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.

scholarly journals V2282 Sgr Revisited

2014 ◽  
Vol 1 (1) ◽  
pp. 118-122
Author(s):  
Roberto Nesci ◽  
Corinne Rossi ◽  
Antonio Frasca ◽  
Ettore Marilli ◽  
Paolo Persi ◽  
...  
Keyword(s):  
Light Curve ◽  
Accretion Disk ◽  
Main Sequence ◽  
Optical Spectra ◽  
Emission Lines ◽  
Main Sequence Star ◽  
Strong Emission ◽  
X Ray ◽  
Type Spectrum

The nature of V2282 Sgr is examined on the basis of several multiband observations: a 20 years long I-band light curve of V2282 Sgr obtained from archive photographic plates of the Asiago and Catania Observatories; a CCD R-band light curve obtained at Cornero Observatory; JHK photometry from 2MASS and UKDISS; <em>Spitzer</em> IRAC and MIPS images; optical spectra from Loiano Observatory; X-ray flux from <em>CHANDRA</em>. The star has a K-type spectrum with strong emission lines and is irregularly variable at all wavebands. The overall evidences suggest that V2282 Sgr is a Pre Main Sequence star with an accretion disk.

scholarly journals X-Ray and Ultraviolet Observations of AG Draconis during Quiescence and Outburst

1987 ◽  
Vol 93 ◽  
pp. 763-763
Author(s):  
A. Cassatella ◽  
F.A. Córdova ◽  
M. Friedjung ◽  
J. Kenyom ◽  
L. Piro ◽  
...  
Keyword(s):  
Orbital Motion ◽  
Uv Light ◽  
Low Energy ◽  
Emission Lines ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Uv Spectrum ◽  
X Ray ◽  
High Ionization ◽  
Ultraviolet Observations

AbstractWe describe the first X-ray monitoring of a symbiotic star during phases of enhanced activity. AG Dra is a Pop II object with a composite spectrum, characterized by a cool K-type component, prominent high ionization emission lines and a strong UV continuum which is attributed to a hot dwarf companion. Periodic variability of the UV radiation during minimum could be attributed to the orbital motion of the system. In April 1980 HEAO-2 detected an intense, soft X-ray flux from AG Dra, stronger than in other symbiotic stars. After one major outburst of November 1980, which continued until 1983, two more outbursts occurred in February 1985 and January 1986, and coordinated X-ray (EXOSAT) and ultraviolet (IUE) observations were organized to study the behaviour of AG Dra during different activity phases. EXOSAT observations made during decline after the 1985 outburst, revealed a weak X-ray flux in the Thin Lexan filter of the Low Energy dedtector. Observations made during minimum, in June and November 1985, at phases 0.22 and 0.50 of the UV light curve, disclosed the presence of an intense X-ray flux, which was not occulted in November. AG Dra was again observed with EXOSAT in February 1986 when the stellar luminosity was still at maximum. No X-ray flux was detected, in spite of the prominent, high ionization UV spectrum observed with IUE.A detailed discussion of the X-ray and ultraviolet results on AG Dra in the light of possible models is in progress.

scholarly journals Ultraviolet observations of RR Telescopii

1982 ◽  
Vol 70 ◽  
pp. 217-218
Author(s):  
D. Ponz ◽  
A. Cassatella ◽  
R. Viotti
Keyword(s):  
Optical Spectrum ◽  
Ultraviolet Spectrum ◽  
Emission Lines ◽  
Symbiotic Star ◽  
Uv Spectrum ◽  
Physical Conditions ◽  
Wide Range ◽  
Forbidden Transitions ◽  
Ultraviolet Observations ◽  
Comprehensive Study

The ultraviolet spectrum of RR Tel was extensively studied with the IUE satellite since 1978 in both the high and low resolution modes. A comprehensive study of these observations was made by Penston et al.(l98l) who measured more than 400 emission lines. As it is clearly shown in figure 1, the UV spectrum of this symbiotic star is very rich in emission lines. Like in the optical spectrum (Thackeray 1977), the UV spectrum presents emission lines of ions belonging to a wide range of ionization energies, from neutral up to four and five times ionized species (OV, MgV, CaVI, etc.). Permitted, intercombination and forbidden transitions were found which may allow a diagnosis of the physical conditions of the emitting regions. Electron temperatures of 1.2-1.9 104°K and densities of 106-108 cm-3 were derived by Penston et al.

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.

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.

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 IUE Observations of the WN-C Star HD 62910

1982 ◽  
Vol 99 ◽  
pp. 491-495
Author(s):  
David J. Stickland ◽  
Allan J. Willis
Keyword(s):  
Wavelength Range ◽  
Emission Lines ◽  
Uv Spectrophotometry ◽  
Low Resolution ◽  
Uv Spectrum ◽  
Strong Emission ◽  
Type Spectrum

We have obtained low resolution UV spectrophotometry of the WN-C star HD 62910 in both the SWP (λλ1150–2000) and LWR (λλ1850–3250) IUE spectrographs, and also for HD 117688, WN6, used for comparison. The UV spectrum of HD 62910 is shown in Fig 1 and is seen to be dominated by many strong emission lines, which by comparison with the IUE spectra of other galactic WR stars (Nussbaumer et al. 1981) is found to reflect a predominantly WN-type spectrum, but in addition, weaker features characteristic of WC spectra are also seen, particularly in the LWR wavelength range. In Table 1 we list the principal observed WN and WC features in HD 62910. A comparison of the relative strengths of the WN emissions with those observed in various WN subtypes (Nussbaumer et al. 1981) and with our spectra of HD 117688 confirms the subtype of HD 62910 as WN6 as inferred in the visible (Smith 1968, Van der Hucht et al. 1981).

scholarly journals XMM–Newton campaign on ultraluminous X-ray source NGC 1313 X-1: wind versus state variability

2020 ◽  
Vol 492 (4) ◽  
pp. 4646-4665 ◽  
Author(s):  
C Pinto ◽  
D J Walton ◽  
E Kara ◽  
M L Parker ◽  
R Soria ◽  
...  
Keyword(s):  
Accretion Rate ◽  
Compact Object ◽  
Accretion Disc ◽  
Emission Lines ◽  
Time Variability ◽  
Strong Emission ◽  
X Ray ◽  
First Time ◽  
Eddington Limit ◽  
Absorption Features

ABSTRACT Most ultraluminous X-ray sources (ULXs) are thought to be powered by neutron stars and black holes accreting beyond the Eddington limit. If the compact object is a black hole or a neutron star with a magnetic field ≲1012 G, the accretion disc is expected to thicken and launch powerful winds driven by radiation pressure. Evidence of such winds has been found in ULXs through the high-resolution spectrometers onboardXMM–Newton, but several unknowns remain, such as the geometry and launching mechanism of these winds. In order to better understand ULX winds and their link to the accretion regime, we have undertaken a major campaign with XMM–Newton to study the ULX NGC 1313 X-1, which is known to exhibit strong emission and absorption features from a mildly relativistic wind. The new observations show clear changes in the wind with a significantly weakened fast component (0.2c) and the rise of a new wind phase which is cooler and slower (0.06–0.08c). We also detect for the first time variability in the emission lines which indicates an origin within the accretion disc or in the wind. We describe the variability of the wind in the framework of variable super-Eddington accretion rate and discuss a possible geometry for the accretion disc.

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 X-Ray spectra of AGN's with strong emission lines

2012 ◽  
Vol 8 (2) ◽  
pp. 160-165
Author(s):  
A.V. Tugay ◽  
A.A. Vasylenko ◽  
T.A. Zaetc
Keyword(s):  
Emission Lines ◽  
Strong Emission ◽  
X Ray
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