Spectroscopic detection of coronal plasma flows in loops undergoing thermal non-equilibrium cycles

Context. Long-period intensity pulsations were recently detected in the EUV emission of coronal loops and attributed to cycles of plasma evaporation and condensation driven by thermal non-equilibrium (TNE). Numerical simulations that reproduce this phenomenon also predict the formation of periodic flows of plasma at coronal temperatures along some of the pulsating loops. Aims. We aim to detect these predicted flows of coronal-temperature plasma in pulsating loops. Methods. We used time series of spatially resolved spectra from the EUV imaging spectrometer (EIS) onboard Hinode and tracked the evolution of the Doppler velocity in loops in which intensity pulsations have previously been detected in images of SDO/AIA. Results. We measured signatures of flows that are compatible with the simulations but only for a fraction of the observed events. We demonstrate that this low detection rate can be explained by line of sight ambiguities combined with instrumental limitations, such as low signal-to-noise ratio or insufficient cadence.

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MULTIPLE COMPONENT OUTFLOWS IN AN ACTIVE REGION OBSERVED WITH THE EUV IMAGING SPECTROMETER ONHINODE

The Astrophysical Journal ◽

10.1088/0004-637x/715/2/1012 ◽

2010 ◽

Vol 715 (2) ◽

pp. 1012-1020 ◽

Cited By ~ 58

Author(s):

P. Bryans ◽

P. R. Young ◽

G. A. Doschek

Keyword(s):

Active Region ◽

Imaging Spectrometer ◽

Multiple Component ◽

Euv Imaging

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DOPPLER SHIFT OF THE QUIET REGION MEASURED BY MERIDIONAL SCANS WITH THE EUV IMAGING SPECTROMETER ON BOARDHINODE

The Astrophysical Journal ◽

10.3847/0004-637x/816/1/14 ◽

2015 ◽

Vol 816 (1) ◽

pp. 14

Author(s):

N. Kitagawa ◽

H. Hara ◽

T. Yokoyama

Keyword(s):

Doppler Shift ◽

Imaging Spectrometer ◽

Quiet Region ◽

Euv Imaging

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A Variational Method for Filling in Missing Data in Doppler Velocity Fields

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-20-0151.1 ◽

2021 ◽

Author(s):

VINCENT T. WOOD ◽

ROBERT P. DAVIES-JONES ◽

ALAN SHAPIRO

Keyword(s):

Missing Data ◽

Doppler Radar ◽

Signal To Noise Ratio ◽

Original Data ◽

Radar Data ◽

Velocity Fields ◽

Doppler Velocity ◽

Doppler Radar Data ◽

Ground Clutter ◽

Tornado Warnings

AbstractSingle-Doppler radar data are often missing in important regions of a severe storm due to low return power, low signal-to-noise ratio, ground clutter associated with normal and anomalous propagation, and missing radials associated with partial or total beam blockage. Missing data impact the ability of WSR-88D algorithms to detect severe weather. To aid the algorithms, we develop a variational technique that fills in Doppler velocity data voids smoothly by minimizing Doppler velocity gradients while not modifying good data. This method provides estimates of the analysed variable in data voids without creating extrema.Actual single-Doppler radar data of four tornadoes are used to demonstrate the variational algorithm. In two cases, data are missing in the original data, and in the other two, data are voided artificially. The filled-in data match the voided data well in smoothly varying Doppler velocity fields. Near singularities such as tornadic vortex signatures, the match is poor as anticipated. The algorithm does not create any velocity peaks in the former data voids, thus preventing false triggering of tornado warnings. Doppler circulation is used herein as a far-field tornado detection and advance-warning parameter. In almost all cases, the measured circulation is quite insensitive to the data that have been voided and then filled. The tornado threat is still apparent.

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ELECTRON DENSITY OF ACTIVE REGION OUTFLOWS MEASURED BY THE EUV IMAGING SPECTROMETER ON BOARDHINODE

The Astrophysical Journal ◽

10.1088/0004-637x/805/2/97 ◽

2015 ◽

Vol 805 (2) ◽

pp. 97 ◽

Cited By ~ 2

Author(s):

N. Kitagawa ◽

T. Yokoyama

Keyword(s):

Active Region ◽

Electron Density ◽

Imaging Spectrometer ◽

Euv Imaging

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Spectroscopy of small gas components of non-equilibrium low-temperature plasma

Physics-Uspekhi ◽

10.3367/ufne.2021.07.039026 ◽

2021 ◽

Author(s):

Vladimir N. Ochkin

Keyword(s):

Low Temperature ◽

Low Temperature Plasma ◽

Temperature Plasma ◽

Non Equilibrium

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IUE Observations of Quasars

Symposium - International Astronomical Union ◽

10.1017/s007418090006842x ◽

1980 ◽

Vol 92 ◽

pp. 125-126

Author(s):

M. Schmidt ◽

R. F. Green ◽

J. R. Pier ◽

F. B. Estabrook ◽

A. L. Lane ◽

...

Keyword(s):

Signal To Noise Ratio ◽

Neutral Hydrogen ◽

Line Of Sight ◽

Resonance Transition ◽

Energy Distributions ◽

International Ultraviolet Explorer ◽

Visible Spectra ◽

Line Transfer ◽

Net Flux ◽

Low Dispersion

Spectra of six quasars have been obtained with the International Ultraviolet Explorer Satellite. Five of the six show no evidence for strong Lyα absorption between the redshifted and rest wavelengths, for .23≤ zem ≤1.72. In addition, the quasar PG 1115+080 at z=1.72 shows no evidence for strong He I absorption from the resonance transition at λ584 Å. These results confirm that the intergalactic medium must be both tenuous and hot enough to produce an optical depth <0.1 in neutral hydrogen and helium. In no case was the Lyman edge detected in absorption near zem. Four of the objects produce an average Lyα/Hβ intensity ratio of 6.3, in disagreement with the theoretical prediction for Case B optically thick recombination of 30. Also, two of the objects show Lyγ in emission, a result unexpected from Case B line transfer assumptions. The Lyα emission line in 3C 351 shows the identical sharp core plus 20,000 km s−1 broad wings observed in Hβ and Mg II, implying a common origin in the same dynamical ensemble of emitting regions. These quasars show systematically steeper spectral indices when the energy distributions are fit from the ultraviolet through the visible than those derived from the visible spectra alone. PG 1115+080 shows a featureless continuum down to an observed λ1173 Å. The ionizing spectrum, with fν αν−2.0, therefore persists beyond 2 Rydbergs. The spectrum of PG 1247+268, with z=2.038, contains a strong absorption line at observed λ2697 Å, with no net flux detected from λ2000 Å down to the observed limit at λ1150 Å. This result is interpreted as absorption in Lyα and the Ly edge at z=1.218. Low dispersion optical spectra show no evidence for Mg II or C IV absorption in the same system; the signal to noise ratio is too low in the IUE spectrum to confirm Lyβ. We conclude that the line of sight intersects a metal-poor cloud with τ ≲ 1 in the Ly continuum, at (1+zem)/(1 + zabs) = 1.37.

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The VMC survey

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833144 ◽

2018 ◽

Vol 613 ◽

pp. L8 ◽

Cited By ~ 7

Author(s):

F. Niederhofer ◽

M.-R. L. Cioni ◽

S. Rubele ◽

T. Schmidt ◽

K. Bekki ◽

...

Keyword(s):

Near Infrared ◽

Two Dimensions ◽

Magellanic Clouds ◽

Line Of Sight ◽

Main Body ◽

Proper Motions ◽

Velocity Pattern ◽

Spatially Resolved ◽

Magnitude Diagram ◽

Over Time

We present the first spatially resolved map of stellar proper motions within the central (~3.1 × 2.4 kpc) regions of the Small Magellanic Cloud (SMC). The data used for this study encompasses four tiles from the ongoing near-infrared VISTA survey of the Magellanic Clouds system and covers a total contiguous area on the sky of ~6.81 deg2. Proper motions have been calculated independently in two dimensions from the spatial offsets in the Ks filter over time baselines between 22 and 27 months. The reflex motions of approximately 33 000 background galaxies are used to calibrate the stellar motions to an absolute scale. The resulting catalog is composed of more than 690 000 stars which have been selected based on their position in the (J − Ks, Ks) color-magnitude diagram. For the median absolute proper motion of the SMC, we find (μαcos(δ), μδ) = (1.087 ± 0.192 (sys.) ± 0.003 (stat.), −1.187 ± 0.008 (sys.) ± 0.003 (stat.)) mas yr−1, consistent with previous studies. Mapping the proper motions as a function of position within the SMC reveals a nonuniform velocity pattern indicative of a tidal feature behind the main body of the SMC and a flow of stars in the south-east moving predominantly along the line-of-sight.

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Doppler shift oscillations of a sunspot detected by CYRA and IRIS

Astronomy and Astrophysics ◽

10.1051/0004-6361/202039007 ◽

2020 ◽

Vol 642 ◽

pp. A231

Author(s):

D. Li ◽

X. Yang ◽

X. Y. Bai ◽

J. T. Su ◽

Z. J. Ning ◽

...

Keyword(s):

Line Profile ◽

Gaussian Function ◽

Correlation Method ◽

Doppler Velocity ◽

Temperature Minimum ◽

Sunspot Umbra ◽

Spatially Resolved ◽

Doppler Shifts ◽

Time Distance ◽

The Moment

Context. The carbon monoxide (CO) molecular line at around 46655 Å in solar infrared spectra is often used to investigate the dynamic behavior of the cold heart of the solar atmosphere, i.e., sunspot oscillation, especially at the sunspot umbra. Aims. We investigated sunspot oscillation at Doppler velocities of the CO 7-6 R67 and 3-2 R14 lines that were measured by the Cryogenic Infrared Spectrograph (CYRA), as well as the line profile of Mg II k line that was detected by the Interface Region Imaging Spectrograph (IRIS). Methods. A single Gaussian function is applied to each CO line profile to extract the line shift, while the moment analysis method is used for the Mg II k line. Then the sunspot oscillation can be found in the time–distance image of Doppler velocities, and the quasi-periodicity at the sunspot umbra are determined from the wavelet power spectrum. Finally, the cross-correlation method is used to analyze the phase relation between different atmospheric levels. Results. At the sunspot umbra, a periodicity of roughly 5 min is detected at the Doppler velocity range of the CO 7-6 R67 line that formed in the photosphere, while a periodicity of around 3 min is discovered at the Doppler velocities of CO 3-2 R14 and Mg II k lines that formed in the upper photosphere or the temperature minimum region and the chromosphere. A time delay of about 2 min is measured between the strong CO 3-2 R14 line and the Mg II k line. Conclusions. Based on the spectroscopic observations from the CYRA and IRIS, the 3 min sunspot oscillation can be spatially resolved in the Doppler shifts. It may come from the upper photosphere or the temperature minimum region and then propagate to the chromosphere, which might be regarded as a propagating slow magnetoacoustic wave.

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LLAMA: The MBH–σ⋆ relation of the most luminous local AGNs

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936321 ◽

2020 ◽

Vol 634 ◽

pp. A114 ◽

Cited By ~ 2

Author(s):

Turgay Caglar ◽

Leonard Burtscher ◽

Bernhard Brandl ◽

Jarle Brinchmann ◽

Richard I. Davies ◽

...

Keyword(s):

Black Hole ◽

Near Infrared ◽

Velocity Dispersion ◽

Signal To Noise Ratio ◽

Broad Line ◽

Host Galaxies ◽

Spatially Resolved ◽

Stellar Velocity ◽

Black Hole Masses

Context. The MBH–σ⋆ relation is considered a result of coevolution between the host galaxies and their supermassive black holes. For elliptical bulge hosting inactive galaxies, this relation is well established, but there is still discussion concerning whether active galaxies follow the same relation. Aims. In this paper, we estimate black hole masses for a sample of 19 local luminous active galactic nuclei (AGNs; LLAMA) to test their location on the MBH–σ⋆ relation. In addition, we test how robustly we can determine the stellar velocity dispersion in the presence of an AGN continuum and AGN emission lines, and as a function of signal-to-noise ratio. Methods. Supermassive black hole masses (MBH) were derived from the broad-line-based relations for Hα, Hβ, and Paβ emission line profiles for Type 1 AGNs. We compared the bulge stellar velocity dispersion (σ⋆) as determined from the Ca II triplet (CaT) with the dispersion measured from the near-infrared CO (2-0) absorption features for each AGN and find them to be consistent with each other. We applied an extinction correction to the observed broad-line fluxes and we corrected the stellar velocity dispersion by an average rotation contribution as determined from spatially resolved stellar kinematic maps. Results. The Hα-based black hole masses of our sample of AGNs were estimated in the range 6.34 ≤ log MBH ≤ 7.75 M⊙ and the σ⋆CaT estimates range between 73 ≤ σ⋆CaT ≤ 227 km s−1. From the so-constructed MBH − σ⋆ relation for our Type 1 AGNs, we estimate the black hole masses for the Type 2 AGNs and the inactive galaxies in our sample. Conclusions. We find that our sample of local luminous AGNs is consistent with the MBH–σ⋆ relation of lower luminosity AGNs and inactive galaxies, after correcting for dust extinction and the rotational contribution to the stellar velocity dispersion.

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