X-ray and optical variability in the low-mass burst source X1735 – 444

1. Detection of nonthermal optical flares in low mass X-ray binaries. Eleven low-mass X-ray binaries have been observed with the MANIA (Multichannel Analysis of Nanoseconds Intensity Alteration) complex; X0420+32, A0620-00, X1728–169, X1813–14, X1957+11 in 1986 at the 6 m telescope of SAO [7], and 2S0921–630, 4U1543–475, 4U1636–536, 4U1559–487, MXB1735–44, 4U1822–371 in 1991 at the 2.15 m telescope of CASLEO (Argentina) [1]. Analysis of the data using the special y2 and d2 function formalism [4], [6] has shown no brightness variations on time-scales of 10−7... 10 s for all objects except A0620–00 and MXB1735–44.A0620–00. The five millisecond flashes were detected on 1986 February 13 (Fig. 1). The first two flares have durations of 3 ms and 5 ms and their rise times were 1...2 ms. The other three events lasted 0.4…0.5 ms with rise times of about 0.1 ms. The lower limit of the flare amplitudes is 40 counts ms−1 and the corresponding brightness temperatures are 5 109 K for the first two and 5 1011 K for the others.

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Correlated X-ray/ultraviolet/optical variability in the very low mass AGN NGC 4395

Monthly Notices of the Royal Astronomical Society ◽

10.1111/j.1365-2966.2012.20677.x ◽

2012 ◽

Vol 422 (1) ◽

pp. 902-912 ◽

Cited By ~ 33

Author(s):

D. T. Cameron ◽

I. McHardy ◽

T. Dwelly ◽

E. Breedt ◽

P. Uttley ◽

...

Keyword(s):

Optical Variability ◽

X Ray ◽

Low Mass ◽

Ngc 4395

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Optical variability of the low-mass, X-ray binary 1556-605

Publications of the Astronomical Society of the Pacific ◽

10.1086/132620 ◽

1990 ◽

Vol 102 ◽

pp. 144 ◽

Cited By ~ 1

Author(s):

Paul C. Schmidtke

Keyword(s):

Optical Variability ◽

X Ray ◽

Low Mass

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Dark Energy Survey identification of a low-mass active galactic nucleus at redshift 0.823 from optical variability

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1803 ◽

2020 ◽

Vol 496 (3) ◽

pp. 3636-3647

Author(s):

Hengxiao Guo ◽

Colin J Burke ◽

Xin Liu ◽

Kedar A Phadke ◽

Kaiwen Zhang ◽

...

Keyword(s):

Dark Energy ◽

Active Galactic Nucleus ◽

Spectral Energy Distribution ◽

Broad Band ◽

Host Galaxy ◽

Optical Variability ◽

X Ray ◽

Dark Energy Survey ◽

Low Mass ◽

Energy Survey

ABSTRACT We report the identification of a low-mass active galactic nucleus (AGN), DES J0218−0430, in a redshift z = 0.823 galaxy in the Dark Energy Survey (DES) Supernova field. We select DES J0218−0430 as an AGN candidate by characterizing its long-term optical variability alone based on DES optical broad-band light curves spanning over 6 yr. An archival optical spectrum from the fourth phase of the Sloan Digital Sky Survey shows both broad Mg ii and broad H β lines, confirming its nature as a broad-line AGN. Archival XMM–Newton X-ray observations suggest an intrinsic hard X-ray luminosity of $L_{{\rm 2-12\, keV}}\approx 7.6\pm 0.4\times 10^{43}$ erg s−1, which exceeds those of the most X-ray luminous starburst galaxies, in support of an AGN driving the optical variability. Based on the broad H β from SDSS spectrum, we estimate a virial black hole (BH) mass of M• ≈ 106.43–106.72 M⊙ (with the error denoting the systematic uncertainty from different calibrations), consistent with the estimation from OzDES, making it the lowest mass AGN with redshift > 0.4 detected in optical. We estimate the host galaxy stellar mass to be M* ≈ 1010.5 ± 0.3 M⊙ based on modelling the multiwavelength spectral energy distribution. DES J0218−0430 extends the M•–M* relation observed in luminous AGNs at z ∼ 1 to masses lower than being probed by previous work. Our work demonstrates the feasibility of using optical variability to identify low-mass AGNs at higher redshift in deeper synoptic surveys with direct implications for the upcoming Legacy Survey of Space and Time at Vera C. Rubin Observatory.

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Iron K-Line Emission from X-Ray Binaries

International Astronomical Union Colloquium ◽

10.1017/s0252921100107389 ◽

1988 ◽

Vol 102 ◽

pp. 47-50

Author(s):

K. Masai ◽

S. Hayakawa ◽

F. Nagase

Keyword(s):

Accretion Disk ◽

Radiative Recombination ◽

Characteristic Temperature ◽

Line Emission ◽

Ionization Front ◽

Continuum Radiation ◽

X Ray ◽

Low Mass ◽

X Ray Binaries

AbstractEmission mechanisms of the iron Kα-lines in X-ray binaries are discussed in relation with the characteristic temperature Txof continuum radiation thereof. The 6.7 keV line is ascribed to radiative recombination followed by cascades in a corona of ∼ 100 eV formed above the accretion disk. This mechanism is attained for Tx≲ 10 keV as observed for low mass X-ray binaries. The 6.4 keV line observed for binary X-ray pulsars with Tx> 10 keV is likely due to fluorescence outside the He II ionization front.

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Phase lags of quasi-periodic oscillations across source states in the low-mass X-ray binary 4U 1636–53

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stw1271 ◽

2016 ◽

Vol 461 (1) ◽

pp. 79-92 ◽

Cited By ~ 10

Author(s):

Marcio G. B. de Avellar ◽

Mariano Méndez ◽

Diego Altamirano ◽

Andrea Sanna ◽

Guobao Zhang

Keyword(s):

Periodic Oscillations ◽

X Ray ◽

Phase Lags ◽

Low Mass

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X-ray and UV emission of the ultrashort-period, low-mass eclipsing binary system BX Trianguli

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834116 ◽

2018 ◽

Vol 619 ◽

pp. A138

Author(s):

V. Perdelwitz ◽

S. Czesla ◽

J. Robrade ◽

T. Pribulla ◽

J. H. M. M. Schmitt

Keyword(s):

Binary System ◽

Light Curve ◽

Binary Systems ◽

Uv Light ◽

Close Binary ◽

Eclipsing Binary ◽

X Ray ◽

Uv Emission ◽

Low Mass ◽

Orbital Modulation

Context.Close binary systems provide an excellent tool for determining stellar parameters such as radii and masses with a high degree of precision. Due to the high rotational velocities, most of these systems exhibit strong signs of magnetic activity, postulated to be the underlying reason for radius inflation in many of the components. Aims.We extend the sample of low-mass binary systems with well-known X-ray properties. Methods.We analyze data from a singular XMM-Newton pointing of the close, low-mass eclipsing binary system BX Tri. The UV light curve was modeled with the eclipsing binary modeling tool PHOEBE and data acquired with the EPIC cameras was analyzed to search for hints of orbital modulation. Results.We find clear evidence of orbital modulation in the UV light curve and show that PHOEBE is fully capable of modeling data within this wavelength range. Comparison to a theoretical flux prediction based on PHOENIX models shows that the majority of UV emission is of photospheric origin. While the X-ray light curve does exhibit strong variations, the signal-to-noise ratio of the observation is insufficient for a clear detection of signs of orbital modulation. There is evidence of a Neupert-like correlation between UV and X-ray data.

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Early Science from POSSUM: Shocks, turbulence, and a massive new reservoir of ionised gas in the Fornax cluster

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2021.4 ◽

2021 ◽

Vol 38 ◽

Author(s):

C. S. Anderson ◽

G. H. Heald ◽

J. A. Eilek ◽

E. Lenc ◽

B. M. Gaensler ◽

...

Keyword(s):

X Ray ◽

Main Cluster ◽

Rotation Measure ◽

Sky Survey ◽

Low Mass ◽

Fornax Cluster ◽

Depth Enhancement ◽

Projected Distance ◽

Density Regime ◽

New Reservoir

Abstract We present the first Faraday rotation measure (RM) grid study of an individual low-mass cluster—the Fornax cluster—which is presently undergoing a series of mergers. Exploiting commissioning data for the POlarisation Sky Survey of the Universe’s Magnetism (POSSUM) covering a ${\sim}34$ square degree sky area using the Australian Square Kilometre Array Pathfinder (ASKAP), we achieve an RM grid density of ${\sim}25$ RMs per square degree from a 280-MHz band centred at 887 MHz, which is similar to expectations for forthcoming GHz-frequency ${\sim}3\pi$ -steradian sky surveys. These data allow us to probe the extended magnetoionic structure of the cluster and its surroundings in unprecedented detail. We find that the scatter in the Faraday RM of confirmed background sources is increased by $16.8\pm2.4$ rad m−2 within 1 $^\circ$ (360 kpc) projected distance to the cluster centre, which is 2–4 times larger than the spatial extent of the presently detectable X-ray-emitting intracluster medium (ICM). The mass of the Faraday-active plasma is larger than that of the X-ray-emitting ICM and exists in a density regime that broadly matches expectations for moderately dense components of the Warm-Hot Intergalactic Medium. We argue that forthcoming RM grids from both targeted and survey observations may be a singular probe of cosmic plasma in this regime. The morphology of the global Faraday depth enhancement is not uniform and isotropic but rather exhibits the classic morphology of an astrophysical bow shock on the southwest side of the main Fornax cluster, and an extended, swept-back wake on the northeastern side. Our favoured explanation for these phenomena is an ongoing merger between the main cluster and a subcluster to the southwest. The shock’s Mach angle and stand-off distance lead to a self-consistent transonic merger speed with Mach 1.06. The region hosting the Faraday depth enhancement also appears to show a decrement in both total and polarised radio emission compared to the broader field. We evaluate cosmic variance and free-free absorption by a pervasive cold dense gas surrounding NGC 1399 as possible causes but find both explanations unsatisfactory, warranting further observations. Generally, our study illustrates the scientific returns that can be expected from all-sky grids of discrete sources generated by forthcoming all-sky radio surveys.

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QPOs in compact binaries from small scale eruptions in an inner magnetized disk

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3410 ◽

2020 ◽

Author(s):

Nicolas Scepi ◽

Mitchell C Begelman ◽

Jason Dexter

Keyword(s):

Rapid Heating ◽

Small Scale ◽

Type B ◽

Periodic Oscillations ◽

X Ray ◽

Compact Binaries ◽

Heating And Cooling ◽

Low Mass ◽

X Ray Binaries ◽

Standard Disk

Abstract Dwarf novæ (DNe) and low mass X-ray binaries (LMXBs) are compact binaries showing variability on time scales from years to less than seconds. Here, we focus on explaining part of the rapid fluctuations in DNe, following the framework of recent studies on the monthly eruptions of DNe that use a hybrid disk composed of an outer standard disk and an inner magnetized disk. We show that the ionization instability, that is responsible for the monthly eruptions of DNe, is also able to operate in the inner magnetized disk. Given the low density and the fast accretion time scale of the inner magnetized disk, the ionization instability generates small, rapid heating and cooling fronts propagating back and forth in the inner disk. This leads to quasi-periodic oscillations (QPOs) with a period of the order of 1000 s. A strong prediction of our model is that these QPOs can only develop in quiescence or at the beginning/end of an outburst. We propose that these rapid fluctuations might explain a subclass of already observed QPOs in DNe as well as a, still to observe, subclass of QPOs in LMXBs. We also extrapolate to the possibility that the radiation pressure instability might be related to Type B QPOs in LMXBs.

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