XMM-Newton Observations of NGC 247: X-ray Population and a Supersoft Ultraluminous X-ray Source

Abstract

We report on a new XMM-Newton observation of NGC 247 from December 2009. The galaxy contains a supersoft, ultraluminous X-ray source (ULX) whose spectrum consists of a thermal component with a temperature about 0.1 keV and a power-law tail with a photon index around 2.5. The thermal emission is absolutely the dominant component, contributing 96% of the total luminosity in the 0.3-10 keV band. Variability is detected at timescales of 10^2 s and longer with a ν^-1 power spectrum. These properties are consistent with black hole binaries in the thermal state and suggest the presence of an intermediate mass black hole of at least 600 solar masses. However, the integrated rms power is much higher than typically found in the thermal state. An alternative explanation of the emission could be a photosphere with a radius about 10^9 cm. A possible absorption feature around 1 keV is detected, which may be due to absorption of highly ionized winds. X-ray sources within the disk of NGC 247 have a luminosity function consistent with that found in low mass X-ray binaries. We confirm previous results that X-rays from the quasar PHL 6625 may be absorbed by gas in NGC 247, mainly at energies below 0.3 keV.

accepted for publication in the Astrophysical Journal

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Cited by in corpus (17)

• Ultraluminous X-Ray Sources
• Ultraluminous X-ray Sources in the Chandra and XMM-Newton Era
• X-ray Variability and Hardness of ESO 243-49 HLX-1: Clear Evidence for Spectral State Transitions
• From ultraluminous X-ray sources to ultraluminous supersoft sources: NGC 55 ULX, the missing link
• Optically thick outflows in ultraluminous supersoft sources
• Nature of the soft ULX in NGC 247: super-Eddington outflow and transition between the supersoft and soft ultraluminous regimes
• Revisiting the ultraluminous supersoft source in M101: an optically thick outflow model
• Evidence for Optically Thick, Eddington-limited Winds Driven by Supercritical Accretion
• A State Transition of the Luminous X-ray Binary in the Low-Metallicity Blue Compact Dwarf Galaxy I Zw 18
• The chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1
• Chandra and HST Observations of the Supersoft ULX in NGC 247: Candidate for Standard Disk Emission
• The Void in the Sculptor Group Spiral Galaxy NGC 247
• Identification of a Helium Donor Star in NGC 247 ULX-1
• A Luminous X-ray Flare From The Nucleus of The Dormant Bulgeless Spiral Galaxy NGC 247
• Ultraluminous X-ray Sources in Seven Edge-On Spiral Galaxies
• New outburst from the luminous supersoft source SSS1 in NGC 300 with periodic modulation
• PHL 6625: A Minor Merger-Associated QSO Behind NGC 247