J/ApJ/931/7 Variability of Sgr A* in 2019 July (Boyce+, 2022)
Multiwavelength Variability of Sagittarius A* in 2019 July.
Boyce H., Haggard D., Witzel G., Von Fellenberg S., Willner S.P.,
Becklin E.E., Do T., Eckart A., Fazio G.G., Gurwell M.A., Hora J.L.,
Markoff S., Morris M.R., Neilsen J., Nowak M., Smith H.A., Zhang S.
<Astrophys. J., 931, 7-7 (2022)>
=2022ApJ...931....7B 2022ApJ...931....7B (SIMBAD/NED BibCode)
ADC_Keywords: Black holes ; Spectra, infrared ; Spectra, millimetric/submm ;
X-ray sources ; Spectra, radio
Keywords: Galactic center - black hole physics - accretion -
non-thermal radiation sources - supermassive black holes
Abstract:
We report a timing analysis of near-infrared (NIR), X-ray, and
submillimeter data during a 3 day coordinated campaign observing
Sagittarius A*. Data were collected at 4.5um with the Spitzer Space
Telescope, 2-8keV with the Chandra X-ray Observatory, 3-70keV with
NuSTAR, 340GHz with ALMA, and 2.2um with the GRAVITY instrument on the
Very Large Telescope Interferometer. Two dates show moderate
variability with no significant lags between the submillimeter and the
infrared at 99% confidence. A moderately bright NIR flare (FK∼15mJy)
was captured on July 18 simultaneous with an X-ray flare
(F2-10keV∼0.1counts/s) that most likely preceded bright
submillimeter flux (F_340 GHz_∼5.5Jy) by about 34_-33+14 minutes at
99% confidence. The uncertainty in this lag is dominated by the fact
that we did not observe the peak of the submillimeter emission. A
synchrotron source cooled through adiabatic expansion can describe a
rise in the submillimeter once the synchrotron self-Compton NIR and
X-ray peaks have faded. This model predicts high GHz and THz fluxes at
the time of the NIR/X-ray peak and electron densities well above those
implied from average accretion rates for Sgr A*. However, the higher
electron density postulated in this scenario would be in agreement
with the idea that 2019 was an extraordinary epoch with a heightened
accretion rate. Since the NIR and X-ray peaks can also be fit by a
nonthermal synchrotron source with lower electron densities, we cannot
rule out an unrelated chance coincidence of this bright submillimeter
flare with the NIR/X-ray emission.
Description:
We present simultaneous submillimeter, IR, and X-ray light curves of
Sgr A* from 2019 July. The NuSTAR 3-70keV, Chandra 2-8keV, GRAVITY
2.2um, Spitzer 4.5um, and ALMA 340GHz data shown in Figure 1 of the
paper are given here. The Spitzer data at 4.5 micron are the excess
flux density (mJy) of the pixel containing Sgr A* (see Section 2.1 of
Witzel et al., 2011A&A...525A.130W 2011A&A...525A.130W), dereddened with the extinction
A_Ks=2.42±0.002 from Fritz et al. (2011ApJ...737...73F 2011ApJ...737...73F, Cat.
J/ApJ/737/73). Two flux columns are given, one with the 6.4-s BCD
coadds, and a column with the data binned over 3.5 minutes. Gray
regions shown in the figure on July 21 and 26 indicate where the light
curve is unreliable due to a decreased signal-to-noise ratio. The
GRAVITY light curve was dereddened assuming a K-band extinction of
2.42±0.01mag. The ALMA flux densities have a 1-sigma uncertainty of
0.25Jy.
Objects:
------------------------------------------------
RA (2000) DE Designation(s)
------------------------------------------------
17 45 40.036 -29 00 28.17 Sgr A* = NAME Sgr A*
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
0718alma.dat 41 196 ALMA data for 2019/07/18-19
0718chan.dat 24 191 Chandra data for 2019/07/18-19
0718grav.dat 26 39 GRAVITY data for 2019/07/18-19
0718nust.dat 27 107 NuSTAR data for 2019/07/18-19
0718sptz.dat 33 6856 Spitzer/IRAC data for 2019/07/18-19
0721alma.dat 41 188 ALMA data for 2019/07/21
0721chan.dat 24 192 Chandra data for 2019/07/21
0721sptz.dat 33 6856 Spitzer/IRAC data for 2019/07/21
0726alma.dat 41 196 ALMA data for 2019/07/26
0726chan.dat 24 192 Chandra data for 2019/07/26
0726sptz.dat 33 6856 Spitzer/IRAC data for 2019/07/26
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See also:
J/ApJ/755/90 : [NeII] emission line observations from SgrA West
(Irons+, 2012)
J/MNRAS/428/2731 : SgrA* emission at 7mm (Beaklini+, 2013)
J/A+A/582/A118 : OH-streamer in SgrA at 1665 and 1667MHz (Karlsson+, 2015)
J/ApJ/820/90 : 4yr 1.3mm VLBI observations of SgrA* with EHT (Fish+, 2016)
J/A+A/618/A35 : ALMA images of the CND and SgrA* (Goicoechea+, 2018)
J/A+A/618/L10 : SgrA* orbital motions with GRAVITY
(GRAVITY Collaboration, 2018)
J/ApJ/863/15 : Spitzer, VLT and Keck NIR light curves of SgrA*
(Witzel+, 2018)
J/A+A/621/A119 : SgrA* and NRAS530 86GHz images (Brinkerink+, 2019)
Byte-by-byte Description of file: 0718alma.dat 0721alma.dat 0726alma.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 min Minutes Minutes since first observation in series
11- 21 F11.5 d MJD Modified Julian Date
23- 33 F11.5 d BMJD Barycentric Modified Julian Date
35- 41 F7.5 Jy Flux ALMA 340GHz Sgr A* flux density
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Byte-by-byte Description of file: 0718chan.dat 0721chan.dat 0726chan.dat
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Bytes Format Units Label Explanations
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1- 10 F10.4 d BMJD Barycentric Modified Julian Date
12- 17 F6.4 ct/s Flux Chandra 2-8keV Sgr A* flux in counts/s
19- 24 F6.4 ct/s e_Flux Sgr A* flux uncertainty in counts/s
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Byte-by-byte Description of file: 0718grav.dat
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Bytes Format Units Label Explanations
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1- 11 F11.5 d BMJD Barycentric Modified Julian Date
13- 19 F7.4 mJy Flux GRAVITY 2.2um Sgr A* flux density
21- 26 F6.4 mJy e_Flux Sgr A* flux density uncertainty
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Byte-by-byte Description of file: 0718nust.dat
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Bytes Format Units Label Explanations
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1- 13 F13.7 d BMJD Barycentric Modified Julian Date
15- 20 F6.4 ct/s Flux NuSTAR 3-70keV Sgr A* flux in counts/s
22- 27 F6.4 ct/s e_Flux Sgr A* flux uncertainty in counts/s
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Byte-by-byte Description of file: 0718sptz.dat 0721sptz.dat 0726sptz.dat
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Bytes Format Units Label Explanations
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1- 13 F13.7 d BMJD Barycentric Modified Julian Date
15- 23 F9.6 Jy FluxE Spitzer 4.5um Sgr A* excess flux density
25- 33 F9.6 Jy Flux3.5 Spitzer 4.5um Flux density binned over
3.5 minute interval
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Acknowledgements:
Joseph L. Hora, jhora(at)cfa.harvard.edu
(End) Patricia Vannier [CDS] 01-Aug-2022