GRANDMA Observations of SN 2023wrk, a Luminous Type Ia Supernova with Significant Unburned Carbon in the Outer Ejecta

CRISTINA ANDRADE,<fnref n="1" /> PIERRE-ALEXANDRE DUVERNE,<fnref n="2" /> JIALIAN LIU,<fnref n="3" /> FELIPE NAVARETE,<fnref n="4" />

ABDELAZIZ E. ABDELAZIZ,<fnref n="5" /> MOHAMED ABDELKAREEM,<fnref n="5" /> ILMAH ABDI,<fnref n="6" /> MOHAMED ABOUEISHA,<fnref n="5" /> CHRISTOPHE ADAMI,<fnref n="7" />

SHABNAM AGAYEVA,<fnref n="8" /> VOVA AIVAZYAN,<fnref n="9" /> LEANDRO DE ALMEIDA,<fnref n="10" /> DALYA AKL,<fnref n="11" /> SARAH ANTIER,<fnref n="12" />

YVAN ARNAUD,<fnref n="13" /> SAAD A. ATA,<fnref n="5" /> WAGEEH A. BADAWY,<fnref n="5" /> CHUNHAI BAI,<fnref n="14" /> REDA BENDARY,<fnref n="5" />

ZOUHAIR BENKHALDOUN,<fnref n="15" /> KEVIN BORROT,<fnref n="13" /> ERIC BROENS,<fnref n="16" />,<fnref n="17" /> YONGZHI CAI,<fnref n="18" />,<fnref n="19" />,<fnref n="20" /> OLIVIER CLERGET,<fnref n="13" />

WAGNER CORRADI,<fnref n="10" /> MICHAEL W. COUGHLIN,<fnref n="21" /> NICOLAS DELAUNOY,<fnref n="13" /> FRANKY DUBOIS,<fnref n="22" />,<fnref n="16" />

JEAN-GRÉGOIRE DUCOIN,<fnref n="23" /> ESLAM ELHOSSEINY,<fnref n="5" /> THOMAS M. ESPOSITO,<fnref n="24" />,<fnref n="25" />,<fnref n="26" /> ALI ESAMDIN,<fnref n="14" /> PASCAL FOULON,<fnref n="27" />

ROLAND FOULON,<fnref n="27" /> MICHAEL FREEBERG,<fnref n="16" />,<fnref n="28" />,<fnref n="29" /> CHARLES GALDIES,³⁰ PRIYADARSHINI GOKULDASS,³¹

BRUNO GUILLET,<fnref n="13" /> GAMAL M. HAMED,<fnref n="5" /> BRUNO HAREMZA,<fnref n="13" /> PATRICE HELLO,³² YASSER HENDY,<fnref n="5" />

PATRICK HUTH,<fnref n="13" /> RAGULI INASARIDZE,<fnref n="9" /> ABDUSAMATJAN ISKANDAR,<fnref n="14" />,³³ AZIZ KAEOUACH,³⁴ TAREK M. KAMEL,<fnref n="5" />

SERGEY KARPOV,³⁵ RAYMOND KNEIP,³⁶ NINO KOCHIASHVILI,<fnref n="9" /> PETRI KUOSSARI,<fnref n="13" /> LIPING LI,<fnref n="18" />,<fnref n="19" />,<fnref n="20" /> XIN LI,³⁷

JINZHONG LIU,<fnref n="14" /> MARKUS LORBER,<fnref n="13" /> RAOUF H. MABROUK,<fnref n="5" /> DENIS MARCHAIS,³⁸ ELISABETH MARIS,<fnref n="16" />

ISABEL MÁRQUEZ,³⁹ MARTIN MAŠEK,⁴⁰ ROGER MÉNARD,<fnref n="16" /> NICOLA MENEGHELLI,<fnref n="13" /> MIKE MITCHELL,<fnref n="13" />

KANTHANAKORN NOYSENA,⁴¹ MOHAMMAD ODEH,⁴² WATARU ONO,<fnref n="13" /> GÉRARD PARENT,<fnref n="16" /> BRUCE PARKER,<fnref n="13" />

JULIEN PELOTON,⁴³ ADAM POPOWICZ,⁴⁴ THIERRY PRADIER,⁴⁵ STEPHEN PRICE,<fnref n="13" /> OLEKSANDRA PYSHNA,⁴⁶

YODGOR RAJABOV,⁴⁷ FADI SAIBI,<fnref n="13" /> SOPHIE SAIBI,<fnref n="13" /> DENIS SAINT-GELAIS,<fnref n="16" />,⁴⁸ NELIO SASAKI,<fnref n="10" />,⁴⁹

MARC SERRAU,<fnref n="16" />,⁵⁰ MASAO SHIMIZU,<fnref n="13" /> AHMED SHOKRY,<fnref n="5" /> ANDRI SIMON,⁵¹,⁵² OLEKSII SOKOLIUK,⁵³,⁵⁴

ALI TAKEY,<fnref n="5" /> MANASANUN TANASAN,⁵⁵ YUSUF TILLAYEV,⁴⁷,⁵⁶ GISEPPE DI TOMMASO,<fnref n="13" /> IARA TOSTA E MELO,⁵⁷

DAMIEN TURPIN,⁵⁸ XIAOFENG WANG,⁵⁹ ZHENYU WANG,<fnref n="18" />,<fnref n="19" />,<fnref n="20" />,⁶⁰ IBRAHIM ZEAD,<fnref n="5" /> AND JUJIA ZHANG<fnref n="18" />,<fnref n="19" />,<fnref n="20" />

<footnote n="1">¹School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA</footnote>

<footnote n="2">² Université Paris Cité, CNRS, Astroparticule et Cosmologie, F-75013 Paris, France</footnote>

<footnote n="3">³Physics Department, Tsinghua University, Beijing 100084, China</footnote>

<footnote n="4">⁴SOAR Telescope/NSF's NOIRLab Avda Juan Cisternas 1500, 1700000, La Serena, Chile</footnote>

<footnote n="5">⁵National Research Institute of Astronomy and Geophysics (NRIAG), 1 El-marsad St., 11421 Helwan, Cairo, Egypt</footnote>

<footnote n="6">⁶Physics Department, American University of Sharjah, Sharjah, UAE</footnote>

<footnote n="7">⁷Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France</footnote>

<footnote n="8">⁸N. Tusi, *Shamakhy Astrophysical Observatory, Azerbaijan*, National Academy of Sciences, settl. Y. Mammadaliyev, AZ 5626, Shamakhy, Azerbaijan</footnote>

<footnote n="9">⁹E. Kharadze, *Georgian National Astrophysical Observatory*, Mt. Kanobili, Abastumani, 0301, Adigeni, Georgia</footnote>

<footnote n="10">¹⁰Laboratório Nacional de Astrofísica, R. dos Estados Unidos, 154 - Nações, Itajubá - MG, 37504-364, Brazil</footnote>

<footnote n="11">¹¹Physics Department, American University of Sharjah, Sharjah, UAE</footnote>

<footnote n="12">¹²*Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Boulevard de l'Observatoire, 06304 Nice, France*</footnote>

<footnote n="13">¹³*Unistellar Network*</footnote>

<footnote n="14">¹⁴Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi, Xinjiang, 830011, China</footnote>

<footnote n="15">¹⁵*Oukaimeden Observatory, High Energy Physics and Astrophysics Laboratory, FSSM, Cadi Ayyad University, Morocco.*</footnote>

<footnote n="16">¹⁶GRANDMA: Kilonova-Catcher</footnote>

<footnote n="17">¹⁷Vereniging Voor Sterrenkunde, Balen-Neetlaan 18A, B-2400, Mol, Belgium</footnote>

<footnote n="18">¹⁸Yunnan Observatories, Chinese Academy of Sciences, Kunming 650216, China</footnote>

<footnote n="19">¹⁹International Centre of Supernovae, Yunnan Key Laboratory, Kunming 650216, China</footnote>

<footnote n="20">²⁰Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650216, China</footnote>

<footnote n="21">²¹School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA</footnote>

<footnote n="22">²²Adonis Observatory (private obs.) Poelkapellestraat 57 Langemark 8920 Belgium</footnote>

<footnote n="23">²³CPPM, Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France</footnote>

<footnote n="24">²⁴SETI Institute, Carl Sagan Center, 339 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA</footnote>

<footnote n="25">²⁵Unistellar, 5 allée Marcel Leclerc, bâtiment B, Marseille, 13008, France</footnote>

<footnote n="26">²⁶Department of Astronomy, University of California, Berkeley, CA 94720, USA</footnote>

<footnote n="27">²⁷"Peyrole Observatory MPC D26" F-81310 Peyrole</footnote>

<footnote n="28">²⁸American Association of Variable Star Observers</footnote>

<footnote n="29">²⁹*Hidden Valley Observatory (HVO), Colfax, WI, USA; iTelescope, Utah Desert Remote Observatory, Beryl Junction, Utah, USA*</footnote>
<sup>30</sup>Institute of Earth Systems, University of Malta

<sup>31</sup>RAU. Department of Physical Sciences, College of Arts and Sciences, Embry-Riddle Aeronautical University, Daytona beach, Florida, USA

<sup>32</sup>IJCLab, Univ Paris-Saclay, CNRS/IN2P3, Orsay, France

<sup>33</sup>School of Astronomy and Space Science, University of Chinese Academy of Sciences, Beijing 100049, China

<sup>34</sup>Oukaimeden Observatory HAO telescope, Oukaimeden, Morocco.

<sup>35</sup>CEICO, Institute of Physics of the Czech Academy of Sciences, Na Slovance 1999/2, CZ-182 21, Praha, Czech Republic

<sup>36</sup>K26 / Contern Observatory (private obs.), 1, beim Schmilberbour, 5316 Contern, Luxembourg

<sup>37</sup>Beijing Planetarium, Beijing Academy of Science and Technology, Beijing 100044, China

<sup>38</sup>Observatoire du Crous des Gats, F-31550 Cintegabelle, France

<sup>39</sup>Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía, 18008 Granada, Spain

<sup>40</sup>FZU - Institute of Physics of the Czech Academy of Sciences, Na Slovance 1999/2, CZ-182 21, Praha, Czech Republic

<sup>41</sup>National Astronomical Research Institute of Thailand (Public Organization), 260, Moo 4, T. Donkaew, A. Mae Rim, Chiang Mai, 50180, Thailand

<sup>42</sup>International Astronomical Center

<sup>43</sup>IJCLab, Univ Paris-Saclay, CNRS/IN2P3, Orsay, France

<sup>44</sup>Silesian University of Technology, Department of Electronics, Electrical Engineering and Microelectronics, Akademicka 16, 44-100 Gliwice, Poland

<sup>45</sup>Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France

<sup>46</sup>Astronomical Observatory of Taras Shevchenko National University of Kyiv, Observatorna Str. 3, Kyiv, 04053, Ukraine

<sup>47</sup>Ulugh Beg Astronomical Institute, Uzbekistan Academy of Sciences, Astronomy str. 33, Tashkent 100052, Uzbekistan

<sup>48</sup>Sociedad Astronomica Queretana, Mexico, RAPAS Observatoire de Paris, France, Le club des Astronome Amateur de Rosemère du Québec, Canada

<sup>49</sup>NEPA, Universidade do Estado do Amazonas, Rd. Odovaldo Novo, Parintins - AM, 69152-470, Brazil

<sup>50</sup>Société Astronomique de France, Observatoire de Dauban, FR 04150 Banon, France

<sup>51</sup>Astronomy and Space Physics Department, Taras Shevchenko National University of Kyiv, Glushkova ave., 4, Kyiv, 03022, Ukraine

<sup>52</sup>National Center Junior academy of sciences of Ukraine, 38-44, Dehtiarivska St., Kyiv, 04119, Ukraine

<sup>53</sup>Astronomical Observatory Taras Shevchenko National University of Kyiv, Observatorna str. 3, Kyiv, 04053, Ukraine

<sup>54</sup>Main Astronomical Observatory of National Academy of Sciences of Ukraine, 27 Acad. Zabolotnoho Str., Kyiv, 03143, Ukraine

<sup>55</sup>National Astronomical Research Institute of Thailand (Public Organization), 260, Moo 4, T. Donkaew, A. Mae Rim, Chiang Mai, 50180, Thailand

<sup>56</sup>National University of Uzbekistan, 4 University str., Tashkent 100174, Uzbekistan

<sup>57</sup>Department of Physics and Astronomy, University of Catania, 95125 Catania, Italy

<sup>58</sup>Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191, Gif-sur-Yvette, France

<sup>59</sup>Physics Department, Tsinghua University, Beijing 100084, China

<sup>60</sup>University of Chinese Academy of Sciences, Beijing 100049, China

## ABSTRACT

First detected on 2023-11-04 by the Gravitational-wave Optical Transient Observer (GOTO), SN 2023wrk is a Type Ia Supernova (SNe Ia) at 40 Mpc, with significant unburned carbon in the outer ejecta. In this note, we present photometric and spectroscopic observations and analysis conducted by the Global Rapid Advanced Network Devoted to the Multi-messenger Addict (GRANDMA) over a 115-day period, which includes 78 days of measurements. The observations were contributed by both amateur and professional astronomers. Liu et al. (2024) analyzed the physical processes involved, and compared the evolution of color and spectral lines. We conclude that SN 2023wrk is the second 1999aa-like object with strong carbon absorption lines that has ever been found, which enriches our understanding of the subclass of 1999aa-like SNe.

## 1. GRANDMA

The Global Rapid Advanced Network Devoted to the Multi-messenger Addict (GRANDMA) collaboration is a network of ground-based facilities dedicated to time-domain astronomy, focused on electromagnetic follow-up of gravitational-wave progenitors and other transients. The network contains 36 telescopes from 30 observatories, 42 institutions, and groups from 20 countries. GRANDMA utilizes wide and narrow field-of-view telescopes distributed across five continents (Antier et al. 2020a,b; Aivazyan et al. 2022; Kann et al. 2023).
GRANDMA's network extends to its citizen science project titled Kilonova-Catcher (KNC) <fnref n="1" /> that allows amateur astronomers to contribute to the GRANDMA campaigns. GRANDMA uses a dedicated web application SkyPortal (van der Walt et al. 2019; Coughlin et al. 2023), integrated into GRANDMA's communication system, which sends out alerts to the network with the coordinates of potential candidates and allows for real-time coordination and analysis by the collaboration.

## 2. OBSERVATIONS

GRANDMA observed SN 2023wrk on 2023-11-06 with the TRT-SRO instrument in Thailand at 2023-11-06 11:56:16, approximately 28 hours after the GOTO detection on 2023-11-04 05:29:46. Observations concluded on 2024-02-26 19:49:19 UTC with the TNT telescope, 115 days after the first observation. The full dataset comprises more than 300 images obtained from 10 professional telescopes, along with more than additional 300 data points collected from 17 amateur telescopes. These observations span multiple bands, including Johnson Cousins *B*, *V*, *R*, *I* and Sloan filters in *g*, *r*, *i*, *z*.

In this note, we present GRANDMA contribution related to SN 2023wrk. These observations build upon the results presented in Liu et al. (2024), Early-Time Observations of SN 2023wrk: A Luminous Type Ia Supernova with Significant Unburned Carbon in the Outer Ejecta (hereafter referred to as L24).

## 3. ANALYSIS

The images underwent telescope-specific pre-processing, including: bias, dark subtraction, and flat-fielding. For some images, image co-addition was performed using the Swarp software (Bertin 2010) to enhance signal-to-noise ratio and astrometric solutions were acquired using Astrometry.net (Lang et al. 2010).

The photometric analysis was conducted using STDPipe <fnref n="2" /> (Karpov 2021), a python package using pre-configured scripts for image analysis. In particular, we used the online implementation of the package called STDweb, available at http://stdweb.favor2.info/.

The analysis process starts by masking saturated pixels, image edges and cosmic rays removal using the AstroSCRAPPY (McCully & Tewes 2019) code implementing the original LACosmic (Dokkum (van) 2001) algorithm. Then, we performed the photometry using circular apertures with the radius equal to the average FWHM of stars in each image. FWHM, in turn, was estimated using the median of values measured for every star by SExtractor (Bertin & Arnouts 1996), with saturated stars and those with $S/N < 20$ excluded. The background for every star was estimated locally using a circular annulus with the inner and outer radii of 5 and $7 \times \text{FWHM}$.

For photometric calibration, we selected the catalogues based on the filter used for the images – for the ones acquired in Sloan-like filters the Pan-STARRS DR1 (Chambers et al. 2016), while for the ones in Johnson-Cousins we used the Gaia DR3 Syntphot (Gaia Collaboration et al. 2023) catalogue that provides synthetic photometry from low-resolution (XP) spectra of stars observed by Gaia.

In addition, the images taken without a filter of KNC-Unistellar span a wide band from near UV to near IR, posing challenges for standard calibration. We addressed these images by using the *G* band of the Gaia eDR3 catalogue (Gaia Collaboration et al. 2023) as it covers a similar range to Unistellar instruments. It resulted in a color term correction $\le 0.1$, rendering it negligible.

The data reduction for OHP spectra employed the MISTRAL tool<fnref n="3" />, a Python-based reduction package. Spectral data from OHP and TNG were delivered in absolute fluxes, while KNC provided relative fluxes. Absolute calibration of KNC spectra involved utilizing standard stars and SDSS-r or Bessel-V magnitudes for correction. OHP's wavelength calibration relied on Hg, Ar, and Xe lamps, with flux calibration referencing the Hiltner 600 spectro-photometric standard.

## 4. RESULTS

The left panel in Figure 1 shows the photometric lightcurves acquired by GRANDMA and KNC <fnref n="4" />. A summary of our photometric observations is presented in Table 2 of L24 (Liu et al. 2024), including telescope names, their filters and number of images. The complete photometric data of SN 2023wrk is listed in Table 3 of the same paper.

<footnote n="1">¹ http://kilonovacatcher.in2p3.fr/</footnote>

<footnote n="2">² https://gitlab.in2p3.fr/icare/stdpipe</footnote>

<footnote n="3">³ https://github.com/cylammarco/ASPIRED</footnote>

<footnote n="4">⁴ without YFOSC contribution presented in Liu et al. (2024)</footnote>
<figure><img src="image_1.png" /><figcaption>**Figure 1.** The left panel shows the UV/Optical photometric lightcurves obtained by GRANDMA and kilonova-Catcher. The plots also includes the Swift observations of SN 2023wrk. The right panel corresponds to the various spectra obtained by GRANDMA OHP and TNG facilities along with the KNC observations.</figcaption></figure>

The right panel of Figure 1 illustrates the optical spectral evolution of SN2023wrk from Nov 11th, 2023 to Jan 20th, 2024. Each curve corresponds to the spectrum of the source taken at different epochs.

A redshift of $z=-0.02351$ was estimated from the SiII λ6355Å absorption feature on its rest wavelength frame on 2023-12-02 (MJD=2460280.556). The identified absorption features in the rest frame, include SiIIλ4128Å, MgIIλ4481Å, SiIIλ5041Å, FeIIλ5169Å, NaDλ5850Å, SIIλ5654Å, HeIλ5876Å, and SiIIλ6355Å. The central wavelength ($\lambda_{central}$) was used to estimate the redshift of the line. The radial velocity of the ejecta ($v_{rad,ejecta}$) was estimated by considering the radial velocity of the host galaxy IC 694 (-3280 km/s, Aalto et al. 1997).

Details of each spectroscopic observation are summarized in Table 5 of L24 (Liu et al. 2024), highlighting: date, phase relative to the B-band maximum, range, exposure(s), and instrument/telescope.

Our main results are:

(i) The strong carbon absorption at first may be related to a collision of the ejecta and nearby, unbound carbon. Then, this carbon feature disappears quickly in subsequent evolution but it reappears at around the time of peak brightness. The reappearance of the carbon feature indicates that the carbon is located deeper in the ejecta, becoming visible at a later phase as the supernova expands and increases in transparency. This allows us to see deeper regions that were initially obscured.

(ii) The constant B–V color at early times can be explained by outward-mixing $^{56}$Ni ((see 2016ApJ...826...96P)) predicted by the simulation of 3d delayed-detonation (see 2005ApJ...623..337G).

(iii) The diversity of carbon features at very early times among SNe Ia with evident carbon lines may be due to variations in the mass and density of unbound carbon in different supernovae which show prominent carbon features.

All these observational properties of SN 2023wrk are consistent with pulsational delayed-detonation or carbon-rich CSM interaction models.

Acknowledgments for this work are available in the online repository of the GRANDMA collaboration.

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