Variable Infrared Emission from the Supermassive Black Hole at the Center of the Milky Way

By A. Ghez, S. Wright, K. Matthews, D. Thompson, D. L. Mignant, A. Tanner, S. Hornstein, Mark R. Morris, E. Becklin, B. Ucla and 2 more. 2003

225 citations recorded by the source corpus.

We report the detection of a variable point source, imaged at L′ (3.8 μm) with the Keck II 10 m telescope's adaptive optics system, that is coincident to within 18 mas (1 σ) of the Galaxy's central supermassive black hole and the unique radio source Sgr A*. While in 2002 this source (Sgr A* IR) was confused with the stellar source S0-2, in 2003 these two sources are separated by 87 mas, allowing the new source's properties to be determined directly. On four separate nights, its observed L′ magnitude ranges from 12.2 to 13.8, which corresponds to a dereddened flux density of 4-17 mJy; no other source in this region shows such large variations in flux density—a factor of 4 over a week and a factor of 2 over 40 minutes. In addition, it has a K-L′ color greater than 2.1, which is at least 1 mag redder than any other source detected at L′ in its vicinity. Based on this source's coincidence with the Galaxy's dynamical center, its lack of motion, its variability, and its red color, we conclude that it is associated with the central supermassive black hole. The short timescale for the 3.8 μm flux density variations implies that the emission arises quite close to the black hole, within 5 AU, or 80Rs. We suggest that both the variable 3.8 μm emission and the X-ray flares arise from the same underlying physical process, possibly the acceleration of a small population of electrons to ultrarelativistic energies. In contrast to the X-ray flares, which are only detectable ~2% of the time, the 3.8 μm emission provides a new, constantly accessible window into the physical conditions of the plasma in close proximity to the central black hole.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/3c0eda6c48a6fa3b58c07d6e834355b98c0f6b85

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Ramesh Narayan
2. T. Johannsen
3. T. Alexander
4. F. Yuan
5. J. McKinney
6. J. Dexter
7. R. Genzel
8. Abraham Loeb

In Nuclear and High Energy Physics

1. Ramesh Narayan
2. F. Yuan
3. J. Dexter
4. J. McKinney
5. T. Johannsen
6. Abraham Loeb
7. A. Broderick
8. A. Tchekhovskoy

Citations in the corpus

• Imaging optically-thin hotspots near the black hole horizon of Sgr A* at radio and near-infrared wavelengths (2005, background): “However, observations of near-infrared (NIR) and X-ray flaring of Sgr A∗ have implied that the inner regions of the accretion flow are non-uniform (Baganoff et al. 2001; Genzel et al. 2003; Goldwurm et al. 2003; Eckart et al. 2004; Ghez et al. 2004).”
• Polarimetry of near-infrared flares from Sagittarius A* (2006, background): “In July 2005 six and June 2004 four polarization angles could thus be observed in rapid sequence within less than 3.5 min which is short compared to the typical time scales expected for flares (Eckart et al. 2004; Genzel et al. 2003a; Ghez et al. 2004; Eckart et al. 2006).”
• Hot Accretion Flows Around Black Holes (2014, background): “4.1.3 Multiwaveband flares Flares have been observed in Sgr A* in many wavebands, but are strongest in X-rays (Baganoff et al. 2001) and infrared (Genzel et al. 2003, Ghez et al. 2004, Gillessen et al. 2006), where the flux can increase by up to a factor of 100 and 5, respectively.”
• DISCOVERY OF A SUPERLUMINAL Fe K ECHO AT THE GALACTIC CENTER: THE GLORIOUS PAST OF Sgr A* PRESERVED BY MOLECULAR CLOUDS (2010, background): “Although Sgr A* is known to display flares in X-rays (Baganoff et al. 2001; Goldwurm et al. 2003) and near-infrared (Genzel et al. 2003; Ghez et al. 2004), during which the X-ray intensity increases by factors up to 160 (Porquet et al. 2003) from the quiescent value, the bolometric luminosity still…”
• Stellar Orbits around the Galactic Center Black Hole (2003, background): “…note that after submission of this paper, a variable source coincident with Sgr A* was detected at near-infrared wavelengths (Genzel et al. 2003a; Ghez et al. 2004); its characteristics are consistent with our nondetection of a steady source brighter than 15.5 mag. stars effectively represent an…”
• First simultaneous NIR/X-ray detection of a flare from Sgr A (2004, background): “…at X-ray (Baganoff et al. 2001, 2003; Porquet et al. 2003; Goldwurm et al. 2003, Eckart et al. 2003) than at IR wavelengths (Genzel et al. 2003, Ghez et al. 2004), so that the spectral index could be smaller than aboutαX/NIR≤1.0 if we simply take the most extreme fluxes so far measured atboth…”
• Imaging bright-spots in the accretion flow near the black hole horizon of Sgr A* (2005, background): “…and X-ray bands revealed flaring activity on short time-scales (Baganoff et al. 2001; Genzel et al. 2003; Goldwurm et al. 2003; Porquet et al. 2003; Aschenbach et al. 2004; Eckart et al. 2004; Ghez et al. 2004), indicating strong inhomogeneities in the emission close to the black hole horizon.”
• An X-Ray, Infrared, and Submillimeter Flare of Sagittarius A* (2007, background): “Since the discovery of X-ray and IR flares in Sgr A* (Baganoff et al. 2001; Genzel et al. 2003; Ghez et al. 2004), transient events have been studied extensively.”
• Peering through the veil: near-infrared photometry and extinction for the Galactic nuclear star cluster (2009, methodology): “These extinction values are different from the ones that have typically been used in the analysis of NIR lightcurves from Sgr A*, e.g., AH = 4.3, AK = 2.8, AL′ = 1.8 (Genzel et al. 2003; Eckart et al. 2006), AK = 3.3 (Do et al. 2009b), or AL′ = 1.8 (Ghez et al. 2004).”
• SINFONI in the Galactic Center: Young Stars and Infrared Flares in the Central Light-Month (2005, background): “The infrared flares probably come from hot or relativistic gaswithin a few times the event horizon (Genzel et al. 2003a; Ghez et al. 2004; Yuan et al. 2002, 2003, 2004; Liu et al. 2004).”
• Measuring Distance and Properties of the Milky Way’s Central Supermassive Black Hole with Stellar Orbits (2008, methodology): “…of the dynamical center from S0-2’s orbit is statistically consistent with Sgr A Yradio/ IR, which is the emissive source associated with the central black hole (e.g., Melia & Falcke 2001; Genzel et al. 2003a; Ghez et al. 2004; 2005b; Hornstein et al. 2007), the solution from S0-16 is not (see Fig.”
• Flaring Activity of Sagittarius A* at 43 and 22 GHz: Evidence for Expanding Hot Plasma (2006, background): “Stellar orbit measurements have shown a mass 3-4 ×106 M⊙ coincident within 45 AU of Sgr A*, and have created a much better picture of this object since its discovery more than 30 years ago (Balick & Brown 1974; Schödel et al. 2002; Ghez et al. 2004).”
• THE SUBMILLIMETER BUMP IN Sgr A* FROM RELATIVISTIC MHD SIMULATIONS (2010, background): “Sgr A* is moderately variable in the radio and millimeter (Zhao et al. 2003; Eckart et al. 2008; Marrone et al. 2008; Li et al. 2009; Yusef-Zadeh et al. 2009) with order of magnitude flares in the IR and X-ray (Baganoff et al. 2001; Genzel et al. 2003; Ghez et al. 2004).”
• DETECTING FLARING STRUCTURES IN SAGITTARIUS A* WITH HIGH-FREQUENCY VLBI (2008, background): “…of minutes to hours in the radio, millimeter, NIR, and X-ray bands (e.g., Baganoff et al. 2001; Aschenbach et al. 2004; Genzel et al. 2003; Ghez et al. 2004; Bélanger et al. 2006; Meyer et al. 2006; Yusef-Zadeh et al. 2006; Marrone et al. 2006; Hornstein et al. 2007), and flare rise…”