2009ApJ...703.1386S


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.08CEST06:39:29

2009ApJ...703.1386S - Astrophys. J., 703, 1386-1393 (2009/October-1)

Evidence for an intermediate-mass black hole in NGC 5408 X-1.

STROHMAYER T.E. and MUSHOTZKY R.F.

Abstract (from CDS):

We report the discovery with XMM-Newton of correlated spectral and timing behavior in the ultraluminous X-ray source (ULX) NGC 5408 X-1. An ~100 ks pointing with XMM/Newton obtained in 2008 January reveals a strong 10 mHz quasi-periodic oscillation (QPO) in the >1 keV flux, as well as flat-topped, band-limited noise breaking to a power law. The energy spectrum is again dominated by two components, a 0.16 keV thermal disk and a power law with an index of ~2.5. These new measurements, combined with results from our previous 2006 January pointing in which we first detected QPOs, show for the first time in a ULX a pattern of spectral and temporal correlations strongly analogous to that seen in Galactic black hole (BH) sources, but at much higher X-ray luminosity and longer characteristic timescales. We find that the QPO frequency is proportional to the inferred disk flux, while the QPO and broadband noise amplitude (rms) are inversely proportional to the disk flux. Assuming that QPO frequency scales inversely with the BH mass at a given power-law spectral index we derive mass estimates using the observed QPO frequency-spectral index relations from five stellar-mass BH systems with dynamical mass constraints. The results from all sources are consistent with a mass range for NGC 5408 X-1 from 1000 to 9000 M. We argue that these are conservative limits, and a more likely range is from 2000 to 5000 M. Moreover, the recent relation from Gierlinski et al. that relates the BH mass to the strength of variability at high frequencies (above the break in the power spectrum) is also indicative of such a high mass for NGC 5408 X-1. Importantly, none of the above estimates appears consistent with a BH mass less than ~1000 M for NGC 5408 X-1. We argue that these new findings strongly support the conclusion that NGC 5408 X-1 harbors an intermediate-mass BH.

Abstract Copyright:

Journal keyword(s): black hole physics - galaxies: individual: NGC 5408 - stars: oscillations - X-rays: stars - X-rays: galaxies

Simbad objects: 14

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Number of rows : 14

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NAME IC 10 X-1 HXB 00 20 29.09 +59 16 51.9           ~ 148 0
2 NAME M33 X-7 HXB 01 33 34.13 +30 32 11.3 17.50 18.80 18.70     O 127 2
3 NAME M82 ULX-1 UX? 09 55 50.01 +69 40 46.0           ~ 241 1
4 NGC 4395 Sy2 12 25 48.8639154223 +33 32 48.694684028 10.84 10.54 10.11 9.98   ~ 993 1
5 [FK2005] 25 ULX 14 03 19.63 -41 22 58.7           ~ 196 0
6 NGC 5408 EmG 14 03 20.907 -41 22 39.75   12.59   11.96 12.2 ~ 315 3
7 V* V381 Nor HXB 15 50 58.6520652623 -56 28 35.309070422   17.95 16.6     K3III 1021 0
8 X Nor X-1 LXB 16 34 01.610 -47 23 34.80           ~ 418 0
9 V* V821 Ara HXB 17 02 49.3810714542 -48 47 23.163091737 16.20 16.30 15.5     ~ 1764 0
10 NAME XTE J17464-3213 LXB 17 46 15.59637 -32 14 00.8600           ~ 597 0
11 V* V406 Vul HXB 18 58 41.580 +22 39 29.40 15.00 15.65 15.31     G5V-K0V 316 0
12 Granat 1915+105 LXB 19 15 11.54938 +10 56 44.7585           ~ 2282 0
13 HD 226868 HXB 19 58 21.6758193269 +35 12 05.782512305 9.38 9.72 8.91 8.42   O9.7Iabpvar 3923 0
14 NAME Local Group GrG ~ ~           ~ 6970 0

    Equat.    Gal    SGal    Ecl

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2020.07.08-06:39:29

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