DOCSLIB.ORG

The Bright Side of the Black Hole: Flares from Sgr A*

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Bright Side of the Black Hole: Flares from Sgr A* The Bright Side of the Black Hole: Flares from Sgr A* Katie Dodds-Eden M¨unchen 2010 The Bright Side of the Black Hole: Flares from Sgr A* Katie Dodds-Eden Dissertation an der Fakult¨at f¨ur Physik der Ludwig–Maximilians–Universit¨at M¨unchen vorgelegt von Katie Dodds-Eden aus Canberra, Australia M¨unchen, den 28. September 2010 Erstgutachter: Prof. Dr. Reinhard Genzel Zweitgutachter: Prof. Dr. Andreas Burkert Tag der m¨undlichen Pr¨ufung: 13. December 2010 To the dear memory of my grandmother, Reta Dodds, my uncle, Ken Moyse, and my granddad, Francis Eden. vi Contents Zusammenfassung xv Summary xvii 1 Black Holes in Nature 1 1.1 ATheoreticalCuriosity. .. 1 1.1.1 Schwarzschild black holes . 1 1.1.2 Kerrblackholes............................. 2 1.2 TheSearchforRealBlackHoles. .. 3 1.3 RadiationfromAccretion . 4 2 The Massive Black Hole at the Galactic Center 9 2.0.1 SgrA*: theRadiotoSubmmSource . 10 2.0.2 Near-infraredand X-ray Flares fromSgr A* . ... 13 2.1 ModelsforSgrA*................................ 16 2.1.1 Thesubmm-radiosource . 16 2.1.2 FlareModels .............................. 16 3 Radiation Processes 19 3.1 SimpleRadiativeTransfer . .. 19 3.1.1 HomogeneousSphere . .. .. 20 3.2 SynchrotronEmission. 21 3.2.1 PropertiesoftheSpectrum. 22 3.3 InverseComptonScattering . .. 28 4 Multiwavelength Observations and the Emission Mechanism 31 4.1 Introduction................................... 32 4.2 Observations................................... 34 4.2.1 IR/NIRObservations. 35 4.2.2 X-rayObservations ........................... 38 4.2.3 Mid-InfraredObservations . 39 4.3 Results...................................... 41 4.3.1 Simultaneity of infrared and X-ray flare . .... 41 viii CONTENTS 4.3.2 GeneralLightcurveShape . 41 4.3.3 Substructure .............................. 42 4.3.4 Shortesttime-scalevariations . ... 42 4.3.5 PowerSpectra.............................. 42 4.3.6 SpectralEnergyDistribution. .. 43 4.4 ModellingtheflarestateSEDofSgrA* . .. 45 4.4.1 icmodel: inverse Compton scattered submm bump photons . 48 4.4.2 sscmodel: inverse Compton scattered NIR flare photons . 51 4.4.3 powerlaw: single power law synchrotron emission . 51 4.4.4 powerlawcool: power law synchrotron emission with cooling break 51 4.5 Flare Evolution: Lightcurve Shape and Substructure . ......... 52 4.6 Discussion.................................... 54 4.6.1 Why inverse Compton scenarios don’t work . .. 54 4.6.2 Comparison with past multiwavelength studies . ...... 56 4.6.3 The electron energy distribution . ... 58 4.6.4 Thejetmodel.............................. 61 4.6.5 Substructure in the context of an orbiting hot spot model...... 61 4.7 Conclusions ................................... 62 5 Time Dependent Flare Models 65 5.1 Introduction................................... 65 5.2 Flaring in Accretion Disk Simulations . ...... 67 5.2.1 Numerical Setup and Initial Conditions . .... 68 5.2.2 SimulationResults ........................... 68 5.3 LightcurveModeling .............................. 72 5.3.1 NumericalModel ............................ 73 5.3.2 Lightcurves ............................... 75 5.3.3 Quasi-stationaryFlareModel . 80 5.3.4 Expanding Plasma: a “Coronal Mass Ejection” . ... 80 5.3.5 Energetics and the Size of the Emitting Region . .... 86 5.3.6 Effect of the Decreasing Magnetic Field on the Steady State Emission 87 5.3.7 LightcurveSubstructure . 88 5.4 Conclusions ................................... 89 5.4.1 Conclusions:NIRandX-ray. 90 5.4.2 Conclusions: Millimeter and radio . ... 92 5.4.3 FinalRemarks ............................. 93 6 Six year lightcurve from Sgr A* 95 6.1 Introduction................................... 95 6.2 Data....................................... 97 6.2.1 Aperture Photometry of Ks-band data 2004-2009 . .... 101 6.2.2 PSFphotometryofKs-banddatafrom2009 . 105 6.3 Results...................................... 108 Inhaltsverzeichnis ix 6.3.1 FluxDistribution ............................ 108 6.3.2 Is Sgr A* really continuously variable? . .... 111 6.3.3 The Effect of Observation Errors on the Flux Distribution ..... 113 6.3.4 Long timescale variability ( weekstomonths). 114 ∼ 6.4 Discussion/Interpretation. ..... 115 6.4.1 TwostatesofSgrA*inthenear-infrared . 115 6.4.2 Consistency with previous measurements of Sgr A* at low Ks-band fluxes117 6.4.3 Comparison with X-ray binary variability . ..... 118 6.4.4 WavelengthDependence . 119 6.4.5 TimingAnalysis............................. 119 6.5 Conclusions ................................... 120 7 Conclusions 121 Acknowledgements 131 x Inhaltsverzeichnis List of Figures 1.1 LightcurveofCygnusX-1 . .. .. 6 2.1 Night view of the Galactic Center with the VLT Laser Guide Star ..... 10 2.2 The Galactic Center in the near-infrared . ...... 11 2.3 NIRFlaresfromSgrA* ............................ 13 3.1 Synchrotron spectrum emitted by monoenergetic distribution of electrons . 23 3.2 Synchrotron spectrum from a power-law electron distribution........ 24 3.3 Comparison of angle-averaged spectrum with φ = arcsin π/4 approximation 25 3.4 The self-absorption frequency for a power law distribution of electrons. 26 3.5 Comparison with analytic models. ... 27 3.6 Properties of Synchrotron Self-Compton spectra . ......... 28 3.7 The Klein-Nishina limit for inverse Compton scattering............ 29 4.1 SgrA*NIRlightcurve,April1-62007 . ... 36 4.2 SgrA*L’-bandflare,April4,2007 . .. 37 4.3 Simultaneous L’-band and X-ray flare, April 4, 2007. ........ 40 4.4 Power spectra for L’-band and X-ray lightcurves, April 4,2007....... 43 4.5 Spectral Energy Distribution for Sgr A*, April 4, 2007 . ......... 44 4.6 XSPECmodelsfortheApril4,2007flare. ... 49 4.7 Photon density in Yuan et al. 2003 model . ... 50 4.8 Best fit SEDs, power law distribution . .... 59 4.9 A submm inverse Compton model, for jet model . .... 61 5.1 2D MHD simulations: magnetic field contour plots . ....... 69 5.2 2D MHD simulations: temperature contour plots . ...... 71 5.3 X-rayandNIRmodellightcurves . .. 76 5.4 Time-dependent model SEDs . 77 5.5 X-ray and NIR model lightcurves with decreasing magneticfield ...... 81 5.6 An adiabatic expansion model: expansion and velocity profiles ....... 82 5.7 Adiabatic expansion models for radio-mm emission: varying Ri and vexp .. 83 5.8 Adiabatic expansion models for radio-mm emission: varying B(R) and p . 84 5.9 NIR lightcurve: substructures from magnetic field fluctuations ....... 89 5.10 SummarymodelforApril4,2007flare . ... 91 xii Abbildungsverzeichnis 6.1 2004-2009Ks-bandlightcurveofSgrA*. ..... 100 6.2 SgrA*Ks-bandflare: August5th,2008 . 103 6.3 SgrA*sourceposition,2007to2008 . 105 6.4 2009,Starfinderdetectedpositions . ..... 106 6.5 2009 lightcurves: Starfinder and Aperture Photometry . ......... 107 6.6 Flux distributions for Sgr A* and comparison star . ........ 110 6.7 Sgr A* flux distribution: non-continuously variable model.......... 112 6.8 Sgr A* flux distribution: comparison of Starfinder and Aperture Photometry 113 6.9 Sgr A* flux distribution: effect of observation errors . .......... 115 List of Tables 4.1 Models:FitParameters ............................ 47 4.2 Models:FitParameters ............................ 60 5.1 Properties of L’-band and X-ray flares in the time-dependent synchrotron model 79 6.1 Flux comparison of Sgr A* reported in the literature: I. brightstates . 98 6.2 Flux comparison of Sgr A* reported in the literature: II. faintstates. 99 6.3 Fits to the observed flux distribution . ..... 109 xiv Tabellenverzeichnis Zusammenfassung Sgr A*, die Strahlungsquelle, die dem schweren schwarzen Loch im Zentrum der Milch- straße entspricht, bietet uns die besondere M¨oglichkeit, Ph¨anomene in der unmittelbaren N¨ahe eines schwarzen Lochs zu beobachten. Da Sgr A* nur mit 10−8 seiner Eddington- Leuchtkraft strahlt, geh¨ort die Quelle zu den schw¨achsten bekannten strahlenden schwarzen L¨ochern (sogenannte Low Luminosity Active Galactic Nuclei, LLAGN). Sgr A* ist die am besten untersuchbare Quelle dieser Art, da sie vergleichsweise nah, n¨amlich in unserer eigenen Milchstraße lokalisiert ist. W¨ahrend das Vorhandensein eines schwarzen Lochs im Galaktischen Zentrum lange angezweifelt wurde, stellt die Beobachtung der Bewe- gung einzelner Sterne in Umlaufbahnen um Sgr A* heute den besten Beleg daf¨ur da, dass schwarze L¨ocher ¨uberhaupt existieren. Durch Beobachtung und Modellierung der langwelligen Emission von Sgr A* (Radio- bis submm-Bereich) ist bekannt, dass die relativ konstante Emission in diesen Wellenl¨angen- bereichen durch Synchrotron-Strahlung eines stark magnetisierten, d¨unnen, relativistis- chen Plasmas in einem mehrschichtigen, strahlungsineffizienten Akkretionsfluss erzeugt wird. Im inneren Bereich in der N¨ahe des schwarzen Lochs liegen die typische magnetis- che Flussdichte, die Dichte und der Gamma-Faktor des Plasmas bei etwa B 30 G, n 107 cm−3 und γ 10. Andererseits ist die physikalische Ursache f¨ur≈ die spo- e ≈ ≈ radischen Strahlungsausbr¨uche (Flares im folgenden), die etwa eine Stunde dauern und im Nahinfrarot- (NIR) und R¨ontgenbereich h¨aufig beobachtet werden, weiterhin ein un- gel¨ostes R¨atsel. Sie wurden erst in den letzten zehn Jahren entdeckt. Das Ziel dieser Arbeit ist es, den physikalischen Ursprung der Flares von Sgr A* zu untersuchen. Diese Arbeit beginnt mit drei einf¨uhrenden Kapiteln: Zun¨achst werden astrophysikalis- che schwarze L¨ocher im allgemeinen besprochen (Kapitel 1), danach die Beobachtungen von Sgr A* in Kapitel 2. In Kapitel 3 dann werden die Eigenschaften der wichtigsten Strahlungsprozesse f¨ur die Quelle, Synchrotron-Strahlung und inverse
Load more

Recommended publications
  • Arxiv:Astro-Ph/0301210V1 13 Jan 2003 Bevtr Ftecrei Nttto Fwashington
    1 The Optical Gravitational Lensing Experiment. Planetary and Low-Luminosity Object Transits in the Carina Fields of the Galactic Disk∗ A. Udalski1, O. Szewczyk1, K. Z˙ e b r u ´n1, G. Pietrzy´nski2,1, M. Szyma´nski1, M. Kubiak1, I. Soszy´nski1, andL. Wyrzykowski1 1Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland e-mail: (udalski,szewczyk,zebrun,pietrzyn,msz,mk,soszynsk,wyrzykow)@astrouw.edu.pl 2 Universidad de Concepci´on, Departamento de Fisica, Casilla 160–C, Concepci´on, Chile ABSTRACT We present results of the second “planetary and low-luminosity object transit” campaign conducted by the OGLE-III survey. Three fields (35′ ×35′ each) located in the Carina regions of the Galactic disk (l ≈ 290◦) were monitored continuously in February–May 2002. About 1150 epochs were collected for each field. The search for low depth transits was conducted on about 103 000 stars with photometry better than 15 mmag. In total, we discovered 62 objects with shallow depth (≤ 0.08 mag) flat-bottomed transits. For each of these objects several individual transits were detected and photometric elements were determined. Also lower limits on radii of the primary and companion were calculated. The 2002 OGLE sample of stars with transiting companions contains considerably more objects that may be Jupiter-sized (R< 1.6 RJup) compared to our 2001 sample. There is a group of planetary candidates with the orbital periods close to or shorter than one day. If confirmed as planets, they would be the shortest period extrasolar planetary systems. In general, the transiting objects may be extrasolar planets, brown dwarfs, or M-type dwarfs.
    [Show full text]
  • On the 2PN Pericentre Precession in the General Theory of Relativity and the Recently Discovered Fast-Orbiting S-Stars in Sgr A∗
    universe Article On the 2PN Pericentre Precession in the General Theory of Relativity and the Recently Discovered Fast-Orbiting S-Stars in Sgr A∗ Lorenzo Iorio Ministero dell’Istruzione, dell’Università e della Ricerca (M.I.U.R.)-Istruzione, Viale Unità di Italia 68, 70125 Bari (BA), Italy; [email protected] Abstract: Recently, the secular pericentre precession was analytically computed to the second post- Newtonian (2PN) order by the present author with the Gauss equations in terms of the osculating Keplerian orbital elements in order to obtain closer contact with the observations in astronomical and astrophysical scenarios of potential interest. A discrepancy in previous results from other authors was found. Moreover, some of such findings by the same authors were deemed as mutually inconsistent. In this paper, it is demonstrated that, in fact, some calculation errors plagued the most recent calculations by the present author. They are explicitly disclosed and corrected. As a result, all of the examined approaches mutually agree, yielding the same analytical expression for the total 2PN pericentre precession once the appropriate conversions from the adopted parameterisations are made. It is also shown that, in the future, it may become measurable, at least in principle, for some of the recently discovered short-period S-stars in Sgr A∗, such as S62 and S4714. Citation: Iorio, L. On the 2PN Keywords: general relativity and gravitation; celestial mechanics Pericentre Precession in the General Theory of Relativity and the Recently Discovered Fast-Orbiting S-Stars in Sgr A∗. Universe 2021, 7, 37. https://doi.org/10.3390/ 1. Introduction universe7020037 The analytical calculation of the secular second post-Newtonian (2PN)1 pericentre2 precession w˙ 2PN of a gravitationally bound two-body system made of two mass monopoles Academic Editor: Philippe Jetzer MA, MB with the perturbative Gauss equations for the variation of the osculating Keplerian Received: 1 January 2021 orbital elements (e.g., [5,6]) was the subject of Iorio [7].
    [Show full text]
  • An Update on Monitoring Stellar Orbits in the Galactic Center S
    Draft version November 29, 2016 Preprint typeset using LATEX style emulateapj v. 5/2/11 AN UPDATE ON MONITORING STELLAR ORBITS IN THE GALACTIC CENTER S. Gillessen1, P.M. Plewa1, F. Eisenhauer1, R. Sari2, I. Waisberg1, M. Habibi1, O. Pfuhl1, E. George1, J. Dexter1, S. von Fellenberg1, T. Ott1, R. Genzel1,3 Draft version November 29, 2016 ABSTRACT Using 25 years of data from uninterrupted monitoring of stellar orbits in the Galactic Center, we present an update of the main results from this unique data set: A measurement of mass of and distance to Sgr A*. Our progress is not only due to the eight year increase in time base, but also due to the improved definition of the coordinate system. The star S2 continues to yield the best 6 constraints on the mass of and distance to Sgr A*; the statistical errors of 0:13 × 10 M and 0:12 kpc have halved compared to the previous study. The S2 orbit fit is robust and does not need any prior information. Using coordinate system priors, also the star S1 yields tight constraints on mass and distance. For a combined orbit fit, we use 17 stars, which yields our current best estimates for mass 6 and distance: M = 4:28 ± 0:10jstat: ± 0:21jsys × 10 M and R0 = 8:32 ± 0:07jstat: ± 0:14jsys kpc. These numbers are in agreement with the recent determination of R0 from the statistical cluster parallax. The positions of the mass, of the near-infrared flares from Sgr A* and of the radio source Sgr A* agree to within 1 mas.
    [Show full text]
  • Detection of Faint Stars Near Sagittarius A* with GRAVITY GRAVITY Collaboration?: R
    A&A 645, A127 (2021) Astronomy https://doi.org/10.1051/0004-6361/202039544 & c GRAVITY Collaboration 2021 Astrophysics Detection of faint stars near Sagittarius A* with GRAVITY GRAVITY Collaboration?: R. Abuter8, A. Amorim6,12, M. Bauböck1, J. P. Berger5,8, H. Bonnet8, W. Brandner3, Y. Clénet2, Y. Dallilar1, R. Davies1, P. T. de Zeeuw10,1, J. Dexter13,1, A. Drescher1,16, F. Eisenhauer1, N. M. Förster Schreiber1, P. Garcia7,12, F. Gao1,??, E. Gendron2, R. Genzel1,11, S. Gillessen1, M. Habibi1, X. Haubois9, G. Heißel2, T. Henning3, S. Hippler3, M. Horrobin4, A. Jiménez-Rosales1, L. Jochum9, L. Jocou5, A. Kaufer9, P. Kervella2, S. Lacour2, V. Lapeyrère2, J.-B. Le Bouquin5, P. Léna2, D. Lutz1, M. Nowak15,2, T. Ott1, T. Paumard2;??, K. Perraut5, G. Perrin2, O. Pfuhl8,1, S. Rabien1, G. Rodríguez-Coira2, J. Shangguan1, T. Shimizu1, S. Scheithauer3, J. Stadler1, O. Straub1, C. Straubmeier4, E. Sturm1, L. J. Tacconi1, F. Vincent2, S. von Fellenberg1, I. Waisberg14,1, F. Widmann1, E. Wieprecht1, E. Wiezorrek1, J. Woillez8, S. Yazici1,4, and G. Zins9 1 Max Planck Institute for extraterrestrial Physics, Giessenbachstraße 1, 85748 Garching, Germany 2 LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, 92195 Meudon, France 3 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany 4 1st Institute of Physics, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany 5 Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France 6 Universidade de Lisboa – Faculdade de Ciências, Campo Grande, 1749-016 Lisboa, Portugal 7 Faculdade de Engenharia, Universidade do Porto, rua Dr.
    [Show full text]
  • Stellar Motion Near the Supermassive Black Hole in the Galactic Center
    Stellar Motion Near the Supermassive Black Hole in the Galactic Center INAUGURAL-DISSERTATION zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultät der Universität zu Köln vorgelegt von Marzieh Parsa aus Shiraz, Iran Köln 2018 Berichterstatter: Prof. Dr. Andreas Eckart Prof. Dr. J. Anton Zensus Tag der mündlichen Prüfung: 10. Oktober 2017 Abstract General relativity is the least tested theory of physics. The close environment of the supermassive black hole provides us with the perfect laboratory for the investigation of the predictions of this theory. Therefore, the Observation of S-stars in the Galactic center in the near-infrared wavelengths provides the opportunity to study the physics in the vicinity of a supermassive black hole and conduct unique dynamical tests of the theory of general relativity. In my thesis, I use near-infrared high angular resolution adaptive optics images of the central stellar cluster acquired with the NACO instrument at the Very Large Telescope of the European Southern Observatory, from 2002 to 2015. In addition, I employ the published astrometric and line of sight velocity data obtained with the Keck telescope from 1995 to 2013. I use the SiO maser sources in the wide field of view of the NACO S27 camera. The positions and motions of these maser sources and the position of Sgr A*, the supermassive black hole in the center of the Galaxy, is known in the radio regime. Therefore, I find the connection between the near-infrared data and the radio reference frame. Next, I connect the images of the S27 camera to the images of the S13 camera, in which the S-stars are observable in the central arcsecond, using six overlap stars.
    [Show full text]
  • Fastest Star Ever Seen Is Moving at 8% the Speed of Light 14 August 2020, by Brian Koberlein
    Fastest star ever seen is moving at 8% the speed of light 14 August 2020, by Brian Koberlein The most studied star orbiting SgrA* is known as S2. It is a bright, blue giant star that orbits the black hole every 16 years. In 2018, S2 made its closest approach to the black hole, giving us a chance to observe an effect of relativity known as gravitational redshift. If you toss a ball up into the air, it slows down as it rises. If you shine a beam of light into the sky, the light doesn't slow down, but gravity does take away some of its energy. As a result, a beam of light becomes redshifted as it climbs out of a gravitational well. This effect has been observed in the lab, but S2 gave us a chance to see it in the real world. Sure enough, at the close approach, the light of S2 shifted to the red just as predicted. The distance of SgrA* stars at closest approach. Credit: Florian Peißker, et al In the center of our galaxy, hundreds of stars closely orbit a supermassive black hole. Most of these stars have large enough orbits that their motion is described by Newtonian gravity and Kepler's laws of motion. But a few orbit so closely that their orbits can only be accurately described by Einstein's theory of general relativity. The star A simulation of how S2 moves so fast that it’s redshifted. with the smallest orbit is known as S62. Its closest Credit: ESO/M.
    [Show full text]
  • Arxiv:2008.04764V1 [Astro-Ph.GA] 11 Aug 2020
    Draft version August 12, 2020 Typeset using LATEX twocolumn style in AASTeX63 S62 and S4711: Indications of a population of faint fast moving stars inside the S2 orbit S4711 on a 7.6 year orbit around Sgr A* Florian Peiβker ,1 Andreas Eckart ,1, 2 Michal Zajacekˇ ,3, 1 Basel Ali,1 and Marzieh Parsa1 1I.Physikalisches Institut der Universit¨atzu K¨oln, Z¨ulpicherStr. 77, 50937 K¨oln,Germany 2Max-Plank-Institut f¨urRadioastronomie, Auf dem H¨ugel69, 53121 Bonn, Germany 3Center for Theoretical Physics, Al. Lotnikw 32/46, 02-668 Warsaw, Poland (Received June 1, 2019; Revised January 10, 2019; Accepted August 12, 2020) Submitted to ApJ ABSTRACT We present high-pass filtered NACO and SINFONI images of the newly discovered stars S4711- S4715 between 2004 and 2016. Our deep H+K-band (SINFONI) and K-band (NACO) data shows the S-cluster star S4711 on a highly eccentric trajectory around Sgr A* with an orbital period of 7.6 years and a periapse distance of 144 AU to the super massive black hole (SMBH). S4711 is hereby the star with the shortest orbital period and the smallest mean distance to the SMBH during its orbit to date. The used high-pass filtered images are based on co-added data sets to improve the signal to noise. The spectroscopic SINFONI data let us determine detailed stellar properties of S4711 like the mass and the rotational velocity. The faint S-cluster star candidates, S4712-S4715, can be observed in a projected distance to Sgr A* of at least temporarily ≤ 120 mas.
    [Show full text]
  • S62 on a 9.9 Yr Orbit Around Sgra
    Draft version February 7, 2020 Typeset using LATEX twocolumn style in AASTeX62 S62 on a 9.9-year orbit around SgrA* Florian Peiβker,1 Andreas Eckart,1, 2 and Marzieh Parsa1 1I.Physikalisches Institut der Universit¨atzu K¨oln,Z¨ulpicherStr. 77, 50937 K¨oln,Germany 2Max-Plank-Institut f¨urRadioastronomie, Auf dem H¨ugel69, 53121 Bonn, Germany (Received; Revised; Accepted) Submitted to ApJ ABSTRACT We present the Keplerian orbit of S62 around the supermassive black hole SgrA* in the center of our Galaxy. We monitor this S-star cluster member over more than a full orbit around SgrA* using the Very Large Telescope with the near-infrared instruments SINFONI and NACO. For that, we are deriving positional information from deconvolved images. We apply the Lucy Richardson algorithm to the data-sets. The NACO observations cover data of 2002 to 2018, the SINFONI data a range between 2008 and 2012. S62 can be traced reliably in both data-sets. Additionally, we adapt one KECK data-point for 2019 that supports the re-identification of S62 after the peri-center passage of S2. With tperiod = 9:9 yr and a periapse velocity of approximately 10% of the speed of light, S62 has the shortest known stable orbit around the supermassive black hole in the center of our Galaxy to date . From the analysis, we also derive the enclosed mass from a maximum likelihood method to be 6 4:15 ± 0:6 × 10 M . Keywords: black holes | SgrA* | nuclei of galaxies | infrared 1. INTRODUCTION tions of individual stars (Eckart & Genzel 1996, 1997; With the development of better instrumentation and Ghez et al.
    [Show full text]
  • Relativistic Effects in Orbital Motion of the S-Stars at the Galactic Center
    universe Article Relativistic Effects in Orbital Motion of the S-Stars at the Galactic Center Rustam Gainutdinov 1,2,* and Yurij Baryshev 2* 1 SPb Branch of Special Astrophysical Observatory of Russian Academy of Sciences, 65 Pulkovskoye Shosse, 196140 St. Petersburg, Russia 2 Astrophysics Department, Mathematics & Mechanics Faculty, Saint Petersburg State University, 28 Universitetskiy Prospekt, 198504 St. Petersburg, Russia * Correspondence: [email protected] (R.G.); [email protected] (Y.B.) Received: 19 September 2020; Accepted: 8 October 2020; Published: 14 October 2020 Abstract: The Galactic Center star cluster, known as S-stars, is a perfect source of relativistic phenomena observations. The stars are located in the strong field of relativistic compact object Sgr A* and are moving with very high velocities at pericenters of their orbits. In this work we consider motion of several S-stars by using the Parameterized Post-Newtonian (PPN) formalism of General Relativity (GR) and Post-Newtonian (PN) equations of motion of the Feynman’s quantum-field gravity theory, where the positive energy density of the gravity field can be measured via the relativistic pericenter shift. The PPN 00 parameters b and g are constrained using the S-stars data. The positive value of the Tg component of the gravity energy–momentum tensor is confirmed for condition of S-stars motion. Keywords: Parameterized Post-Newtonian formalism; relativistic celestial mechanics; Galactic Center 1. Introduction The S-stars cluster in the Galactic Center [1–4] is a unique observable object to investigate. Once for the orbital period, the stars pass their pericenters, where they reach high velocities ( 0.01 or even 0.1 ∼ ∼ of the speed of light for the most recent discovered stars [5]) and get close to the relativistic compact object Sgr A*.
    [Show full text]
  • Detection of Faint Stars Near Sagittarius A* with GRAVITY R
    Detection of faint stars near Sagittarius A* with GRAVITY R. Abuter, A. Amorim, M. Bauböck, J.P. Berger, H. Bonnet, W. Brandner, Y. Clénet, Y. Dallilar, R. Davies, P.T. de Zeeuw, et al. To cite this version: R. Abuter, A. Amorim, M. Bauböck, J.P. Berger, H. Bonnet, et al.. Detection of faint stars near Sagit- tarius A* with GRAVITY. Astron.Astrophys., 2021, 645, pp.A127. 10.1051/0004-6361/202039544. hal-03171389 HAL Id: hal-03171389 https://hal.archives-ouvertes.fr/hal-03171389 Submitted on 17 Mar 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. A&A 645, A127 (2021) Astronomy https://doi.org/10.1051/0004-6361/202039544 & c GRAVITY Collaboration 2021 Astrophysics Detection of faint stars near Sagittarius A* with GRAVITY GRAVITY Collaboration?: R. Abuter8, A. Amorim6,12, M. Bauböck1, J. P. Berger5,8, H. Bonnet8, W. Brandner3, Y. Clénet2, Y. Dallilar1, R. Davies1, P. T. de Zeeuw10,1, J. Dexter13,1, A. Drescher1,16, F. Eisenhauer1, N. M. Förster Schreiber1, P. Garcia7,12, F. Gao1,??, E. Gendron2, R. Genzel1,11, S. Gillessen1, M. Habibi1, X. Haubois9, G. Heißel2, T.
    [Show full text]
  • The S-Star Cluster at the Center of the Milky Way⋆
    A&A 545, A70 (2012) Astronomy DOI: 10.1051/0004-6361/201219203 & c ESO 2012 Astrophysics The S-star cluster at the center of the Milky Way On the nature of diffuse NIR emission in the inner tenth of a parsec N. Sabha1,A.Eckart1,2, D. Merritt3, M. Zamaninasab2,G.Witzel1, M. García-Marín1, B. Jalali1, M. Valencia-S.1,2, S. Yazici1, R. Buchholz1, B. Shahzamanian1,2,C.Rauch1, M. Horrobin1, and C. Straubmeier1 1 I. Physikalisches Institut, Universität zu Köln, Zülpicher Str.77, 50937 Köln, Germany e-mail: [email protected] 2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany 3 Department of Physics and Center for Computational Relativity and Gravitation, Rochester Institute of Technology, Rochester, NY 14623, USA Received 9 March 2012 / Accepted 4 June 2012 ABSTRACT Sagittarius A*, the super-massive black hole at the center of the Milky Way, is surrounded by a small cluster of high velocity stars, known as the S-stars. We aim to constrain the amount and nature of stellar and dark mass associated with the cluster in the immediate vicinity of Sagittarius A*. We use near-infrared imaging to determine the Ks-band luminosity function of the S-star cluster members, and the distribution of the diffuse background emission and the stellar number density counts around the central black hole. This allows us to determine the stellar light and mass contribution expected from the faint members of the cluster. We then use post-Newtonian N-body techniques to investigate the effect of stellar perturbations on the motion of S2, as a means of detecting the number and masses of the perturbers.
    [Show full text]
  • The Fastest Star Ever Observed 17 August 2020, by Bob Yirka
    The fastest star ever observed 17 August 2020, by Bob Yirka indicate their closeness to Sagittarius A*. Prior research had identified a star called S2 as likely existing the closest to Sagittarius A*, and at its closest to the black hole, was measured to be traveling at approximately 3% of the speed of light. Then last year, the researchers with this new effort found another star that circled more closely to the black hole and therefore traveled even faster, at approximately 6.7% the speed of light. Since that time, the team has continued studying the fast- moving stars and have found five more that appear to travel even faster: S4714, S4711, S4713 and S4715. Of these, two stand out from the others—S4714 and S4711. S4711 is a blue star with an orbit shorter than S2, suggesting it might be the closest of all the stars to the black hole. And S4714 has proven to be the speediest of them all—it has a longer orbit, but its orbit is elliptical, which means it is elongated, giving it time, perhaps, to pick up more speed as it moves closer to the black hole—up to 24,000 kilometers per second, or approximately 8% of the S4711 on its orbit around Sgr A*. Credit: speed of light. The researchers suggest the stars arXiv:2008.04764 [astro-ph.GA] are good squeezar candidates, particularly S4714 and. S4711. More information: Florian Peißker et al. S62 and A team of researchers has observed the fastest S4711: Indications of a Population of Faint Fast- moving star ever recorded.
    [Show full text]