scholarly journals Flare and CME Onset: UV Spectra Show Fast 3-D Flow

2001 ◽  
Vol 203 ◽  
pp. 374-376
Author(s):  
D. E. Innes
Keyword(s):  
Coronal Loop ◽  
Optical Emission ◽  
Uv Spectra ◽  
Emission Lines ◽  
Loop Structure ◽  
The Sun ◽  
The West ◽  
X Ray ◽  
West Limb ◽  
High Cadence

We present observations taken in the corona above a flare that occurred on the west limb of the Sun. SUMER spectra show large red (350 km s−1) and blue (650 km s−1) Dopplershifts in Fe XX (107 K), Cr XVI (5 × 106 K), Si IX (106 K) and O III (105 K) emission lines. These shifts are associated with a fast moving (400 km s−1) optical emission front detected in high cadence images, taken with the coronagraph MICA. SXT images show fast soft X-ray ejecta that can be extrapolated back to the position of pre-flare coronal arcade structure seen in EIT 195 images. The observations are interpreted as evidence of a blast wave propagating through the active region coronal loop structure very early in the flare evolution.

scholarly journals Discovery and follow-up of ASASSN-19dj: an X-ray and UV luminous TDE in an extreme post-starburst galaxy

2020 ◽  
Vol 500 (2) ◽  
pp. 1673-1696 ◽  
Author(s):  
Jason T Hinkle ◽  
T W-S Holoien ◽  
K Auchettl ◽  
B J Shappee ◽  
J M M Neustadt ◽  
...  
Keyword(s):  
Optical Emission ◽  
Starburst Galaxy ◽  
Late Time ◽  
X Rays ◽  
Tidal Disruption ◽  
X Ray ◽  
Bolometric Luminosity ◽  
Order Of Magnitude ◽  
High Cadence

ABSTRACT We present observations of ASASSN-19dj, a nearby tidal disruption event (TDE) discovered in the post-starburst galaxy KUG 0810+227 by the All-Sky Automated Survey for Supernovae (ASAS-SN) at a distance of d ≃ 98 Mpc. We observed ASASSN-19dj from −21 to 392 d relative to peak ultraviolet (UV)/optical emission using high-cadence, multiwavelength spectroscopy and photometry. From the ASAS-SN g-band data, we determine that the TDE began to brighten on 2019 February 6.8 and for the first 16 d the rise was consistent with a flux ∝t2 power law. ASASSN-19dj peaked in the UV/optical on 2019 March 6.5 (MJD = 58548.5) at a bolometric luminosity of L = (6.2 ± 0.2) × 1044 erg s−1. Initially remaining roughly constant in X-rays and slowly fading in the UV/optical, the X-ray flux increased by over an order of magnitude ∼225 d after peak, resulting from the expansion of the X-ray emitting region. The late-time X-ray emission is well fitted by a blackbody with an effective radius of ∼1 × 1012 cm and a temperature of ∼6 × 105 K. The X-ray hardness ratio becomes softer after brightening and then returns to a harder state as the X-rays fade. Analysis of Catalina Real-Time Transient Survey images reveals a nuclear outburst roughly 14.5 yr earlier with a smooth decline and a luminosity of LV ≥ 1.4 × 1043 erg s−1, although the nature of the flare is unknown. ASASSN-19dj occurred in the most extreme post-starburst galaxy yet to host a TDE, with Lick HδA = 7.67 ± 0.17 Å.

scholarly journals Fraction of the X-ray selected AGNs with optical emission lines in galaxy groups

2017 ◽  
Vol 362 (4) ◽  
Author(s):  
Feng Li ◽  
Qirong Yuan ◽  
Weihao Bian ◽  
Xi Chen ◽  
Pengfei Yan
Keyword(s):  
Optical Emission ◽  
Emission Lines ◽  
X Ray ◽  
Galaxy Groups

VI. Account of some recent observation on Sun-spots, made at the Kew Observatory

1868 ◽  
Vol 16 ◽  
pp. 447-447
Keyword(s):  
Recent Observation ◽  
Solar Physics ◽  
The Sun ◽  
The West ◽  
West Limb ◽  
Sun Spots

The authors, after reviewing briefly the two theories on the nature of sun-spots, which are still subjects of dispute, refer to the stereoscopic views obtained and the results published in their ‘Researches on Solar Physics,’ and state the reasons which have led them to believe that sun-spots are cavities and at a lower level than the sun s photosphere. Their opinion has been recently strengthened by observations of a sun-spot on the 7th of May, which in disappearing produced in two successive photograms indentations in the west limb. After proving by the measurements made, which, with the calculations, are appended to their paper, that there can be no doubt about the identity of the heliographical elements of the previously observed spot and the successive indentations, they prove from the established details of the phenomena of sun-spots that such indentations must under all circumstances be very rare occurrences, and state fully the conditions favourable to the recurrence of similar observations, inviting observers to give their particular attention to them.

scholarly journals The Needs and Requirements from the Standpoint of the Ultraviolet Solar Observations

1968 ◽  
Vol 1 ◽  
pp. 538-540
Author(s):  
E.M. Reeves
Keyword(s):  
Spatial Resolution ◽  
Time Resolution ◽  
Solar Disk ◽  
Emission Lines ◽  
High Time Resolution ◽  
The Sun ◽  
X Ray ◽  
Solar Observations ◽  
Partial Success

Extending from the present to the early part of 1969 there are three Orbiting Solar Observatories to be launched, and these will all be capable of constructing spectroheliograms of the Sun in solar emission lines of the EUV and X-ray region. The recently launched and highly successful OSO-III has obtained EUV and X-ray spectra with high-time resolution, but without spatial resolution on the solar disk. The later OSO satellites will provide spatial resolution of 1′ of arc to 30″ of arc, and will provide the basis for the extension to even higher spatial resolution in the future.The comparatively short periods covered by these satellites, coupled with a real probability of only partial success, make it particularly important to obtain the fullest possible use of the data by implementing a complementary and simultaneous series of ground-based observations.

scholarly journals Optical Emission Lines and the X-Ray Properties of Type 1 Seyfert Galaxies

2011 ◽  
Vol 20 (3) ◽  
pp. 442-447
Author(s):  
G. La Mura ◽  
S. Ciroi ◽  
V. Cracco ◽  
D. Ilić ◽  
L. Č. Popović ◽  
...  
Keyword(s):  
Structural Model ◽  
Optical Emission ◽  
Seyfert Galaxies ◽  
Emission Lines ◽  
Line Profiles ◽  
Energy Bands ◽  
X Ray ◽  
Line Region ◽  
Spectral Components

Abstract In this contribution we report on the study of the optical emission lines and X-ray spectra of a sample of Type 1 AGNs, collected from the SDSS database and observed by the XMM-Newton satellite. Using different instruments onboard XMM, we identify the spectral components of the soft and hard energy bands (in the range from 0.3 keV to 10 keV). The properties of the X-ray continuum and of the Fe Kα line feature are related to the optical broad emission line profiles and intensity ratios. The resulting picture of emission, absorption and reflection processes is interpreted by means of a structural model of the broad line region, developed on the basis of independent optical and radio observations.

Three Frequency Observations of a Moving Type IV Burst at the Limb

1977 ◽  
Vol 3 (2) ◽  
pp. 159-162 ◽  
Author(s):  
G. J. Nelson
Keyword(s):  
The Sun ◽  
Type Ii ◽  
Two Dimensional ◽  
The West ◽  
Type Iii ◽  
Type Iv ◽  
West Limb ◽  
Herringbone Structure

On 1975 August 22 an outburst above the west limb of the Sun was observed with the Culgoora radioheliograph at 43, 80 and 160 MHz. The first stages of the event included intense type III/V bursts followed by a type II burst with multiple, fundamental and harmonic bands and herringbone structure. While the type II burst was still in progress a moving type IV burst appeared. It was eventually observed out to a distance of more than 3 R⊙. This was the first moving type IV burst observed with the two-dimensional radioheliograph operating at three frequencies; as such it provides valuable constraints on models of moving type IV sources.

scholarly journals Multispacecraft observations of a prominence eruption

2009 ◽  
Vol 27 (10) ◽  
pp. 3841-3851 ◽  
Author(s):  
A. Bemporad ◽  
G. Del Zanna ◽  
V. Andretta ◽  
G. Poletto ◽  
M. Magrí
Keyword(s):  
High Spatial Resolution ◽  
Flux Rope ◽  
Spectral Lines ◽  
Sudden Increase ◽  
The West ◽  
Line Intensities ◽  
First Approximation ◽  
West Limb ◽  
Different Temperatures ◽  
High Cadence

Abstract. On 9 May 2007 a prominence eruption occurred at the West limb. Remarkably, the event was observed by the STEREO/EUVI telescopes and by the HINODE/EIS and SOHO/UVCS spectrometers. We present results from all these instruments. High-cadence (~37 s) data from STEREO/EUVI A and B in the He II λ304 line were used to study the 3-D shape and expansion of the prominence. The high spatial resolution EUVI images (~1.5"/pixel) have been used to infer via triangulation the 3-D shape and orientation of the prominence 12 min after the eruption onset. At this time the prominence has mainly the shape of a "hook" highly inclined southward, has an average thickness of 0.068 R⊙, a length of 0.43 R⊙ and lies, in first approximation, on a plane. Hence, the prominence is mainly a 2-D structure and there is no evidence for a twisted flux rope configuration. HINODE/EIS was scanning with the 2" slit the region where the filament erupted. The EIS spectra show during the eruption remarkable non-thermal broadening (up to ~100 km s−1) in the region crossed by the filament in spectral lines emitted at different temperatures, possibly with differences among lines from higher Fe ionization stages. The CME was also observed by the SOHO/UVCS instrument: the spectrograph slit was centered at 1.7 R⊙, at a latitude of 5° SW and recorded a sudden increase in the O VI λλ1032–1037 and Si XII λ520 spectral line intensities, representative of the CME front transit.

scholarly journals Intriguing X-ray and optical variations of the γ Cassiopeiae analog HD 45314

2018 ◽  
Vol 615 ◽  
pp. A44 ◽  
Author(s):  
G. Rauw ◽  
Y. Nazé ◽  
M. A. Smith ◽  
A. S. Miroshnichenko ◽  
J. Guarro Fló ◽  
...  
Keyword(s):  
Optical Spectrum ◽  
Optical Emission ◽  
Magnetic Interaction ◽  
Emission Lines ◽  
Magnetic Star ◽  
Optical Monitoring ◽  
X Ray ◽  
Direct Association ◽  
Intensity Changes ◽  
Observed Behaviour

Context. A growing number of Be and Oe stars, named the γ Cas stars, are known for their unusually hard and intense X-ray emission. This emission could either trace accretion by a compact companion or magnetic interaction between the star and its decretion disk. Aims. To test these scenarios, we carried out a detailed optical monitoring of HD 45314, the hottest member of the class of γ Cas stars, along with dedicated X-ray observations on specific dates. Methods. High-resolution optical spectra were taken to monitor the emission lines formed in the disk, while X-ray spectroscopy was obtained at epochs when the optical spectrum of the Oe star was displaying peculiar properties. Results. Over the last four years, HD 45314 has entered a phase of spectacular variations. The optical emission lines have undergone important morphology and intensity changes including transitions between single- and multiple-peaked emission lines as well as shell events, and phases of (partial) disk dissipation. Photometric variations are found to be anti-correlated with the equivalent width of the Hα emission. Whilst the star preserved its hard and bright X-ray emission during the shell phase, the X-ray spectrum during the phase of (partial) disk dissipation was significantly softer and weaker. Conclusions. The observed behaviour of HD 45314 suggests a direct association between the level of X-ray emission and the amount of material simultaneously present in the Oe disk as expected in the magnetic star-disk interaction scenario.

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