J/ApJS/278/36 ATCA obs. of eROSITA tidal disruption events (Goodwin+, 2025)
A systematic analysis of the radio properties of 22 X-ray-selected tidal
disruption event candidates with the Australia Telescope Compact Array.
Goodwin A.J., Burn M., Anderson G.E., Miller-Jones J.C.A., Grotova I.,
Baldini P., Liu Z., Malyali A., Rau A., Salvato M.
<Astrophys. J. Suppl. Ser., 278, 36 (2025)>
=2025ApJS..278...36G 2025ApJS..278...36G
ADC_Keywords: Transient; X-ray sources; Radio continuum
Keywords: Radio continuum emission ; Black hole physics ; Accretion ;
Tidal disruption
Abstract:
We present a systematic analysis of the radio properties of an
X-ray-selected sample of tidal disruption event (TDE) candidates
discovered by the eROSITA telescope. We find radio sources coincident
with half of the transient events (11 TDEs), with eight radio sources
showing statistically significant variability over a 6 month period.
We model the radio spectra of six sources with sufficiently bright
radio emission and find the sources show radio spectra consistent with
optically thin synchrotron emission and radio outflow minimum radii of
1016-1017cm, velocities 0.01c-0.05c, and energies 1048-1051erg.
On comparison with the radio properties of an optically selected TDE
sample at similar late times, we find no significant difference in the
radio luminosity range or radio detection rate. We find a tentative
positive trend with peak radio and X-ray luminosity, but require
further observations to determine if this is real or due to
observational bias due to the large range in distances of the events.
Interestingly, none of the X-ray-selected events show late-rising
radio emission, compared to 45% of radio-detected sources of an
optically selected sample that showed late-rising radio emission. We
propose that this may indicate that many TDEs launch radio outflows at
or near peak X-ray luminosity, which can be significantly delayed from
peak optical luminosity. This study presents the first systematic
analysis of the radio properties of an X-ray-selected sample of TDEs,
and gives insight into the possible link between the physical
processes that power X-ray and radio emission in TDEs.
Description:
The eROSITA sample of tidal disruption event (TDE) candidates we
followed up was identified through systematically searching eRO-ExTra,
a catalog of non-AGN extragalactic transients and variables from
eRASS1 and eRASS2 (Grotova+ 2025A&A...697A.159G 2025A&A...697A.159G).
In this work, we subselected the TDE candidates for sources that are
visible to the Australia Telescope Compact Array (ATCA; decl.<15°
and not -4°<decl.<4°), that had a redshift measurement
available at the time the sample selection was carried out, and were
associated with a nearby host galaxy at z<0.35. This selection
resulted in 22 TDE candidates in our sample for which we obtained
dedicated ATCA radio follow-up observations.
See Section 2.
In order to search for transient radio emission associated with the
X-ray flares, we observed the coordinates of each TDE candidate in the
sample a minimum of two times with ATCA. The two observations of each
source were spaced approximately 6 months apart. Five sources were
observed between 2022 October and 2023 June (ATCA program C3513; PI
Goodwin) and 15 sources were observed between 2024 April and October
(ATCA program C3513; PI Goodwin).
The remaining two sources in the sample (eRASSt J234403-352641 and
eRASSt J164649-692539) were observed via a separate triggered ATCA
program (program C3334; PI: Goodwin) in an independent study.
All sources were observed using the 4cm observing band with the dual
5.5 and 9GHz receivers with 2GHz of bandwidth at each frequency
divided into 2048 spectral channels. Additionally, some sources were
observed in the 2.1GHz observing band with 2GHz of bandwidth divided
into 2048 spectral channels.
See Section 3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 66 22 The eROSITA TDE candidates in our sample
table2.dat 55 139 ATCA radio observations of each of the 22 TDE
candidates in our sample
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See also:
J/A+A/356/445 : ROSAT-FIRST AGN correlation (Brinkmann+, 2000)
J/ApJS/133/77 : VLA radio continuum survey of Seyfert galaxies (Ho+, 2001)
J/ApJ/716/30 : SED of Fermi bright blazars (Abdo+, 2010)
J/A+A/672/A167 : eRASSt J234402.9-352640 optical photometry (Homan+, 2023)
J/other/PASA/41.3 : Rapid ASKAP Cont. Survey. V. 1367.5MHz (Duchesne+, 2024)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- --- [eRASSt]
8- 23 A16 --- eRASSt Source name
25- 35 F11.7 deg RAdeg [18.6/356.1] Right ascension (J2000)
37- 48 F12.8 deg DEdeg [-84.4/19.5] Declination (J2000)
50- 54 F5.3 --- z [0.017/0.33] Redshift
56- 59 F4.2 --- e_z [0.02/0.09]? Lower uncertainty on z
61- 64 F4.2 --- E_z [0.06/0.23]? Upper uncertainty on z
66 A1 --- f_z Flag on z (1)
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Note (1): Flag as follows:
a = Photometric redshift, see Grotova+ (2025A&A...697A.159G 2025A&A...697A.159G) for
a discussion on how this was calculated.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- --- [eRASSt]
8- 23 A16 --- eRASSt Source name
25- 28 I4 yr Obs.Y [2022/2024] Year of the epoch observation
30- 31 I2 "month" Obs.M [4/12] Month of the epoch observation
33- 34 I2 d Obs.D [1/30] Day of the epoch observation
36- 39 I4 d Deltat [668/1720] Time from peak eROSITA X-ray
flux measurement
41- 43 F3.1 GHz Freq [2.1/9.5] Frequency
45- 45 A1 --- l_Flux Limit flag on Flux
46- 52 F7.2 uJy Flux [29/1047] Flux density at Freq
54- 55 I2 uJy e_Flux [5/62]? Uncertainty in Flux
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 18-Feb-2026