SN 2020bvc : A Broad-line Type Ic Supernova with a Double-peaked Optical Light Curve and a Luminous X-Ray and Radio Counterpart

We present optical, radio, and X-ray observations of SN 2020bvc (=ASASSN-20bs, ZTF 20aalxlis), a nearby (z = 0.0252; d.=.114Mpc) broad-line (BL) Type Ic supernova (SN) and the first double-peaked Ic-BL discovered without a gamma-ray burst (GRB) trigger. Our observations show that SN 2020bvc shares several properties in common with the Ic-BL SN 2006aj, which was associated with the low-luminosity gamma-ray burst (LLGRB) 060218. First, the 10 GHz radio luminosity (L-radio approximate to 10(37) erg s(-1)) is brighter than ordinary core-collapse SNe but fainter than LLGRB SNe such as SN 1998bw (associated with LLGRB 980425). We model our VLA observations (spanning 13-43 days) as synchrotron emission from a mildly relativistic (v greater than or similar to 0.3c) forward shock. Second, with Swift and Chandra, we detect X-ray emission (L-X approximate to 10(41) erg s(-1)) that is not naturally explained as inverse Compton emission or part of the same synchrotron spectrum as the radio emission. Third, high-cadence (6x night(-1)) data from the Zwicky Transient Facility (ZTF) show a double-peaked optical light curve, the first peak from shock cooling of extended low-mass material (mass M-e 10(12) cm) and the second peak from the radioactive decay of 56Ni. SN 2020bvc is the first double-peaked Ic-BL SN discovered without a GRB trigger, so it is noteworthy that it shows X-ray and radio emission similar to LLGRB SNe. For four of the five other nearby (z less than or similar to 0.05) Ic-BL SNe with ZTF high-cadence data, we rule out a first peak like that seen in SN 2006aj and SN 2020bvc, i.e., that lasts approximate to 1 day.and reaches a peak luminosity M approximate to -18. Follow-up X-ray and radio observations of Ic-BL SNe with well-sampled early optical light curves will establish whether double-peaked optical light curves are indeed predictive of LLGRB-like X-ray and radio emission.Peer reviewe

The prevalence and influence of circumstellar material around hydrogen-rich supernova progenitors

Narrow transient emission lines (flash-ionization features) in early supernova (SN) spectra trace the presence of circumstellar material (CSM) around the massive progenitor stars of core-collapse SNe. The lines disappear within days after the SN explosion, suggesting that this material is spatially confined, and originates from enhanced mass loss shortly (months to a few years) prior to explosion. We performed a systematic survey of H-rich (Type II) SNe discovered within less than two days from explosion during the first phase of the Zwicky Transient Facility (ZTF) survey (2018-2020), finding thirty events for which a first spectrum was obtained within $< 2$ days from explosion. The measured fraction of events showing flash ionisation features ($>36\%$ at $95\%$ confidence level) confirms that elevated mass loss in massive stars prior to SN explosion is common. We find that SNe II showing flash ionisation features are not significantly brighter, nor bluer, nor more slowly rising than those without. This implies that CSM interaction does not contribute significantly to their early continuum emission, and that the CSM is likely optically thin. We measured the persistence duration of flash ionisation emission and find that most SNe show flash features for $\approx 5$ days. Rarer events, with persistence timescales $>10$ days, are brighter and rise longer, suggesting these may be intermediate between regular SNe II and strongly-interacting SNe IIn

Early Ultraviolet Observations of Type IIn Supernovae Constrain the Asphericity of Their Circumstellar Material

We present a survey of the early evolution of 12 Type IIn supernovae (SNe IIn) at ultraviolet and visible light wavelengths. We use this survey to constrain the geometry of the circumstellar material (CSM) surrounding SN IIn explosions, which may shed light on their progenitor diversity. In order to distinguish between aspherical and spherical CSM, we estimate the blackbody radius temporal evolution of the SNe IIn of our sample, following the method introduced by Soumagnac et al. We find that higher-luminosity objects tend to show evidence for aspherical CSM. Depending on whether this correlation is due to physical reasons or to some selection bias, we derive a lower limit between 35% and 66% for the fraction of SNe IIn showing evidence for aspherical CSM. This result suggests that asphericity of the CSM surrounding SNe IIn is common—consistent with data from resolved images of stars undergoing considerable mass loss. It should be taken into account for more realistic modeling of these events

Genetic control of immunity to turnip mosaic virus (TuMV) pathotype 1 in Brassica rapa (Chinese cabbage)

Turnip mosaic virus (TuMV) is the major virus infecting crops of the genus Brassica worldwide. A dominant resistance gene, TuRB01b, that confers immunity to the virus isolate UK 1 (a representative pathotype 1 isolate of TuMV) on Brassica rapa was identified in the Chinese cabbage cultivar Tropical Delight. The TuRB01b locus was mapped to a 2.9-cM interval on B. rapa chromosome 6 (A6) that was flanked by RFLP markers pN101e1 and pW137e1. This mapping used a first backcross (B1) population segregating for the resistance gene at TuRB01b and sets of RFLP markers employed in previous mapping experiments in Brassica. Virus–plant interaction phenotypes were assayed in inbred progeny derived from B1 individuals to allow different virus isolates to be tested. Comparative mapping confirmed that A6 of B. rapa was equivalent to chromosome 6 of Brassica napus (A6) and that the map position of TuRB01b in B. rapa could be identical to that of TuRB01 in B. napus. Detailed evaluation of plant–virus interactions showed that TuRB01 and TuRB01b had indistinguishable specificities to a range of TuMV isolates. The possibility that TuRB01 and TuRB01b represent similar or identical alleles at the same A genome resistance locus suggests that B. napus acquired TuRB01 from the B. rapa gene pool

Broad-spectrum resistance to turnip mosaic virus in Brassica rapa (Chinese cabbage)

TuMV is a member of the Potyvirus genus, infects a wide range of cultivated plant species and causes significant economic losses in Brassica crops (Shattuck, 1992). It is a positive strand RNA virus (genome comprises 9830- 9835 nucleotides) and is the subject of advanced molecular characterisation in terms of its interaction with brassicas (Walsh & Jenner, 2002). Plant genes for resistance to TuMV have been mapped in lettuce (Tu, Robbins et al., 1994), B. napus (TuRB01, Walsh et al., 1999; TuRB03, Hughes et al., 2003; TuRB04 and TuRB05, Walsh & Lydiate, unpublished) and B. rapa (TuRB01b, Rusholme et al., unpublished). All these brassica genes are dominant R genes that control resistance to narrow spectra of TuMV isolates; the viral avirulence determinants for these genes have been identified (Jenner et al., 2000; Walsh et al., 2002; Jenner et al., 2002; Jenner et al., 2003). The B. rapa line RLR22 is resistant to a diverse range of TuMV isolates from different regions of the world, different pathotypes, different serotypes and different genetic groups (Walsh et al., 2002; Rusholme et al., 2007). A B. rapa genetic map based on 213 marker loci segregating in 120 first backcross (B1) individuals was established. B1 individuals were self-pollinated to produce B1S1 families. The existence of two loci controlling resistance to TuMV isolate CDN 1 was established from contrasting patterns of segregation for resistance and susceptibility in the B1S1 families. The first gene recessive TuMV resistance 01 (retr01) had a recessive allele for resistance, was located on the upper portion of chromosome R4 and was epistatic to the second gene. The second gene Conditional TuMV Resistance 01 (ConTR01) possessed a dominant allele for resistance and was located on the upper portion of chromosome R8. These genes also controlled resistance to TuMV isolate CZE 1 and might be sufficient to explain the broad-spectrum resistance of RLR22. The dominant resistance gene, ConTR01, was coincident with one of the three eukaryotic initiation factor 4E (eIF4E) loci of B. rapa and the recessive resistance gene retr01 was apparently co-incident with one of the three loci of eIF(iso)4E in the Agenome of B. napus and therefore, by inference, in the B. rapa genome. This suggested a mode of action for the resistance that is based on denying the viral RNA access to the translation initiation complex of the plant host. retr01 is the first example of a recessive resistance gene mapped in a brassica

Evidence for GC preference by monocot Dicer-like proteins

Dicot Dicer-like (DCL) enzymes operate preferably on GC rich regions when producing small interfering (si)RNA and micro (mi)RNA. This GC bias, however, is not generic in monocot miRNA productions. From wild Dactylis glomerata naturally infected by Cocksfoot streak potyvirus (CSV), CSV-siRNAs had a greater GC% than the virus genome, indicating that GC rich regions were also preferred by the grass DCLs. This supports the notion that GC preference is an ancient feature for plant DCLs, and suggests that monocot miRNA genes might have evolved to a high GC% resulting in GC bias being not detectable during mature miRNA production

Identification of novel small RNAs in tomato (Solanum lycopersicum)

To date, the majority of plant small RNAs (sRNA) have been identified in rice, poplar and Arabidopsis. To identify novel tomato sRNAs potentially involved in tomato specific processes such as fruit development and/or ripening, we cloned 4,018 sRNAs from tomato fruit tissue at the mature green stage. From this pool of sRNAs, we detected tomato homologues of nine known miRNAs, including miR482; a poplar miRNA not conserved in Arabidopsis or rice. We identified three novel putative miRNAs with flanking sequence that could be folded into a stem-loop precursor structure and which accumulated as 19-24nt RNA. One of these putative miRNAs (Put-miRNA3) exhibited significantly higher expression in fruit compared with leaf tissues, indicating a specific role in fruit development processes. We also identified nine sRNAs that accumulated as 19-24nt RNA species in tomato but genome sequence was not available for these loci. None of the nine sRNAs or three putative miRNAs possessed a homologue in Arabidopsis that had a precursor with a predicted stem-loop structure or that accumulated as a sRNA species, suggesting that the 12 sRNAs we have identified in tomato may have a species specific role in this model fruit species