GRAVITY: getting to the event horizon of Sgr A*

Eisenhauer, F.; Perrin, G.; Brandner, W.; Straubmeier, C.; Richichi, A.; Gillessen, S.; Berger, J.‐P.; Hippler, S.; Eckart, A.; Schöller, M.; Rabien, S.; Cassaing, F.; Lenzen, R.; Thiel, Markus; Clénet, Y.; Ramos, J.; Kellner, S.; Fédou, P.; Baumeister, Harald; Hofmann, R.; Gendron, É.; Boehm, Armin; Bartko, H.; Haubois, X.; Klein, Ralf; Dodds-Eden, K.; Houairi, K.; Hormuth, F.; Gräter, A.; Jocou, L.; Naranjo, V.; Genzel, R.; Kervella, P.; Henning, Thomas; Hamaus, Nico; Lacour, S.; Neumann, Udo; Haug, M.; Malbet, Fabien; Laun, W.; Kolmeder, J.; Paumard, T.; Rohloff, Ralf-Rainer; Pfuhl, O.; Perraut, K.; Ziegleder, J.; Rouan, D.; Rousset, G.

doi:10.1117/12.788407

Cited by 64 publications

(44 citation statements)

References 20 publications

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“…In this paper we used two of them: MIRA and WISARD. Both are presented and compared in Le Besnerais (2008) and in Lacour et al (2008). The major advantage of such methods is that they can reveal structures by reconstructing an image which fits the data and which is also close to an a priori image of the object.…”

Section: Image Reconstruction and Asymmetriesmentioning

confidence: 99%

“…Around 2013, the VLTI is expected to receive the first second-generation general user instruments making use of 4 telescopes simultaneously. These are Matisse working in the L, M, N bands (Lopez et al, 2008) and Gravity with dual beam operation and an astrometric capability (Eisenhauer et al, 2008).…”

Section: Vltimentioning

confidence: 99%

“…Using an image of the star obtained at the diffraction limit of a large telescope when performing the image reconstruction would probably solve this issue like single dish observation in radio astronomy. The latter problem is partly due to an insufficient angular resolution in this particular simulation: Lacour et al (2008) show that the limb darkening can be reconstructed if the data sample the 2nd and 3rd lobe of the visibility curve, and a limb-darkened prior is chosen for the image reconstruction. Given the highly variable nature of many evolved stars, it is important that real observations come as close as possible to snapshot images.…”

Section: Molecular Layers Around Late-type Starsmentioning

confidence: 99%

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Imaging the heart of astrophysical objects with optical long-baseline interferometry

Berger

Malbet

Baron

et al. 2012

Astron Astrophys Rev

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The number of publications of aperture-synthesis images based on optical longbaseline interferometry measurements has recently increased due to easier access to visible and infrared interferometers. The interferometry technique has now reached a technical maturity level that opens new avenues for numerous astrophysical topics requiring milliarcsecond model-independent imaging. In writing this paper our motivation was twofold: 1) review and publicize emblematic excerpts of the impressive corpus accumulated in the field of optical interferometry image reconstruction; 2) discuss future prospects for this technique by selecting four representative astrophysical science cases in order to review the potential benefits of using optical long baseline interferometers.For this second goal we have simulated interferometric data from those selected astrophysical environments and used state-of-the-art codes to provide the reconstructed images that are reachable with current or soon-to-be facilities. The image reconstruction process was "blind" in the sense that reconstructors had no knowledge of the input brightness distributions. We discuss the impact of optical interferometry in those four astrophysical fields. We show that image reconstruction software successfully provides accurate morphological information on a variety of astrophysical topics and review the current strengths and weaknesses of such reconstructions. We investigate how to improve image reconstruction and the quality of the image possibly by upgrading the current facilities. We finally argue that optical interferometers and their corresponding instrumentation, existing or to come, with 6 to 10 telescopes, should be well suited to provide images of complex sceneries.

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Section: Image Reconstruction and Asymmetriesmentioning

confidence: 99%

Section: Vltimentioning

confidence: 99%

Section: Molecular Layers Around Late-type Starsmentioning

confidence: 99%

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Imaging the heart of astrophysical objects with optical long-baseline interferometry

Berger

Malbet

Baron

et al. 2012

Astron Astrophys Rev

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“…Further in progress developments consider the use of complex IO components as VSI (VLTI Spectro Imager) [13] and Gravity [14] for the second generation instrument of the VLTI. For space borne applications, if the compactness is a trivial advantage, with a direct impact on the payload of the instrument, one may mention also the strong advantages of such integrated instrument.…”

Section: Integrated Optics Applied To Interferometrymentioning

confidence: 99%

On-chip spectro-detection for fully integrated coherent beam combiners

Kern¹,

Coarer²,

Bénech³

2009

Opt. Express

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This paper presents how photonics associated with new arising detection technologies is able to provide fully integrated instrument for coherent beam combination applied to astrophysical interferometry. The feasibility and operation of on-chip coherent beam combiners has been already demonstrated using various interferometric combination schemes. More recently we proposed a new detection principle aimed at directly sampling and extracting the spectral information of an input signal together with its flux level measurement. The so-called SWIFTS demonstrated concept that stands for Stationary-Wave Integrated Fourier Transform Spectrometer, provides full spectral and spatial information recorded simultaneously thanks to a motionless detecting device. Due to some newly available detection principles considered for the implementation of the SWIFTS concept, some technologies can even provide photo-counting operation that brought a significant extension of the interferometry domain of investigation in astrophysics . The proposed concept is applicable to most of the interferometric instrumental modes including fringe tracking, fast and sensitive detection, Fourier spectral reconstruction and also to manage a large number of incoming beams. The paper presents three practical implementations, two dealing with pair-wise integrated optics beam combinations and the third one with an all-in-one 8 beam combination. In all cases the principles turned into a pair wise baseline coding after proper data processing.

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“…Therefore, in order to follow the same scheme of detection of inner stellar kinematics and of the masses of MBHs in distant galaxies, we need the Very Large Telescope interferometer and one of the next-generation instruments, either the VSI or GRAVITY [29,30]. Only then can we improve our astrometric accuracy by the necessary factor of ∼10.…”

Section: Introductionmentioning

confidence: 99%

Fake plunges are very eccentric real EMRIs in disguise

Amaro-Seoane

Sopuerta

Brem

2012

EPJ Web of Conferences

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Abstract. The capture of a compact object in a galactic nucleus by a massive black hole (MBH) is the best way to map space and time around it. Compact objects such as stellar black holes on a capture orbit with a very high eccentricity have been wrongly assumed to be lost for the system after an intense burst of radiation, which has been described as a "direct plunge". We prove that these very eccentric capture orbits spend actually a similar number of cycles in a LISA-like detector as those with lower eccentricities if the central MBH is spinning. Although the rates are higher for high-eccentricity EMRIs, the spin also enhances the rates of lower-eccentricity EMRIs. This last kind have received more attention because of the fact that higheccentricity EMRIs were thought to be direct plunges and thus negligible. On the other hand, recent work on stellar dynamics has demonstrated that there seems to be a complot in phase space acting on these lower-eccentricity captures, since their rates decrease significantly by the presence of a blockade in the rate at which orbital angular momenta change takes place. This socalled "Schwarzschild barrier" is a result of the impact of relativistic precession on to the stellar potential torques, and thus it affects the enhancement on lower-eccentricity EMRIs that one would expect from resonant relaxation. We confirm and quantify the existence of this barrier using a statitical sample of 2,500 direct-summation N−body simulations using both a post-Newtonian but also, and for the first time, a geodesic approximation for the relativistic orbits. The existence of the barrier prevents "traditional EMRIs" from approaching the central MBH, but if the central MBH is spinning the rate will be anyway dominated by highlyeccentric extreme-mass ratio inspirals, which insolently ignore the presence of the barrier, because they are driven by two-body relaxation.

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GRAVITY: getting to the event horizon of Sgr A*

Cited by 64 publications

References 20 publications

Imaging the heart of astrophysical objects with optical long-baseline interferometry

Imaging the heart of astrophysical objects with optical long-baseline interferometry

On-chip spectro-detection for fully integrated coherent beam combiners

Fake plunges are very eccentric real EMRIs in disguise

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