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doi:10.1111/mnr.2011.414.issue-3

Cited by 15 publications

(7 citation statements)

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“…Observationally, Janiuk and Czerny pushed for searches for excess variability in galactic sources, outbursts that last tens to hundreds of seconds. These would be caused by the radiation pressure instability and might not be strictly periodic or clear in periodograms (Janiuk & Czerny 2011). We believe the additional fluctuations seen in our light curves may be partially attributed to limit-cycle oscillations in the disk, perhaps propagating out into the jet or in response to jet instabilities.…”

Section: Accretion Disk Limit Cyclementioning

confidence: 83%

“…It is caused by an inherent, hysteretic relationship between vertically integrated viscous stress and surface density at a fixed radius in the accretion disk. Based on various modeling efforts (Cannizzo 1992(Cannizzo , 1993(Cannizzo , 1998Janiuk & Czerny 2011), it is believed that the limit-cycle mechanism operates in most AGN during the quasar era, solving the problem of feeding quasars at the required rates.…”

Section: Accretion Disk Limit Cyclementioning

confidence: 99%

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A QPO in Mkn 421 from Archival RXTE Data

Smith¹,

Oramas²,

Perlman³

2023

ApJ

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We report a 325(−7, +8) day quasi-periodic oscillation (QPO) in the X-ray emission of the blazar Mkn 421 based on data obtained with the Rossi X-ray Timing Explorer satellite. The QPO is seen prominently in the ASM data (at least 15 cycles) due to the fact that it has had near-continuous sampling for more than a decade. The PCA data, where the sampling is not uniform and shows many large gaps, provide supporting evidence at lower significance. The QPOs are an important observable in accretion disks, can be modulated by various orbital timescales, and may be generated by a number of mechanisms. They have been studied extensively in X-ray binaries and should be present in active galactic nuclei (AGN) if they are governed by a common set of physical principles. In jetted sources, QPOs can probe jet–disk interactions or helical oscillations. This QPO has previously been claimed intermittently in X-ray, radio, and gamma-ray data, but the continuous, 15 yr extent (1996–2011) of the ASM observations (in which Mkn 421 is the brightest AGN observed) provides a unique window. The QPO appears to be present for nearly the entire extent of the ASM observations. We explore various physical origins and modulating mechanisms, particularly interpretations of the QPO as a result of disk–jet interactions, due to either an accretion disk limit cycle, jet instabilities, or helical motions. Limit cycle oscillations would not interact with either Keplerian or Lense–Thirring modulated oscillations; however, those associated with jet instabilities or helical motions in the jet would likely be modulated by Lense–Thirring precession.

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Section: Accretion Disk Limit Cyclementioning

confidence: 83%

Section: Accretion Disk Limit Cyclementioning

confidence: 99%

A QPO in Mkn 421 from Archival RXTE Data

Smith¹,

Oramas²,

Perlman³

2023

ApJ

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“…The J-Factor strongly depends on the halo model. [56] profile. Figure 8 shows the integrated J-Factors for the three models.…”

Section: Dark Mattermentioning

confidence: 99%

Searches for exotica and dark matter with neutrino telescopes

Margiotta

2019

Phil. Trans. R. Soc. A.

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Neutrino telescopes are designed to search for neutrino sources in the Universe, exploiting the Cherenkov light emitted along the path of the charged particles produced in interactions occurring close to the detector volume. Their huge size and the shield offered by large water or ice overburden make them excellent tools to search for exotic and rare particles in the cosmic radiation. In particular, they are sensitive to particles not predicted by the Standard Model that could be messenger of new physics. An overview of the experimental scenario and the relevant results obtained looking for magnetic monopoles, dark matter candidates and other exotic relic particles with neutrino telescopes is given, together with the description of possible new perspectives. This article is part of a discussion meeting issue ‘Topological avatars of new physics’.

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“…This complicated behavior can lead to misinterpretation, and so various chromospheric lines should be considered when studying stellar activity and related atmospheric properties. The chromospheric lines of the Ca II infrared triplet (IRT) (λλ = 8500.4, 8544.4, 8664.5 Å) and Na I D doublet (λλ = 5891.6, 5897.6 Å) constitute other tracers used for activity-related investigations (e.g., Gomes da Silva et al 2011;Martínez-Arnáiz et al 2011;Robertson et al 2016;Martin et al 2017). While the Hα line is formed in the upper chromosphere, the Ca II IRT and Na I D lines can be used to characterize the lower chromosphere (e.g., Hintz et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Modeling the Chromosphere and Transition Region of Planet-hosting Star GJ 436

Hintz,

Peacock,

Barman

et al. 2023

ApJ

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Ahead of upcoming space missions intending to conduct observations of low-mass stars in the ultraviolet (UV) spectral region it becomes imperative to simultaneously conduct atmospheric modeling from the UV to the visible (VIS) and near-infrared (NIR). Investigations on extended spectral regions will help to improve the overall understanding of the diversity of spectral lines arising from very different atmospheric temperature regions. Here we investigate atmosphere models with a chromosphere and transition region for the M2.5V star GJ 436, which hosts a close-in Hot Neptune. The atmosphere models are guided by observed spectral features from the UV to the VIS/NIR originating in the chromosphere and transition region of GJ 436. High-resolution observations from the Hubble Space Telescope and Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs (CARMENES) are used to obtain an appropriate model spectrum for the investigated M dwarf. We use a large set of atomic species considered in nonlocal thermodynamic equilibrium conditions within our PHOENIX model computations to approximate the physics within the low-density atmospheric regions. In order to obtain an overall match for the nonsimultaneous observations, it is necessary to apply a linear combination of two model spectra, where one of them better reproduces the UV lines while the other better represents the lines from the VIS/NIR range. This is needed to adequately handle different activity states across the observations.

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Cited by 15 publications

References 0 publications

A QPO in Mkn 421 from Archival RXTE Data

A QPO in Mkn 421 from Archival RXTE Data

Searches for exotica and dark matter with neutrino telescopes

Modeling the Chromosphere and Transition Region of Planet-hosting Star GJ 436

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