J/A+A/702/A269 BVRIgri photometry of AT 2023txn (Munari+, 2025)
AT 2023txn (= Gaia23cse): A new symbiotic star undergoing a puzzling outburst.
Munari U., Dallaporta S., Valisa P., Masetti N., Maitan A.
<Astron. Astrophys. 702, A269 (2025)>
=2025A&A...702A.269M 2025A&A...702A.269M (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, cataclysmic ; Novae ; Photometry ; Optical
Keywords: accretion, accretion disks - binaries: symbiotic -
novae, cataclysmic variables - stars: individual: AT 2023txn
Abstract:
The outburst of AT 2023txn, started in 2022 and still unfolding
through multiple maxima and deep minima which bring the system well
below quiescence brightness, has been monitored with BVRIgri
photometry, low and high resolution spectroscopy, and Swift XRT+UVOT
observations. AT 2023txn turns out to be a previously unknown
symbiotic star, harboring an M6III red giant of great photometric
stability during quiescence. A large and cold accretion disk around
the white dwarf companion provided about 3/4 of the system brightness
at blue wavelengths during quiescence, but was unable to power a
significant emission-line spectrum as implied by the observations from
the IPHAS riHalpha survey and Gaia DR3 BP-RP spectrum. The outburst
begun toward the end of 2021, passed through a first unnoticed maximum
in March 2022, and was eventually announced as transient Gaia23cse
about 19 months later in September 2023 when the object was peaking at
a second and brighter maximum. Close to that epoch we measured 1500
Lsun as the luminosity radiated by the outbursting component over the
2000-9000Å interval, with an upper limit of 1L☉ to the X-ray
luminosity over the 0.3-10keV range. The emission-line spectrum has
been characterized by persistent low ionization conditions, with FeII
and Balmer series being the dominating species and varying their
integrated flux in phase with the brightness evolution during the
outburst. Three deep minima separated by about 866 days brought the
system 1.5mag below the g-band brightness in quiescence, but they
have no counterpart prior to the start of the outburst season.
Interpreting them as eclipses of the hot component by the red giant
encounters severe difficulties, and alternative explanations are
considered in the framework of a massive accretion disk similar to
T CrB which transfers mass to the WD only episodically via a collapse
affecting the inner radii.
Description:
CCD photometry of AT 2023txn in the Landolt BVRI and SLOAN gri bands
is presented. The data are fully transformed via color equations solved
for each observation from the local instantaneous photometric system to
the Landolt standard one. The quoted uncertainties are the total error
budget, which quadratically combine the Poisson error and the error
associated with the transformation to the standard system via the
color equations (usually the dominating term). The observations have
been aquired with various ANS Collaboration telescopes and with the
Asiago 67/92cm Schmidt camera, and cover from 2023 to 2025.
The file tablea1.dat lists the B-band magnitude measured by the DASCH
project (digitization of Harvard historical photographic plates) for
the 13 plates on which a counterpart of AT 2023txn is detected, and
(to help guessing the confidence on such detections) the B-band
limiting magnitude for the closest-in-time plates bracketing each
detection.
Objects:
-------------------------------------------------
RA (2000) DE Designation(s)
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19 50 33.32 +30 28 22.4 AT 2023txn = Gaia23cse
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 91 143 BVRI photometry of AT 2023txn
tablea1.dat 54 35 AT 2023txn on Harvard historical plates
tableb1.dat 70 22 gri photometry of AT 2023txn
listsp.dat 67 21 List of spectra
fig2sp/* . 9 Individual spectra
fig3sp/* . 12 Individual normalized spectra
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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2- 15 A14 "date" Date UT heliocentric observing date (YYYY/MM/DD.ddd)
17- 27 F11.3 d HJD Heliocentric Julian day
31- 36 F6.3 mag Bmag ? B band magnitude
38- 42 F5.3 mag e_Bmag ? Error of B band magnitude
45- 50 F6.3 mag Vmag V band magnitude
52- 56 F5.3 mag e_Vmag Error of V band magnitude
59- 64 F6.3 mag Rmag ? R band magnitude
66- 70 F5.3 mag e_Rmag ? Error of R band magnitude
73- 78 F6.3 mag Imag ? I band magnitude
80- 84 F5.3 mag e_Imag ? Error of I band magnitude
88- 91 A4 --- Inst Telescope code
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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2- 15 F14.6 d HJD Heliocentric Julian day
18- 28 F11.6 --- Date UT heliocentric observing date
34- 38 F5.2 mag Bmag ? B band magnitude
43- 46 F4.2 mag e_Bmag ? Error of B band magnitude
50- 54 F5.2 mag Bmaglim Limiting B band magnitude
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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2- 15 A14 "date" Date UT heliocentric observing date (YYYY/MM/DD.ddd)
17- 27 F11.3 d HJD Heliocentric Julian day
31- 36 F6.3 mag gmag g band magnitude
38- 42 F5.3 mag e_gmag Error of B band magnitude
45- 50 F6.3 mag rmag r band magnitude
52- 56 F5.3 mag e_rmag Error of V band magnitude
59- 64 F6.3 mag imag i band magnitude
66- 70 F5.3 mag e_imag Error of R band magnitude
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Byte-by-byte Description of file: listsp.dat
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Bytes Format Units Label Explanations
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1- 25 A25 --- FileName Name of the spectrum file
27- 67 A41 --- Title Title
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Byte-by-byte Description of file (#): fig2sp/*
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Bytes Format Units Label Explanations
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2- 10 F9.4 0.1nm lambda Wavelength
12- 26 E15.7 10mW/m2/nm Flux Flux (in erg/cm2/s/Å)
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Byte-by-byte Description of file (#): fig3sp/*
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Bytes Format Units Label Explanations
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1- 16 F16.11 0.1nm lambda Wavelength
18- 32 E15.7 --- NFlux Normalized flux
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Acknowledgements:
Ulisse Munari, ulisse.munari(at)inaf.it
(End) Ulisse Munari [INAF, Padova], Patricia Vannier [CDS] 22-Aug-2025