Luis González

SN 2005bf: a possible transition event between type Ib/c supernovae and gamma-ray bursts

We present ugriBV photometry and optical spectroscopy of the Type Ib/Ic SN 2005bf covering the first �100 days following discovery. The ugBV light curves displayed an unprecedented morphology among Type Ib/Ic supernovae, with an initial maximum some 2 weeks after discovery, and a second, main maximum about 25 days after that. The bolometric light curve indicates that SN 2005bf was a remarkably luminous event, radiating at least 6.3×10 42 erg s −1 at maximum light, and a total of 2.1 × 10 49 erg during the first 75 days after the explosion. Spectroscopically, SN 2005bf underwent a unique transformation

The normal Type Ia SN 2003hv out to very late phases

Aims. We study a thermonuclear supernova (SN), emphasizing very late phases. Methods. An extensive dataset for SN 2003hv that covers the flux evolution from maximum light to day +786 is presented. This includes 82 epochs of optical imaging, 24 epochs of near-infrared (NIR) imaging, and 10 epochs of optical spectroscopy. These data are combined with published nebular-phase IR spectra, and the observations are compared to model light curves and synthetic nebular spectra. Results. SN 2003hv is a normal Type Ia supernova (SN Ia) with photometric and spectroscopic properties consistent with its rarely observed B-band decline-rate parameter, Δm15(B) = 1.61 ± 0.02. The blueshift of the most isolated [Fe ii] lines in the nebular-phase optical spectrum appears consistent with those observed in the IR at similar epochs. At late times there is a prevalent color evolution from the optical toward the NIR bands. We present the latest-ever detection of a SN Ia in the NIR in Hubble Space Telescope images. The study of the ultraviolet/optical/infrared (UVOIR) light curve reveals that a substantial fraction of the flux is “missing” at late times. Between 300 and 700 days past maximum brightness, the UVOIR light curve declines linearly following the decay of radioactive 56 Co, assuming full and instantaneous positron trapping. At 700 days we detect a possible slowdown of the decline in optical-bands, mainly in the V-band. Conclusions. The data are incompatible with a dramatic infrared catastrophe (IRC). However, the idea that an IRC occurred in the densest regions before 350 days can explain the missing flux from the UVOIR wavelengths and the flat-topped profiles in the NIR. We argue that such a scenario is possible if the ejecta are clumpy. The observations suggest that positrons are most likely trapped in the ejecta.

Optical and infrared photometry of the nearby type Ia supernovae 1999ee, 2000bh, 2000ca, and 2001ba

We present near-infrared photometry of the Type Ia supernova (SN) 1999ee; also, optical and infrared photometry of the Type Ia SNe 2000bh, 2000ca, and 2001ba. For SNe 1999ee and 2000bh, we present the first-ever SN photometry at 1.035 μm (the Y band). We present K-corrections that transform the infrared photometry in the observers frame to the supernova rest frame. Using our infrared K-corrections and stretch factors derived from optical photometry, we construct JHK templates that can be used to determine the apparent magnitudes at maximum if one has some data in the window -12 to +10 days with respect to T(Bmax). Following up previous work on the uniformity of V minus IR loci of Type Ia supernovae of midrange decline rates, we present unreddened loci for slow decliners. We also discuss evidence for a continuous change of color at a given epoch as a function of decline rate.

SUPERNOVA 2003bg: THE FIRST TYPE IIb HYPERNOVA

Optical and near-infrared photometry and optical spectroscopy are reported for SN 2003bg, starting a few days after explosion and extending for a period of more than 300 days. Our early-time spectra reveal the presence of broad, high-velocity Balmer lines. The nebular-phase spectra, on the other hand, show a remarkable resemblance to those of Type Ib/c supernovae, without clear evidence for hydrogen. Near maximum brightness SN 2003bg displayed a bolometric luminosity comparable to that of other Type I hypernovae unrelated to gamma-ray bursts, implying a rather normal amount of 56Ni production (0.1-0.2 M ☉) compared with other such objects. The bolometric light curve of SN 2003bg, on the other hand, is remarkably broad, thus suggesting a relatively large progenitor mass at the moment of explosion. These observations, together with the large value of the kinetic energy of expansion established in the accompanying paper, suggest that SN 2003bg can be regarded as a Type IIb hypernova.

Diferulate and lignin formation is related tobiochemical differences of wall-bound peroxidases

Abstract Purified cell walls from oat coleoptiles contain ionically and covalently bound peroxidaseactivity which correspond to 06% of the total peroxidase activity in the coleoptile Ionicallywall-bound peroxidases showed a 2–3-fold higher efficacy than peroxidases in the covalentfraction in the use of H 2 O 2 and phenolic substrates that are precursors of diferulate bridges andlignin The NADH oxidase activity in both fractions was effectively enhanced by p -coumaric acidand the ionic fraction showed a higher efficacy over the covalent one for NADH utilization in thepresence of this phenol Moreover the isoelectrofocusing pattern revealed marked differences inisoform composition for ionically and covalently bound wall peroxidases A cationic group ofisoperoxidases (pI∼96) was present only in the ionic fraction while the covalent fraction wasenriched with anionic forms (pI∼40–65) In excised coleoptiles incubated for 24 h the ionicallywall-bound peroxidase activity increased by 50% over covalently bound activity for 4 h ofincubation The increase of peroxidase activity preceded the accumulation of diferulic acid andlignin in oat cell walls Thus the evidence here reported suggest a possible functional differenceof peroxidase wall fractions studied related to diferulate and lignin synthesis in oat coleoptiles ©1998 Elsevier Science Ltd All rights reserved

Role of wall peroxidases in oat growth inhibition by DIMBOA

Abstract 2,4-Dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), an effective growth-inhibitor of oat coleoptiles, enhanced 1524 and 246 times the rate of NADH oxidation by ionically and covalently bound oat cell wall peroxidases, a reaction that generates H 2 O 2 . This effect was similar to that of p -coumaric acid, while ferulic acid was a poor activator of this reaction. Coniferyl alcohol did not activate NADH oxidation. DIMBOA was poorly utilized by ionic or covalent oat wall peroxidases in the presence of H 2 O 2 . With horseradish peroxidase, DIMBOA efficiently promoted compound III breakdown with a decomposition rate constant of 4.88×10 −2 s −1 . This effect was 14 times higher than that obtained with p -coumaric acid that gave a decomposition rate constant of 0.35×10 −2 s −1 . The diferulate and lignin levels in the cell walls from oat coleoptiles increased by 56 and 30%, respectively, upon DIMBOA treatment. The effect of DIMBOA on oat wall peroxidases would thus contribute to its growth inhibitory effect by promoting H 2 O 2 synthesis and phenol coupling at the cell wall level.

Do the photometric colors of Type II-P Supernovae allow accurate determination of host galaxy extinction?

We present infrared photometry of supernova (SN) 1999em, plus optical photometry, infrared photometry, and optical spectroscopy of SN 2003hn. Both objects were Type II-P SNe. The V – [RIJHK] color curves of these SNe evolved in a very similar fashion until the end of the plateau phase. This allows us to determine how much more extinction the light of SN 2003hn suffered compared to SN 1999em. Since we have an estimate of the total extinction suffered by SN 1999em from model fits of ground-based and space-based spectra as well as photometry of SN 1999em, we can estimate the total extinction and absolute magnitudes of SN 2003hn with reasonable accuracy. Since the host galaxy of SN 2003hn also produced the Type Ia SN 2001el, we can directly compare the absolute magnitudes of these two SNe of different types.

UBVRIz LIGHT CURVES OF 51 TYPE II SUPERNOVAE

Author(s): Galbany, L; Hamuy, M; Phillips, MM; Suntzeff, NB; Maza, J; Jaeger, TD; Moraga, T; Gonzalez-Gaitan, S; Krisciunas, K; Morrell, NI; Thomas-Osip, J; Krzeminski, W; Gonzalez, L; Antezana, R; Wishnjewski, M; McCarthy, P; Anderson, JP; Gutierrez, CP; Stritzinger, M; Folatelli, G; Anguita, C; Galaz, G; Green, EM; Impey, C; Kim, YC; Kirhakos, S; Malkan, MA; Mulchaey, JS; Phillips, AC; Pizzella, A; Prosser, CF; Schmidt, BP; Schommer, RA; Sherry, W; Strolger, LG; Wells, LA; Williger, GM | Abstract:

Optical Photometry of the Type Ia Supernova 1999ee and the Type Ib/c Supernova 1999ex in IC 5179

We present UBVRIz lightcurves of the Type Ia SN 1999ee and the Type Ib/c SN 1999ex, both located in the galaxy IC 5179. SN 1999ee has an extremely well sampled lightcurve spanning from 10 days before Bmax through 53 days after peak. Near maximum we find systematic differences ~0.05 mag in photometry measured with two different telescopes, even though the photometry is reduced to the same local standards around the supernova using the specific color terms for each instrumental system. We use models for our bandpasses and spectrophotometry of SN 1999ee to derive magnitude corrections (S-corrections) and remedy this problem. This exercise demonstrates the need of accurately characterizing the instrumental system before great photometric accuracies of Type Ia supernovae can be claimed. It also shows that this effect can have important astrophysical consequences since a small systematic shift of 0.02 mag in the B-V color can introduce a 0.08 mag error in the extinction corrected peak B magnitudes of a supernova and thus lead to biased cosmological parameters. The data for the Type Ib/c SN 1999ex present us with the first ever observed shock breakout of a supernova of this class. These observations show that shock breakout occurred 18 days before Bmax and support the idea that Type Ib/c supernovae are due to core collapse of massive stars rather than thermonuclear disruption of white dwarfs.

Stimulatory effect of DIMBOA on NADH oxidation catalysed by horseradish peroxidase

Abstract 2,4-Dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) effectively enhanced the rate of NADH oxidation catalysed by horseradish peroxidase isoenzyme C (HRPC), a reaction that generates H 2 O 2 . The effect showed saturation kinetics with increasing DIMBOA concentrations and the extrapolated maximum rate gave an activating factor of 246 for this hydroxamic acid. After 80% of the NADH had been oxidized, DIMBOA had converted into a species that showed absorption bands centered at 430 and 345 nm. A product with the same absorption properties was formed upon oxidation of DIMBOA with H 2 O 2 . The V max for the latter reaction was 3.3 times lower than the maximum rate of NADH oxidation in the presence of DIMBOA. Ferulic and p -coumaric acids were also stimulators of NADH oxidase activity of HRPC, giving saturating kinetics. Maximum rates obtained for these effectors give activating factors of 35 and 1170, respectively. The DIMBOA analogue 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA) that lacks the methoxy substitution in the aromatic ring was only 16% efficient in stimulating NADH oxidase as compared with DIMBOA at the 0.1 mM level. On the other hand, the benzoxazolinones 6-methoxy-benzoxazolin-2-one (MBOA) and benxoxazolin-2-one (BOA) had negligible effect on the rate of NADH oxidation and did not alter the activating effect of DIMBOA over this reaction.