Browsing by Author "Hoeflich, P."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Expanding the parameter space of 2002es-like type Ia supernovae: On the underluminous ASASSN-20jq/SN 2020qxp
    (2025) Bose, S.; Stritzinger, M. D.; Ashall, C.; Baron, E.; Hoeflich, P.; Galbany, L.; Hoogendam, W. B.; Jensen, E. A. M.; Kochanek, C. S.; Post, R. S.; Reguitti, A.; Elias-Rosa, N.; Stanek, K. Z.; Lundqvist, P.; Auchettl, K.; Clocchiatti, Alejandro; Fiore, A.; Gutierrez, C. P.; Hinkle, J. T.; Huber, M. E.; de Jaeger, T.; Pastorello, A.; Payne, A. V.; Phillips, M.; Shappee, B. J.; Tucker, M. A.
    We present optical photometric and spectroscopic observations of the peculiar Type Ia supernovae (SNe Ia) ASASSN-20jq/SN 2020qxp. It is a low-luminosity object, with a peak absolute magnitude of M-B = -17.1 +/- 0.5 mag, while its post-peak light-curve decline rate of Delta m(15)(B) = 1.35 +/- 0.09 mag and color-stretch parameter of s(BV) & gap; 0.82 is similar to that of normal luminosity SNe Ia. That makes it a prevalent outlier in both the SN Ia luminosity-width and the luminosity-color-stretch relations. The analysis of the early light curves indicates a possible "bump" during the first approximate to 1.4 days of explosion. ASASSN-20jq synthesized a low radioactive Ni-56 mass of 0.09 +/- 0.01 M-circle dot. The near-maximum light spectra of the supernova show strong Si II absorption lines, indicating a cooler photosphere than normal SNe Ia; however, it lacks Ti II absorption lines. Additionally, it shows unusually strong absorption features of O I lambda 7773 and the Ca II near-infrared triplet. The nebular spectra of ASASSN-20jq show a remarkably strong but narrow forbidden [Ca II] lambda lambda 7291, 7324 doublet emission that has not been seen in SNe Ia except for a handful of Type Iax events. There is also a marginal detection of the [O I] lambda lambda 6300, 6364 doublet emission in nebular spectra, which is extremely rare. Both the [Ca II] and [O I] lines are redshifted by roughly 2000 km s(-1). ASASSN-20jq also exhibits a strong [Fe II] lambda 7155 emission line with a tilted-top line profile, which is identical to the [Fe II] lambda 16433 line profile. The asymmetric [Fe II] line profiles, along with the redshifted [Ca II] and emission lines, suggest a high central density white dwarf progenitor that underwent an off-center delayed-detonation explosion mechanism, synthesizing roughly equal amounts of Ni-56 during the deflagration and detonation burning phases. The equal production of Ni-56 in both burning phases distinguishes ASASSN-20jq from normal bright and subluminous SNe Ia. Assuming this scenario, we simultaneously modeled the optical and near-infrared nebular spectra, achieving a good agreement with the observations. The light curve and spectroscopic features of ASASSN-20jq do not align with any single sub-class of SNe Ia. However, the significant deviation from the luminosity versus light-curve shape relations (along with several light-curve and spectroscopic features) exhibits similarities to some 2002es-like objects. Therefore, we have identified ASASSN-20jq as an extreme candidate within the broad and heterogeneous parameter space of 2002es-like SNe Ia.
  • Thumbnail Image
    Item
    The young and nearby normal type Ia supernova 2018gv : UV-optical observations and the earliest spectropolarimetry
    (2020) Yang, Y.; Hoeflich, P.; Baade, D.; Maund J. R.; Wang, L.; Brown, P. J.; Stevance, H. F.; Arcavi, I.; Burke, J.; Clocchiatti, Alejandro; Cikota, A.; Gal-Yam, A.; Graham, M. L.; Hiramatsu, D.; Hosseinzadeh, G.; Howell, D. A.; Jha, S. W.; McCully, C.; Patat, F.; Sand, D. J.; Schulze, S.; Spyromilio, J.; Valenti, S.; Vinkó, J.; Wang, X.; Wheeler, J. C.; Yaron, O.; Zhang, J.