Outburst Duration Research Articles

The curious case of Swift J1753.5−0127: a black hole low-mass X-ray binary analogue to Z cam type dwarf novae

Swift J1753.5-0127 (J1753) is a candidate black hole low-mass X-ray binary (BH-LMXB) that was discovered in outburst in May 2005. It remained in outburst for $\sim12$ years, exhibiting a wide range of variability on various timescales, before entering quiescence after two short-lived, low-luminosity "mini-outbursts" in April 2017. The unusually long outburst duration in such a short-period ($P_{\rm orb}\approx3.24$ hrs) source, and complex variability observed during this outburst period, challenges the predictions of the widely accepted disc-instability model, which has been shown to broadly reproduce the behaviour of LMXB systems well. The long-term behaviour observed in J1753 is reminiscent of the Z Cam class of dwarf novae, whereby variable mass transfer from the companion star drives unusual outbursts, characterized by stalled decays and abrupt changes in luminosity. Using sophisticated modelling of the multi-wavelength light curves and spectra of J1753, during the $\sim12$ years the source was active, we investigate the hypothesis that periods of enhanced mass transfer from the companion star may have driven this unusually long outburst. Our modelling suggests that J1753 is in fact a BH-LMXB analogue to Z Cam systems, where the variable mass transfer from the companion star is driven by the changing irradiation properties of the system, affecting both the disc and companion star.

A faint outburst of the accreting millisecond X-ray pulsar SAX J1748.9-2021 in NGC 6440

SAX J1748.9-2021 is an accreting X-ray millisecond pulsar observed in outburst five times since its discovery in 1998. In early October 2017, the source started its sixth outburst, which lasted only ~13 days, significantly shorter than the typical 30 days duration of the previous outbursts. It reached a 0.3-70 keV unabsorbed peak luminosity of $\sim3\times10^{36}$ erg/s. This is the weakest outburst ever reported for this source to date. We analyzed almost simultaneous XMM-Newton, NuSTAR and INTEGRAL observations taken during the decaying phase of its 2017 outburst. We found that the spectral properties of SAX J1748.9-2021 are consistent with an absorbed Comptonization plus a blackbody component. The former, characterized by an electron temperature of ~20 keV, a photon index of ~1.6-1.7 keV and seed photon temperature of 0.44 keV, can be associated to a hot corona or the accretion column, while the latter is more likely originating from the neutron star surface (kT$_{bb}\sim0.6$ keV, R$_{bb}\sim2.5$ km). These findings suggest that SAX J1748.9-2021 was observed in a $hard$ spectral state, as it is typically the case for accreting millisecond pulsars in outburst.

Recurrent Outbursts Revealed in 3XMM J031820.8-663034

Abstract 3XMM J031820.8-663034, first detected by ROSAT in NGC 1313, is one of a few known transient ultraluminous X-ray sources (ULXs). In this paper, we present decades of X-ray data of this source from ROSAT, XMM-Newton, Chandra, and the Neil Gehrels Swift Observatory. We find that its X-ray emission experienced four outbursts since 1992, with a typical recurrent time ∼1800 days, an outburst duration ∼240–300 days, and a nearly constant peak X-ray luminosity ∼1.5 × 1039 erg s−1. The upper limit of X-ray luminosity at the quiescent state is ∼5.6 × 1036 erg s−1, and the total energy radiated during one outburst is ∼1046 erg. The spectra at the high luminosity states can be described with an absorbed disk blackbody, and the disk temperature increases with the X-ray luminosity. We compare its outburst properties with other known transient ULXs including ESO 243-49 HLX-1. As its peak luminosity only marginally puts it in the category of ULXs, we also compare it with normal transient black hole binaries. Our results suggest that the source is powered by an accreting massive stellar-mass black hole, and the outbursts are triggered by the thermal-viscous instability.

Characterizing the Outburst of the Supermassive Black Hole in M87

AbstractM87, in the Virgo cluster, allows us to study the interaction of a supermassive black hole (SMBH) with its hot gaseous atmosphere. Deep Chandra observations reveal a nearly circular shock front with a Mach number of 1.2 and a radius of 13 kpc which is driven by a central cavity inflated by an SMBH outburst began 12 million years ago. An outburst with an energy of a ~5×57 ergs and a duration of ~2 Myrs provides a good match to all the constraints. For an outburst repetition rate of about 12 Myrs (the outburst age), the outburst energy is sufficient to balance the radiative cooling of the gas. The outburst duration in M87 argues for a “gentle” (long duration) outburst that does not generate strong shocks and where much of the outburst energy is deposited in the cavities that then transfer energy to the surrounding gas as they buoyantly rise.

Aggression in Attention-Deficit/Hyperactivity Disorder: When Do Psychotropics Backfire?

Case: A healthy 9-year-old girl who is taking dexmethylphenidate extended-release (ER) (Focalin XR) 10 mg daily presents with residual attention-deficit/hyperactivity disorder (ADHD) symptoms and 1-2 episodes per month of aggressive tantrums. To treat the residual ADHD symptoms, dexmethylphenidate ER is increased to 15 mg daily. The family instantly notices an improvement in the girl’s concentration, but also an increase in the severity, frequency, and duration of aggressive outbursts in the afternoon. These outbursts remit on weekends, when the medication is not administered. The possibility of stimulant rebound is considered, and a booster dose is added, resulting in worsening episodes of severe aggression throughout the evening. Guanfacine is added with little improvement. Dexmethylphenidate ER is tapered off successfully, and dextroamphetamine/amphetamine ER (Adderall XR) is started. Her ADHD symptoms improve, and her aggressive tantrums resolve.

Modified viscosity in accretion disks

Black holes (BHs) surrounded by accretion disks are present in the Universe at different scales of masses, from microquasars up to the active galactic nuclei (AGNs). The current picture remains ad hoc due to the complexity of the magnetic field action. In addition, accretion disks at high Eddington rates can be radiation-pressure dominated and, according to some of the heating prescriptions, thermally unstable. The observational verification of their resulting variability patterns may shed light on both the role of radiation pressure and magnetic fields. We compute the structure and time evolution of an accretion disk, using the code GLADIS (which models the global accretion disk instability). We supplement this model with a modified viscosity prescription, which can to some extent describe the magnetisation of the disk. We study the results for a large grid of models, to cover the whole parameter space, and we derive conclusions separately for different scales of black hole masses, which are characteristic for various types of cosmic sources. We show the dependencies between the flare or outburst duration, its amplitude, and period, on the accretion rate and viscosity scaling. We show that if the heating rate in the accretion disk grows more rapidly with the total pressure and temperature, the instability results in longer and sharper flares. In general, we confirm that the disks around the supermassive black holes are more radiation-pressure dominated and present relatively brighter bursts. Our method can also be used as an independent tool for the black hole mass determination, which we confront now for the intermediate black hole in the source HLX-1.

Discovery of a new accreting millisecond X-ray pulsar in the globular cluster NGC 2808

We report on the discovery of coherent pulsations at a period of 2.9 ms from the X-ray transient MAXI J0911−655 in the globular cluster NGC 2808. We observed X-ray pulsations at a frequency of ~339.97 Hz in three different observations of the source performed with XMM-Newton and NuSTAR during the source outburst. This newly discovered accreting millisecond pulsar is part of an ultra-compact binary system characterised by an orbital period of 44.3 min and a projected semi-major axis of ~17.6 lt-ms. Based on the mass function, we estimate a minimum companion mass of 0.024 M⊙, which assumes a neutron star mass of 1.4 M⊙ and a maximum inclination angle of 75° (derived from the lack of eclipses and dips in the light-curve of the source). We find that the Roche-lobe of the companion star could either be filled by a hot (5 × 106 K) pure helium white dwarf with a 0.028 M⊙ mass (implying i ≃ 58°) or an old (>5 Gyr) brown dwarf with metallicity abundances between solar/sub-solar and mass ranging in the interval 0.065 to 0.085 (16 < i < 21). During the outburst, the broad-band energy spectra are well described by a superposition of a weak black-body component (kT ~ 0.5 keV) and a hard cut-off power-law with photon index Γ ~ 1.7 and cut-off at a temperature kTe ~ 130 keV. Up until the latest Swift-XRT observation performed on 19th July, 2016, the source had been observed in outburst for almost 150 days, which makes MAXI J0911−655 the second accreting millisecond X-ray pulsar with outburst duration longer than 100 days.

THE UNIVERSAL “HEARTBEAT” OSCILLATIONS IN BLACK HOLE SYSTEMS ACROSS THE MASS-SCALE

ABSTRACT The hyperluminous X-ray source (HLX-1, peak X-ray luminosity ) near the spiral galaxy ESO 243-49, which underwent recurrent outbursts within a period of ∼400 days, is possibly the best candidate for an intermediate mass black hole (IMBH). The physical reason for this quasiperiodic variability is still unclear. We explore the possibility of radiation-pressure instability in the accretion disk by modeling the light curve of HLX-1, and find that it can roughly reproduce the duration, period, and amplitude of the recurrent outbursts in HLX-1 with an IMBH of . Our result provides a possible mechanism to explain the recurrent outbursts in HLX-1. We further find a universal correlation between the outburst duration and the bolometric luminosity for the black hole (BH) sources with a very broad mass range (e.g., X-ray binaries, HLX-1, and active galactic nuclei), which is roughly consistent with the prediction of radiation-pressure instability of the accretion disk. These results imply that “heartbeat” oscillations triggered by radiation-pressure instability may appear in different-scale BH systems.

Analysis of R-band observations of an outburst of Comet 29P/Schwassmann-Wachmann 1 to place constraints on the nucleus’ rotation state

We present analysis of five nights of R-band observations of Comet 29P/Schwassmann-Wachmann 1 (SW1) taken on September 2008 which show the comet undergoing an outburst. Coma morphology shows a projected asymmetric shell of material expanding radially and four linear features on the northern side of the coma at position angles 37°, 78°, 300°, and 353°. Using the measured projected radial outflow velocity of 0.11 ±0.02 km/s for the shell material, we calculate an outburst time of UT 2008-09-21.03 ±0.95 days. By tracking the inner and outer extent of the northern linear features, we found that the features are fully contained within the expanding shell of material. This suggested both shell and linear features originated during the same event and activity originating from different regions on the nuclear surface are not necessary to generate both types of morphological structure observed. A 3-D Monte Carlo coma model was used to model the outburst. Morphological features present in the observations were modeled allowing constraints to be placed on the spin state of SW1’s nucleus. The evolution of morphological features allows constraints on the rotation period P assuming an outburst duration Δt and the spin period constraints are expressed in terms of their ratio P/Δt. Since the spin-pole orientation could not be constrained, four spin-pole orientations were chosen for modeling the coma. Spin-period constraints for each assumed pole orientation are discussed. Overall, modeling suggested either a spin period on the order of days, a spin-pole orientation nearly along the sub-Earth direction, or a combination of both. To place an independent constraint on the outburst duration, radial surface-brightness profiles of the observations were compared with profiles from synthetic models, giving an upper-limit of Δt ≤ 1.5 days. Longer outbursts resulted in a higher number of dust grains in close proximity to the nucleus during the observations and a profile slope too steep to model observations. Lastly, from photometry of the five nights of observation, a lower limit of (1.8 ± 0.07) × 109 kg was estimated for the total amount of dust emitted during the outburst. Assuming the outburst was triggered by either the sublimation of pure CO or CO2 ice and a dust to gas ratio of ∼4 (Rosetta results for Comet 67P, Rotundi et al. 2015), a lower limit for the outburst duration on the order of hours was obtained.

V346 Normae: first post-outburst observations of an FU Orionis star

Abstract During their formation phase, stars gain most of their mass in violent episodic accretion events, such as observed in FU Orionis (FUor) and EXor stars. V346 Normae is a well-studied FUor that underwent a strong outburst beginning around 1980. Here, we report on photometric and spectroscopic observations, which show that the visual/near-infrared brightness has decreased dramatically between the 1990s and 2010 (ΔR ≈ 10.9 mag, ΔJ ≈ 7.8 mag and ΔK ≈ 5.8 mag). The spectral properties of this fading event cannot be explained by variable extinction alone, but indicate a drop in accretion rate by two to three orders of magnitude. This is the first time that a member of the FUor class has been observed to switch to a very low accretion phase. Remarkably, in the last few years (2011–2015) V346 Nor has brightened again at all near-infrared wavelengths, indicating the onset of a new outburst event. The observed behaviour might be consistent with the clustered luminosity bursts that have been predicted by recent gravitational instability and fragmentation models for the early stages of protostellar evolution. Given V346 Nor's unique characteristics (concerning outburst duration, repetition frequency and spectroscopic diagnostics), our results also highlight the need to revisit the FUor/EXor classification scheme.

Statistical analysis of properties of dwarf novae outbursts

We present a statistical study of all measurable photometric features of a large sample of dwarf novae during their outbursts and superoutbursts. We used all accessible photometric data for all our objects to make the study as complete and up-to-date as possible. Our aim was to check correlations between these photometric features in order to constrain theoretical models which try to explain the nature of dwarf novae outbursts. We managed to confirm a few of the known correlations, that is the Stolz and Schoembs Relation, the Bailey Relation for long outbursts above the period gap, the relations between the cycle and supercycle lengths, amplitudes of normal and superoutbursts, amplitude and duration of superoutbursts, outburst duration and orbital period, outburst duration and mass ratio for short and normal outbursts, as well as the relation between the rise and decline rates of superoutbursts. However, we question the existence of the Kukarkin-Parenago Relation but we found an analogous relation for superoutbursts. We also failed to find one presumed relation between outburst duration and mass ratio for superoutbursts. This study should help to direct theoretical work dedicated to dwarf novae.

Photometry and spectroscopy of the luminous red nova PSNJ14021678+5426205 in the galaxy M101

We present the results of the study of the red nova PSN J14021678+5426205 based on the observations carried out with the Russian 6-m telescope (BTA) along with other telescopes of SAO RAS and SAI MSU. To investigate the nova progenitor, we used the data from the Digital Sky Survey and amateur photos available on the internet. In the period between April 1993 and July 2014, the brightness of the progenitor gradually increased by 2.2 mag in the V band. At the peak of the first outburst in mid-November of 2014, the star reached an absolute visual magnitude of -12.75 mag but was discovered later, in February 2015, in a repeated outburst at the absolute magnitude of -11.65 mag. The amplitude of the outburst was minimum among the red novae, only 5.6 mag in the V band. The H alpha emission line and the continuum of a cool supergiant with a gradually decreasing surface temperature were observed in the spectra. Such process is typical for red novae, although the object under study showed extreme parameters: maximum luminosity, maximum outburst duration, minimum outburst amplitude, unusual shape of the light curve. This event is interpreted as a massive OB star system components merging accompanied by the formation of a common envelope and then the expansion of this envelope with minimal energy losses.

X-RAY OUTBURSTS OF ESO 243-49 HLX-1: COMPARISON WITH GALACTIC LOW-MASS X-RAY BINARY TRANSIENTS

We studied the outburst properties of the hyper-luminous X-ray source ESO 243-49 HLX-1, using the full set of Swift monitoring observations. We quantified the increase in the waiting time, recurrence time, and e-folding rise timescale along the outburst sequence, and the corresponding decrease in outburst duration, total radiated energy, and e-folding decay timescale, which confirms previous findings. HLX-1 spends less and less time in outburst and more and more time in quiescence, but its peak luminosity remains approximately constant. We compared the HLX-1 outburst properties with those of bright Galactic low-mass X-ray binary transients (LMXBTs). Our spectral analysis strengthens the similarity between state transitions in HLX-1 and those in Galactic LMXBTs. We also found that HLX-1 follows the nearly linear correlations between the hard-to-soft state transition luminosity and the peak luminosity, and between the rate of change of X-ray luminosity during the rise phase and the peak luminosity, which indicates that the occurrence of the hard-to-soft state transition of HLX-1 is similar to those of Galactic LMXBTs during outbursts. We found that HLX-1 does not follow the correlations between total radiated energy and peak luminosity, and between total radiated energy and e-folding rise/decay timescales we had previously identified in Galactic LMXBTs. HLX-1 would follow those correlations if the distance were several hundreds of kiloparsecs. However, invoking a much closer distance for HLX-1 is not a viable solution to this problem, as it introduces other, more serious inconsistencies with the observations.

X-RAY OUTBURSTS OF LOW-MASS X-RAY BINARY TRANSIENTS OBSERVED IN THERXTEERA

We have performed a statistical study of the properties of 110 bright X-ray outbursts in 36 low-mass X-ray binary transients (LMXBTs) seen with the All-Sky Monitor (2--12 keV) on board the {\it Rossi X-ray Timing Explorer} ({\it RXTE}) in 1996--2011. We have measured a number of outburst properties, including peak X-ray luminosity, rate of change of luminosity on a daily timescale, $e$-folding rise and decay timescales, outburst duration, and total radiated energy. We found that the average properties such as peak X-ray luminosity, rise and decay timescales, outburst duration, and total radiated energy of black hole LMXBTs, are at least two times larger than those of neutron star LMXBTs, implying that the measurements of these properties may provide preliminary clues as to the nature of the compact object of a newly discovered LMXBT. We also found that the outburst peak X-ray luminosity is correlated with the rate of change of X-ray luminosity in both the rise and the decay phases, which is consistent with our previous studies. Positive correlations between total radiated energy and peak X-ray luminosity, and between total radiated energy and the $e$-folding rise or decay timescale, are also found in the outbursts. These correlations suggest that the mass stored in the disk before an outburst is the primary initial condition that sets up the outburst properties seen later. We also found that the outbursts of two transient stellar-mass ULXs in M31 also roughly follow the correlations, which indicate that the same outburst mechanism works for the brighter outbursts of these two sources in M31 that reached the Eddington luminosity.

CONSTRAINING THE PHYSICS OF AM CANUM VENATICORUM SYSTEMS WITH THE ACCRETION DISK INSTABILITY MODEL

Recent work by Levitan et al has expanded the long-term photometric database for AM CVn stars. In particular, their outburst properties are well-correlated with orbital period, and allow constraints to be placed on the secular mass transfer rate between secondary and primary if one adopts the disk instability model for the outbursts. We use the observed range of outbursting behavior for AM CVn systems as a function of orbital period to place a constraint on mass transfer rate versus orbital period P. We infer a rate ~5 x 10^{-9} Msun/yr (P/1000 s)^{-5.2}. We show the functional form so obtained is consistent with the recurrence time-orbital period relation found by Levitan et al using a simple theory for the recurrence time. Also, we predict their steep dependence of outburst duration on orbital period will flatten considerably once the longer orbital period systems have more complete observations.

ASASSN-14cc: A likely helium analog of RZ Leonis Minoris

Abstract We identified that ASASSN-14cc is a very active dwarf nova spending approximately 60% of the time in outburst. Our long-term photometry revealed that the object shows long outbursts recurring with a period of 21–33 d and very brief short outbursts lasting less than 1 d. The maximum fading rate exceeds 2.8 mag d−1. The duration of the long outbursts is 9–18 d, comprising 50%–60% of the recurrence time of long outbursts. We detected 0.01560–0.01562 d (22.5 min) modulations during long outbursts, which we identified as superhumps. These features indicate that ASASSN-14cc has outburst parameters very similar to the extremely unusual dwarf nova RZ LMi but with a much shorter superhump period. All the observations can be naturally understood, considering that this object is a helium analog (AM CVn-type object) of RZ LMi. The highest outburst activity among AM CVn-type objects can be understood as the high-mass transfer rate expected for the orbital period giving a condition close to the stability limit of the accretion disk. In contrast to RZ LMi, this object shows little evidence for premature quenching of the superoutburst, which has been proposed to explain the unusual outburst parameters in RZ LMi.

NY Serpentis: SU UMa-type nova in the period gap with diversity of normal outbursts

Abstract We present a photometric study of NY Ser, an in-the-gap SU UMa-type nova, in 2002 and 2013. We determined the duration of its superoutburst and the mean period of its superhump are 18 d and 0.10458 d, respectively. We detected in 2013 that NY Ser showed two distinct states separated by a superoutburst. A state of rather infrequent normal outbursts lasted at least 44 d before the superoutburst, and a state of frequent outbursts started immediately after the superoutburst and lasted at least 34 d. Unlike a typical SU UMa star with a bimodal distribution of outburst duration, NY Ser displayed a diversity of normal outbursts. In the state of infrequent outbursts, we detected a wide ∼ 12 d outburst accompanied by 0.098 d orbital modulation but without superhumps ever established in NY Ser. We classified this as a “wide normal outburst.” The orbital period was dominant both in quiescence and during normal outbursts in this state. In the state of the most frequent normal outbursts, the 0.10465 d positive superhump period was dominant and coexisted with the orbital modulation. In 2002 we detected the normal outburst of “intermediate” 5–6 d duration that was also accompanied by orbital modulations.

Importance of thermal diffusion in the gravomagnetic limit cycle

We consider the role of thermal diffusion due to turbulence and radiation on accretion bursts that occur in protoplanetary discs which contain dead zones. Using 1D viscous disc models we show that diffusive radial transport of heat is important during the gravo-magnetic limit cycle, and can strongly modify the duration and frequency of accretion outbursts. When the Prandtl number is large - such that turbulent diffusion of heat is unimportant - radial radiative diffusion reduces the burst duration compared to models with no diffusive transport of heat. When the Prandtl number is small ($\lesssim 25$) we find that turbulent diffusion dominates the radial transport of heat, reducing the burst duration to $\lesssim 10^3$ years as well as increasing the burst frequency. Furthermore, inclusion of radial transport of heat extends the range of infall rates under which the disc undergoes accretion bursts from $10^{-8}$ to $10^{-6}$ M$_\odot$ yr$^{-1}$ with no diffusion, to $10^{-8}$ to $\gtrsim10^{-4}$ M$_\odot$ yr$^{-1}$ with radiative and strong turbulent diffusion. The relative roles of radiative and turbulent thermal diffusion are likely to vary during an accretion burst, but simple estimates suggest that the expected Prandtl numbers are of the order of 10 in protoplanetary discs, and hence that turbulent diffusion is likely to be an important process during accretion outbursts due to the gravo-magnetic limit cycle.

Supermassive black holes (SMBH) at work: M87, a case study of the effects of SMBH outbursts

AbstractSupermassive black holes (SMBHs) play key roles in galaxy and cluster evolution. This is most clearly seen in the “fossil record” that is imprinted in the gas rich atmospheres of early type galaxies, groups, and clusters by powerful SMBH outbursts. From a detailed X-ray study of M87, we present the properties of a typical SMBH outburst, its evolution, and the energy partition between shocks and the enthalpy of the gas cavities inflated by the SMBH. About 12 Myr ago, the SMBH in M87 inflated a cavity of relativistic plasma which is still centered near the galaxy nucleus. This outburst drove a shock into the surrounding gas. For M87, we show that the outburst duration is a few Myr and that about 50% of the total energy (5 × 1057 ergs) resides in the bubble inflated by the jet from the SMBH, that 25% of the outburst energy is deposited directly into the ambient atmosphere by the shock, and that 25% of the outburst energy is lost from the radiatively bright core as the weak shock moves to large radii. We conclude by describing a future X-ray mission, SMART-X, with &lt; 1” angular resolution that would allow us to study the evolution of SMBHs and the hot, X-ray emitting atmospheres from high redshifts to the present for M87-like systems.

A TRANSIENT SUPERGIANT X-RAY BINARY IN IC 10: AN EXTRAGALACTIC SFXT?

We report the discovery of a large amplitude (factor of $\sim$100) X-ray transient (IC 10 X-2, CXOU J002020.99+591758.6) in the nearby dwarf starburst galaxy IC10 during our Chandra monitoring project. Based on the X-ray timing and spectral properties, and an optical counterpart observed with Gemini, the system is a high mass X-ray binary (HMXB) consisting of a luminous blue supergiant and a neutron star (NS). The highest measured luminosity of the source was 1.8$\times$10$^{37}$ erg s$^{-1}$ during an outburst in 2003. Observations before, during and after a second outburst in 2010 constrain the outburst duration to be less than 3 months (with no lower limit). The X-ray spectrum is a hard powerlaw ($\Gamma$=0.3) with fitted column density ($N_H$=6.3$\times$10$^{21}$ atom cm$^{-2}$) consistent with the established absorption to sources in IC10. The optical spectrum shows hydrogen Balmer lines strongly in emission, at the correct blueshift (-340 km/s) for IC10. The NIII triplet emission feature is seen, accompanied by He II [4686] weakly in emission. Together these features classify the star as a luminous blue supergiant of the OBN subclass, characterized by enhanced nitrogen abundance. Emission lines of HeI are seen, at similar strength to H$\beta$. A complex of FeII permitted and forbidden emission lines are seen, as in B[e] stars. The system closely resembles galactic supergiant fast X-ray transients (SFXTs), in terms of its hard spectrum, variability amplitude and blue supergiant primary.