An X-ray Emitting Black Hole in a Globular Cluster

AbstractWe present optical and X-ray data for the first object showing strong evidence for being a black hole in a globular cluster. We show the initial X-ray light curve and X-ray spectrum which led to the discovery that this is an extremely bright, highly variable source, and thus must be a black hole. We present the optical spectrum which unambiguously identifies the optical counterpart as a globular cluster, and which shows a strong, broad [O III] emission line, most likely coming from an outflow driven by the accreting source.

Download Full-text

Slow decline and rise of the broad [O iii] emission line in globular cluster black hole candidate RZ2109

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2514 ◽

2019 ◽

Vol 489 (4) ◽

pp. 4783-4790 ◽

Cited By ~ 1

Author(s):

Kristen C Dage ◽

Stephen E Zepf ◽

Arash Bahramian ◽

Jay Strader ◽

Thomas J Maccarone ◽

...

Keyword(s):

Black Hole ◽

Emission Line ◽

Globular Clusters ◽

X Ray ◽

Hydrogen Emission ◽

Black Hole Candidate ◽

The Core ◽

Spectroscopic Monitoring ◽

Slow Decline ◽

Over Time

ABSTRACT RZ2109 is the first of several extragalactic globular clusters shown to host an ultraluminous X-ray source. RZ2109 is particularly notable because optical spectroscopy shows it has broad, luminous [O iii] λλ4959,5007 emission, while also having no detectable hydrogen emission. The X-ray and optical characteristics of the source in RZ2109 make it a good candidate for being a stellar mass black hole accreting from a white dwarf donor (i.e. an ultracompact black hole X-ray binary). In this paper we present optical spectroscopic monitoring of the [O iii]5007 emission line from 2007 to 2018. We find that the flux of the emission line is significantly lower in recent observations from 2016 to 2018 than it was in earlier observations in 2007–2011. We also explore the behaviour of the emission line shape over time. Both the core and the wings of the emission line decline over time, with some evidence that the core declines more rapidly than the wings. However, the most recent observations (in 2019) unexpectedly show the emission line core rebrightening

Download Full-text

Swift/XRT, Chandra, and XMM–Newton observations of IGR J17091–3624 as it returns into quiescence

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2009 ◽

2020 ◽

Vol 497 (1) ◽

pp. 1115-1126

Author(s):

M Pereyra ◽

D Altamirano ◽

J M C Court ◽

N Degenaar ◽

R Wijnands ◽

...

Keyword(s):

Black Hole ◽

Neutron Star ◽

Time Scales ◽

Strong Evidence ◽

Spectral Properties ◽

X Ray ◽

Term Evolution ◽

Wide Range ◽

Low Mass

ABSTRACT IGR J17091–3624 is a low-mass X-ray binary (LMXB), which received wide attention from the community thanks to its similarities with the bright black hole system GRS 1915+105. Both systems exhibit a wide range of highly structured X-ray variability during outburst, with time-scales from few seconds to tens of minutes, which make them unique in the study of mass accretion in LMXBs. In this work, we present a general overview into the long-term evolution of IGR J17091–3624, using Swift/XRT observations from the onset of the 2011–2013 outburst in 2011 February till the end of the last bright outburst in 2016 November. We found four re-flares during the decay of the 2011 outburst, but no similar re-flares appear to be present in the latter one. We studied, in detail, the period with the lowest flux observed in the last 10 yr, just at the tail end of the 2011–2013 outburst, using Chandra and XMM-Newton observations. We observed changes in flux as high as a factor of 10 during this period of relative quiescence, without strong evidence of softening in the spectra. This result suggests that the source has not been observed at its true quiescence so far. By comparing the spectral properties at low luminosities of IGR J17091–3624 and those observed for a well-studied population of LMXBs, we concluded that IGR J17091–3624 is most likely to host a black hole as a compact companion rather than a neutron star.

Download Full-text

The optical counterpart of the ultraluminous X-ray source NGC6946 ULX-1

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307005029 ◽

2006 ◽

Vol 2 (S238) ◽

pp. 229-232

Author(s):

P. K. Abolmasov ◽

S. N. Fabrika ◽

O. N. Sholukhova

Keyword(s):

Emission Line ◽

Spectral Data ◽

Line Source ◽

Total Power ◽

High Excitation ◽

Optical Counterpart ◽

Additional Source ◽

X Ray ◽

Long Time ◽

Integral Field

AbstractWe present a study of a peculiar nebula MF16 associated with an Ultraluminous X-ray Source NGC6946 ULX-1. We use integral-field and long-slit spectral data obtained with the 6-m telescope (Russia). The nebula was for a long time considered powered by strong shocks enhancing both high-excitation and low-excitation lines. However, kinematical properties point to rather moderate expansion rates (VS ∼ 100÷200 km s−1). The total power of the emission-line source exceeds by one or two orders of magnitude the power observed expansion rate can provide, that points towards the existence of an additional source of excitation and ionization. Using CLOUDY96.01 photoionization code we derive the properties of the photoionizing source. Its total UV/EUV luminosity must be about 1040 erg/s.

Download Full-text

The MAVERIC survey: a hidden pulsar and a black hole candidate in ATCA radio imaging of the globular cluster NGC 6397

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa631 ◽

2020 ◽

Vol 493 (4) ◽

pp. 6033-6049 ◽

Cited By ~ 4

Author(s):

Yue Zhao ◽

Craig O Heinke ◽

Vlad Tudor ◽

Arash Bahramian ◽

James C A Miller-Jones ◽

...

Keyword(s):

Black Hole ◽

Globular Cluster ◽

Radio Observation ◽

Millisecond Pulsar ◽

Radio Flux ◽

X Ray ◽

Black Hole Candidate ◽

Radio Imaging ◽

Low Mass ◽

Compact Array

ABSTRACT Using a 16.2-h radio observation by the Australia Telescope Compact Array and archival Chandra data, we found >5σ radio counterparts to four known and three new X-ray sources within the half-light radius (rh) of the Galactic globular cluster NGC 6397. The previously suggested millisecond pulsar (MSP) candidate, U18, is a steep-spectrum (Sν ∝ να; $\alpha =-2.0^{+0.4}_{-0.5}$) radio source with a 5.5-GHz flux density of 54.7 ± 4.3 $\mu \mathrm{ Jy}$. We argue that U18 is most likely a ‘hidden’ MSP that is continuously hidden by plasma shocked at the collision between the winds from the pulsar and companion star. The non-detection of radio pulsations so far is probably the result of enhanced scattering in this shocked wind. On the other hand, we observed the 5.5-GHz flux of the known MSP PSR J1740−5340 (U12) to decrease by a factor of >2.8 during epochs of 1.4-GHz eclipse, indicating that the radio flux is absorbed in its shocked wind. If U18 is indeed a pulsar whose pulsations are scattered, we note the contrast with U12’s flux decreases in eclipse, which argues for two different eclipse mechanisms at the same radio frequency. In addition to U12 and U18, we also found radio associations for five other Chandra X-ray sources, four of which are likely background galaxies. The last, U97, which shows strong H α variability, is mysterious; it may be either a quiescent black hole low-mass X-ray binary or something more unusual.

Download Full-text

Phase connected X-ray light curve and He II radial velocity measurements of NGC 300 X-1

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318007615 ◽

2018 ◽

Vol 14 (S346) ◽

pp. 187-192

Author(s):

S. Carpano ◽

F. Haberl ◽

P. Crowther ◽

A. Pollock

Keyword(s):

Black Hole ◽

Light Curve ◽

Radial Velocity ◽

Orbital Period ◽

High Mass ◽

Velocity Measurements ◽

X Ray ◽

Black Hole Radiation ◽

Ic 10 ◽

Binary Evolution

Abstract. NGC 300 X-1 and IC 10 X-1 are currently the only two robust extragalactic candidates for being Wolf-Rayet/black hole X-ray binaries, the Galactic analogue being Cyg X-3. These systems are believed to be a late product of high-mass X-ray binary evolution and direct progenitors of black hole mergers. From the analysis of Swift data, the orbital period of NGC 300 X-1 was found to be 32.8 h. We here merge the full set of existing data of NGC 300 X-1, using XMM-Newton, Chandra and Swift observations to derive a more precise value of the orbital period of 32.7932 ± 0.0029 h above a confidence level of 99.99%. This allows us to phase connect the X-ray light curve of the source with radial velocity measurements of He II lines performed in 2010. We show that, as for IC 10 X-1 and Cyg X-3, the X-ray eclipse corresponds to maximum of the blueshift of the He II lines, instead of the expected zero velocity. This indicates that for NGC 300 X-1 as well, the wind of the WR star is completely ionised by the black hole radiation and that the emission lines come from the region of the WR star that is in the shadow. We also present for the first time the light curve of two recent very long XMM-Newton observations of the source, performed on the 16th to 20th of December 2016.

Download Full-text

A RADIO-SELECTED BLACK HOLE X-RAY BINARY CANDIDATE IN THE MILKY WAY GLOBULAR CLUSTER M62

The Astrophysical Journal ◽

10.1088/0004-637x/777/1/69 ◽

2013 ◽

Vol 777 (1) ◽

pp. 69 ◽

Cited By ~ 86

Author(s):

Laura Chomiuk ◽

Jay Strader ◽

Thomas J. Maccarone ◽

James C. A. Miller-Jones ◽

Craig Heinke ◽

...

Keyword(s):

Black Hole ◽

Globular Cluster ◽

Milky Way ◽

X Ray

Download Full-text

An accretion disk laboratory in the Seyfert 1.9 galaxy NGC 2992

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307004826 ◽

2006 ◽

Vol 2 (S238) ◽

pp. 123-126

Author(s):

Tahir Yaqoob ◽

Kendrah D. Murphy ◽

Yuichi Terashima

Keyword(s):

Black Hole ◽

Emission Line ◽

Accretion Disk ◽

Large Amplitude ◽

Gravitational Energy ◽

Test Bed ◽

Central Black Hole ◽

X Ray ◽

Order Of Magnitude ◽

The Continuum

AbstractOver twenty five years of X-ray observations of the Seyfert 1.9 galaxy NGC 2992 show that it is a promising test-bed for severely constraining accretion disk models. The previous interpretation of the historical activity of NGC 2992 in terms of the accretion disk slowly becoming dormant over many years and then ‘re-building’ itself is not supported by new data. A recent year-long monitoring campaign with RXTE showed that the X-ray continuum varied by more than an order of magnitude on a timescale of weeks. During the large-amplitude flares the centroid energy of the Fe K emission-line complex became significantly redshifted, indicating that the violent activity was occurring close to the putative central black hole where gravitational energy shifts can be sufficiently large. For the continuum, the Compton-y parameter remains roughly constant despite the large-amplitude luminosity variability, with (kT) τ ∼ 20–50.

Download Full-text