Impact of intrinsic polarisation of Sgr A* historical flares on (polarisation) properties of their X-ray echoes

Abstract

Reflection of X-ray emission on molecular clouds in the inner $\sim$ 100 pc of our Galaxy reveals that, despite being extremely quiet at the moment, our supermassive black hole Sgr A* should have experienced bright flares of X-ray emission in the recent past. Thanks to the improving characterisation of the reflection signal, we are able to infer parameters of the most recent flare(s) (age, duration and luminosity) and relative line-of-sight disposition of the brightest individual molecular complexes. We show that combining these data with measurements of polarisation in the reflected X-ray continuum will not only justify Sgr A* as the primary source but also allow deriving intrinsic polarisation properties of the flare emission. This will help to identify radiation mechanisms and underlying astrophysical phenomena behind them. For the currently brightest reflecting molecular complex, Sgr A, the required level of sensitivity might be already accessible with upcoming X-ray polarimeters.

arXiv comment7 pages, 4 figures, updated to correspond to the accepted version

References in corpus (44)

• The Galactic Center Massive Black Hole and Nuclear Star Cluster
• An All-Sky Analysis of Polarization in the Microwave Background
• Statistics of Cosmic Microwave Background Polarization
• Near-infrared flares from accreting gas around the supermassive black hole at the Galactic Centre
• Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre
• Evidence for X-ray synchrotron emission from simultaneous mid-IR to X-ray observations of a strong Sgr A* flare
• Polarimetry of near-infrared flares from Sagittarius A*
• Constraining the Accretion Rate Onto Sagittarius A* Using Linear Polarization
• A Chandra/HETGS Census of X-ray Variability From Sgr A* During 2012
• Discovery of a superluminal Fe K echo at the Galactic Center: The glorious past of Sgr A* preserved by molecular clouds
• First Simultaneous NIR/X-ray Detection of a Flare from SgrA*
• Hard X-ray view of the past activity of Sgr A* in a natural Compton mirror
• A powerful flare from Sgr A* confirms the synchrotron nature of the X-ray emission
• Variable accretion and emission from the stellar winds in the Galactic centre
• Equivalent width, shape and proper motion of the iron fluorescent line emission from the molecular clouds as an indicator of the illuminating source X-ray flux history
• The XMM-Newton view of the central degrees of the Milky Way
• A strongly magnetized pulsar within grasp of the Milky Way's supermassive black hole
• Echoes of multiple outbursts of Sagittarius A* revealed by Chandra
• Thermal disc emission from a rotating black hole: X-ray polarization signatures
• Source-intrinsic near-infrared properties of Sgr A*: Total intensity measurements
• Time Dependent Models of Flares from Sagittarius A*
• The nature of the E-B decomposition of CMB polarization
• Discovery of Variable Iron Fluorescence from Reflection Nebulae in the Galactic Center
• Sgr A* flares: tidal disruption of asteroids and planets?
• Traces of past activity in the Galactic Centre
• X-ray Echo from the Sagittarius C Complex and 500-year Activity History of Sagittarius A*
• The X-ray lightcurve of Sgr A* over the past 150 years inferred from Fe-Ka line reverberation in Galactic Centre molecular clouds
• Chandra Spectral and Timing Analysis of Sgr A*'s Brightest X-ray Flares
• Hard X-ray Morphological and Spectral Studies of The Galactic Center Molecular Cloud Sgr B2: Constraining Past Sgr A* Flaring Activity
• Polarization of X-ray emission from the Sgr B2 cloud
• Polarized light from Sgr A* in the near-infrared $K_s$-band
• Not that long time ago in the nearest galaxy: 3D slice of molecular gas revealed by a 110 years old flare of Sgr A*
• Simultaneous X-ray and Infrared Observations of Sagittarius A*'s Variability
• Polarization and long-term variability of Sgr A* X-ray echo
• Glimpses of the past activity of Sgr A* inferred from X-ray echoes in Sgr C
• An X-ray survey of the central molecular zone: variability of the Fe Ka emission line
• Prospects of 3D mapping of the Galactic Centre clouds with X-ray polarimetry
• "Failed" tidal disruption events and X-ray flares from the Galactic Center
• Can Sgr A* flares reveal the molecular gas density PDF?
• NuSTAR and XMM-Newton observations of the Arches cluster in 2015: fading hard X-ray emission from the molecular cloud
• Probing the clumping structure of Giant Molecular Clouds through the spectrum, polarisation and morphology of X-ray Reflection Nebulae
• Reflection nebulae in the Galactic Center: the case for soft X-ray imaging polarimetry
• X-raying molecular clouds with a short flare: probing statistics of gas density and velocity fields
• ESA Voyage 2050 white paper: A Polarized View of the Hot and Violent Universe

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