SOFIA upGREAT/FIFI-LS Emission-line Observations of Betelgeuse during the Great Dimming of 2019/2020

2021 ◽  
Vol 162 (6) ◽  
pp. 246
Author(s):  
Graham M. Harper ◽  
Edward Chambers ◽  
William D. Vacca ◽  
Helmut Wiesemeyer ◽  
Dario Fadda ◽  
...  
Keyword(s):  
Emission Line ◽  
Radiation Field ◽  
Flux Measurement ◽  
Circumstellar Envelope ◽  
Space Observatory ◽  
Potential Explanation ◽  
Heating Source ◽  
Velocity Models ◽  
Outflow Velocity ◽  
Gas Drag

Abstract We report NASA-DLR SOFIA upGREAT circumstellar [O i] 63.2 μm and [C ii] 157.7 μm emission profiles and FIFI-LS [O i] 63.2 μm, [O i] 145.5 μm, and [C ii] 157.7 μm fluxes obtained shortly after Betelgeuse’s 2019/2020 Great Dimming event. Haas et al. noted a potential correlation between the [O i] 63.2 μm flux and V magnitude based on three Kuiper Airborne Observatory observations made with the CGS and FIFI instruments. The FIFI observation was obtained when V ≃ 0.88 and revealed a 3σ non-detection at a quarter of the previous CGS flux measurement made when V ≃ 0.35. A potential explanation could be a change in dust-gas drag heating by circumstellar silicates caused by variations in the photospheric radiation field. SOFIA observations provide a unique test of this correlation because the V-band brightness went to its lowest value on record, V ≃ 1.61, with the SOFIA observations being made when V FIFI−LS ≃ 1.51 and V upGREAT ≃ 1.36. The upGREAT spectra show a [O i] 63.2 μm flux larger than previous space observatory measurements obtained when V ≃ 0.58. The profile is consistent with formation in the slower, more turbulent inner S1 outflow, while the [C ii] 157.7 μm profile is consistent with formation farther out in the faster S2 outflow. Modeling of dust-gas drag heating, combined with 25 yr of Wing three-filter and V photometry, reveals that it is unlikely that the S1 circumstellar envelope and [O i] 63.2 μm fluxes are dominated by the dust-gas drag heating and that another heating source is also active. The [O i] 63.2 μm profile is hard to reconcile with existing outflow velocity models.

scholarly journals The Ionization of Planetary Nebulae

1968 ◽  
Vol 34 ◽  
pp. 190-204 ◽  
Author(s):  
Robert E. Williams
Keyword(s):  
Ionizing Radiation ◽  
Emission Line ◽  
Radiation Field ◽  
Planetary Nebulae ◽  
Model Atmosphere ◽  
Evolutionary Sequence ◽  
Lyman Continuum ◽  
The Mean ◽  
Central Stars

The ionization of the most abundant elements in planetary nebulae has been determined for a number of models of nebulae at different epochs in their expansion. The values used for the temperatures and radii of the central stars and the sizes and densities of the shells have come from Seaton's evolutionary sequence. The ionizing radiation field has been taken from model atmosphere calculations of the central stars by Gebbie and Seaton, and Böhm and Deinzer. Emission-line fluxes have been calculated for the models and compared with observations of planetary nebulae by O'Dell, Osterbrock's group, and Aller and his collaborators. Results indicate that the central stars have strong He+ Lyman continuum excesses, similar to those predicted by Gebbie and Seaton. The mean abundance determinations for the nebulae made by Aller are confirmed, with the exception of nitrogen, which appears to be 3 or 4 times more abundant than his value. It is also seen that the electron temperatures of the nebulae are higher than previous theoretical determinations, providing better agreement with empirically derived values.

scholarly journals Stellar Pulsation: (II) Multiple Distinct Shells

1993 ◽  
Vol 134 ◽  
pp. 169-172
Author(s):  
Yu Zhi-Yao
Keyword(s):  
Emission Line ◽  
Circumstellar Envelope ◽  
Stellar Pulsation

AbstractWe can find the conclusion with our analysis for VLA observation of OH maser and CO (2–1) emission line that they are distributed on some different distinct shells in the circumstellar envelope, respectively.

scholarly journals Simultaneous Spectroscopy and Polarimetry of Be Stars

1987 ◽  
Vol 92 ◽  
pp. 84-86
Author(s):  
D. R. Gies ◽  
David McDavid
Keyword(s):  
Mass Loss ◽  
Emission Line ◽  
Absorption Line ◽  
Line Profile ◽  
Circumstellar Envelope ◽  
Be Stars ◽  
Line Profiles ◽  
Initial Attempt ◽  
Rapid Variability ◽  
Hα Emission

Evidence is now accumulating that many Be stars display photospheric line profile variations on timescales of days or less that are probably caused by nonradial pulsations (Baade 1984; Penrod 1986). In some circumstances these pulsations can promote mass loss into the circumstellar envelope, and consequently the conditions in the inner part of the envelope may vary on similar timescales. Changes in the envelope could produce variations in the polarization and emission line profiles, and observers have reported rapid variability in both. We describe here an initial attempt to search for simultaneous variations in continuum polarization, Hα emission, and the He I λ6678 photospheric absorption line in order to investigate correlated changes on short timescales.

scholarly journals Emission Line Variability in the Be Star X-Ray Binaries 4U1258-61 and 4U2206+54

1987 ◽  
Vol 92 ◽  
pp. 311-313
Author(s):  
Robin H.D. Corbet
Keyword(s):  
Emission Line ◽  
Circumstellar Envelope ◽  
X Ray ◽  
Be Star ◽  
X Ray Binaries

AbstractResults of programs to monitor Ha emission line variability in two Be star X-ray binaries are presented. These systems provide a means of investigating the influence of a binary companion on the circumstellar envelope of a Be star.

scholarly journals Nebular abundances in galaxies: Beware of biases

2009 ◽  
Vol 5 (S262) ◽  
pp. 93-96 ◽  
Author(s):  
Grażyna Stasińska
Keyword(s):  
Ionizing Radiation ◽  
Emission Line ◽  
Structural Properties ◽  
Radiation Field ◽  
Dwarf Galaxies ◽  
Strong Line ◽  
Compact Galaxies

AbstractThe derivation of nebular abundances in galaxies using strong line methods is simple and quick. Various indices have been designed and calibrated for this purpose, and they are widely used. However, abundances derived with such methods may be significantly biased, if the objects under study have different structural properties (hardness of the ionizing radiation field, morphology of the nebulae) than those used to calibrate the methods. Special caution is required when comparing the metallicities of different samples, like, for example, blue compact galaxies and other emission line dwarf galaxies, or samples at different redshifts.

scholarly journals Paschen and Brackett Lines in Be stars

2000 ◽  
Vol 175 ◽  
pp. 472-475
Author(s):  
L. Cidale ◽  
J. Zorec ◽  
J.P. Maillard ◽  
N. Morrell
Keyword(s):  
Emission Line ◽  
Stellar Atmosphere ◽  
Velocity Fields ◽  
Circumstellar Envelope ◽  
Be Stars ◽  
Line Profiles ◽  
Circumstellar Envelopes ◽  
Hydrogen Line ◽  
Stellar Activity ◽  
Central Stars

AbstractThe activities detected in Be stars indicate that the formation of the circumstellar envelope and its structure cannot be studied independently of the phenomena taking place in the outermost layers of the central stars. Assuming that related to the stellar activity there is an expanding atmospheric region with temperatures Te > Teff followed by an envelope with a decreasing temperature, we calculated hydrogen line profiles for different velocity fields and different positions of temperature maxima relative to the underlying photosphere. Results show that the Hα line is not very sensitive to changes introduced to the stellar atmosphere and to the nearby circumstellar layers. Moreover, the Hα emission line profiles look like those produced by disc-like circumstellar envelopes seen pole-on, although the model for the circumstellar envelope is spherical. However, the first members of the Paschen and Brackett series are strongly sensitive to any changes introduced in the photospheric and exophotospheric layers. We conclude that the study of these lines may then be valuable to obtain new insight on the activity of central stars and on the phenomena involved in circumstellar envelope formation in Be stars.

scholarly journals Area Spectroscopy of the Extended Emission Line Region in the Seyfert Galaxy NGC 3516

1995 ◽  
Vol 149 ◽  
pp. 203-204
Author(s):  
K. Aoki ◽  
H. Ohtani ◽  
G. Kosugi ◽  
M. Yoshida
Keyword(s):  
Emission Line ◽  
Radiation Field ◽  
Seyfert Galaxy ◽  
Hii Regions ◽  
Nuclear Radiation ◽  
Ngc 4151 ◽  
Dust Clouds ◽  
Line Region ◽  
Extended Emission

The researches into extended emission line region (EELR) give us the valuable informations about the nucleus. A recent study of the EELR in the Seyfert 1 galaxy NGC 4151 by Yoshida and Ohtani (1993) have revealed that a strongly asymmetric radiation field in this typical Seyfert 1. They have suggested the anisotropy may be caused inside the BLR. It is important to examine if any other Seyfert 1 galaxy has an anisotropic nuclear radiation.The famous Seyfert 1 galaxy NGC 3516 has EELR which extends ∼ 10” on either side of the nucleus. The morphology of the EELR is Z-shape. This nearby (D=38.9Mpc) galaxy is of type SBO for which the object is expected to be free from contamination by HII regions and dust clouds.

scholarly journals ISOPHOT Observations of a Cold Filament in the Local Hot Bubble

1997 ◽  
Vol 166 ◽  
pp. 117-120
Author(s):  
Uwe Herbstmeier ◽  
Alexandre Wennmacher
Keyword(s):  
Radiation Field ◽  
Uv Radiation ◽  
Cirrus Clouds ◽  
Space Observatory ◽  
Infrared Space Observatory ◽  
Dust Temperature ◽  
Dust Component

AbstractWe report on FIR measurements of the dust component towards LVC 88+36–2, a dense neutral filament in the Local Hot Bubble. The measurements were performed with ISOPHOT, the photometer on-board ESA’s Infrared Space Observatory ISO. The dust temperature derived is about 18 K and stays constant across the filament. Limb brightening at 60μm is measured in agreement with cirrus clouds not located in the Local Hot Bubble. No evidence for an increased UV radiation field along the boundaries of the cloud is found.

scholarly journals ALMA spectrum of the extreme OH/IR star OH 26.5+0.6

2018 ◽  
Vol 14 (S343) ◽  
pp. 436-437
Author(s):  
K. Justtanont ◽  
S. Muller ◽  
M. J. Barlow ◽  
D. Engels ◽  
D. A. García-Hernández ◽  
...  
Keyword(s):  
Mass Loss ◽  
Emission Line ◽  
Gas Phase ◽  
Chemical Processes ◽  
Emission Lines ◽  
High Mass ◽  
Dust Formation ◽  
Circumstellar Envelope ◽  
High Mass Loss

AbstractWe present ALMA band 7 data of the extreme OH/IR star, OH 26.5+0.6. In addition to lines of CO and its isotopologues, the circumstellar envelope also exhibits a number of emission lines due to metal-containing molecules, e.g., NaCl and KCl. A lack of C18O is expected, but a non-detection of C17O is puzzling given the strengths of H217O in Herschel spectra of the star. However, a line associated with Si17O is detected. We also report a tentative detection of a gas-phase emission line of MgS. The ALMA spectrum of this object reveals intriguing features which may be used to investigate chemical processes and dust formation during a high mass-loss phase.

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