scholarly journals Constraining Soft and Hard X-Ray Irradiation in Ultraluminous X-Ray Sources

2021 ◽  
Vol 922 (2) ◽  
pp. 91
Author(s):  
Yanli Qiu ◽  
Hua Feng
Keyword(s):  
Optical Emission ◽  
Current Data ◽  
Compact Objects ◽  
X Rays ◽  
Optical Counterpart ◽  
X Ray ◽  
Outer Disk ◽  
Stringent Constraint ◽  
Supercritical Accretion ◽  
Key Questions

Abstract Most ultraluminous X-ray sources (ULXs) are argued to be powered by supercritical accretion onto compact objects. One of the key questions regarding these objects is whether or not the hard X-rays are geometrically beamed toward the symmetric axis. We propose testing the scenario using disk irradiation to see how much the outer accretion disk sees the central hard X-rays. We collect a sample of 11 bright ULXs with an identification of a unique optical counterpart, and model their optical fluxes considering two irradiating sources: soft X-rays from the photosphere of the optically thick wind driven by supercritical accretion, and if needed in addition, hard X-rays from the Comptonization component. Our results indicate that the soft X-ray irradiation can account for the optical emission in the majority of ULXs, and the fraction of hard X-rays reprocessed on the outer disk is constrained to be no more than ∼10−2 in general. Such an upper limit is well consistent with the irradiation fraction expected in the case of no beaming. Therefore, no stringent constraint on the beaming effect can be placed according to the current data quality.

scholarly journals ROSAT observation of the HII region RCW 49 Possible discovery of a new Wolf-Rayet ring nebula

1995 ◽  
Vol 163 ◽  
pp. 76-77
Author(s):  
S. Mereghetti ◽  
T. Belloni
Keyword(s):  
Optical Emission ◽  
Young Star ◽  
Star Cluster ◽  
X Rays ◽  
Diffuse Emission ◽  
Hii Region ◽  
X Ray ◽  
Ring Nebula

We have observed the southern HII region RCW 49 with the ROSAT PSPC instrument. Part of the diffuse X-ray and optical emission present in this region might be associated with the X-ray selected WR star Th35-42 (WR20c). The young star cluster Westerlund 2 (which contains WR20a) is seen in X-rays as a centrally peaked, resolved source, surrounded by fainter diffuse emission.

scholarly journals Effect of Compact Objects Near Be Stars

1987 ◽  
Vol 92 ◽  
pp. 516-518
Author(s):  
Krishna M.V. Apparao ◽  
S.P. Tarafdar
Keyword(s):  
Black Holes ◽  
Neutron Star ◽  
Rotation Period ◽  
Compact Object ◽  
Compact Objects ◽  
X Rays ◽  
Be Stars ◽  
Eccentric Orbit ◽  
X Ray ◽  
Be Star

Several Be stars are identified with bright X-ray sources. (Rappaport and Van den Heuvel, 1982). The bright X-ray emission and observed periodicities indicate the existence of compact objects (white dwarfs, neutron stars or black holes) near the Be stars. A prime example is the brightest X-ray source A0538-66 in LMC, which contains a neutron star with a rotation period of 59 ms. Apparao (1985) explained the X-ray emission, which occurs in periodic flares, by considering an inclined eccentric orbit for the neutron star around the assumed Be-star. The neutron star when it enters a gas ring (around the Be-star) accreting matter giving out X-rays.The X-ray emission from the compact objects, when the gas ring from the Be-star envelopes the objects, has interesting consequences. The X-ray emission produces an ionized region (compact object Stromgren sphere or COSS) in the gas surrounding the compact object (CO).

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 Gamma-ray-emitting narrow-line Seyfert 1 galaxies: the Swift view

2020 ◽  
Vol 496 (2) ◽  
pp. 2213-2229 ◽  
Author(s):  
F D’Ammando
Keyword(s):  
Gamma Ray ◽  
Thermal Emission ◽  
Optical Emission ◽  
X Rays ◽  
Narrow Line ◽  
X Ray ◽  
Relativistic Jet ◽  
Photon Index ◽  
Γ Ray ◽  
Lower Variability

ABSTRACT We report the analysis of all Swift observations available up to 2019 April of γ-ray-emitting narrow-line Seyfert 1 galaxies (NLSy1). The distribution of X-ray luminosities (and fluxes) indicates that the jet radiation significantly contributes to their X-ray emission, with Doppler boosting making values higher than other radio-loud NLSy1. The 0.3–10 keV photon indices are on average harder with respect to radio-quiet and radio-loud NLSy1, confirming a dominant jet contribution in X-rays. However, the lower variability amplitude with respect to blazars and the softening of the spectrum in some periods suggests that also the corona radiation contributes to the X-ray emission. In optical and ultraviolet (UV) significant flux changes have been observed on daily, weekly, and monthly time-scale, providing a clear indication of the significant contribution of the jet radiation in this part of spectrum. A strong correlation between X-ray, UV, and optical emission and simultaneous flux variations have been observed in 1H 0323+342, SBS 0846+513, PMN J0948+0022 as expected in case the jet radiation is the dominant mechanism. Correlated multiband variability favours the jet-dominated scenario also in FBQS J1644+2619 and PKS 2004−447. The summed X-ray Telescope spectra of 1H 0323+342, SBS 0846+513, PMN J0948+0022, and FBQS J1644+2619 are well fitted by a broken power law with a break around 2 keV. The spectrum above 2 keV is dominated by the non-thermal emission from a beamed relativistic jet, as suggested by the hard photon index. A Seyfert-like feature like the soft X-ray excess has been observed below 2 keV, making these γ-ray-emitting NLSy1 different from typical blazars.

scholarly journals Face-on SS 433 Stars as a Possible New Type of Extragalactic X-Ray Sources

2001 ◽  
Vol 205 ◽  
pp. 268-269 ◽  
Author(s):  
S. Fabrika ◽  
A. Mescheryakov
Keyword(s):  
X Rays ◽  
Relativistic Jets ◽  
Expected Frequency ◽  
X Ray ◽  
Ss 433 ◽  
Sky Survey ◽  
Supercritical Accretion ◽  
The Face ◽  
New Type ◽  
Positive Correlations

The object SS433 is a well-known source of relativistic jets, which are formed in supercritical accretion disk. It is very probable that the disk has polar channels and their radiation is collimated (the photo-cones). A face-on SS433 object can appear as ultra-bright and highly variable X-ray source, Lx ˜ 1040 − 1042 erg/s. We discuss the properties of these hypothetical objects and their frequency expected in galaxies. We describe a search for such objects using the ROSAT All Sky Survey and RC3 catalog of galaxies. Among the total 418 positive correlations we find that 142 sources in S and Irr galaxies are unknown as AGNs. Nuclear sources among them still contain many AGNs. Non-nuclear (offset) sources are rather hard, their X-ray luminosities are 1039 − 1041 erg/s. Their observed frequency is about 4–5% per galaxy, that is in agreement with expected frequency of the face-on SS 433 stars. The only way to recognize such stars is their expected violent variability in X rays.

scholarly journals Optical counterparts of an ultraluminous X-Ray Source X-1 in NGC 2500

2019 ◽  
Vol 488 (4) ◽  
pp. 5935-5940 ◽  
Author(s):  
N Aksaker ◽  
A Akyuz ◽  
S Avdan ◽  
H Avdan
Keyword(s):  
Hubble Space Telescope ◽  
Optical Emission ◽  
Spectral Energy ◽  
Wide Field ◽  
Nearby Galaxy ◽  
X Rays ◽  
Energy Distributions ◽  
X Ray ◽  
Photon Index ◽  
Absolute Magnitudes

ABSTRACT We present the results of a search for optical counterparts of ultraluminous X-ray source (ULX) X-1 in the nearby galaxy NGC 2500 by using archival images taken with the Hubble Space Telescope Wide Field Camera (WFC3)/UVIS. We identified four optical sources as possible counterparts within the 2σ error radius of 0$^{\prime \prime }_{.}$3 in the images. However, only two of them were investigated as candidates for counterparts due to their point-like features and their identification in various filters. These two faint candidates have absolute magnitudes of MV ≈ −3.4 and −3.7. The spectral energy distributions of two candidates were modelled by a power-law spectrum with a photon index (α) ∼1.5, but the spectrum of one candidate shows a deviation. This may suggest that at least two components are responsible for the optical emission. The red part of the spectrum could arise from the companion star and the blue part could be interpreted as an evidence of reprocessing of the X-rays from the disc.

scholarly journals X-Ray Properties of Extragalactic Compact Objects

1984 ◽  
Vol 110 ◽  
pp. 85-94
Author(s):  
G. Zamorani
Keyword(s):  
Optical Emission ◽  
Seyfert Galaxies ◽  
Compact Objects ◽  
Relative Importance ◽  
Bl Lac Objects ◽  
X Ray ◽  
Working Definition ◽  
The Subject ◽  
Definition Of ◽  
5 Ghz

The compact objects which are the subject of this talk are essentially quasars and Seyfert galaxies; I will only briefly mention a couple of results about BL Lac objects. Before describing the X-ray properties of these objects, it is useful to introduce a “working” definition of radio-quiet and radio-loud quasars: I will call radio-loud quasars all the objects which have been detected at radio frequencies and have a spectral index between radio (5 GHz) and optical frequencies (2500 A) greater than 0.35 (Zamorani et al. 1981); all the other objects will be considered radio-quiet. Note that this definition is independent of distance and is a function only of the relative importance of radio and optical emission.

scholarly journals Accretion-outflow connection in the outliers of the “universal” radio/X-ray correlation

2010 ◽  
Vol 6 (S275) ◽  
pp. 255-259
Author(s):  
M. Coriat ◽  
S. Corbel ◽  
L. Prat ◽  
J. C. A. Miller-Jones ◽  
D. Cseh ◽  
...  
Keyword(s):  
Black Hole ◽  
Compact Objects ◽  
X Rays ◽  
X Ray ◽  
Black Hole Candidate ◽  
Long Term Study ◽  
Hard State ◽  
Universal Correlation ◽  
X Ray Binaries

AbstractIn recent years, numerous efforts have been devoted to unravel the connection between accretion flow and jets in accreting compact objects. Here we report new constraints on these issues, through the long term study of the radio and X-ray behaviour of the black hole candidate H 1743–322. This source is known to be one of the “outliers” of the universal radio/X-ray correlation, i.e. a group of stellar mass accreting black holes displaying fainter radio emission for a given X-ray luminosity, than expected from the correlation. In this work we find, at high X-ray luminosity in the hard state, a tight radio/X-ray correlation with an unusual steep slope of b = 1.38 ± 0.03. This correlation then breaks below ~5 × 10−3LEdd (M/10M⊙)−1 in X-rays and becomes shallower. When compared with radio/X-ray data from other black hole X-ray binaries, we see that the deviant points of H 1743–322 join the universal correlation and seem to follow it at low luminosity. Based on these results, we investigate several hypotheses that could explain both the b ~ 1.4 slope and the transition toward the universal correlation.

scholarly journals X-Ray and Optical Observations of the X-Ray Source EX0020528+1454.8

1987 ◽  
Vol 93 ◽  
pp. 697-700
Author(s):  
R. Hudec ◽  
W. Wenzel ◽  
W. Goetz ◽  
B. Valníček ◽  
R. Peřestý ◽  
...  
Keyword(s):  
Optical Observations ◽  
X Rays ◽  
Optical Counterpart ◽  
Optical Photometry ◽  
X Ray ◽  
Preliminary Results ◽  
Flare Stars

AbstractWe present preliminary results of the EXOSAT X-ray observations and quasisimultaneous and simultaneous optical photometry of the X-ray source EX0020528+1454.8 = 1E0205+149 found independently as an serendipitous source both with Einstein and EXOSAT satellites. The optical counterpart is a pair of dMe stars, Our results indicate that the object is variable both in X-rays and optical wavelenghts, and probably belongs to dMe flare stars.

scholarly journals Multiwavelength power-spectrum analysis of NGC 5548

2020 ◽  
Vol 499 (2) ◽  
pp. 1998-2006
Author(s):  
C Panagiotou ◽  
I E Papadakis ◽  
E S Kammoun ◽  
M Dovčiak
Keyword(s):  
Power Spectrum ◽  
Time Lag ◽  
Optical Emission ◽  
X Rays ◽  
Short Term ◽  
X Ray ◽  
Uv Emission ◽  
Accretion Rates ◽  
Measured Time ◽  
Ngc 5548

ABSTRACT NGC 5548 was recently monitored intensively from NIR to X-rays as part of the STORM campaign. Its disc emission was found to lag behind the observed X-rays, while the measured time lag was increasing with wavelength. These results are consistent with the assumption that short-term variability in AGN emission is driven by the X-ray illumination of the accretion disc. In this work, we studied the power spectrum of UV/optical and X-ray emission of NGC 5548, using the data of the STORM campaign as well as previous Swift data, in order to investigate the relation between the UV/optical and X-ray variability and to examine its consistency with the above picture. We demonstrate that even the power spectrum results are compatible with a standard disc being illuminated by X-rays, with low accretion rates, but the details are not entirely consistent with the results from the modelling of the ‘τ versus λ’ relation. The differences indicate that the inner disc might be covered by a ‘warm corona’ which does not allow the detection of UV/optical emission from the inner disc. Finally, we found strong evidence that the UV emission of NGC 5548 is not stationary.

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