J/A+A/710/L6 Sgr A* MeerKAT 2.79GHz light curve (Kaur+, 2026)
Variability of Sagittarius A* at 3 GHz on minute-scale with MeerKAT.
Kaur K., Rammala-Zitha I., Basu A., Witzel G., Wielgus M., Balakrishnan V.,
Barr E.D., Brunthaler A., Buchner S., Champion D.J., Hoeft M., Khan S.,
Kloeckner H.-R., Koenig C., Kramer M., Venkatraman Krishnan V., Ma Y.K.,
Mao S.A., Padmanabh P.V., Ranchod S., Sridhar S.S., Wagenveld J.D.,
Wharton R.S., Wucknitz O.
<Astron. Astrophys. 710, L6 (2026)>
=2026A&A...710L...6K 2026A&A...710L...6K (SIMBAD/NED BibCode)
ADC_Keywords: Black holes ; Radio sources ; Interferometry
Keywords: techniques: interferometric - Galaxy: centre
Abstract:
The supermassive black hole Sagittarius A* (Sgr A*) exhibits temporal
and spectral variability across the electromagnetic spectrum. However,
variability at radio frequencies below ∼5GHz for timescales
shorter than a day remains largely unexplored. We investigate the
variability of Sgr A* at 2.79GHz on short timescales (1-min), to
probe an under-explored regime of its emission process. Through
point-source model fitting in the uv-domain, we analyse the flux
density variation of Sgr A* over an 8h observation. We detect flux
variation on a few tens of minute timescale with a modulation index of
6.11%, a mean flux density of 827±0.1(stat)±33(sys)mJy, and a
mean spectral slope of 0.08±0.03. Furthermore, we measure the slope
of the structure function of the observed light curve as 0.81±0.05
with a characteristic timescale of about 120-min. Our study at low
radio frequencies is a critical step toward constraining the physical
mechanisms that drive Sgr A*'s variable emission and its spectral
energy distribution. Our study suggests that variability at centimetre
and millimetre wavelengths is likely more closely related than
previously thought.
Description:
The table presents the observational timestamps in UTC alongside the
corresponding flux density measurements in Jy derived from
point-source fitting performed in the uv-domain over a uv-range of
50000 λ to 67403.3 λ. The observations were conducted on
21 March 2024 at a central frequency of 2.79GHz using the MeerKAT
Radio Telescope. For each timestamp, the total flux density
uncertainty in Jy is reported, calculated by adding a 4% absolute flux
scale error in quadrature to the statistical uncertainty obtained from
the CASA task uvmodelfit. Additionally, the table includes the in-band
spectral index values and their uncertainties.
Objects:
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RA (2000) DE Designation(s)
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17 45 40.03 -29 00 28.1 Sgr A* = NAME Sagittarius A*
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sgralc.dat 38 360 Flux density and spectral index values of
Sagittarius A* at 2.79GHz with MeerKAT
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See also:
J/AJ/127/3399 : Sgr A* variability at cm wavelengths (Herrnstein+, 2004)
J/ApJ/793/120 : Spitzer/IRAC Sgr A* light curve data (Hora+, 2014)
J/ApJ/802/69 : VLA, ALMA and SMA monitoring of Sgr A* (Bower+, 2015)
J/MNRAS/454/1525 : XMM-Newton and Chandra monitoring of Sgr A* (Ponti+, 2015)
J/A+A/589/A116 : Multiwavelength study of Sgr A* (Mossoux+, 2016)
J/A+A/599/A135 : NH3 Odin observations towards Sgr A (Sandqvist+, 2017)
J/A+A/601/A80 : LABOCA 345GHz observations of Sgr A* (Subroweit+, 2017)
J/ApJ/859/60 : Sgr A* 1.3mm VLBI observations with EHT in 2013 (Lu+, 2018)
J/ApJ/931/7 : Variability of Sgr A* in 2019 July (Boyce+, 2022)
Byte-by-byte Description of file: sgralc.dat
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Bytes Format Units Label Explanations
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1- 9 A9 "h:m:s" Timestamp Observational timestamp in UTC on
21 March 2024
11- 16 F6.4 Jy FluxDens Flux density derived from point-source fitting
performed in the uv-domain over a UV-range
of 50000 lambda to 67403.3 lambda.
18- 23 F6.4 Jy e_FluxDens Flux Total flux density uncertainty (1)
25- 31 F7.4 --- SPI In-band spectral index
33- 38 F6.4 --- e_SPI In-band spectral index uncertainty
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Note (1): calculated by adding a 4% absolute flux scale error in quadrature to
the statistical uncertainty obtained from the CASA task uvmodelfit.
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Acknowledgements:
Kamalpreet Kaur, kkaur(at)mpifr-bonn.mpg.de
License: CC-BY-4.0
(End) Patricia Vannier [CDS] 29-Apr-2026