J/A+A/704/A143 Gamma-ray emitting region location in 4C +01.28 (Roesch+, 2025)
Pinpointing the location of the gamma-ray emitting region in the FSRQ 4C +01.28.
Roesch F., Kadler M., Ros E., Ricci L., Gurwell M.A., Hovatta T.,
MacDonald N.R., Readhead A.C.S.
<Astron. Astrophys. 704, A143 (2025)>
=2025A&A...704A.143R 2025A&A...704A.143R (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Radio sources ; Gamma rays
Keywords: galaxies: active - galaxies: jets - gamma rays: galaxies -
quasars: individual: 4C +01.28
Abstract:
The flat-spectrum radio quasar (FSRQ) 4C +01.28 is a bright and highly
variable radio and gamma-ray emitter. We aim to pinpoint the location
of the gamma-ray emitting region within its jet in order to derive
strong constraints on gamma-ray emission models for blazar jets.
We use radio and gamma-ray monitoring data obtained with the Atacama
Large Millimeter/submillimeter Array (ALMA), the Owens Valley Radio
Observatory (OVRO), the Submillimeter Array (SMA) and the Large Area
Telescope on board the Fermi Gamma-ray Space Telescope (Fermi/LAT) to
study the cross-correlation between gamma-ray and multi-frequency
radio light curves. Moreover, we employ Very Long Baseline Array
(VLBA) observations at 43GHz over a period of around nine years to
study the parsec-scale jet kinematics of 4C +01.28. To pinpoint the
location of the gamma-ray emitting region, we use a model in which
outbursts shown in the gamma-ray and radio light curves are produced
when moving jet components pass through the gamma-ray emitting and the
radio core regions.
We find two bright and compact newly ejected jet components that are
likely associated with a high activity period visible in the Fermi/LAT
gamma-ray and different radio light curves. The kinematic analysis of
the VLBA observations leads to a maximum apparent jet speed of
betaapp=19±10 and an upper limit on the viewing angle of phi<4deg.
Furthermore, we determine the power law indices that are
characterizing the jet geometry, brightness temperature distribution
and core shift to be l=0.974±0.098, s=-3.31±0.31 and
kr=1.09±0.17, respectively, which are all in agreement with a
conical jet in equipartition. A cross-correlation analysis shows that
the radio light curves follow the gamma-ray light curve. We pinpoint
the location of the gamma-ray emitting region with respect to the jet
base to the range of 2.6pc<dgamma<20pc.
Our derived observational limits places the location of gamma-ray
production in 4C +01.28 beyond the expected extent of the broad-line
region (BLR) and therefore challenges blazar-emission models that rely
on inverse Compton up-scattering of seed photons from the BLR.
Description:
The images of 4C +01.28 presented here were observed with the VLBA at
43GHz as part of the Boston University (BU) Blazar Monitoring Program
BEAM-ME (http://www.bu.edu/blazars/BEAM-ME.html). To study the time
evolution of the parsec-scale jet structure of 4C +01.28, we fitted
the fully calibrated visibility data of 51 epochs with 2D Gaussian
components using the MODELFIT task within DIFMAP. Here, we present the
parameters of these Gaussian components.
Objects:
-------------------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------------------
10 58 29.60 +01 33 58.8 4C +01.28 = QSO J1058+0133
-------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablec2.dat 77 192 MODELFIT parameters of the fitted Gaussian jet
components
list.dat 220 51 List of fits images (Figs. 1, B1 and B2)
fits/* . 51 Individual fits images
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See also:
J/ApJS/260/12 : Jet kinematics of blazars at 43GHz with 10yrs obs.
(Weaver+, 2022)
Byte-by-byte Description of file: tablec2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "date" Date UTC observation date
12- 16 A5 --- ID Identification of the components (1)
20- 25 F6.3 mas oRA Right ascension relative to the phase center
27- 32 F6.3 mas oDE Declination relative to the phase center
34 A1 --- l_MajAxis Upper limit flag on MajAxis
35- 39 F5.3 mas MajAxis FWHM of the major axis of the components (2)
42 A1 --- l_MinAxis Upper limit flag on MinAxis
43- 47 F5.3 mas MinAxis FWHM of the minor axis of the components (2)
50- 55 F6.1 deg PA [] Position angle of the components
(north through east)
57- 61 F5.3 Jy S Flux density of the components at 43GHz (3)
63 A1 --- l_Tb Lower limit flag on Tb
64- 77 I14 K Tb Brightness temperature of the components (4)
--------------------------------------------------------------------------------
Note (1): ID code as follows:
C = core component
S1 = first stationary jet component
S2 = second stationary jet component
J1 = first moving jet component
J2 = second moving jet component
J3 = third moving jet component
J4 = fourth moving jet component
J5 = fifth moving jet component
If two IDs are given, the first ID corresponds to kinematic model 1 and the
second one to kinematic model
Note (2): Relative uncertainties of 20% are assumed. For unresolved axes, the
corresponding resolution limit is given as an upper limit.
Note (3): Relative uncertainties of 5% are assumed.
Note (4): Relative uncertainties of 29% are assumed. For unresolved components,
their brightness temperature was calculated using the resolution limits of the
corresponding unresolved axes and is therefore given as an lower limit.
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Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 37 A10 "datime" Obs.date Observation date
39- 49 E11.6 Hz Freq Observed frequency
51- 55 I5 Kibyte size Size of FITS file
57- 88 A32 --- FileName Name of FITS file, in subdirectory fits
90-220 A131 --- Title Title of the FITS file
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Acknowledgements:
Florian Roesch, florian.roesch(at)uni-wuerzburg.de
(End) Patricia Vannier [CDS] 03-Oct-2025