Author(s):  
Thomas Rivinius
Keyword(s):  
Line Emission ◽  
Spectral Lines ◽  
Emission Lines ◽  
Be Stars ◽  
Medium Term ◽  
Monitoring Period ◽  
Stellar Orbit

AbstractWe observed a sample of several southern Be stars from 1995 to 1997 typically for several months in each season using our spectrograph HEROS. One of these stars, μ Cen, was found to be in the process of continued gradual recovery of the Hydrogen emitting disk which had been lost from 1977-1989. During the monitoring period numerous line emission outbursts were observed. A generalized pattern of an outburst cycle is derived from observations of different circumstellar lines at times of various levels of emission from the disk. Relative quiescence in which mostly periodic varaibiltiy is seen, rapid decreases of emission (precursor), outburst, and subsequent relaxation can be distinguished as the main constituing phases, even though there are distinct differences between different groups of spectral lines. Based on this empirical phenomenology, a schematic picture of the associated ejection of matter into a near-stellar orbit is sketched and similarities between μ Cen and other stars will be outlined.

scholarly journals One year of CNR-IMAA multi-wavelength Raman lidar measurements in correspondence of CALIPSO overpass: Level 1 products comparison

2009 ◽  
Vol 9 (2) ◽  
pp. 8429-8468 ◽  
Author(s):  
L. Mona ◽  
G. Pappalardo ◽  
A. Amodeo ◽  
G. D'Amico ◽  
F. Madonna ◽  
...  
Keyword(s):  
Relative Difference ◽  
Raman Lidar ◽  
Continental Scale ◽  
Tropospheric Aerosol ◽  
Lidar Measurements ◽  
Multi Wavelength ◽  
The Mean ◽  
Level 1 ◽  
The Difference ◽  
Mean Differences

Abstract. At CNR-IMAA, an aerosol lidar system is operative since May 2000 in the framework of EARLINET (European Aerosol Research Lidar Network), the first lidar network for tropospheric aerosol study on continental scale. High quality multi-wavelength measurements make this system a reference point for the validation of data products provided by CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations), the first satellite-borne lidar specifically designed for aerosol and cloud study. Since 14 June 2006, devoted measurements are performed at CNR-IMAA in coincidence of CALIPSO overpasses. For the first time, results on 1-year comparisons between ground-based multi-wavelength Raman lidar measurements and corresponding CALIPSO lidar Level 1 profiles are presented. A methodology for the comparison is presented and discussed into details. Cases with the detection of cirrus clouds in CALIPSO data are separately analysed for taking into account eventual multiple scattering effects. For cirrus cloud cases, few cases are available to draw any conclusions. For clear sky conditions, the comparison shows good performances of the CALIPSO on-board lidar: the mean relative difference between the ground-based and CALIPSO Level 1 measurements is always within its standard deviation at all altitudes, with a mean difference in the 3–8 km altitude range of (−2±12)%. At altitude ranges corresponding to the typical PBL height observed at CNR-IMAA, a mean underestimation of (−24±20)% is observed in CALIPSO data, probably due to the difference in the aerosol content at the location of PEARL and CALIPSO ground-track location. Finally, the mean differences are on average lower for the closest overpasses (at about 40 km), with an increment of the differences at all altitude ranges when the 80 km overpasses are considered.

scholarly journals Promise of Persistent Multi-Messenger Astronomy with the Blazar OJ 287

Galaxies ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 1
Author(s):  
Mauri J. Valtonen ◽  
Lankeswar Dey ◽  
Achamveedu Gopakumar ◽  
Staszek Zola ◽  
S. Komossa ◽  
...  
Keyword(s):  
Black Hole ◽  
Spectral Lines ◽  
Host Galaxy ◽  
Central Engine ◽  
Multi Wavelength ◽  
Hole Model ◽  
Electromagnetic Signals ◽  
The Times ◽  
Spectral Survey ◽  
Blazar Oj 287

Successful observations of the seven predicted bremsstrahlung flares from the unique bright blazar OJ 287 firmly point to the presence of a nanohertz gravitational wave (GW) emitting supermassive black hole (SMBH) binary central engine. We present arguments for the continued monitoring of the source in several electromagnetic windows to firmly establish various details of the SMBH binary central engine description for OJ 287. In this article, we explore what more can be known about this system, particularly with regard to accretion and outflows from its two accretion disks. We mainly concentrate on the expected impact of the secondary black hole on the disk of the primary on 3 December 2021 and the resulting electromagnetic signals in the following years. We also predict the times of exceptional fades, and outline their usefulness in the study of the host galaxy. A spectral survey has been carried out, and spectral lines from the secondary were searched for but were not found. The jet of the secondary has been studied and proposals to discover it in future VLBI observations are mentioned. In conclusion, the binary black hole model explains a large number of observations of different kinds in OJ 287. Carefully timed future observations will be able to provide further details of its central engine. Such multi-wavelength and multidisciplinary efforts will be required to pursue multi-messenger nanohertz GW astronomy with OJ 287 in the coming decades.

scholarly journals Effects of Abundance Changes on the Spectra of Very Cool White Dwarfs

1976 ◽  
Vol 72 ◽  
pp. 25-25
Author(s):  
R. Wehrse
Keyword(s):  
White Dwarfs ◽  
Wavelength Dependence ◽  
Abundance Ratio ◽  
Spectral Lines ◽  
Line Density ◽  
Metal Line ◽  
Metal Contents ◽  
The Difference ◽  
Cool White Dwarfs ◽  
Blue Spectral Region

In order to study the atmospheres of cool white dwarfs of spectral types DA, DF and DG, model atmospheres have been calculated for temperatures 5000 ≤ Teff ≤ 7000 K and gravities 7 ≤ log g ≤ 8.5. The helium to hydrogen abundance ratio ranges from 0.1 to 1000. The abundances of the metals ∈M (relative to hydrogen) vary between the solar value ∈⊙M and ∈⊙M/1000. The models are hydrogen and metal line blanketed and in radiative equilibrium. The models with increased He abundance are characterized by a decreased mean opacity since the absorption cross-section of He is much smaller than that of H–. As a result, the spectral lines become stronger and – due to the much higher pressures – much broader. A reduction of the metal contents also increases the pressures. In this case it is caused by the shortage of electron suppliers. Here the spectral lines also become broader, but in general weaker.These effects strengthen the overlap of the lines due to the high gravity of white dwarfs and more or less lead to a quasi-continuum which may be much below the true continuum. Because of the wavelength dependence of the line density the depression is strongest in the UV and blue spectral region, whereas for wavelengths λ ≥ 4500 Å the difference from the true continuum is only a few per cent. The details will be published elsewhere.

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