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.

CXO CDFS J033260.0-274748: A quasar with unusual spectra possibly blueshifted?1This paper is being published without benefit of authors’ corrections.

2011 ◽  
Vol 89 (10) ◽  
pp. 985-990 ◽  
Author(s):  
D. Basu
Keyword(s):  
Optical Spectrum ◽  
Optical Emission ◽  
Emission Lines ◽  
Absorption Feature ◽  
X Ray ◽  
Physical Conditions ◽  
Ejection Mechanism ◽  
X Ray Absorption ◽  
High Bulk

CXO CDFS J033260.0-274748 is a quasi-stellar object (QSO) and identification of several emission lines observed in its optical spectrum has led to the determination of its redshift as 2.579. On the other hand, the Chandra ACIS-I spectrum has detected a strong absorption feature at the observed wavelength around 6.3 keV that cannot be identified under normal physical conditions. The authors have invoked an unusually large outflow bulk velocity of 0.7c–0.8c to explain the feature. However, such extraordinarily high bulk velocities are unprecedented in the extragalactic literature. We show here that the optical emission lines and the X-ray absorption feature can be identified with search lines of longer wavelengths that have been blueshifted and do not need any unusual physical conditions to be invoked. The blueshifted spectra are explained as being due to the net motion of the QSO along with the absorbing cloud towards the observer. Two scenarios are proposed, namely, the ejection mechanism and the multiverse.

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

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.

scholarly journals A major optical and X-ray outburst from the Magellanic Bridge source RX J0209.6–7427

2020 ◽  
Vol 494 (1) ◽  
pp. 1424-1429 ◽  
Author(s):  
M J Coe ◽  
I M Monageng ◽  
E S Bartlett ◽  
D A H Buckley ◽  
A Udalski
Keyword(s):  
Optical Spectrum ◽  
Magellanic Clouds ◽  
Emission Lines ◽  
Tidal Dynamics ◽  
X Ray ◽  
Class A ◽  
Size And Structure

ABSTRACT RX J0209.6–7427 is an X-ray source in the Magellanic Bridge that was first detected in 1993, but not seen again till 2019. It has been identified as a member of the Be/X-ray binary class, a category of objects that are well established as bright, often-unpredictable transients. Such systems are rarely known in the Bridge, possibly because they lie outside the area most commonly studied by X-ray telescopes. Whatever be the reason for the sparse number of such systems in the Bridge, they can provide useful tools for trying to understand the result of the tidal dynamics of the two Magellanic Clouds. In this paper, the nature of the object is explored with the help of new data obtained during the latest outburst. In particular, the first optical spectrum of the counterpart is presented to help classify the star, plus measurements of the Balmer emission lines over several years are used to investigate changes in the size and structure of the circumstellar disc.

Discovery of new changing look in NGC 1566

2019 ◽  
Vol 15 (S356) ◽  
pp. 127-131
Author(s):  
Victor L. Oknyansky ◽  
Sergey S. Tsygankov ◽  
Vladimir M. Lipunov ◽  
Evgeny S. Gorbovskoy ◽  
Nataly V. Tyurina
Keyword(s):  
South African ◽  
Astronomical Observatory ◽  
Emission Lines ◽  
Optical Monitoring ◽  
X Ray ◽  
Broad Emission ◽  
High Ionization ◽  
The Galaxy ◽  
Multi Wavelength ◽  
Bright Phase

AbstractWe present continuation of the multi-wavelength (from X-ray to optical) monitoring of the nearby changing look (CL) active galactic nucleus in the galaxy NGC 1566 performed with the Neil Gehrels Swift Observatory,the MASTER Global Robotic Network over the period 2007–2019. We also present continuation of optical spectroscopy using the South African Astronomical Observatory 1.9-m telescope between Aug. 2018 and Mar. 2019. We investigate remarkable re-brightenings in of the light curve following the decline from the bright phase observed at Dec. 2018 and at the end of May 2019. For the last optical spectra (31 Nov. 2018–28 Mar. 2019) we see dramatic changes compared to 2 Aug. 2018, accompanied by the fading of broad emission lines and high-ionization [FeX]6374Å line. Effectively, one more CL was observed for this object: changing from Sy1.2 to the low state as Sy 1.8–Sy1.9 type. Some possible explanations of the observed CL are discussed.

scholarly journals X-ray and Radio Studies of the candidate Millisecond Pulsar Binary 4FGL J0935.3+0901

2021 ◽  
Author(s):  
冬 郑 ◽  
Zhong-Xiang Wang ◽  
Yi Xing ◽  
Jithesh Vadakkumthani
Keyword(s):  
Power Law ◽  
Distinctive Feature ◽  
Optical Spectrum ◽  
Emission Lines ◽  
Millisecond Pulsar ◽  
X Ray ◽  
Upper Limit ◽  
Radio Pulsation ◽  
Radio Studies ◽  
Γ Ray

Abstract 4FGL J0935.5+0901, a γ-ray source recently identified as a candidate redback-type millisecond pulsar binary (MSP), shows an interesting feature of having double-peaked emission lines in its optical spectrum. The feature would further suggest the source as a transitional MSP system in the sub-luminous disk state. We have observed the source with XMM-Newton and Five-hundred-meter Aperture Spherical radio Telescope (FAST) at X-ray and radio frequencies respectively for further studies. From the X-ray observation, a bimodal count-rate distribution, which is a distinctive feature of the transitional MSP systems, is not detected, while the properties of X-ray variability and power-law spectrum are determined for the source. These results help establish the consistency of it being a redback in the radio pulsar state. However no radio pulsation signals are found in the FAST observation, resulting an upper limit on the flux density of ∼ 4 µJy. Implications of these results are discussed.

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 A compact X-ray emitting binary in likely association with 4FGL J0935.3+0901

2020 ◽  
Vol 493 (4) ◽  
pp. 4845-4851 ◽  
Author(s):  
Zhongxiang Wang ◽  
Yi Xing ◽  
Jujia Zhang ◽  
Konstantina Boutsia ◽  
Gege Wang ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Optical Emission ◽  
Emission Lines ◽  
Large Area ◽  
Time Resolved ◽  
X Ray ◽  
Current State ◽  
Low Mass ◽  
Γ Ray ◽  
Error Circle

ABSTRACT 4FGL J0935.3+0901 is a γ-ray source detected by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope. We have conducted detailed analysis of the LAT data for this source and multiwavelength studies of the source field. Its γ-ray emission can be described with a power law (Γ = 2.0 ± 0.2) with an exponential cut-off (Ec = 2.9 ± 1.6 GeV), while the flux shows significant long-term variations. From analysis of archival Neil Gehrels Swift Observatory X-Ray Telescope data, we find only one X-ray source in the LAT’s 2σ error region. Within a $3.7\,{\rm arcsec}$ radius error circle of the X-ray source, there is only one optical object down to r′ ∼ 23 mag. Time-resolved photometry of the optical object indicates a likely 2.5 h periodic modulation, while its spectrum shows double-peaked hydrogen and helium emission lines (similar to those seen in accretion discs in low-mass X-ray binaries). Combining these results, we conclude that we have discovered a compact X-ray emitting binary in likely association with 4FGL J0935.3+0901, i.e. a millisecond pulsar (MSP) binary. We discuss the implication of the optical spectral features: this binary could be a transitional MSP system at a subluminous disc state, although the other possibility, the binary in a rotation-powered state showing the optical emission lines due to intrabinary interaction processes, cannot be excluded. Further observational studies will help to determine detailed properties of this candidate MSP binary and thus clarify its current state.

scholarly journals Multiwavelength study of the WO star Sand 2

1995 ◽  
Vol 163 ◽  
pp. 66-67
Author(s):  
L. Norci ◽  
V.F. Polcaro ◽  
C. Rossi ◽  
R. Viotti
Keyword(s):  
Optical Spectrum ◽  
Emission Lines ◽  
Uv Spectrum ◽  
Strong Emission ◽  
X Ray ◽  
Optical Continuum ◽  
Resonance Doublet

We present the results of a multifrequency observation of the WO star Sand 2 in the LMC. Two ROSAT PSPC observations, with exposure times of 8953 s and 4540 s, are used to investigate possible X-ray emission from Sand 2. The optical spectrum observed with the ESO 2.2m telescope close to the time of the ROSAT observations, shows strong emission lines of HeII, CIV, OV and OVI. All lines have a velocity broadening of 4 200±100 km s−1. The UV spectrum from the IUE archive shows a CIV resonance doublet at 155 nm with a P-Cygni absorption at ∼ −5 000 km s−1, with wings extending to about −8 000 km s−1. A combination of two different BB temperatures (80 000 K and 25 000 K) are required to fit the UV-optical continuum, dereddened by EB-V = 0.25.

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