Optical studies of the low velocity gradient type Ia supernovae 2009an and 2009ig

UBVRI photometry and medium resolution spectroscopy of two Type Ia supernovae, SN 2009an and SN 2009ig, are presented. Their Δm15(B) indicate these two SNe marginally deviate from “normal” Type Ia events. Spectroscopically, both SNe belong to the low velocity gradient group. The estimated mass of 56Ni ejected is almost a factor of two different for these two objects, with the estimates being ~0.4M☉ for SN 2009an and ~0.8 M☉ for SN 2009ig

The Peculiar Type Ib Supernova 2006jc: A WCO Wolf-Rayet Star Explosion

We present a theoretical model for Type Ib supernova (SN) 2006jc. We calculate the evolution of the progenitor star, hydrodynamics and nucleosynthesis of the SN explosion, and the SN bolometric light curve (LC). The synthetic bolometric LC is compared with the observed bolometric LC constructed by integrating the UV, optical, near-infrared (NIR), and mid-infrared (MIR) fluxes. The progenitor is assumed to be as massive as $40M_\odot$ on the zero-age main-sequence. The star undergoes extensive mass loss to reduce its mass down to as small as $6.9M_\odot$, thus becoming a WCO Wolf-Rayet star. The WCO star model has a thick carbon-rich layer, in which amorphous carbon grains can be formed. This could explain the NIR brightening and the dust feature seen in the MIR spectrum. We suggest that the progenitor of SN 2006jc is a WCO Wolf-Rayet star having undergone strong mass loss and such massive stars are the important sites of dust formation. We derive the parameters of the explosion model in order to reproduce the bolometric LC of SN 2006jc by the radioactive decays: the ejecta mass $4.9M_\odot$, hypernova-like explosion energy $10^{52}$ ergs, and ejected $^{56}$Ni mass $0.22M_\odot$. We also calculate the circumstellar interaction and find that a CSM with a flat density structure is required to reproduce the X-ray LC of SN 2006jc. This suggests a drastic change of the mass-loss rate and/or the wind velocity that is consistent with the past luminous blue variable (LBV)-like event.Comment: 12 pages, 11 figures. Accepted for publication in the Astrophysical Journa

Optical studies of SN 2009jf: A type Ib supernova with an extremely slow decline and aspherical signature

Optical $UBVRI$ photometry and medium resolution spectroscopy of the type Ib supernova SN 2009jf, during the period $\sim -15$ to +250days with respect to the $B$ maximum are reported. The light curves are broad, with an extremely slow decline. The early post-maximum decline rate in the $V$ band is similar to SN 2008D, however, the late phase decline rate is slower than other studied type Ib supernovae. With an absolute magnitude of $M_{V} = -17.96\pm0.19$ magnitude at peak, SN 2009jf is a normally bright supernova. The peak bolometric luminosity and the energy deposition rate via $^{56}$Ni $\rightarrow$ $^{56}$Co chain indicate that $\sim {0.17}^{+0.03}_{-0.03}$ M$_{\odot}$ of $^{56}$Ni was ejected during the explosion. He\,I 5876 \AA\ line is clearly identified in the first spectrum of day $\sim -15$, at a velocity of $\sim 16000$ km sec$^{-1}$. The [O\,I] 6300-6364 \AA\ line seen in the nebular spectrum has a multi-peaked and asymmetric emission profile, with the blue peak being stronger. The estimated flux in this line implies \ga 1.34 M$_\odot$ oxygen was ejected. The slow evolution of the light curves of SN 2009jf indicates the presence of a massive ejecta. The high expansion velocity in the early phase and broader emission lines during the nebular phase suggest it to be an explosion with a large kinetic energy. A simple qualitative estimate leads to the ejecta mass of M$_{\rm ej} = 4-9$ M$_\odot$, and kinetic energy E$_{\rm K} = 3-8 \times 10^{51}$ erg. The ejected mass estimate is indicative of an initial main-sequence mass of \ga 20- 25 M$_\odot$.Comment: 14 pages, 13 figures; accepted for publication in MNRA

Optical photometry and spectroscopy of the type Ibn supernova SN 2006jc until the onset of dust formation

We present optical UBVRI photometric and spectroscopic data of the type Ibn supernova SN 2006jc, until the onset of the dust forming phase. The optical spectrum shows a blue continuum and is dominated by the presence of moderately narrow (velocity ~2500 km/s) He I emission lines superimposed over a relatively weak supernova spectrum. The helium lines are produced in a pre-existing He rich circumstellar shell. The observed helium line fluxes indicate the circumstellar shell is dense, with a density of ~10^9 - 10^{10} cm^{-3}. The helium mass in this shell is estimated to be <~0.07 Msun. The optical light curves show a clear signature of dust formation, indicated by a sharp decrease in the magnitudes around day 50, accompanied by a reddening of the colours. The evolution of the optical light curves during the early phase and that of the uvoir bolometric light curve at all phases is reasonably similar to normal Ib/c supernovae.Comment: Accepted for publication in MNRA

Spectroscopic Monotoring of the Symbiotic Star BX Monocerotis

Low resolution optical spectra of the symbiotic star BX Monocerotis in the 3500-9000 Å range obtained during 1999–2010 are described. the spectrum of BX Mon at all phases is dominated by the cool component, with a red continuum and TiO absorption. Emission lines, predominantly due to HI, He I, He II, Fe II, Ca II and [O III] are seen superimposed on the spectrum of the M5III star, with variable intensities. the observed variations in the spectra seem to be correlated with the orbital phases

A tale of two GRB-SNe at a common redshift of z=0.54

none74We present ground-based and Hubble Space Telescope optical observations of the optical transients (OTs) of long-duration Gamma Ray Bursts (GRBs) 060729 and 090618, both at a redshift of z=0.54. For GRB 060729, bumps are seen in the optical light curves (LCs), and the late-time broad-band spectral energy distributions (SEDs) of the OT resemble those of local Type Ic supernovae (SNe). For GRB 090618, the dense sampling of our optical observations has allowed us to detect well-defined bumps in the optical LCs, as well as a change in colour, that are indicative of light coming from a core-collapse SN. The accompanying SNe for both events are individually compared with SN1998bw, a known GRB supernova, and SN1994I, a typical Type Ic supernova without a known GRB counterpart, and in both cases the brightness and temporal evolution more closely resemble SN1998bw. We also exploit our extensive optical and radio data for GRB 090618, as well as the publicly available Swift-XRT data, and discuss the properties of the afterglow at early times. In the context of a simple jet-like model, the afterglow of GRB 090618 is best explained by the presence of a jet-break at t − to > 0.5 d. We then compare the rest-frame, peak V-band absolute magnitudes of all of the GRB and X-Ray Flash (XRF)-associated SNe with a large sample of local Type Ibc SNe, concluding that, when host extinction is considered, the peak magnitudes of the GRB/XRF-SNe cannot be distinguished from the peak magnitudes of non-GRB/XRF SNe.noneZ. Cano; D. Bersier; C. Guidorzi; R. Margutti; K.M Svensson; S. Kobayashi; A. Melandri; K. Wiersema; A. Pozanenko; A.J. van der Horst; G. G. Pooley; A. Fernandez-Soto; A.J. Castro-Tirado; A. de Ugarte Postigo; M. Im; A.P. Kamble; D. Sahu; M. Alexander; Jorge Alonso-Lorite; G. Anupama; J. L. Bibby; M. J. Burgdorf; N. Clay; P.A. Curran; T. A. Fatkhullin; A. S. Fruchter; P. Garnavich; A. Gomboc; J. Gorosabel; J. F. Graham; U. Gurugubelli; J. Haislip; K. Huang; A. Huxor; M. Ibrahimov; Y. Jeon; Y-B. Jeon; K. Ivarsen; D. Kasen; E. Klunko; C. Kouveliotou; A. LaCluyze; A. J. Levan; V. Loznikov; P.A. Mazzali; C. Mottram; C. G. Mundell; P.E. Nugent; M. Nysewander; P. T. OBrien; W. -K. Park; V. Peris; E. Pian; D. Reichart; J. E. Rhoads; E. Rol; V. Rumyantsev; V. Scowcroft; D. Shakhovskoy; E. Small; R. J. Smith; V. V. Sokolov; R.L.C. Starling; I. Steele; R. Strom; N. R. Tanvir; Y. Tsapras; Y. Urata; O. Vaduvescu; A. Volnova; A. Volvach; R. A. M. J. Wijers; S. E. Woosley; D. R. YoungZ., Cano; D., Bersier; Guidorzi, Cristiano; R., Margutti; K. M., Svensson; S., Kobayashi; A., Melandri; K., Wiersema; A., Pozanenko; A. J., van der Horst; G. G., Pooley; A., Fernandez Soto; A. J., Castro Tirado; A., de Ugarte Postigo; M., Im; A. P., Kamble; D., Sahu; M., Alexander; Jorge Alonso, Lorite; G., Anupama; J. L., Bibby; M. J., Burgdorf; N., Clay; P. A., Curran; T. A., Fatkhullin; A. S., Fruchter; P., Garnavich; A., Gomboc; J., Gorosabel; J. F., Graham; U., Gurugubelli; J., Haislip; K., Huang; A., Huxor; M., Ibrahimov; Y., Jeon; Y. B., Jeon; K., Ivarsen; D., Kasen; E., Klunko; C., Kouveliotou; A., Lacluyze; A. J., Levan; V., Loznikov; P. A., Mazzali; C., Mottram; C. G., Mundell; P. E., Nugent; M., Nysewander; P. T., Obrien; W. K., Park; V., Peris; E., Pian; D., Reichart; J. E., Rhoads; E., Rol; V., Rumyantsev; V., Scowcroft; D., Shakhovskoy; E., Small; R. J., Smith; V. V., Sokolov; R. L. C., Starling; I., Steele; R., Strom; N. R., Tanvir; Y., Tsapras; Y., Urata; O., Vaduvescu; A., Volnova; A., Volvach; R. A. M. J., Wijers; S. E., Woosley; D. R., Youn