Searching for late-time interaction signatures in Type Ia supernovae from the Zwicky Transient Facility

The nature of the progenitor systems and explosion mechanisms that give rise to Type Ia supernovae (SNe Ia) are still debated. The interaction signature of circumstellar material (CSM) being swept up by expanding ejecta can constrain the type of system from which it was ejected. Most previous studies have focused on finding CSM ejected shortly before the SN Ia explosion still residing close to the explosion site, resulting in short delay times until the interaction starts. We use a sample of 3627 SNe Ia from the Zwicky Transient Facility discovered between 2018 and 2020 and search for interaction signatures over 100 days after peak brightness. By binning the late-time light curve data to push the detection limit as deep as possible, we identify potential late-time rebrightening in 3 SNe Ia (SN 2018grt, SN 2019dlf, SN 2020tfc). The late-time detections occur between 550 and 1450 d after peak brightness, have mean absolute $r$-band magnitudes of -16.4 to -16.8 mag and last up to a few hundred days, significantly brighter than the late-time CSM interaction discovered in the prototype SN 2015cp. The late-time detections all occur within 0.8 kpc of the host nucleus and are not easily explained by nuclear activity, another transient at a similar sky position, or data quality issues. This suggests environment or specific progenitor characteristics playing a role in producing potential CSM signatures in these SNe Ia. By simulating the ZTF survey we estimate that <0.5 per cent of normal SNe Ia display late-time strong H $\alpha$-dominated CSM interaction. This is equivalent to an absolute rate of $8_{-4}^{+20}$ to $54_{-26}^{+91}$ Gpc$^{-3}$ yr$^{-1}$ assuming a constant SN Ia rate of $2.4\times10^{-5}$ Mpc$^{-3}$ yr$^{-1}$ for $z \leq 0.1$. Weaker interaction signatures, more similar to the strength seen in SN 2015cp, could be more common but are difficult to constrain with our survey depth.Comment: 24 pages, 13 figures, 6 tables, A&A accepte

SN 2022joj: A Peculiar Type Ia Supernova Possibly Driven by an Asymmetric Helium-shell Double Detonation

We present observations of SN 2022joj, a peculiar Type Ia supernova (SN Ia) discovered by the Zwicky Transient Facility (ZTF). SN 2022joj exhibits an unusually red $g_\mathrm{ZTF}-r_\mathrm{ZTF}$ color at early times and a rapid blueward evolution afterwards. Around maximum brightness, SN 2022joj shows a high luminosity ($M_{g_\mathrm{ZTF},\mathrm{max}}\simeq-19.7$ mag), a blue broadband color ($g_\mathrm{ZTF}-r_\mathrm{ZTF}\simeq-0.2$ mag), and shallow Si II absorption lines, consistent with those of overluminous, SN 1991T-like events. The maximum-light spectrum also shows prominent absorption around 4200 \r{A}, which resembles the Ti II features in subluminous, SN 1991bg-like events. Despite the blue optical-band colors, SN 2022joj exhibits extremely red ultraviolet $-$ optical colors at maximum luminosity ($u-v\simeq1.6$ mag and $uvw1 - v\simeq4.0$ mag), suggesting a suppression of flux between $\sim$2500--4000 \r{A}. Strong C II lines are also detected at peak. We show that these unusual spectroscopic properties are broadly consistent with the helium-shell double detonation of a sub-Chandrasekhar mass ($M\simeq1\mathrm{M_\odot}$) carbon/oxygen (C/O) white dwarf (WD) from a relatively massive helium shell ($M_s\simeq0.04$--$0.1\mathrm{M_\odot}$), if observed along a line of sight roughly opposite to where the shell initially detonates. None of the existing models could quantitatively explain all the peculiarities observed in SN 2022joj. The low flux ratio of [Ni II] $\lambda$7378 to [Fe II] $\lambda$7155 emission in the late-time nebular spectra indicates a low yield of stable Ni isotopes, favoring a sub-Chandrasekhar mass progenitor. The significant blueshift measured in the [Fe II] $\lambda$7155 line is also consistent with an asymmetric chemical distribution in the ejecta, as is predicted in double-detonation models.Comment: 24 pages, 11 figures, 6 tables. Submitted to Ap

Tip-Ia süpernova adaylarının uzun dönemli ışık değişimleri

Type-Ia supernovae are commonly accepted as the high-energy thermonuclear explosions of a carbon-oxygen white dwarf in a binary system. These explosions are seen as a brightness increase in the system. When followed over long periods, they are of great importance in terms of revealing and understanding the differences in the light curve evolutions of type-Ia supernovae with different spectral groups. In this thesis, long-term light curve evolutions of type-Ia supernovae candidates, taking into account the spectra when available, have been investigated. Photometric observations of 18 type-Ia supernovae were collected with TUG T60 and TJO telescopes. By applying the fit method from the light curve analysis programs and making comparisons between SN 2017fgc, whose photometric observations were carried out with the TUG T60 telescope, and other well observed type-Ia supernovae with sufficient data in the literature, the light curve characteristics of type-Ia supernovae with two different spectral groups were studied. The results from the analysis of the data obtained revealed that the type-Ia supernovae belonging to different spectral groups also have different light curve characteristics.Tip-Ia süpernovaları, bileşeninden madde alan Kabron-Oksijen beyaz cücesini barındıran bir çift yıldız sisteminde beyaz cücenin patlaması ile oluşan yüksek enerjili termonükleer patlamalar olarak kabul görmektedir. Sistemde parlaklık artışı olarak görülen bu patlamalar, uzun dönemlerde takip edildiğinde farklı tayfsal gruplara sahip tip-Ia süpernovalarının ışık eğrilerindeki farklılıkların ortaya konulması ve anlaşılması açısından büyük önem taşımaktadır. Bu tezde tip-Ia süpernova adaylarının uzun dönemli ışık eğrileri, yapılan fotometrik gözlemler ve mümkün olduğunda tayfları da çalışmalara dahil edilerek incelenmiştir. Toplamda 18 adet tip-Ia süpernova adayına ait fotometrik gözlemler TUG T60 ve TJO teleskopları ile yapılmıştır. İki farklı tayfsal grubu bulunan tip-Ua süpernovalarının ışık eğrilerinde gösterdiği karakteristik özellikler, fotometrik gözlemleri TUG T60 teleskobu ile yapılan SN 2017fgc sisteminin, literatürde yeterli veriye sahip diğer tip Ia süpernovalarının ışık eğrisi analiz programları ile fit yöntemi kullanılarak kıyaslanması ve çalışılması sonucu elde edilmiştir. Yapılan analizler sonucu elde edilen veriler farklı tip-Ia süpernovalarına ait tayfsal grupların aynı zamanda farklı ışık eğrisi özellikleri barındırdığını ortaya koymuştur

Basal damage and oxidative DNA damage in children with chronic kidney disease measured by use of the comet assay

One consequence of chronic kidney disease (CKD) is an elevated risk for cancer. There is sufficient evidence to conclude that there is an increased incidence of at least some cancers in kidney-dialysis patients. Cancer risk after kidney transplantation has mainly been attributed to immunosuppressive therapy. There are no data evaluating DNA damage in children with CKD, in dialysis patients, or following kidney transplantation. In this study, the comet assay and the enzyme-modified comet assay - with the use of endonuclease III (Endo III) and formamidopyrimidine glycosylase (FPG) enzymes - were conducted to investigate the basal damage and the oxidative DNA damage as a result of treatment in peripheral blood lymphocytes of children. Children at various stages of treatment for kidney disease, including pre-dialysis patients (PreD) (n = 17), regular hemodialysis patients (HD) (n = 15), and those that received kidney transplants (Tx) (n = 17), comprised the study group. They were compared with age- and gender-matched healthy children (n = 20) as a control group. Our results show that the %DNA intensity, a measure of basal damage, was significantly increased in children with CKD (mean +/- SD) (5.22 +/- 1.57) and also in each of the PreD, HD, and Tx groups [(4.92 +/- 1.23), (4.91 +/- 1.35), and (5.79 +/- 1.94), respectively, vs the healthy children (2.74 +/- 2.91) (p < 0.001). Significant increases in oxidative DNA damage were only found in the FPG-sensitive sites for the PreD and Tx groups, compared with control and HD groups (p < 0.05), suggesting that basal DNA damage was more evident for the PreD, HD, and Tx groups. The findings of the present study indicate a critical need for further research on genomic damage with different endpoints and also for preventive measures and improvements in treatment of pediatric patients, in order to improve their life expectancy. (C) 2011 Elsevier B.V. All rights reserved