Chromospheric activity in red giants, and related phenomena

1970 ◽  
Vol 36 ◽  
pp. 199-208
Author(s):  
Armin J. Deutsch
Keyword(s):  
Emission Line ◽  
Spectral Type ◽  
Time Scale ◽  
Vacuum Ultraviolet ◽  
Time Variable ◽  
Emission Lines ◽  
Absorption Lines ◽  
Red Giants ◽  
Chromospheric Activity ◽  
Near Ultraviolet

Normal red giants of a given spectral type are shown to be heterogeneous with respect to the following chromospheric features: the Balmer absorption lines, the emission line at H∊, and the double-reversed emission lines at Caii H and K. These chromospheric lines are also shown to be strongly time variable, in at least some red giants, on a time scale of a few months or years. Other chromospheric features that require study lie in the infrared (Hei 10830), the near ultraviolet (Feii emission lines), and the vacuum ultraviolet.

scholarly journals Absorption Systems in High Redshift QSOs

1977 ◽  
Vol 74 ◽  
pp. 193-222 ◽  
Author(s):  
A. Boksenberg
Keyword(s):  
Emission Line ◽  
Absorption Line ◽  
High Redshift ◽  
Ground Level ◽  
Emission Lines ◽  
Absorption Lines ◽  
Absorption System ◽  
Characteristic Emission

In addition to the characteristic emission lines, absorption lines frequently are seen in the spectra of QSOs, usually those with high redshift (zem ≳ 1.8). About 10 percent of all QSOs listed in the compilation of Burbidge et al. (1976a) are recorded as having at least one ‘identified’ absorption system, meaning that a pattern of several selected observed lines can be matched with the apparent wavelengths of transitions (generally from the ground level) in a physical plausible group of atoms or ions at the same, although arbitrary, redshift (Bahcall 1968, Aaronson et al. 1975). Identified absorption line redshifts range from being comparable with the associated emission line redshifts, to having very much smaller values with relative velocities exceeding 0.5c in the QSO frame. Added to this, there are many QSOs having absorption lines not yet recognised as belonging to identified systems, both those objects already having one or more identifications, and others with none.

scholarly journals X-ray Grating Observations of Recent Recurrent Novae

2011 ◽  
Vol 7 (S281) ◽  
pp. 181-185
Author(s):  
Marina Orio ◽  
Ehud Behar ◽  
J. Gallagher ◽  
A. Bianchini ◽  
E. Chiosi ◽  
...  
Keyword(s):  
White Dwarf ◽  
Peak Temperature ◽  
Carbon Accounting ◽  
Emission Lines ◽  
Absorption Lines ◽  
Red Giants ◽  
X Ray ◽  
Secular Evolution ◽  
Show Evidence ◽  
Collisional Ionization

AbstractTwo recurrent novae (RNe) that do not host red giants were observed in outburst at the beginning of 2009 and 2010, respectively. The first nova was LMC 2009a, and the second one was U Scorpii. Nova LMC 2009a was a relatively slow RN, and it was quite luminous both at optical and X-ray wavelengths. U Sco is the fastest nova ever recorded. Its supersoft X-ray phase started a couple of weeks after optical maximum and lasted for about a month, while for Nova LMC 2009a this phase started four months after maximum and lasted for 5 months. For both novae, the first X-ray spectrum taken while the luminous supersoft X-ray source was beginning to emerge is remarkably similar with broad and prominent emission lines of nitrogen and carbon accounting for at least 30% of the X-ray flux. Blue-shifted absorption and red-shifted emission form apparent P-Cyg profiles. We attribute the emission features to the ejecta and show evidence that they are largely due to collisional ionization. In the case of U Sco the absorption lines were embedded in the emission features after the first observation. We find evidence that in U Scorpii we were observing the Thomson reflected spectrum at a distance of ≃ 3 R⊙ from the white dwarf rather than the atmosphere itself. For both novae, the peak temperature was remarkably high, probably close to 900,000 K for U Sco, and about 600,000 K for Nova LMC 2009a. We suggest that these two objects represent different stages of RNe secular evolution.

THE PHOTOELECTRIC TEMPERATURES OF THE P CYGNI STARS

1948 ◽  
Vol 26a (3) ◽  
pp. 149-166
Author(s):  
C. S. Beals ◽  
R. D. Hatcher
Keyword(s):  
Emission Line ◽  
Spectral Type ◽  
Temperature Scale ◽  
Emission Lines ◽  
Graphical Methods ◽  
Lower Range ◽  
Line Intensities

The photoelectric temperatures of 52 P Cygni stars of spectral type from A4 to O5 have been determined from emission lines by Zanstra's method. For approximately half the stars, accurate spectrophotometric measures of emission line intensities were available and for the remainder the intensities were estimated on the basis of published descriptions of spectra. The computed temperatures were found to range from 10,000° to 42,000° K. and after smoothing by graphical methods a temperature scale for the O, B, and A type stars showed the following values: A0, 16,000°; B0, 35,000°; O5, 40,000° K. Comparisons are made with temperatures derived by other methods and reasons are given for attributing greater weight to the values from B0 to O5 than to those in the lower range of the sequence.

scholarly journals Evidence for disks around certain luminous Magellanic cloud stars from the study of FeII

1987 ◽  
Vol 122 ◽  
pp. 443-444
Author(s):  
G. Muratorio ◽  
M. Friedjung
Keyword(s):  
Energy Distribution ◽  
Emission Line ◽  
Line Emission ◽  
Magellanic Cloud ◽  
Emission Lines ◽  
Absorption Lines ◽  
Line Of Sight ◽  
Continuous Energy

Study of FeII emission lines in emission and absorption using both emission line self absorption curves and ultraviolet spectral synthetis, shows that line emission is produced in the case of certain luminous Magellanic Cloud stars, in a region not in front of the photosphere. This region is most easily understood as being a disk. Absorption lines of FeII are either produced by a wind, or if the disk inclination is small with respect to the line of sight, in layers associated with the disk. The presence of disks also helps one to explain the form of the continuous energy distribution.

A Search for HI Absorption in the Radio Spectra of the Quasi-Stellar Objects 4C 05.34 and PKS 0237-23

1975 ◽  
Vol 2 (6) ◽  
pp. 365-366 ◽  
Author(s):  
B.A. Peterson ◽  
J.D. Murray ◽  
A.E. Wright
Keyword(s):  
Emission Line ◽  
Intergalactic Medium ◽  
Mass Density ◽  
Emission Lines ◽  
Absorption Lines ◽  
Stellar Objects ◽  
Upper Limit ◽  
Quasi Stellar Objects ◽  
No Absorption

The ratio of the mass density in visible galaxies to the upper limit for the HI mass density determined from the lack of continuous Ly-α absorption in QSO spectra is 3 × 104. Thus, if galaxies form by condensation from an intergalactic medium, the process must be extremely efficient. Although no absorption due to a continuous distribution of intergalactic HI has been detected, many QSOs have been discovered that have absorption lines in their spectra, which have redshifts very different from the emission lines, and may be produced in clouds of integalactic HI. As would be expected if this were the case, the proportion of QSOs with absorption lines in their spectra is greatest for those which have large emission line redshifts. Another possibility, especially for those absorption lines in redshift systems with Zabs nearly equal to Zem , is that the absorption lines are produced in clouds surrounding the QSO.

scholarly journals Chemical Composition of Nova Cygni 1975

1977 ◽  
Vol 42 ◽  
pp. 274-278
Author(s):  
A.A. Boyarchuk
Keyword(s):  
Chemical Composition ◽  
Spectral Type ◽  
Growth Analysis ◽  
Crimean Astrophysical Observatory ◽  
Emission Lines ◽  
Absorption Lines ◽  
Strong Emission ◽  
Light Maximum ◽  
No Emissions

AbstractThe chemical composition of Nova Cygni 1975 was determined by a curve-of-growth analysis. A strong excess of helium and the CNO -group abundances and a normal Si abundance was found.Spectral observations of N Cyg 1975 were begun at the Crimean Astrophysical Observatory on 29 August 1975, at 18h 50m UT, one day before light maximum (Boyarchuk et al. 1977). Twelve spectrograms with a dispersion of 4,6 and 12 Å/mm were taken during this night. The spectral type of the Nova was B2 Ia+ and no emissions appeared in the spectrum. During the following night, 10 spectrograms were obtained. The spectral type of the Nova was A2 Ia+ qe, and strong emission lines with P Cygni-type profiles could be detected. Since absorption lines were not observed on 30 August, only the spectrograms taken on 29 August can be used for a curve-of-growth analysis.

scholarly journals The massive Wolf-Rayet binary WR 98 (WN7/WC+08-9)

2003 ◽  
Vol 212 ◽  
pp. 184-185 ◽  
Author(s):  
Roberto C. Gamen ◽  
Virpi S. Niemela
Keyword(s):  
Emission Line ◽  
Circular Orbit ◽  
Orbital Motion ◽  
Emission Lines ◽  
Absorption Lines ◽  
Line Spectrum ◽  
Mass Ratio ◽  
Orbital Elements ◽  
Spectroscopic Binary ◽  
Emission Line Spectrum

We present the discovery of OB type absorption lines superimposed to the emission line spectrum, and the first double-lined orbital elements, for the massive Wolf-Rayet binary WR 98 (HDE 318016, WN7/C+08-9), a spectroscopic binary in a circular orbit with a period of 47.825 d. The semi-amplitudes of the orbital motion of the emission lines differ from line to line, indicating a mass ratio in the range q ≡ MWR/MOB = 1–1.8.

scholarly journals HIGH-RESOLUTION SPECTROSCOPY OF THE B[e] STAR MWC 645

2021 ◽  
Vol 34 ◽  
pp. 59-64
Author(s):  
A.S. Nodyarov ◽  
A.S. Miroshnichenko ◽  
S.A. Khokhlov ◽  
S.V. Zharikov ◽  
N. Manset ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Emission Line ◽  
Spectroscopic Data ◽  
Emission Lines ◽  
Absorption Lines ◽  
High Resolution Spectroscopy ◽  
Cool Component ◽  
Spectroscopic Observations ◽  
First Time

Optical high-resolution spectroscopic observations of the emission-line star MWC645 are presented. The spectrum exhibits strong variable double-peaked Balmer emission lines as well as low-excitation emission lines of FeII, [FeII], and [OI] which are signatures of the B[e] phenomenon, while lines of helium have not been found. In addition to the emission lines, for the first time we identified absorption lines of neutral metals (e.g., LiI 6708  A, CaI 6717 A, and a number of FeI and TiI lines) that indicate the presence of a cool component in the system. The heliocentric radial velocity measured in our best spectrum was found to be −65.1±1.0 kms −1 for the emission lines and −23.2±0.4 kms −1 for the absorption lines. Using a combination of photometric and spectroscopic data as well as the Gaia EDR3 distance (D=6.5±0.9 kpc), we disentangled the component contributions and estimated their temperatures and luminosities (∼15000 K and ∼4000 K, log L/L ? = 3.8±0.2 and 2.8±0.2 for the hot and cool component, respectively).

scholarly journals Gaia-assisted discovery of a detached low-ionisation BAL quasar with very large ejection velocities

2020 ◽  
Vol 634 ◽  
pp. A111 ◽  
Author(s):  
J. P. U. Fynbo ◽  
P. Møller ◽  
K. E. Heintz ◽  
J. N. Burchett ◽  
L. Christensen ◽  
...  
Keyword(s):  
Emission Line ◽  
Absorption Line ◽  
Emission Lines ◽  
Broad Absorption ◽  
Broad Absorption Line ◽  
Red Edge ◽  
First Case ◽  
Bl Lac ◽  
Spatially Extended ◽  
Extended Emission

We report on the discovery of a peculiar broad absorption line (BAL) quasar identified in our Gaia-assisted survey of red quasars. The systemic redshift of this quasar was difficult to establish because of the absence of conspicuous emission lines. Based on deep and broad BAL troughs of at least Si IV, C IV, and Al III, a redshift of z = 2.41 was established under the assumption that the systemic redshift can be inferred from the red edge of the BAL troughs. However, we observe a weak and spatially extended emission line at 4450 Å that is most likely due to Lyman-α emission, which implies a systemic redshift of z = 2.66 if correctly identified. There is also evidence for the onset of Lyman-α forest absorption bluewards of 4450 Å and evidence for Hα emission in the K band consistent with a systemic redshift of z = 2.66. If this redshift is correct, the quasar is an extreme example of a detached low-ionisation BAL quasar. The BALs must originate from material moving with very large velocities ranging from 22 000 km s−1 to 40 000 km s−1. To our knowledge, this is the first case of a systemic-redshift measurement based on extended Lyman-α emission for a BAL quasar. This method could also be useful in cases of sufficiently distant BL Lac quasars without systemic-redshift information.

scholarly journals The SAMI Galaxy Survey: reconciling strong emission line metallicity diagnostics using metallicity gradients

2021 ◽  
Vol 502 (3) ◽  
pp. 3357-3373
Author(s):  
Henry Poetrodjojo ◽  
Brent Groves ◽  
Lisa J Kewley ◽  
Sarah M Sweet ◽  
Sebastian F Sanchez ◽  
...  
Keyword(s):  
Emission Line ◽  
Electron Temperature ◽  
Gas Phase ◽  
Mass Range ◽  
Accurate Method ◽  
Emission Lines ◽  
Mass Relation ◽  
Strong Emission ◽  
Data Release ◽  
Accurate Comparison

ABSTRACT We measure the gas-phase metallicity gradients of 248 galaxies selected from Data Release 2 of the SAMI Galaxy Survey. We demonstrate that there are large systematic discrepancies between the metallicity gradients derived using common strong emission line metallicity diagnostics. We determine which pairs of diagnostics have Spearman’s rank coefficients greater than 0.6 and provide linear conversions to allow the accurate comparison of metallicity gradients derived using different strong emission line diagnostics. For galaxies within the mass range 8.5 < log (M/M⊙) < 11.0, we find discrepancies of up to 0.11 dex/Re between seven popular diagnostics in the metallicity gradient–mass relation. We find a suggestion of a break in the metallicity gradient–mass relation, where the slope shifts from negative to positive, occurs between 9.5 < log (M/M⊙) < 10.5 for the seven chosen diagnostics. Applying our conversions to the metallicity gradient–mass relation, we reduce the maximum dispersion from 0.11 dex/Re to 0.02 dex/Re. These conversions provide the most accurate method of converting metallicity gradients when key emission lines are unavailable. We find that diagnostics that share common sets of emission line ratios agree best, and that diagnostics calibrated through the electron temperature provide more consistent results compared to those calibrated through photoionization models.

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