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Fazio GG, Hora JL, Witzel G, Willner SP, Ashby MLN, Baganoff F, Becklin E, Carey S, Haggard D, Gammie C, Ghez A, Gurwell MA, Ingalls J, Marrone D, Morris MR, Smith HA. Multiwavelength Light Curves of Two Remarkable Sagittarius A* Flares. Astrophys J 2019; 864:58. [PMID: 32801381 PMCID: PMC7422726 DOI: 10.3847/1538-4357/aad4a2] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Sgr A*, the supermassive black hole (SMBH) at the center of our Milky Way Galaxy, is known to be a variable source of X-ray, near-infrared (NIR), and submillimeter radiation and therefore a prime candidate to study the electromagnetic radiation generated by mass accretion flow onto a black hole and/or a related jet. Disentangling the power source and emission mechanisms of this variability is a central challenge to our understanding of accretion flows around SMBHs. Simultaneous multiwavelength observations of the flux variations and their time correlations can play an important role in obtaining a better understanding of possible emission mechanisms and their origin. This paper presents observations of two flares that both apparently violate the previously established patterns in the relative timing of submillimeter/NIR/X-ray flares from Sgr A*. One of these events provides the first evidence of coeval structure between NIR and submillimeter flux increases, while the second event is the first example of the sequence of submillimeter/X-ray/NIR flux increases all occurring within ~1 hr. Each of these two events appears to upend assumptions that have been the basis of some analytic models of flaring in Sgr A*. However, it cannot be ruled out that these events, even though unusual, were just coincidental. These observations demonstrate that we do not fully understand the origin of the multiwavelength variability of Sgr A* and show that there is a continued and important need for long-term, coordinated, and precise multiwavelength observations of Sgr A* to characterize the full range of variability behavior.
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Affiliation(s)
- G G Fazio
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-65, Cambridge, MA 02138, USA
| | - J L Hora
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-65, Cambridge, MA 02138, USA
| | - G Witzel
- University of California, Los Angeles, 475 Portola Plaza, Los Angeles, CA 90095, USA
| | - S P Willner
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-65, Cambridge, MA 02138, USA
| | - M L N Ashby
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-66, Cambridge, MA 02138, USA
| | - F Baganoff
- Massachusetts Institute of Technology, 77 Massachusetts Avenue, 37-555, Cambridge, MA 02139, USA
| | - E Becklin
- University of California, Los Angeles, Los Angeles, CA 90095-1562, USA
| | - S Carey
- California Institute of Technology, MS 314-6, Pasadena, CA 91125, USA
| | - D Haggard
- McGill University, 3600 University Street, Montreal, QC H3A 2T8, Canada
| | - C Gammie
- University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801, USA
| | - A Ghez
- University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - M A Gurwell
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-42, Cambridge, MA 02138, USA
| | - J Ingalls
- California Institute of Technology, MS 314-6, Pasadena, CA 91125, USA
| | - D Marrone
- University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
| | - M R Morris
- University of California, Los Angeles, Box 951547, Los Angeles, CA 90095-1547, USA
| | - H A Smith
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-65, Cambridge, MA 02138, USA
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Witzel G, Martinez G, Hora J, Willner SP, Morris MR, Gammie C, Becklin EE, Ashby MLN, Baganoff F, Carey S, Do T, Fazio GG, Ghez A, Glaccum WJ, Haggard D, Herrero-Illana R, Ingalls J, Narayan R, Smith HA. Variability Timescale and Spectral Index of Sgr A* in the Near Infrared: Approximate Bayesian Computation Analysis of the Variability of the Closest Supermassive Black Hole. Astrophys J 2018; 863:15. [PMID: 32855558 PMCID: PMC7449233 DOI: 10.3847/1538-4357/aace62] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Sagittarius A* (Sgr A*) is the variable radio, near-infrared (NIR), and X-ray source associated with accretion onto the Galactic center black hole. We present an analysis of the most comprehensive NIR variability data set of Sgr A* to date: eight 24 hr epochs of continuous monitoring of Sgr A* at 4.5 μm with the IRAC instrument on the Spitzer Space Telescope, 93 epochs of 2.18 μm data from Naos Conica at the Very Large Telescope, and 30 epochs of 2.12 μm data from the NIRC2 camera at the Keck Observatory, in total 94,929 measurements. A new approximate Bayesian computation method for fitting the first-order structure function extracts information beyond current fast Fourier transformation (FFT) methods of power spectral density (PSD) estimation. With a combined fit of the data of all three observatories, the characteristic coherence timescale of Sgr A* isτ b = 243 - 57 + 82 minutes (90% credible interval). The PSD has no detectable features on timescales down to 8.5 minutes (95% credible level), which is the ISCO orbital frequency for a dimensionless spin parameter a = 0.92. One light curve measured simultaneously at 2.12 and 4.5 μm during a low flux-density phase gave a spectral index α s = 1.6 ± 0.1( F ν ∝ ν - α s ) . This value implies that the Sgr A* NIR color becomes bluer during higher flux-density phases. The probability densities of flux densities of the combined data sets are best fit by log-normal distributions. Based on these distributions, the Sgr A* spectral energy distribution is consistent with synchrotron radiation from a non-thermal electron population from below 20 GHz through the NIR.
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Affiliation(s)
- G Witzel
- University of California, Los Angeles, CA, USA
| | - G Martinez
- University of California, Los Angeles, CA, USA
| | - J Hora
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - S P Willner
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - M R Morris
- University of California, Los Angeles, CA, USA
| | - C Gammie
- Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801, USA
| | - E E Becklin
- University of California, Los Angeles, CA, USA
- SOFIA Science Center, Moffett Field, CA, USA
| | - M L N Ashby
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - F Baganoff
- MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA 02139, USA
| | - S Carey
- Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA
| | - T Do
- University of California, Los Angeles, CA, USA
| | - G G Fazio
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - A Ghez
- University of California, Los Angeles, CA, USA
| | - W J Glaccum
- Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA
| | - D Haggard
- Department of Physics, McGill University, 3600 University Street, Montreal, QC H3A 2T8, Canada
- McGill Space Institute, McGill University, Montreal, QC H3A 2A7, Canada
| | - R Herrero-Illana
- European Southern Observatory (ESO), Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago de Chile, Chile
| | - J Ingalls
- Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA
| | - R Narayan
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - H A Smith
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
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Lisse CM, Vancleve J, Adams AC, A'hearn MF, Fernández YR, Farnham TL, Armus L, Grillmair CJ, Ingalls J, Belton MJS, Groussin O, McFadden LA, Meech KJ, Schultz PH, Clark BC, Feaga LM, Sunshine JM. Spitzer Spectral Observations of the Deep Impact Ejecta. Science 2006; 313:635-40. [PMID: 16840662 DOI: 10.1126/science.1124694] [Citation(s) in RCA: 260] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Spitzer Space Telescope imaging spectrometer observations of comet 9P/Tempel 1 during the Deep Impact encounter returned detailed, highly structured, 5- to 35-micrometer spectra of the ejecta. Emission signatures due to amorphous and crystalline silicates, amorphous carbon, carbonates, phyllosilicates, polycyclic aromatic hydrocarbons, water gas and ice, and sulfides were found. Good agreement is seen between the ejecta spectra and the material emitted from comet C/1995 O1 (Hale-Bopp) and the circumstellar material around the young stellar object HD100546. The atomic abundance of the observed material is consistent with solar and C1 chondritic abundances, and the dust-to-gas ratio was determined to be greater than or equal to 1.3. The presence of the observed mix of materials requires efficient methods of annealing amorphous silicates and mixing of high- and low-temperature phases over large distances in the early protosolar nebula.
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Affiliation(s)
- C M Lisse
- Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA
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