227 research outputs found
Stability analysis of a ratio-dependent predator-prey system with diffusion and stage structure
A two-species predator-prey system with diffusion term and stage
structure is discussed, local stability of the system is studied
using linearization method, and global stability of the system is
investigated by strong upper and lower solutions. The asymptotic
behavior of solutions and the negative effect of stage structure
on the permanence of populations are given
A Mid-infrared Flare in the Active Galaxy MCG-02-04-026: Dust Echo of a Nuclear Transient Event
We report the discovery of a mid-infrared (MIR) flare using Wide field Infrared Survey Explorer data in the center of the nearby Seyfert 1.9 galaxy MCG-02-04-026. The MIR flare began in the first half of 2014, peaked around the end of 2015, and faded in 2017. During these years, energy of more than 7 Ć 10āµā° erg was released in the infrared, and the flare's MIR color was generally turning red. We detected neither optical nor ultraviolet (UV) variation corresponding to the MIR flare based on available data. We explained the MIR flare using a dust echo model in which the radiative transfer is involved. The MIR flare can be well explained as thermal reradiation from dust heated by UVāoptical photons of a primary nuclear transient event. Although the transient event was not seen directly owing to dust obscuration, we can infer that it may produce a total energy of at least ~10āµĀ¹ erg, most of which was released in less than ~3 yr. The nature of the transient event could be a stellar tidal disruption event by the central supermassive black hole (SMBH), or a sudden enhancement of the existing accretion flow onto the SMBH, or a supernova that was particularly bright
A Mid-infrared Flare in the Active Galaxy MCG-02-04-026: Dust Echo of a Nuclear Transient Event
We report the discovery of a mid-infrared (MIR) flare using WISE data in the
center of the nearby Seyfert 1.9 galaxy MCG-02-04-026. The MIR flare began in
the first half of 2014, peaked around the end of 2015, and faded in 2017.
During these years, energy more than erg was released in the
infrared, and the flare's MIR color was generally turning red. We detected
neither optical nor ultraviolet (UV) variation corresponding to the MIR flare
based on available data. We explained the MIR flare using a dust echo model in
which the radiative transfer is involved. The MIR flare can be well explained
as thermal reradiation from dust heated by UV-optical photons of a primary
nuclear transient event. Although the transient event was not seen directly due
to dust obscuration, we can infer that it may produce a total energy of at
least erg, most of which was released in less than 3 years.
The nature of the transient event could be a stellar tidal disruption event by
the central supermassive black hole (SMBH), or a sudden enhancement of the
existing accretion flow onto the SMBH, or a supernova which was particularly
bright.Comment: 44 pages, 13 figures; Accepted to be published in Ap
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