GRAVITY: Microarcsecond Astrometry and Deep Interferometric Imaging with the VLT

Eisenhauer, F.; Perrin, Guillaume; Brandner, W.; Straubmeier, C.; Böhm, A.; Baumeister, Harald; Cassaing, F.; Clénet, Y.; Dodds-Eden, K.; Eckart, A.; Gendron, É.; Genzel, R.; Gillessen, S.; Gräter, A.; Gueriau, C.; Hamaus, Nico; Haubois, X.; Haug, M.; Henning, Th.; Hippler, S.; Hofmann, R.; Hormuth, F.; Houairi, K.; Kellner, S.; Kervella, P.; Klein, Ralf; Kolmeder, J.; Laun, W.; Léna, Pierre; Lenzen, R.; Marteaud, M.; Naranjo, V.; Neumann, Uwe; Paumard, T.; Rabien, S.; Ramos, J.; Reess, J. M.; Rohloff, R.-R.; Rouan, D.; Rousset, G.; Ruyet, Bertrand Le; Sevin, Arnaud; Thiel, Markus; Ziegleder, J.; Ziegler, D.

doi:10.1007/978-1-4020-9190-2_61

Cited by 20 publications

(14 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…With the aim of getting more precise values for the above referred parameters and quantities, and directly characterizing the assumed black hole hosted at the center of our galaxy, in the near future there will be new experiments to come: GRAVITY will track with more accuracy the orbits of stars around the centre of our galaxy [9], whereas the Event Horizon Telescope will focus on the black hole event horizon looking for traces of its shadow measuring signals in the infrared spectrum [10].…”

Section: Introductionmentioning

confidence: 99%

Kerr black hole parameters in terms of the redshift/blueshift of photons emitted by geodesic particles

Herrera–Aguilar

Nucamendi

2015

Phys. Rev. D

View full text Add to dashboard Cite

We are motivated by the recently reported dynamical evidence of stars with short orbital periods moving around the center of the Milky Way and the corresponding hypothesis about the existence of a supermassive black hole hosted at its center. In this paper we show how the mass and rotation parameters of a Kerr black hole (assuming that the putative supermassive black hole is of this type), as well as the distance that separates the black hole from the Earth, can be estimated in a relativistic way in terms of i) the red and blue shifts of photons that are emitted by geodesic massive particles (stars and galactic gas) and travel along null geodesics towards a distant observer, and ii) the radius of these star/gas orbits.As a concrete example and as a first step towards a full relativistic analysis of the above mentioned star orbits around the center of our galaxy, we consider stable equatorial circular orbits of stars and express their corresponding red/blue shifts in terms of the metric parameters (mass and angular momentum per unit mass) and the orbital radii of both the emitter star (and/or galactic gas) and the distant observer.In principle, these expressions allow one to statistically estimate the mass and rotation parameters of the Kerr black hole, and the radius of our orbit, through a Bayesian fitting, i.e., with the aid of observational data: the red/blue shifts measured at certain points of stars' orbits and their radii, with their respective errors, a task that we hope to perform in the near future. We also point to several astrophysical phenomena, like accretion discs of rotating black holes, binary systems and active galactic nuclei, among others, to which this formalism can be applied. Keywords: Kerr black hole, black holes rotation curves, red/blue shifts, determination of mass, angular momentum and distance to the black hole.

show abstract

Section: Introductionmentioning

confidence: 99%

Kerr black hole parameters in terms of the redshift/blueshift of photons emitted by geodesic particles

Herrera–Aguilar

Nucamendi

2015

Phys. Rev. D

View full text Add to dashboard Cite

show abstract

Section: Introductionmentioning

confidence: 99%

“…Gaia is a space observatory of the European Space Agency (ESA) launched on 19 December 2013, and is performing the astrometric, photometric, and spectroscopic observations for more than 1 billion stars in our Milky Way and neighboring galaxies. While Gaia satellite is observing the full sky, follow-up astrometric surveys of the interesting microlensing events are planned to be obtained by ground-based instruments as GRAVITY, which is a Very Large Telescope Interferometer build by the European Southern Observatory and the Max Planck Institute for Extraterrestrial Physics [21,22].The first attempts to characterize the FFP population in our Galaxy have been conducted by Sumi et al [23]. They analyzed the light curves of 474 microlensing events observed during a 2-year survey by the MOA-II collaboration towards the Galactic bulge and by analyzing their timescale distribution, which reported the discovery of planetary-mass objects either very distant from their host star (i.e., orbiting at distances larger than 100 AU) or fully unbound.…”

mentioning

confidence: 99%

Free-floating planets in the Milky Way

et al. 2019

View full text Add to dashboard Cite

Gravitational microlensing is a powerful method to search for and characterize exoplanets, and it was first proposed by Paczyński in 1986. We provide a brief historical excursus of microlensing, especially focused on the discoveries of free-floating planets (FFPs) in the Milky Way. We also emphasize that, thanks to the technological developments, it will allow to estimate the physical parameters (in particular the mass and distance) of FFPs towards the center of our Galaxy, through the measure of the source finite radius, Earth or satellite parallax, and/or astrometric effects.Mathematics Subject Classification 85-xx · 85-08 IntroductionDiscovery of the extrasolar planets in our Galaxy is one of the most discussed issues in the scientific community. These objects are outside our solar system and have masses smaller than about 0.01M . Their detection is being achieved using different methods and, until now, we have 3824 confirmed exoplanes (see the website http://exoplanet.eu). Most exoplanets are discovered by the Transit method (∼ 74%) and by Radial Velocity method (∼ 20%). A few exoplanets have been detected using the Direct Imaging technique. Until now, only ∼ 2% of exoplanets have been detected through gravitational microlensing.In recent years, several unbound objects with mass possibly as small as a few times that of Jupiter (M J = 9.5 × 10 −4 M ) have been found in many young star-forming region using infrared imaging surveys [1]. These objects are called free-floating planets or also rogue planets, nomads, or orphan planets (see [2] and references therein). Examples of objects of this kind are WISE 0855-0714, about 2.4 pc away from the Earth [3], and Cha 110913-773444 in the Chamaeleon I star-forming region at a distance of about 160 pc. It is difficult to find this kind of objects by infrared imaging at large distances, so we need the development of alternative methods to search for them. The origin of the FFPs is doubtful, and their formation mechanism remains an open theoretical question in astrophysics. One possibility is that they originally formed around a host star and then scattered out from orbit. A second option is that they may form on their own through gas cloud direct collapse, similarly to star formation.Paczyński [4] first envisaged the search of Galactic dark matter in compact form using gravitational lensing method, which happens when a massive object passes close enough to the line of sight to a distant source star. Since the angular separation of the lensed images are of the order of microarcseconds, such phenomena are often called microlensing [5,6]. In his calculations, Paczyński showed that the chance (or optical depth) of a massive object in the Galactic halo to serve as a lens and magnify a background star in nearby galaxy is 10 −6 . Also, he suggested that, based on modern instruments, we could be able to catch such microlensing events by monitoring a dense stellar field with several millions of stars simultaneously. Therefore, several groundbased experiments such as MACHO (Massiv...

show abstract

“…GRAVITY, currently in its construction phase, will operate on K-Band and combine the light of the four VLT unittelescopes interferometrically [1,2,3,4] .…”

Section: Introductionmentioning

confidence: 99%

The GRAVITY spectrometers: metrology laser blocking system

Araujo-Hauck

Fischer

Gillessen

et al. 2012

Optical and Infrared Interferometry III

View full text Add to dashboard Cite

A two stage blocking system is implemented in the GRAVITY science and the fringe tracking spectrometer optical design. The blocking system consists of a dichroic beam splitter and two long wave band-pass filters with the top level requirements of high transmission of the science light in the K-Band (1.95 -2.45 μm) region and high blocking power optical density (OD) ≥ 8 for each filter at the metrology laser wavelength of 1.908 μm. The laser metrology blocking filters were identified as one critical optical component in the GRAVITY science and fringe tracker spectrometer design.During the Phase-C study of GRAVITY all the filters were procured and individually tested in terms of spectral response at K-band, transmission, blocking (OD) and reflection at the metrology laser wavelength. We present the measurements results of the full metrology blocking system in its final configuration as to be implemented in the GRAVITY spectrometers.

show abstract

GRAVITY: Microarcsecond Astrometry and Deep Interferometric Imaging with the VLT

Cited by 20 publications

References 0 publications

Kerr black hole parameters in terms of the redshift/blueshift of photons emitted by geodesic particles

Kerr black hole parameters in terms of the redshift/blueshift of photons emitted by geodesic particles

Free-floating planets in the Milky Way

The GRAVITY spectrometers: metrology laser blocking system

Contact Info

Product

Resources

About