A UV Flare at the Center of the Elliptical Galaxy NGC 4552

A self-consistent analysis of near-UV, HST/FOC images of the elliptical galaxy NGC 4552 is used to show that its central spike has brightened by a factor ˜ 4.5 between 1991 and 1993, and has decreased its luminosity by a factor ˜ 2.0 between 1993 and 1996. A strong UV continuum over the energy distribution of the underlying galaxy is concurrently revealed shortward of λ ˜ 3200 Å by our FOS spectra extending from the near-UV to red wavelengths. Nuclear emission-line profiles of both permitted and forbidden lines are best modelled with a combination of broad and narrow components, with FWHM of ˜ 3000 km s−1 and ˜ 700 km s−1, respectively. Current diagnostics based on the emission line intensity ratios definitely places the spike among AGNs, just at the border between Seyferts and LINERs. This evidence argues for the variable central spike being produced by a modest accretion event onto a central massive black hole (BH), with the accreted material having possibly being stripped from a star in a close fly-by with the BH. In this regard, one has to look at NGC 4552 as the faintest known AGN.

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Possible Evidence for a Binary Massive Black Hole in the Galactic Nucleus

Symposium - International Astronomical Union ◽

10.1017/s0074180900229811 ◽

1996 ◽

Vol 169 ◽

pp. 285-286

Author(s):

E.J.A. Meurs

Keyword(s):

Black Hole ◽

Emission Line ◽

Velocity Component ◽

Orbital Motion ◽

Galactic Centre ◽

Line Profiles ◽

Radial Velocity Component ◽

Massive Black Hole ◽

Ir Stars ◽

Sgr A

The Galactic Centre candidate Sgr A∗ may exhibit a 40 km/s radial velocity component, which is not observed for OH/IR stars around the centre. This could be interpreted as orbital motion of one member of a binary massive black hole. In other galaxies such pairs may be inferred from radio jet precession and emission line profiles.

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O(1D2-3P2,1,0) 630.0, 636.4, and 639.2 nm Forbidden Emission Line Intensity Ratios Measured in the Terrestrial Nightglow†

The Journal of Physical Chemistry A ◽

10.1021/jp056163x ◽

2006 ◽

Vol 110 (21) ◽

pp. 6707-6710 ◽

Cited By ~ 19

Author(s):

B. D. Sharpee ◽

T. G. Slanger

Keyword(s):

Emission Line ◽

Line Intensity ◽

Intensity Ratios

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X-Ray Observations of M32 with ASCA

Symposium - International Astronomical Union ◽

10.1017/s0074180900115190 ◽

1998 ◽

Vol 188 ◽

pp. 291-292

Author(s):

T. Toneri ◽

K. Hayashida ◽

M. Loewenstein

Keyword(s):

Black Hole ◽

Mass Concentration ◽

Elliptical Galaxy ◽

Broad Band ◽

The Other ◽

Central Black Hole ◽

Massive Black Hole ◽

X Ray ◽

Eddington Limit

M32 is the nearest dwarf elliptical galaxy. Its center is known to have a mass concentration of 3 × 106 M⊙, which is usually interpreted as an evidence of a super massive black hole. We observed M32 with ASCA two times in July and August of 1996. An X-ray source was detected at the center of M32 and its first broad-band X-ray spectra were obtained. ASCA observations of M32 limit the activity of the central black hole to be less than 10−6 times of the Eddington limit. We also found two other bright sources within 12 arcmin from the M32 center. One is the newly appeared X-ray source and the other is G144. In this paper, we summarize the results on the new source and G144. For M32, please refer to the publication (Loewenstein et al. 1997).

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How Massive is the Black Hole in M87?

Highlights of Astronomy ◽

10.1017/s1539299600011977 ◽

1995 ◽

Vol 10 ◽

pp. 535-538

Author(s):

S.K. Chakrabarti

Keyword(s):

Black Hole ◽

Dwarf Galaxy ◽

Hubble Space Telescope ◽

Elliptical Galaxy ◽

Wide Field ◽

Line Profiles ◽

Present Contribution ◽

Doppler Shifts ◽

Spiral Structures ◽

Armed Spiral

Using the Faint Object Spectrograph (FOS) on Hubble Space Telescope (HST), Harms et al. (1994, H94) have recently reported the spectroscopy of central region of the elliptical galaxy M87. Ford et al. 1994 (hereafter F94), using Wide Field Planetary Camera-2 have imaged the region around the nucleus in Hα+[NII] and find an ionized disk with spiral structures of mainly two arms. From the kinematical argument, based on the Doppler shifts of several lines emitted from the disk, and assuming a Keplerian motion of the emitting gas, they conclude that the mass of the disk plus the nucleus: Mc(R < 18pc) = (2.4± 0.7)× 109M⊙ and the inclination angle of the disk with the line of sight is i = (42±5)°. However, if the bright spiral structures are real, and represent shocked region in the disk, we expect that the disk is strongly non-Keplerian and therefore the mass of the black hole must be higher than above estimation.In the present contribution, we provide a complete description of the velocity field of the ionized disk and compute the shape of typical line profiles expected from various parts of the disk. Our analysis is based on the solution of a non-axisymmetric disk which includes two armed spiral density waves. We find a very good agreement between the theoretical and observed line profiles as regards to the Doppler shifts, line widths and the intensity ratios and estimate the mass of the black hole to be (4 ± 0.2) × 109M⊙. Details of this work will be published elsewhere (Chakrabarti, 1995).In a binary system with a thin accretion disk, the binary companion can induce two armed spiral shocks in the disk (e.g., Matsuda et al. 1987, Spruit 1987, Chakrabarti & Matsuda, 1992). In the case of active galaxies, a passing companion (or a globular cluster or a dwarf galaxy) which is more massive than the disk can induce the same effect.

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