Study of recent outburst in the Be/X-ray binary RX J0209.6−7427 with AstroSat: a new ultraluminous X-ray pulsar in the Magellanic Bridge?

ABSTRACT We present the timing and spectral studies of RX J0209.6–7427 during its rare 2019 outburst using observations with the Soft X-ray Telescope (SXT) and Large Area X-ray Proportional Counter (LAXPC) instruments on the AstroSat satellite. Pulsations having a periodicity of 9.29 s were detected for the first time by the NICER mission in the 0.2–10 keV energy band and, as reported here, by AstroSat over a broad energy band covering 0.3–80 keV. The pulsar exhibits a rapid spin-up during the outburst. Energy resolved folded pulse profiles are generated in several energy bands in 3–80 keV. To the best of our knowledge this is the first report of the timing and spectral characteristics of this Be binary pulsar in hard X-rays. There is suggestion of evolution of the pulse profile with energy. The energy spectrum of the pulsar is determined and from the best-fitting spectral values, the X-ray luminosity of RX J0209.6−7427 is inferred to be 1.6 × 1039 erg s−1. Our timing and spectral studies suggest that this source has features of an ultraluminous X-ray pulsar in the Magellanic Bridge. Details of the results are presented and discussed in terms of the current ideas.

A Study on the Energy Condition and Quantitative Analysis of the Occurrence of a Coal and Gas Outburst

With mining depths increasing, coal and gas outburst disasters are becoming more and more serious and complicated, which directly restricts the production efficiency of coal mines. In order to study the rules of energy dissipation during the occurrence of a coal and gas outburst based on the occurrence mechanisms, a simulation experiment of a coal and gas outburst with a ground stress of 16 MPa and a gas pressure of 0.5 MPa was carried out using a self-developed large-scale coal and gas outburst simulation experimental system. A quantitative analysis was given based on the energy model. The results showed the following: (1) In the process of the coal and gas outburst, the main energy source originated from the elastic potential energy of the coal body and the gas internal energy. The main energy loss was used for coal crushing and throwing. (2) The outburst coal sample in this experiment had a mass of 18.094 kg, and the relative outburst intensity was 1.21%. Additionally, the farthest throwing distance of the outburst coal samples was 3.3 m away from the outburst hole wall. The distribution of the outburst coal sample decreased along the roadway, and the proportion of the coal sample grain size in each area first decreased and then increased with the decrease of the grain size. The coal samples with a grain size less than 0.2 mm after the outburst accounted for 6.34% of the mass of the total coal samples. (3) The elastic potential energy of the coal body accounted for 0.34% of the total outburst energy, while the gas internal energy accounted for 99.66%. It was verified that gas internal energy was the key energy source for the coal and gas outburst, and this internal energy was two orders of magnitude more than the elastic potential energy, playing a leading role in the outburst process. After the outburst initiation, most of the energy was consumed in coal crushing, which was in the same order of magnitude as the gas internal energy. Moreover, the energy losses due to friction, vibration, and sound during the outburst process comprised no more than 10% of the total energy. The research results can provide certain guidance for clarifying the mechanism of a coal and gas outburst and the quantitative analysis of outburst energy.

Characterizing the Outburst of the Supermassive Black Hole in M87

M87, 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.

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

Supermassive 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 < 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.

Measurements of Outburst Characteristics, Temperatures, Densities and Abundances in the Ejecta of Nova Muscae 1983

We present results for IUE, optical and IR observations of Nova Muscae 1983, from early outburst to January 1986 obtained by the European IUE Target of Opportunity Team. A detailed description of the data will appear elsewhere (Hassall et al., 1989), but here we summarise the most important results.The outburst lightcurve initially indicated a fast speed class for this nova, but was later characterised by a rather slow optical decline with two or more secondary outbursts with sudden doubling of the bolometric flux. In Figure 1, we show the contributions of X-ray, UV, optical and IR to the total luminosity for 1200 days following outburst, assuming a distance of 4.3kpc and an interstellar extinction E(B-V)=0.5. In the absence of dust formation, first the UV and later the X-ray flux (Ögelman et al, 1984) dominate the radiative energy late into the nebular phase. There was a plateau stage lasting about 500 days, with a bolometric luminosity of ~ 1038ergs s−1 near the Eddington limit. The secondary outbursts were thus super-Eddington. We estimate a total outburst energy (including kinetic and gravitational potential energy of the ejecta) of ~ 5·l046 ergs, corresponding to a mass of ~ 4·10−6Mº of hydrogen burnt in the thermonuclear runaway.

On the Nature of the Outflow from Nova Stars Occurring Immediately After Ejection of an Envelope

According to modern conceptions the cause of nova outbursts is a thermal runaway (TR) taking place in the deep layers of the accreted envelope of a white dwarf (WD), component of a close binary system. The theory of TR was considered by many authors and, especially, has been developed in detail by Starrfield et al. (1974, 1984). It has been shown that when the pressure at some level in the envelope reaches a critical value Pcr, the thermonuclear reactions of the “hot” CNO cycle become very fast, and after a time interval of several tenths seconds the temperature at this level rises to (2 ÷ 3)× 108 K. If the CNO abundances are high enough, the total outburst energy may exceed 1047 ergs. As a consequence of TR, a considerable fraction of the envelope mass (20% ÷ 50%) must be torn off by shock waves. As suggested by Starrfield et al. (1974), the remaining matter forms an extended atmosphere (R ≃ 1011 cm) and the star transforms itself into a supergiant having a luminosity L* ≲ Ledd during several months.