#IGR J17091

[celestialdaily]

The celestial object of the day is IGR J17091-3624!

This black hole has in its accretion disk the fastest winds ever discovered, at 32 million km/h (20 million miles per hour) or 3% of the speed of light. And just like the black hole GRS 1915+105, it also has X-ray variability patterns or 'heartbeats.' While fainter than the ones of GRS 1915+105, IGR J17091's are faster!

[spaceexp]

NASA's Rossi X-ray Timing Explorer Leaves Scientific ‘Treasure Trove’

NASA - Rossi X-ray Timing Explorer (RXTE) logo. May 3, 2018 NASA’s decommissioned Rossi X-ray Timing Explorer (RXTE) satellite re-entered Earth’s atmosphere on April 30. Orbiting for more than 22 years, the 6,700-pound satellite operated from 1996 to 2012, providing scientists with an unprecedented look into the extreme environments around neutron stars — also known as pulsars — and black holes.

NASA - RXTE Detects 'Heartbeat' Of Smallest Black Hole Candidate

Video above: This animation compares the X-ray “heartbeats” of two different black holes that ingest gas from their companion stars. GRS 1915 has nearly five times the mass of IGR J17091, which at three solar masses may be the smallest black hole known. Video Credits: NASA's Goddard Space Flight Center. The strong gravity of these objects can pull streams of gas from a nearby companion star and corral it in a vast storage zone called an accretion disk. The orbiting gas becomes heated by friction and reaches temperatures of millions of degrees — so hot, it emits X-rays. As the gas spirals inward, powerful bursts, flares and rapid pulsations can occur in the innermost accretion disk and on the surfaces of neutron stars. These X-ray signals vary on time scales ranging from a few seconds to less than a millisecond, providing important information on the nature of the compact object. “Observing these X-ray phenomena with precise high-resolution timing was RXTE’s specialty,” said Jean Swank, an astrophysicist emeritus at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who served as the mission’s project scientist until 2010. “During RXTE’s run, no other observatory could provide these measurements.” RXTE far exceeded its original science goals and leaves behind an important scientific legacy. All data from the mission is open to the public and is maintained by Goddard’s High Energy Astrophysics Science Archive Research Center. “The data remain a treasure trove for studying compact objects, whether pulsars and stellar-mass black holes in our own galaxy or supermassive black holes in the cores of distant galaxies,” said Goddard’s Tod Strohmayer, who served as RXTE’s project scientist from 2010 through the end of the mission. “So far, more than 3,100 published papers in refereed journals, totaling over 95,000 citations, include RXTE measurements.”

Image above: NASA's Rossi X-ray Timing Explorer undergoes processing in Hangar AO at Cape Canaveral Air Station, Florida, in summer 1995. The spacecraft is shown being installed onto the Delta launch vehicle’s payload attach fitting in preparation for transport to Pad A, Complex 17, and mating with the second stage of its Delta II rocket. Image Credits: NASA's Kennedy Space Center. Watching how matter behaves in the vicinity of a black hole helps astronomers glimpse details about the nature of gravity itself. In 1997, RXTE provided what is widely regarded as the first observational evidence of “frame dragging,” an effect predicted 79 years earlier by Austrian physicists Joseph Lense and Hans Thirring using Einstein’s general theory of relativity. In binary systems where black holes strip gas from a normal companion star, fast X-ray oscillations track hot blobs of gas orbiting deep within the accretion disk. These changes indicate that the inner disk wobbles in just the way relativity predicts. Like a bowling bowl spinning in molasses, the rotating black hole drags along nearby space-time — and with it, the inner accretion disk. RXTE also showed that black holes of extremely different masses produce similar kinds of X-ray activity, just at varying time scales proportional to their masses. Stellar-mass black holes undergo key changes in a matter of hours, while their supermassive cousins, containing millions of solar masses, exhibit similar changes over years. Only slightly less extreme than a black hole is a neutron star, the crushed core of a massive star that ran out of nuclear fuel, collapsed under its own weight and exploded as a supernova. Each one squeezes more than the Sun’s mass into a ball roughly 12 miles (20 kilometers) across — about the length of New York City's Manhattan Island. Neutron stars typically possess magnetic fields up to 10 trillion times stronger than Earth's. RXTE data helped establish the existence of a new class of neutron stars with magnetic fields a thousand times stronger. Dubbed magnetars, these objects boast the most powerful magnetic fields known in the cosmos. Of some 2,600 neutron stars now cataloged, only 29 rank as magnetars. In the absence of RXTE, NASA’s Neutron star Interior Composition Explorer (NICER), an instrument installed on the skyward side of the International Space Station, continues the study of variable X-ray sources.

Image above: This graph based on RXTE data illustrates the changing character of X-ray outbursts from a neutron star called T5X2 in October and November 2010. As the persistent X-ray emission rises (upward steps in the plot), the number of bursts increases while their brightness declines. The abrupt dropout on Oct. 13 occurred when the Moon briefly eclipsed the source. Image Credits: NASA's Goddard Space Flight Center. “NICER is the successor to RXTE, with an order-of-magnitude improvement in sensitivity, energy resolution and time resolution,” said Goddard’s Keith Gendreau, the mission’s principal investigator. “The X-ray band NICER observes overlaps the lower end of RXTE’s range, which means we can more easily take advantage of its long observational record.” The astronomical community has recognized the importance of RXTE research with five major awards. These include four Bruno Rossi Prizes (1999, 2003, 2006 and 2009) from the High Energy Astrophysics Division of the American Astronomical Society and the 2004 NWO Spinoza Prize, the highest Dutch science award, from the Netherlands Organization for Scientific Research. (To learn more about the mission’s accomplishments, see our RXTE gallery.)

Rossi X-ray Timing Explorer (RXTE) satellite. Image Credit: NASA

The mission was launched as XTE aboard a Delta II 7920 rocket on Dec. 30, 1995, from Cape Canaveral Air Force Station in Florida. It was renamed RXTE in early 1996 to honor Bruno Rossi, an MIT astronomer and a pioneer of X-ray astronomy and space plasma physics who died in 1993. RXTE relayed its last scientific observations to the ground on Jan. 4, 2012. The following day, controllers at Goddard, which managed the mission, powered down the satellite. Related links: RXTE (Rossi X-ray Timing Explorer): http://www.nasa.gov/centers/goddard/missions/rxte.html RXTE gallery: https://svs.gsfc.nasa.gov/Gallery/RXTE.html Neutron star Interior Composition Explorer (NICER): https://www.nasa.gov/nicer 2004 NWO Spinoza Prize: https://www.nwo.nl/en/news-and-events/news/2003/NWO%252FSpinoza+prize+for+economist,+historian+and+two+physicists.html Images, Video, Text, Credits: NASA/Rob Garner/Goddard Space Flight Center, by Francis Reddy. Greetings, Orbiter.ch Full article

[arxt1]

Similarities and Differences in Accretion Flow Properties between GRS 1915+105 and IGR J17091-3624: a Case Study. (arXiv:2101.11854v1 [astro-ph.HE])

We perform a comparative spectro-temporal analysis on the variability classes of GRS 1915+105 and IGR J17091-3624 to draw inferences regarding the underlying accretion flow mechanism. The $\nu$, as well as C2 class Rossi X-Ray Timing Explorer observation, have been considered for analysis. We investigate the intensity variation of the source in different energy domains that correspond to different components of the accretion flow and infer the relative dominance of these flow components during the dip/flare events. We correlate the dependence of the dynamic photon index ($\Theta$) with intensities in different energy bands and comment on the transition of the source to hard/soft phases during soft dips/flares. We also report the presence of sharp QPOs at \sim7.1 Hz corresponding to both softer and harder domain in the case of $\nu$ variability class of GRS 1915+105 and discuss the possible accretion flow configuration it suggests. Sharp QPO around \sim20 mHz is observed in $\nu$ and C2 classes of IGR J17091-3624 in low and mid energy band (2.0-6.0 keV and 6.0-15.0 keV), but remains undetected in high energy (15.0-60.0 keV). The 2.5-25.0 keV background-subtracted spectra have also been fitted with TCAF along with a Compton reflection component. A plausible accretion flow mechanism in order to explain the observed variability has been proposed.

from astro-ph.HE updates on arXiv.org https://ift.tt/2MhJAoN

[awesomesallysoulla]

Black Hole This animation compares the X-ray "heartbeats" of GRS 1915 and IGR J17091, two black holes that ingest gas from companion stars.

[dongsukien]

Bão cấp 5 thổi từ hố đen nhỏ Đài quan sát tia X Chandra của NASA đã phát hiện được một hố đen đang tống ra những luồng gió mạnh đến 20 triệu dặm/giờ.

[watpagin]

[arxt1]

Swift/XRT, Chandra and XMM-Newton observations of IGR J17091-3624 as it returns into quiescence. (arXiv:2007.10487v1 [astro-ph.HE])

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 February 2011 to the end of the last bright outburst in November 2016. We found 4 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 years, 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.

from astro-ph.HE updates on arXiv.org https://ift.tt/3hnrFab

[arxt1]

Correlating nonlinear time series and spectral properties of IGR J17091-3624: Is it similar to GRS 1915+105?. (arXiv:2001.01732v1 [astro-ph.HE])

We explore the nonlinear properties of IGR J17091-3624 in the line of the underlying behaviour for GRS 1915+105, following correlation integral method. We find that while the latter is known to reveal the combination of fractal (or even chaotic) and stochastic behaviours depending on its temporal class, the former mostly shows stochastic behaviour. Therefore, although several observations argue IGR J17091-3624 to be similar to GRS 1915+105 with common temporal classes between them, underlying nonlinear time series analyses offer differently. Nevertheless, the Poisson noise to $rms$ variation value for IGR J17091-3624 turns out to be high, arguing them to be Poisson noise dominated and hence may plausibly lead to suppression of the nonlinear character, if any. Indeed, it is a very faint source compared to GRS 1915+105. However, by increasing time bin some of the temporal classes of IGR J17091-3624 show deviation from stochasticity, indicating plausibility of higher fractal dimension. Along with spectral analysis, overall IGR J17091-3624 argues to reveal three different accretion classes: slim, Keplerian and advective accretion discs.

from astro-ph.HE updates on arXiv.org https://ift.tt/35zfctR

[arxt1]

Simultaneous detection of an intrinsic absorber and a compact jet emission in the X-ray binary IGR J17091-3624 during a hard accretion state. (arXiv:1912.02180v1 [astro-ph.HE])

We present a detailed analysis of three XMM-Newton observations of the black hole low-mass X-ray binary IGR~J17091-3624 taken during its 2016 outburst. Radio observations obtained with the Australia Telescope Compact Array (ATCA) indicate the presence of a compact jet during all observations. From the best X-ray data fit results we concluded that the observations were taken during a transition from a hard accretion state to a hard-intermediate accretion state. For Observations 1 and 2 a local absorber can be identified in the EPIC-pn spectra but not in the RGS spectra, preventing us from distinguishing between absorption local to the source and that from the hot ISM component. For Observation 3, on the other hand, we have identified an intrinsic ionized static absorber in both EPIC-pn and RGS spectra. The absorber, observed simultaneously with a compact jet emission, is characterized by an ionization parameter of 1.96< log({\xi}) <2.05 and traced mainly by Ne X, Mg XII, Si XIII and Fe XVIII.

from astro-ph.HE updates on arXiv.org https://ift.tt/2PiWIaU

[arxt1]

Recurrent Instability in LMXB Accretion Disks: How Strange is GRS 1915+105?. (arXiv:1903.03675v1 [astro-ph.HE])

Low Mass X-Ray Binaries (LMXBs) are systems in which a compact object accretes from a binary companion star via an accretion disk. The X-ray properties of LMXBs show strong variability over timescales ranging from milliseconds to decades, much of which is tied to the extreme environment of the inner accretion disk, hence an understanding of this behaviour is key to understanding how matter behaves in such an environment. GRS 1915+105 and MXB 1730-335 are two LMXBs which show particularly unusual variability. GRS 1915+105 shows a large number of distinct classes of second-to-minute scale variability, consisting of repeated patterns of dips and flares. MXB 1730 shows Type II X-ray Bursts; minute-scale increases in X-ray intensity with a sudden onset and a slow decay. More recently two new objects, IGR J17091-3624 and GRO J1744-28 have been shown to display similar behaviours. In this thesis I present a new framework with which to classify variability in IGR J17091. I perform a comparison study between this source and GRS 1915. In GRS 1915, hard X-rays lag soft X-rays in all variability classes; in IGR J17091, I find that the sign of this lag varies between variability classes. Additionally, while GRS 1915+105 accretes at close to its Eddington Limit, I find that IGR J17091-3624 accretes at only ~5-33% of its Eddington Limit. I also perform a study of variability in GRO J1744 and find that it is more complex than in MXB 1730, consisting of at least 4 separate phenomena which may have separate physical origins. One of these phenomena, `Structured Bursting', consists of patterns of flares and dips similar to those seen in GRS 1915 and IGR J17091. I compare these types of variability and discuss the possibility of a physical link. I also present the alternative hypothesis that Structured Bursting is caused my 'hiccup accretion' similar to that seen in systems approaching the propeller regime.

from astro-ph.HE updates on arXiv.org https://ift.tt/2J7C39J

[arxt1]

The reflection component in the average and heartbeat spectra of the black-hole candidate IGR J17091-3642 during the 2016 outburst. (arXiv:1805.10188v1 [astro-ph.HE])

We present simultaneous NuSTAR and Swift observations of the black hole transient IGR J17091-3642 during its 2016 outburst. By jointly fitting six NuSTAR and four Swift spectra, we found that during this outburst the source evolves from the hard to the hard/soft intermediate and back to the hard state, similar to the 2011 outburst. Unlike in the previous outburst, in this case we observed both a broad emission and an moderately broad absorption line in our observations. Our fits favour an accretion disc with an inclination angle of $\sim$$45\deg$ with respect to the line of sight and a high iron abundance of $3.5\pm0.3$ in units of the solar abundance. We also observed heartbeat variability in one NuSTAR observation. We fitted the phase-resolved spectra of this observation and found that the reflected emission varies independently from the direct emission, whereas in the fits to the average spectra these two quantities are strongly correlated. Assuming that in IGR J17091-3642 the inner radius of the disc both in the average and the phase-resolved spectra is located at the radius of the innermost stable circular orbit, with 90% confidence the spin parameter of the black hole in this system is $-0.13\leq a_{*}\leq0.27$.

from astro-ph.HE updates on arXiv.org https://ift.tt/2GXeqdA

[arxt1]

Spectral and Timing Properties of IGR J17091-3624 in the Rising Hard State During its 2016 Outburst. (arXiv:1711.04421v1 [astro-ph.HE])

We present a spectral and timing study of the NuSTAR and Swift observations of the black hole candidate IGR J17091-3624 in the hard state during its outburst in 2016. Disk reflection is detected in each of the NuSTAR spectra taken in three epochs. Fitting with relativistic reflection models reveals that the accretion disk is truncated during all epochs with $R_{\rm in}>10~r_{\rm g}$, with the data favoring a low disk inclination of $\sim 30^{\circ}-40^{\circ}$. The steepening of the continuum spectra between epochs is accompanied by a decrease in the high energy cut-off: the electron temperature $kT_{\rm e}$ drops from $\sim 64$ keV to $\sim 26$ keV, changing systematically with the source flux. We detect type-C QPOs in the power spectra with frequency varying between 0.131 Hz and 0.327 Hz. In addition, a secondary peak is found in the power spectra centered at about 2.3 times the QPO frequency during all three epochs. The nature of this secondary frequency is uncertain, however a non-harmonic origin is favored. We investigate the evolution of the timing and spectral properties during the rising phase of the outburst and discuss their physical implications.

from astro-ph.HE updates on arXiv.org http://ift.tt/2iXEYlb

[arxt1]

Shocks in the relativistic transonic accretion with low angular momentum. (arXiv:1709.01824v1 [astro-ph.HE])

We perform 1D/2D/3D relativistic hydrodynamical simulations of accretion flows with low angular momentum, filling the gap between spherically symmetric Bondi accretion and disc-like accretion flows. Scenarios with different directional distributions of angular momentum of falling matter and varying values of key parameters such as spin of central black hole, energy and angular momentum of matter are considered. In some of the scenarios the shock front is formed. We identify ranges of parameters for which the shock after formation moves towards or outwards the central black hole or the long lasting oscillating shock is observed. The frequencies of oscillations of shock positions which can cause flaring in mass accretion rate are extracted. The results are scalable with mass of central black hole and can be compared to the quasi-periodic oscillations of selected microquasars (such as GRS 1915+105, XTE J1550-564 or IGR J17091-3624), as well as to the supermassive black holes in the centres of weakly active galaxies, such as Sgr $A^{*}$.

from astro-ph.HE updates on arXiv.org http://ift.tt/2f5qaQs

[arxt1]

An Atlas of Exotic Variability in IGR J17091-3624: A Comparison with GRS 1915+105. (arXiv:1703.09572v1 [astro-ph.HE])

We performed an analysis of all RXTE observations of the Low Mass X-ray Binary and Black Hole Candidate IGR J17091-3624 during the 2011-2013 outburst of the source. By creating lightcurves, hardness-intensity diagrams and power density spectra of each observation, we have created a set of 9 variability `classes' that phenomenologically describe the range of types of variability seen in this object. We compare our set of variability classes to those established by Belloni et al. (2000) to describe the similar behaviour of the LMXB GRS 1915+105, finding that some types of variability seen in IGR J17091-3624 are not represented in data of GRS 1915+105. We also use all available X-ray data of the 2011-2013 outburst of IGR J17091-3624 to analyse its long-term evolution, presenting the first detection of IGR J17091-3624 above 150 keV as well as noting the presence of `re-flares' during the latter stages of the outburst. Using our results we place new constraints on the mass and distance of the object, and find that it accretes at <33% of its Eddington limit. As such, we conclude that Eddington-limited accretion can no longer be considered a sufficient or necessary criterion for GRS 1915+105-like variability to occur in Low Mass X-Ray Binaries.

from astro-ph.HE updates on arXiv.org http://ift.tt/2nyxCIi

[arxt1]

Exploring the Long-Term Evolution of GRS 1915+105. (arXiv:1611.01332v2 [astro-ph.HE] UPDATED)

Among the population of known galactic black hole X-ray binaries, GRS 1915+105 stands out in multiple ways. It has been in continuous outburst since 1992, and has shown a wide range of different states that can be distinguished by their timing and spectral properties. These states, also observed in IGR J17091-3624, have in the past been linked to accretion dynamics. Here, we present the first comprehensive study into the long-term evolution of GRS 1915+105, using the entire data set observed with RXTE over its sixteen-year lifetime. We develop a set of descriptive features allowing for automatic separation of states, and show that supervised machine learning in the form of logistic regression and random forests can be used to efficiently classify the entire data set. For the first time, we explore the duty cycle and time evolution of states over the entire sixteen-year time span, and find that the temporal distribution of states has significantly changed over the span of the observations. We connect the machine classification with physical interpretations of the phenomenology in terms of chaotic and stochastic processes.

from astro-ph.HE updates on arXiv.org http://ift.tt/2eDtMcy