Searching for Massive Outflows in Holmberg IX X-1 and NGC 1313 X-1: The Iron K Band

We have analysed all the good quality XMM-Newton data publicly available for the bright ULXs Holmberg IX X-1 and NGC 1313 X-1, with the aim of searching for discrete emission or absorption features in the Fe K band that could provide observational evidence for the massive outflows predicted if these sources are accreting at substantially super-Eddington rates. We do not find statistically compelling evidence for any atomic lines, and the limits that are obtained have interesting consequences. Any features in the immediate Fe K energy band (6-7 keV) must have equivalent widths weaker than ~30 eV for Holmberg IX X-1, and weaker than ~50 eV for NGC 1313 X-1 (at 99 per cent confidence). In comparison to the sub-Eddington outflows observed in GRS 1915+105, which imprint iron absorption features with equivalent widths of ~30 eV, the limits obtained here appear quite stringent, particularly when Holmberg IX X-1 and NGC 1313 X-1 must be expelling at least 5-10 times as much material if they host black holes of similar masses. The difficulty in reconciling these observational limits with the presence of strong line-of-sight outflows suggests that either these sources are not launching such outflows, or that they must be directed away from our viewing angle.Comment: 11 pages, 5 figures, accepted for publication in MNRA

Large Highly-Ionized Nebulae Around Ultra-luminous X-ray Sources

We present the results of deep optical spectroscopic observations using the LRIS spectrograph on the Keck I 10-m telescope of three ultra-luminous X-ray sources (ULXs), Ho IX X-1; M81 X-6; and Ho II X-1. Our observations reveal the existence of large (100 - 200 pc diameter) highly-ionized nebulae, identified by diffuse He II (4686 Angstrom) emission, surrounding these sources. Our results are the first to find highly-ionized nebulae of this extent, and the detection in all three objects indicates this may be a common feature of ULXs. In addition to the extended emission, Ho IX X-1 has an unresolved central component containing about one-third of the total He II flux, with a significant velocity dispersion of ~ 370 km/s, suggestive of the existence of a photo-ionized accretion disk or an extremely hot early-type stellar counterpart. Most of the He II emission appears to be surrounded by significantly more extended Hbeta emission, and the intensity ratios between the two lines, which range from 0.12 - 0.33, indicate that photo-ionization is the origin of the He II emission. Sustaining these extended nebulae requires substantial X-ray emission, in the range ~ 10^{39} - 10^{40} ergs/s, comparable to the measured X-ray luminosities of the sources. This favors models where the X-ray emission is isotropic, rather than beamed, which includes the interpretation that ULXs harbor intermediate-mass black holes.Comment: Accepted for publication in ApJ Letter

Long-term Spectral Variability of the Ultra-luminous X-ray source Holmberg IX X--1

We investigate the long-term spectral variability in the ultra-luminous X-ray source Holmberg IX X--1. By analyzing the data from eight {\it Suzaku} and 13 {\it XMM-Newton} observations conducted between 2001 and 2015, we perform a detailed spectral modeling for all spectra with simple models and complex physical models. We find that the spectra can be well explained by a disc plus thermal Comptonization model. Applying this model, we unveil correlations between the X-ray luminosity ($L_{\rm X}$) and the spectral parameters. Among the correlations, a particular one is the statistically significant positive correlation between $L_{\rm X}$ and the photon index ($\Gamma$), while at the high luminosities of $> 2\times10^{40}\,{\rm~erg\ s}^{-1}$, the source becomes marginally hard and that results a change in the slope of the $\Gamma - L_{\rm X}$ correlation. Similar variability behavior is observed in the optical depth of the source around $L_{\rm X} \sim 2\times10^{40}\,{\rm~erg\ s}^{-1}$ as the source becomes more optically thick. We consider the scenario that a corona covers the inner part of the disc, and the correlations can be explained as to be driven by the variability of seed photons from the disc input into the corona. On the basis of the disc-corona model, we discuss the physical processes that are possibly indicated by the variability of the spectral parameters. Our analysis reveals the complex variability behavior of Holmberg IX X--1 and the variability mechanism is likely related to the geometry of the X-ray emitting regions.Comment: Accepted for publication in ApJ, 12 Pages, 3 Tables, 3 Figure

Broadband X-ray spectra of the ultraluminous x-ray source Holmberg IX X-1 observed with NuSTAR, XMM-Newton, and Suzaku

We present results from the coordinated broadband X-ray observations of the extreme ultraluminous X-ray source Holmberg IX X-1 performed by NuSTAR, XMM-Newton and Suzaku in late 2012. These observations provide the first high-quality spectra of Holmberg IX X-1 above 10 keV to date, extending the X-ray coverage of this remarkable source up to ~30 keV. Broadband observations were undertaken at two epochs, between which Holmberg IX X-1 exhibited both flux and strong spectral variability, increasing in luminosity from Lx = (1.90+/-0.03)e40 erg/s to Lx = (3.35+/-0.03)e40 erg/s. Neither epoch exhibits a spectrum consistent with emission from the standard low/hard accretion state seen in Galactic black hole binaries, that would have been expected if Holmberg IX X-1 harbors a truly massive black hole accreting at substantially sub-Eddington accretion rates. The NuSTAR data confirm that the curvature observed previously in the 3-10 keV bandpass does represent a true spectral cutoff. During each epoch, the spectrum appears to be dominated by two optically thick thermal components, likely associated with an accretion disk. The spectrum also shows some evidence for a non-thermal tail at the highest energies, which may further support this scenario. The available data allow for either of the two thermal components to dominate the spectral evolution, although both scenarios require highly non-standard behavior for thermal accretion disk emission.Comment: 12 pages, 9 figures, accepted for publication in Ap

An Optical Study of Stellar and Interstellar Environments of Seven Luminous and Ultraluminous X-Ray Sources

We have studied the stellar and interstellar environments of two luminous X-ray sources and five ultraluminous X-ray sources (ULXs) in order to gain insight into their nature. Archival Hubble Space Telescope images were used to identify the optical counterparts of the ULXs Ho IX X-1 and NGC 1313 X-2, and to make photometric measurements of the local stellar populations of these and the luminous source IC 10 X-1. We obtained high-dispersion spectroscopic observations of the nebulae around these seven sources to search for He II lambda-4686 emission and to estimate the expansion velocities and kinetic energies of these nebulae. Our observations did not detect nebular He II emission from any source, with the exception of LMC X-1; this is either because we missed the He III regions or because the nebulae are too diffuse to produce He II surface brightnesses that lie within our detection limit. We compare the observed ionization and kinematics of the supershells around the ULXs Ho IX X-1 and NGC 1313 X-2 with the energy feedback expected from the underlying stellar population to assess whether additional energy contributions from the ULXs are needed. In both cases, we find insufficient UV fluxes or mechanical energies from the stellar population; thus these ULXs may be partially responsible for the ionization and energetics of their supershells. All seven sources we studied are in young stellar environments and six of them have optical counterparts with masses >~7 M_sun; thus, these sources are most likely high-mass X-ray binaries.Comment: 30 pages, 9 figures. Numerous minor revisions, primarily to more accurately cite earlier work by Pakull and Mirioni, and to correct typographical errors. Removed a misleading sentence in the Introduction (re: X-ray photoionization by ULXs). Accepted for publication in The Astrophysical Journal. Figures have been reduced in resolution for space requirements; full-resolution figures may be requested by email to [email protected]

Review of \u3cem\u3eThe Contested Castle: The Gothic Novel and the Subversion of the Domestic Ideology\u3c/em\u3e by Kate Ellis

Kate Ellis\u27s purpose in The Contested Castle is to examine the relationship between two epi-phenomena 0f middle-class culture the idealization of the home and the popularity of the Gothic ( pp. ix-x). According to Ellis, the point of connection between the two is the female reader a newly empowered figure, eagerly courted by publishers for her discretionary time and income. The new gothic novels that these women read so voraciously however did not simply reinforce the gender construction that late eighteenth and early nineteenth-century capitalist culture proferred. The gothic novel also worked to subvert those constructions, particularly the ideology that imprisoned middle-class women in their homes like so many captives in a fictitious paradise regaine

An Optical Study of Stellar and Interstellar Environments of Seven Luminous and Ultraluminous X-Ray Sources

We have studied the stellar and interstellar environments of two luminous X-ray sources and five ultraluminous X-ray sources (ULXs) in order to gain insight into their nature. Archival Hubble Space Telescope images were used to identify the optical counterparts of the ULXs Ho IX X-1 and NGC 1313 X-2, and to make photometric measurements of the local stellar populations of these and the luminous source IC 10 X-1. We obtained high-dispersion spectroscopic observations of the nebulae around these seven sources to search for He II lambda-4686 emission and to estimate the expansion velocities and kinetic energies of these nebulae. Our observations did not detect nebular He II emission from any source, with the exception of LMC X-1; this is either because we missed the He III regions or because the nebulae are too diffuse to produce He II surface brightnesses that lie within our detection limit. We compare the observed ionization and kinematics of the supershells around the ULXs Ho IX X-1 and NGC 1313 X-2 with the energy feedback expected from the underlying stellar population to assess whether additional energy contributions from the ULXs are needed. In both cases, we find insufficient UV fluxes or mechanical energies from the stellar population; thus these ULXs may be partially responsible for the ionization and energetics of their supershells. All seven sources we studied are in young stellar environments and six of them have optical counterparts with masses >~7 M_sun; thus, these sources are most likely high-mass X-ray binaries.Comment: 30 pages, 9 figures. Numerous minor revisions, primarily to more accurately cite earlier work by Pakull and Mirioni, and to correct typographical errors. Removed a misleading sentence in the Introduction (re: X-ray photoionization by ULXs). Accepted for publication in The Astrophysical Journal. Figures have been reduced in resolution for space requirements; full-resolution figures may be requested by email to [email protected]

Optical Properties of the Ultraluminous X-ray Source Holmberg IX X-1 and its Stellar Environment

Holmberg IX X-1 is an archetypal ultraluminous X-ray source (ULX). Here we study the properties of the optical counterpart and of its stellar environment using optical data from SUBARU/Faint Object Camera and Spectrograph,GEMINI/GMOS-N and Hubble Space Telescope (HST)/Advanced Camera for Surveys, as well as simultaneous Chandra X-ray data. The V ~ 22.6 spectroscopically identified optical counterpart is part of a loose cluster with an age <~ 20 Myr. Consequently, the mass upper limit on individual stars in the association is about 20 M_sun. The counterpart is more luminous than the other stars of the association, suggesting a non-negligible optical contribution from the accretion disk. An observed UV excess also points to non-stellar light similar to X-ray active low-mass X-ray binaries. A broad HeII4686 emission line identified in the optical spectrum of the ULX further suggests optical light from X-ray reprocessing in the accretion disk. Using stellar evolutionary tracks, we have constrained the mass of the counterpart to be >~ 10 M_sun, even if the accretion disk contributes significantly to the optical luminosity. Comparison of the photometric properties of the counterpart with binary models show that the donor may be more massive, >~ 25 M_sun, with the ULX system likely undergoing case AB mass transfer. Finally, the counterpart exhibits photometric variability of 0.14 mag between two HST observations separated by 50 days which could be due to ellipsoidal variations and/or disk reprocessing of variable X-ray emission.Comment: 14 pages, 14 figures, accepted for publication in Ap

Середньовічні городища на околицях сіл Которини, Старе Село, Цвітова

The first attempt of detailed publication of materials of field archaeological researches of the unique archaeological complex of five compact Early Medieval hill-forts from IX–X centuries obtained by an author in 1993, 1995 and 1996 is made at this article. Main attention is paid to the results of the first stage of scientific researches: precise definition of location of complex of monuments, character of the defensive fortifications, their component parts,and features of area construction. Basing on findings, the author makes an attempt of generalization of results of researches of medieval hill-forts from IX–X centuries, which are located between the villages of Kotoryny, Stare Selo, Tsvitova, which belonged to Early Medieval formation of annalistic (Carpathians) Croats