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

We present infrared photometry of SN 1999em, plus optical photometry, infrared photometry, and optical spectroscopy of SN 2003hn. Both objects were Type II-P supernovae. The V-[RIJHK] color curves of these supernovae evolved in a very similar fashion until the end of 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.Comment: 24 pages, 6 figure

A Study of Carbon Features in Type Ia Supernova Spectra

One of the major differences between various explosion scenarios of Type Ia supernovae (SNe Ia) is the remaining amount of unburned (C+O) material and its velocity distribution within the expanding ejecta. While oxygen absorption features are not uncommon in the spectra of SNe Ia before maximum light, the presence of strong carbon absorption has been reported only in a minority of objects, typically during the pre-maximum phase. The reported low frequency of carbon detections may be due to low signal-to-noise data, low abundance of unburned material, line blending between C II 6580 and Si II 6355, ejecta temperature differences, asymmetrical distribution effects, or a combination of these. However, a survey of published pre-maximum spectra reveals that more SNe Ia than previously thought may exhibit C II 6580 absorption features and relics of line blending near 6300 Angstroms. Here we present new SN Ia observations where spectroscopic signatures of C II 6580 are detected, and investigate the presence of C II 6580 in the optical spectra of 19 SNe Ia using the parameterized spectrum synthesis code, SYNOW. Most of the objects in our sample that exhibit C II 6580 absorption features are of the low-velocity gradient subtype. Our study indicates that the morphology of carbon-rich regions is consistent with either a spherical distribution or a hemispheric asymmetry, supporting the recent idea that SN Ia diversity may be a result of off-center ignition coupled with observer line-of-sight effects.Comment: 10 papges, 9 figures, 3 table

The Subluminous Supernova 2007qd: A Missing Link in a Family of Low-Luminosity Type Ia Supernovae

We present multi-band photometry and multi-epoch spectroscopy of the peculiar Type Ia supernova (SN Ia) 2007qd, discovered by the SDSS-II Supernova Survey. It possesses physical properties intermediate to those of the peculiar SN 2002cx and the extremely low-luminosity SN 2008ha. Optical photometry indicates that it had an extraordinarily fast rise time of <= 10 days and a peak absolute B magnitude of -15.4 +/- 0.2 at most, making it one of the most subluminous SN Ia ever observed. Follow-up spectroscopy of SN 2007qd near maximum brightness unambiguously shows the presence of intermediate-mass elements which are likely caused by carbon/oxygen nuclear burning. Near maximum brightness, SN 2007qd had a photospheric velocity of only 2800 km/s, similar to that of SN 2008ha but about 4000 and 7000 km/s less than that of SN 2002cx and normal SN Ia, respectively. We show that the peak luminosities of SN 2002cx-like objects are highly correlated with both their light-curve stretch and photospheric velocities. Its strong apparent connection to other SN 2002cx-like events suggests that SN 2007qd is also a pure deflagration of a white dwarf, although other mechanisms cannot be ruled out. It may be a critical link between SN 2008ha and the other members of the SN 2002cx-like class of objects.Comment: To be published in the Astrophysical Journal; 37 pages, 13 figures, 4 table

T-Lymphoblastic Lymphoma Cells Express High Levels of BCL2, S1P1, and ICAM1, Leading to a Blockade of Tumor Cell Intravasation

The molecular events underlying the progression of T-lymphoblastic lymphoma (T-LBL) to acute T-lymphoblastic leukemia (T-ALL) remain elusive. In our zebrafish model, concomitant overexpression of bcl-2 with Myc accelerated T-LBL onset while inhibiting progression to T-ALL. The T-LBL cells failed to invade the vasculature and showed evidence of increased homotypic cell-cell adhesion and autophagy. Further analysis using clinical biopsy specimens revealed autophagy and increased levels of BCL2, S1P1, and ICAM1 in human T-LBL compared with T-ALL. Inhibition of S1P1 signaling in T-LBL cells led to decreased homotypic adhesion in vitro and increased tumor cell intravasation in vivo. Thus, blockade of intravasation and hematologic dissemination in T-LBL is due to elevated S1P1 signaling, increased expression of ICAM1, and augmented homotypic cell-cell adhesion.Stem Cell and Regenerative Biolog

SN 1998A: Explosion of a Blue Supergiant

We present spectroscopic and photometric observations of the peculiar Type II supernova (SN) 1998A. The light curves and spectra closely resemble those of SN 1987A, suggesting that the SN 1998A progenitor exploded when it was a compact blue supergiant. However, the comparison with SN 1987A also highlights some important differences: SN 1998A is more luminous and the spectra show bluer continua and larger expansion velocities at all epochs. These observational properties indicate that the explosion of SN 1998A is more energetic than SN 1987A and more typical of SNe II. Comparing the observational data to simulations, we deduce that the progenitor of SN 1998A was a massive star (~ 25 Mo) with a small pre-supernova radius (< 6 x 10^{12} cm). The Ba II lines, unusually strong in SN 1987A and some faint II--P events, are almost normal in the case of SN 1998A, indicating that the temperature plays a key role in determining their strength.Comment: 15 pages, 16 figures, accepted for publication in MNRA

Direct Analysis of Spectra of Type Ib Supernovae

Synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW are compared to photospheric-phase spectra of Type Ib supernovae (SNe Ib). Although the synthetic spectra are based on many simplifying approximations, including spherical symmetry, they account well for the observed spectra. Our sample of SNe Ib obeys a tight relation between the velocity at the photosphere, as determined from the Fe II features, and the time relative to that of maximum light. From this we infer that the masses and the kinetic energies of the events in this sample were similar. After maximum light the minimum velocity at which the He I features form usually is higher than the velocity at the photosphere, but the minimum velocity of the ejected helium is at least as low as 7000 kms. Previously unpublished spectra of SN 2000H reveal the presence of hydrogen absorption features, and we conclude that hydrogen lines also were present in SNe 1999di and 1954A. Hydrogen appears to be present in SNe Ib in general, although in most events it becomes too weak to identify soon after maximum light. The hydrogen-line optical depths that we use to fit the spectra of SNe 2000H, 1999di, and 1954A are not high, so only a mild reduction in the hydrogen optical depths would be required to make these events look like typical SNe Ib. Similarly, the He I line optical depths are not very high, so a moderate reduction would make SNe Ib look like SNe Ic.Comment: 21 pages and 24 figures, submitted to Ap

Low Luminosity Type II Supernovae: Spectroscopic and Photometric Evolution

In this paper we present spectroscopic and photometric observations for four core collapse supernovae (SNe), namely SNe 1994N, 1999br, 1999eu and 2001dc. Together with SN 1997D, we show that they form a group of exceptionally low-luminosity events. These SNe have narrow spectral lines (indicating low expansion velocities) and low luminosities at every phase (significantly lower than those of typical core-collapse supernovae). The very low luminosity during the ^{56}Co radioactive decay tail indicates that the mass of ^{56}Ni ejected during the explosion is much smaller (M(Ni) ~ 2-8 x 10^{-3} Mo) than the average (M(Ni) ~ 6-10 x 10^{-2} Mo). Two supernovae of this group (SN 1999br and SN 2001dc) were discovered very close to the explosion epoch, allowing us to determine the lengths of their plateaux (~ 100 days) as well as establishiing the explosion epochs of the other, less-completely observed SNe. It is likely that this group of SNe represent the extreme low-luminosity tail of a single continuous distribution of SN II-P events. Their kinetic energy is also exceptionally low. Although an origin from low mass progenitors has also been proposed for low-luminosity core-collapse SNe, recent work provides evidence in favour of the high mass progenitor scenario. The incidence of these low--luminosity SNe could be as high as 4-5$$ of all type II SNe.Comment: 23 pages, 26 figures, accepted for publication in MNRA

The Exceptionally Luminous Type II-L SN 2008es

We report on our early photometric and spectroscopic observations of the extremely luminous Type II supernova (SN) 2008es. With an observed peak optical magnitude of m_V = 17.8 and at a redshift z = 0.213, SN 2008es had a peak absolute magnitude of M_V = -22.3, making it the second most luminous SN ever observed. The photometric evolution of SN 2008es exhibits a fast decline rate (~0.042 mag d^-1), similar to the extremely luminous Type II-L SN 2005ap. We show that SN 2008es spectroscopically resembles the luminous Type II-L SN 1979C. Although the spectra of SN 2008es lack the narrow and intermediate-width line emission typically associated with the interaction of a SN with the circumstellar medium of its progenitor star, we argue that the extreme luminosity of SN 2008es is powered via strong interaction with a dense, optically thick circumstellar medium. The integrated bolometric luminosity of SN 2008es yields a total radiated energy at ultraviolet and optical wavelengths of >10^51 ergs. Finally, we examine the apparently anomalous rate at which the Texas Supernova Search has discovered rare kinds of supernovae, including the five most luminous supernovae observed to date, and find that their results are consistent with those of other modern SN searches.Comment: accepted to ApJ, 10 pages, 7 figures, 6 tables. Minor revisions, conclusions remain unchange

Spectra of Hydrogen-poor Superluminous Supernovae from the Palomar Transient Factory

Most Type I superluminous supernovae (SLSNe-I) reported to date have been identified by their high peak luminosities and spectra lacking obvious signs of hydrogen. We demonstrate that these events can be distinguished from normal-luminosity SNe (including Type Ic events) solely from their spectra over a wide range of light-curve phases. We use this distinction to select 19 SLSNe-I and four possible SLSNe-I from the Palomar Transient Factory archive (including seven previously published objects). We present 127 new spectra of these objects and combine these with 39 previously published spectra, and we use these to discuss the average spectral properties of SLSNe-I at different spectral phases. We find that Mn II most probably contributes to the ultraviolet spectral features after maximum light, and we give a detailed study of the O II features that often characterize the early-time optical spectra of SLSNe-I. We discuss the velocity distribution of O II, finding that for some SLSNe-I this can be confined to a narrow range compared to relatively large systematic velocity shifts. Mg II and Fe II favor higher velocities than O II and C II, and we briefly discuss how this may constrain power-source models. We tentatively group objects by how well they match either SN 2011ke or PTF12dam and discuss the possibility that physically distinct events may have been previously grouped together under the SLSN-I label

Dirty and 40 days in the wilderness: Eliciting childbirth and postnatal cultural practices and beliefs in Nepal.

Background: Pregnancy and childbirth are socio-cultural events that carry varying meanings across different societies and cultures. These are often translated into social expectations of what a particular society expects women to do (or not to do) during pregnancy, birth and/or the postnatal period. This paper reports a study exploring beliefs around childbirth in Nepal, a low-income country with a largely Hindu population. The paper then sets these findings in the context of the wider global literature around issues such as periods where women are viewed as polluted (or dirty even) after childbirth. Methods: A qualitative study comprising five in-depth face-to-face interviews and 14 focus group discussions with mainly women, but also men and health service providers. The qualitative findings in Nepal were compared and contrasted with the literature on practices and cultural beliefs related to the pregnancy and childbirth period across the globe and at different times in history. Results: The themes that emerged from the analysis included: (a) cord cutting & placenta rituals; (b) rest & seclusion; (c) purification, naming & weaning ceremonies and (d) nutrition and breastfeeding. Physiological changes in mother and baby may underpin the various beliefs, ritual and practices in the postnatal period. These practices often mean women do not access postnatal health services. Conclusions: The cultural practices, taboos and beliefs during pregnancy and around childbirth found in Nepal largely resonate with those reported across the globe. This paper stresses that local people’s beliefs and practices offer both opportunities and barriers to health service providers. Maternity care providers need to be aware of local values, beliefs and traditions to anticipate and meet the needs of women, gain their trust and work with them