Big blue bump and transient active regions in seyfert galaxies

Sergei Nayakshin; Fulvio Melia

doi:10.1086/310782

Big blue bump and transient active regions in seyfert galaxies

Sergei Nayakshin, Fulvio Melia

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7 Scopus citations

Abstract

An important feature of the EUV spectrum (known as the Big Blue Bump, hereafter BBB) in Seyfert galaxies is the narrow range in its cutoff energy E_c from source to source, even though the luminosity changes by 4 orders of magnitude. Here we show that if the BBB is due to accretion disk emission, then in order to account for this "universality" in the value of E_c, the emission mechanism is probably optically thin bremsstrahlung. In addition, we demonstrate that the two-phase model with active regions localized on the surface of the cold disk is consistent with this constraint if the active regions are very compact and are highly transient, i.e., they evolve faster than one dynamical timescale.

Original language	English (US)
Pages (from-to)	L103-L106
Journal	Astrophysical Journal
Volume	484
Issue number	2 PART II
DOIs	https://doi.org/10.1086/310782
State	Published - 1997

Keywords

Accretion, accretion disks
Black hole physics
Galaxies: Seyfert
Magnetic fields
Plasmas
Radiative transfer

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1086/310782

Cite this

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title = "Big blue bump and transient active regions in seyfert galaxies",

abstract = "An important feature of the EUV spectrum (known as the Big Blue Bump, hereafter BBB) in Seyfert galaxies is the narrow range in its cutoff energy Ec from source to source, even though the luminosity changes by 4 orders of magnitude. Here we show that if the BBB is due to accretion disk emission, then in order to account for this {"}universality{"} in the value of Ec, the emission mechanism is probably optically thin bremsstrahlung. In addition, we demonstrate that the two-phase model with active regions localized on the surface of the cold disk is consistent with this constraint if the active regions are very compact and are highly transient, i.e., they evolve faster than one dynamical timescale.",

keywords = "Accretion, accretion disks, Black hole physics, Galaxies: Seyfert, Magnetic fields, Plasmas, Radiative transfer",

author = "Sergei Nayakshin and Fulvio Melia",

note = "Funding Information: This work was partially supported by NASA grant NAG 5-3075. We thank T. Kallman for carrying out an ionization balance calculation that allowed us to estimate the importance of the free-bound emission relative to the free-free emission for the conditions similar to the ones assumed in this Letter.",

year = "1997",

doi = "10.1086/310782",

language = "English (US)",

volume = "484",

pages = "L103--L106",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "IOP Publishing Ltd.",

number = "2 PART II",

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TY - JOUR

T1 - Big blue bump and transient active regions in seyfert galaxies

AU - Nayakshin, Sergei

AU - Melia, Fulvio

N1 - Funding Information: This work was partially supported by NASA grant NAG 5-3075. We thank T. Kallman for carrying out an ionization balance calculation that allowed us to estimate the importance of the free-bound emission relative to the free-free emission for the conditions similar to the ones assumed in this Letter.

PY - 1997

Y1 - 1997

N2 - An important feature of the EUV spectrum (known as the Big Blue Bump, hereafter BBB) in Seyfert galaxies is the narrow range in its cutoff energy Ec from source to source, even though the luminosity changes by 4 orders of magnitude. Here we show that if the BBB is due to accretion disk emission, then in order to account for this "universality" in the value of Ec, the emission mechanism is probably optically thin bremsstrahlung. In addition, we demonstrate that the two-phase model with active regions localized on the surface of the cold disk is consistent with this constraint if the active regions are very compact and are highly transient, i.e., they evolve faster than one dynamical timescale.

AB - An important feature of the EUV spectrum (known as the Big Blue Bump, hereafter BBB) in Seyfert galaxies is the narrow range in its cutoff energy Ec from source to source, even though the luminosity changes by 4 orders of magnitude. Here we show that if the BBB is due to accretion disk emission, then in order to account for this "universality" in the value of Ec, the emission mechanism is probably optically thin bremsstrahlung. In addition, we demonstrate that the two-phase model with active regions localized on the surface of the cold disk is consistent with this constraint if the active regions are very compact and are highly transient, i.e., they evolve faster than one dynamical timescale.

KW - Accretion, accretion disks

KW - Black hole physics

KW - Galaxies: Seyfert

KW - Magnetic fields

KW - Plasmas

KW - Radiative transfer

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U2 - 10.1086/310782

DO - 10.1086/310782

M3 - Article

AN - SCOPUS:21744453782

SN - 0004-637X

VL - 484

SP - L103-L106

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2 PART II

ER -

Big blue bump and transient active regions in seyfert galaxies

Abstract

Keywords

ASJC Scopus subject areas

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