_version_ 1866914422678618112
author Könyves-Tóth, Réka
Bodola, Zsófia
Szalai, Tamás
Andrews, Moira
Arcavi, Iair
Bánhidi, Dominik
Bíró, Imre Barna
Bianco, Federica
Burke, Jamison
Csányi, István
Dilday, Benjamin
Farah, Joseph R.
Gonzalez, Estefania Padilla
Hiramatsu, Daichi
Howell, D. Andrew
Kriskovics, Levente
Newsome, Megan
Ni, Yuan Qi
McCully, Curtis
Ordasi, András
Pál, András
Pellegrino, Craig
Szakáts, Róbert
Terreran, Giacomo
Valenti, Stefano
Vida, Krisztián
Wynn, Kathryn
author_facet Könyves-Tóth, Réka
Bodola, Zsófia
Szalai, Tamás
Andrews, Moira
Arcavi, Iair
Bánhidi, Dominik
Bíró, Imre Barna
Bianco, Federica
Burke, Jamison
Csányi, István
Dilday, Benjamin
Farah, Joseph R.
Gonzalez, Estefania Padilla
Hiramatsu, Daichi
Howell, D. Andrew
Kriskovics, Levente
Newsome, Megan
Ni, Yuan Qi
McCully, Curtis
Ordasi, András
Pál, András
Pellegrino, Craig
Szakáts, Róbert
Terreran, Giacomo
Valenti, Stefano
Vida, Krisztián
Wynn, Kathryn
contents {Supernova (SN) siblings are powerful tools used to calibrate and improve distance measurement methods, and to make the systematic uncertainty to distances to their host galaxies considerably lower compared to other techniques.} {In this paper we present distance estimates to NGC6951, a galaxy that hosted the Type IIP SN~2020dpw, the Type Ib SN~2021sjt, and three other SNe.} {Photometric observations of the two objects were carried out using two 80cm RC telescopes located in Hungary, while spectra were obtained from the LCO and the WiseRep database. For the distance estimates, we applied the expanding photosphere method (EPM), which connects the observed angular radius ($θ$) of a SN to its physical radius and is related to the velocity of the photosphere ($v_{\rm ph}$). Although the EPM is mostly applied to derive the distance of Type IIP SNe, in the literature there are several examples of this technique being used for Type IIn and stripped-envelope SNe as well. Therefore, we made another attempt to infer the distance of the Type Ib SN~2021sjt by applying the EPM together with its Type IIP sibling SN~2020dpw. } {Our analysis resulted in a distance of $25.76 \pm 0.34 (\rm random) \pm 5.51$ (systematic) Mpc and $24.57 \pm 1.27 (\rm random) \pm 4.64$ (systematic) Mpc for SN~2020dpw and SN~2021sjt, respectively. Systematic errors were estimated with respect to the used dilution factor, the interstellar reddening, and the date of the explosion (which was fixed to a value between the last non-detection and the first detection for each object).} {The obtained distance values agree with each other and with the literature, which shows the validity of the methods used. In this way, new and perhaps improved distance estimates to NGC 6951 were obtained, and the applicability of the EPM for Type Ib SNe was tested.}
format Preprint
id arxiv_https___arxiv_org_abs_2603_24769
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Distance estimate to NGC 6951 from supernova siblings Type IIP SN 2020dpw and Type Ib SN 2021sjt
Könyves-Tóth, Réka
Bodola, Zsófia
Szalai, Tamás
Andrews, Moira
Arcavi, Iair
Bánhidi, Dominik
Bíró, Imre Barna
Bianco, Federica
Burke, Jamison
Csányi, István
Dilday, Benjamin
Farah, Joseph R.
Gonzalez, Estefania Padilla
Hiramatsu, Daichi
Howell, D. Andrew
Kriskovics, Levente
Newsome, Megan
Ni, Yuan Qi
McCully, Curtis
Ordasi, András
Pál, András
Pellegrino, Craig
Szakáts, Róbert
Terreran, Giacomo
Valenti, Stefano
Vida, Krisztián
Wynn, Kathryn
High Energy Astrophysical Phenomena
{Supernova (SN) siblings are powerful tools used to calibrate and improve distance measurement methods, and to make the systematic uncertainty to distances to their host galaxies considerably lower compared to other techniques.} {In this paper we present distance estimates to NGC6951, a galaxy that hosted the Type IIP SN~2020dpw, the Type Ib SN~2021sjt, and three other SNe.} {Photometric observations of the two objects were carried out using two 80cm RC telescopes located in Hungary, while spectra were obtained from the LCO and the WiseRep database. For the distance estimates, we applied the expanding photosphere method (EPM), which connects the observed angular radius ($θ$) of a SN to its physical radius and is related to the velocity of the photosphere ($v_{\rm ph}$). Although the EPM is mostly applied to derive the distance of Type IIP SNe, in the literature there are several examples of this technique being used for Type IIn and stripped-envelope SNe as well. Therefore, we made another attempt to infer the distance of the Type Ib SN~2021sjt by applying the EPM together with its Type IIP sibling SN~2020dpw. } {Our analysis resulted in a distance of $25.76 \pm 0.34 (\rm random) \pm 5.51$ (systematic) Mpc and $24.57 \pm 1.27 (\rm random) \pm 4.64$ (systematic) Mpc for SN~2020dpw and SN~2021sjt, respectively. Systematic errors were estimated with respect to the used dilution factor, the interstellar reddening, and the date of the explosion (which was fixed to a value between the last non-detection and the first detection for each object).} {The obtained distance values agree with each other and with the literature, which shows the validity of the methods used. In this way, new and perhaps improved distance estimates to NGC 6951 were obtained, and the applicability of the EPM for Type Ib SNe was tested.}
title Distance estimate to NGC 6951 from supernova siblings Type IIP SN 2020dpw and Type Ib SN 2021sjt
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2603.24769