J/A+A/703/A177 SN 2024bch light curves and spectra (Tartaglia+, 2025)
Signatures of anti-social mass-loss in the ordinary Type II SN 2024bch.
A non-interacting supernova with early high-ionisation features.
Tartaglia L., Valerin G., Pastorello A., Reguitti A., Benetti S.,
Tomasella L., Ochner P., Brocato E., Condo L., De Luise F., Onori F.,
Salmaso I.
<Astron. Astrophys. 703, A177 (2025)>
=2025A&A...703A.177T 2025A&A...703A.177T (SIMBAD/NED BibCode)
ADC_Keywords: Supernovae ; Photometry ; Optical ; Ultraviolet ;
Spectra, optical ; Spectra, infrared
Keywords: circumstellar matter - supernovae: general -
supernovae: individual: SN 2024bch
Abstract:
In this paper we analyse the spectro-photometric properties of the
Type II supernova SN 2024bch, exploded in NGC 3206 at a distance of
19.9Mpc. Its early spectra are characterised by narrow high-ionisation
emission lines, often interpreted as signatures of ongoing interaction
between rapidly expanding ejecta and a confined dense circumstellar
medium.
However, we provide a model for the bolometric light curve of the
transient that does not require sources of energy different than
radioactive decays and H recombination. Our model can reproduce the
bolometric light curve of SN 2024bch adopting an ejected mass of
Mbulk~+5M☉ surrounded by an extended envelope of only
0.2M☉ with an outer radius Renv=7.0x1013cm.
An accurate modelling focused on the radioactive part of the light
curve, which accounts for incomplete gamma-ray trapping, gives a
56Ni mass of 0.048M☉. We propose narrow lines to be powered by
Bowen fluorescence induced by scattering of HeII Ly-alpha photons,
resulting in the emission of high-ionisation resonance lines. Simple
light travel time calculations based on the maximum phase of the
narrow emission lines place the inner radius of the H-rich, un-shocked
shell at a radius ~=4.4x1015cm$, compatible with an absence of
ejecta-CSM interaction during the first weeks of evolution.
Possible signatures of interaction appear only ∼69-days after
explosion, although the resulting conversion of kinetic energy into
radiation does not seem to contribute significantly to the total
luminosity of the transient.
Description:
The follow-up campaign of SN 2024bch started soon after discovery
(corresponding to 2024 January 29.29 UT; Wiggins, 2024, Transient Name
Server Discovery Report, 2024-281, 1), with early photometry obtained
on 2024 January 29.92 UT and low-resolution spectroscopy on 2024
January 29.95 UT. Optical observations were mostly carried out with
facilities of the INAF - Osservatorio Astronomico di Padova (i.e., the
1.82m Copernico with the Asiago Faint Object Spectrograph and Camera -
AFOSC - and the 69/92cm Schmidt with a G4-16000LC Moravian camera,
both located in Asiago). Additional ugriz photometry were provided by
the Wide-field Optical Telescope (WOT), a 67/91cm Schmidt telescope
equipped with an Apogee Aspen CG16M camera located at the Campo
Imperatore observatory in l'Aquila (Italy).
Photometric table of SN 2024bch, including UV and optical light curves
studied in the paper.
Ekar182+AFOSC, T122+B&C and TNG+DOLoRes Spectra.
Objects:
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RA (2000) DE Designation(s)
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10 21 49.74 +56 55 40.5 SN 2024bch = SN 2024bch
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
lc.dat 62 351 UV+optical light curves of SN 2024bch
(Figures 2, 7, 8 and 11)
bol.dat 37 40 Parameters of the blackbody fit to the SED
(table 3)
list.dat 159 16 List of fits spectra
fits/* . 16 Individual fits spectra
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Byte-by-byte Description of file: lc.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "date" Date UT date of observation (YYYY/MM/DD)
12- 22 F11.5 d MJD Modified Julian Date of the observation
24- 27 A4 --- Filter Filter (BV UsBsVs ugriz UVM2 UVW1 UVW2)
29- 32 A4 --- System [ab vega] Photometric system of the calibration
34 A1 --- l_mag Limit flag on mag
36- 41 F6.3 mag mag Magnitude in Filter
43- 47 A5 mag e_mag Error on mag in Filter
49- 62 A14 --- Inst Telescope and instrument used
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Byte-by-byte Description of file: bol.dat
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Bytes Format Units Label Explanations
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1- 5 F5.1 d Phase Days from explosion (JD-2460338.0)
7- 11 I5 K Temp Temperature of the blackbody
13- 14 I2 K e_Temp Error on temp
16- 21 F6.3 10+14cm Rad Radius of the blackbody
23- 27 F5.3 10+14cm e_Rad Error on rad
29- 32 F4.2 10+35W Lum Bolometric luminosity (in 10+42erg/s)
34- 37 F4.2 10+35W e_Lum Error on lum (in 10+42erg/s)
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (J2000)
4- 5 I2 min RAm Right ascension (J2000)
7- 11 F5.2 s RAs Right ascension (J2000)
12 A1 --- DE- Declination sign (J2000)
13- 14 I2 deg DEd Declination (J2000)
16- 17 I2 arcmin DEm Declination (J2000)
19- 22 F4.1 arcsec DEs Declination (J2000)
24- 27 I4 --- Nx Number of pixels along X-axis
29 I1 --- Ny ? Number of pixels along Y-axis
31- 53 A23 "datime" Obs.date Observation date
55- 61 F7.2 0.1nm blambda Lower value of wavelength interval
63- 70 F8.2 0.1nm Blambda Upper value of wavelength interval
72- 79 F8.6 0.1nm dlambda Wavelength resolution
81- 82 I2 Kibyte size Size of FITS file
84-159 A76 --- FileName Name of FITS file, in subdirectory fits
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Acknowledgements:
Leonardo Tartaglia, leonardo.tartaglia(at)inaf.it
(End) Patricia Vannier [CDS] 16-Sep-2025