ar X iv : a st ro - p h / 05 03 52 7 v 3 1 2 O ct 2 00 5 Simultaneous Multi - Wavelength Observations of Sgr A *
نویسندگان
چکیده
We observed Sgr A* using the Very Large Array (VLA) and the Giant Metrewave Radio Telescope (GMRT) at multiple cm and mm wavelengths on 17 June 2003. The measured flux densities of Sgr A*, together with those obtained from the Submillimeter Array (SMA) and the Keck II 10 m telescope on the same date, are used to construct a simultaneous spectrum of Sgr A* from 90 cm to 3.8 μm. The simultaneous spectrum shows a spectral break at about 3.6 cm, a possible signature of synchrotron self-absorption of the strong radio outburst which occurred near epoch 17 July 2003. At 90 cm, the flux density of Sgr A* is 0.22± 0.06 Jy, suggesting a sharp decrease in flux density at wavelengths longer than 47 cm. The spectrum at long cm wavelengths appears to be consistent with free-free absorption by a screen of ionized gas with a cutoff ∼100 cm. This cutoff wavelength appears to be three times longer than that of ∼30 cm suggested by Davies, Walsh & Booth based on observations in 1974 and 1975. Our analysis suggests that the flux densities of Sgr A* at wavelengths longer than 30 cm could be attenuated and modulated by stellar winds from massive stars close to Sgr A*. Subject headings: Galaxy: center — radio continuum; galaxies — accretion — black hole physics
منابع مشابه
ar X iv : a st ro - p h / 01 03 44 4 v 1 2 7 M ar 2 00 1 From Centimeter to Millimeter Wavelengths : A High Angular Resolution Study of 3 C 273
We monitored 3C 273 with VLBI at 15–86 GHz since 1990. We discuss component trajectories, opacity effects, a rotating jet, and outburst-ejection relations from Gamma-ray to radio bands.
متن کاملar X iv : a st ro - p h / 05 03 28 0 v 1 1 1 M ar 2 00 5 A VARIABLE INFRARED COUNTERPART TO THE SOFT GAMMA - RAY REPEATER SGR 1806 – 20 1
We present K -band (2.12 μm) imaging observations of the SGR 1806–20 field taken during its very active phase in mid 2004, which reveal brightening of sources within the Chandra X-ray error circle when compared with earlier images obtained in 2002. One source brightened by more than a factor of 2, and so we consider this to be the probable infrared counterpart for SGR 1806–20. The other two sou...
متن کاملar X iv : a st ro - p h / 02 01 09 3 v 1 7 J an 2 00 2 Mid - infrared observations of the SGR 1900 + 14 error box
We report on mid-infrared observations of the compact stellar cluster located in the proximity of SGR 1900+14, and the radio/X-ray position of this soft-gamma repeater. Observations were performed in May and June of 2001 when the bursting source was in an active state. At the known radio and X-ray position of the SGR we did not detect transient mid-IR activity, although the observations were pe...
متن کاملar X iv : a st ro - p h / 05 12 61 7 v 1 2 7 D ec 2 00 5 3 D Spectroscopy of Herbig - Haro objects
متن کامل
ar X iv : a st ro - p h / 05 05 55 5 v 1 2 7 M ay 2 00 5 Pulsars as Tools for Fundamental Physics & Astrophysics
X iv :a st ro -p h/ 05 05 55 5v 1 2 7 M ay 2 00 5 Pulsars as Tools for Fundamental Physics & Astrophysics J. M. Cordes, M. Kramer, T. J. W. Lazio , B. W. Stappers, D. C. Backer, S. Johnston Department of Astronomy and NAIC, Cornell University, Ithaca, NY USA University of Manchester, Jodrell Bank Observatory, Jodrell Bank, UK Naval Research Laboratory, Remote Sensing Division, Washington, DC US...
متن کامل