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تسجيل مستخدم جديدMassive stars exploding in a He-rich circumstellar medium. I. Type Ibn (SN 2006jc-like) events
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We present new spectroscopic and photometric data of the type Ibn supernovae 2006jc, 2000er and 2002ao. We discuss the general properties of this recently proposed supernova family, which also includes SN 1999cq. The early-time monitoring of SN 2000er traces the evolution of this class of objects during the first few days after the shock breakout. An overall similarity in the photometric and spectroscopic evolution is found among the members of this group, which would be unexpected if the energy in these core-collapse events was dominated by the interaction between supernova ejecta and circumstellar medium. Type Ibn supernovae appear to be rather normal type Ib/c supernova explosions which occur within a He-rich circumstellar environment. SNe Ibn are therefore likely produced by the explosion of Wolf-Rayet progenitors still embedded in the He-rich material lost by the star in recent mass-loss episodes, which resemble known luminous blue variable eruptions. The evolved Wolf-Rayet star could either result from the evolution of a very massive star or be the more evolved member of a massive binary system. We also suggest that there are a number of arguments in favour of a type Ibn classification for the historical SN 1885A (S-Andromedae), previously considered as an anomalous type Ia event with some resemblance to SN 1991bg.
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We present ultraviolet, optical and near-infrared data of the Type Ibn supernovae (SNe) 2010al and 2011hw. SN 2010al reaches an absolute magnitude at peak of M(R) = -18.86 +- 0.21. Its early light curve shows similarities with normal SNe Ib, with a r
ise to maximum slower than most SNe Ibn. The spectra are dominated by a blue continuum at early stages, with narrow P-Cygni He I lines indicating the presence of a slow-moving, He-rich circumstellar medium. At later epochs the spectra well match those of the prototypical SN Ibn 2006jc, although the broader lines suggest that a significant amount of He was still present in the stellar envelope at the time of the explosion. SN 2011hw is somewhat different. It was discovered after the first maximum, but the light curve shows a double-peak. The absolute magnitude at discovery is similar to that of the second peak (M(R) = -18.59 +- 0.25), and slightly fainter than the average of SNe Ibn. Though the spectra of SN 2011hw are similar to those of SN 2006jc, coronal lines and narrow Balmer lines are cleary detected. This indicates substantial interaction of the SN ejecta with He-rich, but not H-free, circumstellar material. The spectra of SN 2011hw suggest that it is a transitional SN Ibn/IIn event similar to SN 2005la. While for SN 2010al the spectro-photometric evolution favours a H-deprived Wolf-Rayet progenitor (of WN-type), we agree with the conclusion of Smith et al. (2012) that the precursor of SN 2011hw was likely in transition from a luminous blue variable to an early Wolf-Rayet (Ofpe/WN9) stage.
We present spectroscopic and photometric data of the Type Ibn supernova (SN) 2014av, discovered by the Xingming Observatory Sky Survey. Stringent pre-discovery detection limits indicate that the object was detected for the first time about 4 days aft
er the explosion. A prompt follow-up campaign arranged by amateur astronomers allowed us to monitor the rising phase (lasting 10.6 days) and to accurately estimate the epoch of the maximum light, on 2014 April 23 (JD = 2456771.1 +/- 1.2). The absolute magnitude of the SN at the maximum light is M(R) = -19.76 +/- 0.16. The post-peak light curve shows an initial fast decline lasting about 3 weeks, and is followed by a slower decline in all bands until the end of the monitoring campaign. The spectra are initially characterized by a hot continuum. Later on, the temperature declines and a number of lines become prominent mostly in emission. In particular, later spectra are dominated by strong and narrow emission features of He I typical of Type Ibn supernovae (SNe), although there is a clear signature of lines from heavier elements (in particular O I, Mg II and Ca II). A forest of relatively narrow Fe II lines is also detected showing P-Cygni profiles, with the absorption component blue-shifted by about 1200 km/s. Another spectral feature often observed in interacting SNe, a strong blue pseudo-continuum, is seen in our latest spectra of SN 2014av. We discuss in this paper the physical parameters of SN 2014av in the context of the Type Ibn supernova variety.
We present optical observations of the peculiar Type Ibn supernova (SN Ibn) OGLE-2012-SN-006, discovered and monitored by the OGLE-IV survey, and spectroscopically followed by PESSTO at late phases. Stringent pre-discovery limits constrain the explos
ion epoch with fair precision to JD = 2456203.8 +- 4.0. The rise time to the I-band light curve maximum is about two weeks. The object reaches the peak absolute magnitude M(I) = -19.65 +- 0.19 on JD = 2456218.1 +- 1.8. After maximum, the light curve declines for about 25 days with a rate of 4 mag per 100d. The symmetric I-band peak resembles that of canonical Type Ib/c supernovae (SNe), whereas SNe Ibn usually exhibit asymmetric and narrower early-time light curves. Since 25 days past maximum, the light curve flattens with a decline rate slower than that of the 56Co to 56Fe decay, although at very late phases it steepens to approach that rate. An early-time spectrum is dominated by a blue continuum, with only a marginal evidence for the presence of He I lines marking this SN Type. This spectrum shows broad absorptions bluewards than 5000A, likely O II lines, which are similar to spectral features observed in super-luminous SNe at early epochs. The object has been spectroscopically monitored by PESSTO from 90 to 180 days after peak, and these spectra show the typical features observed in a number of SN 2006jc-like events, including a blue spectral energy distribution and prominent and narrow (v(FWHM) ~ 1900 km/s) He I emission lines. This suggests that the ejecta are interacting with He-rich circumstellar material. The detection of broad (10000 km/s) O I and Ca II features likely produced in the SN ejecta (including the [O I] 6300A,6364A doublet in the latest spectra) lends support to the interpretation of OGLE-2012-SN-006 as a core-collapse event.
We present spectroscopic and photometric observations for the Type Ibn supernova (SN) dubbed PSN J07285387+3349106. Using data provided by amateur astronomers, we monitored the photometric rise of the SN to maximum light, occurred on 2015 February 18
.8 UT (JD(max,V) = 2457072.0 +- 0.8). PSN J07285387+3349106 exploded in the inner region of an infrared luminous galaxy, and is the most reddened SN Ibn discovered so far. We apply multiple methods to derive the total reddening to the SN, and determine a total colour excess E(B-V)(tot) = 0.99 +- 0.48 mag. Accounting for the reddening correction, which is affected by a large uncertainty, we estimate a peak absolute magnitude of M(V) = -20.30 +- 1.50. The spectra are dominated by continuum emission at early phases, and He I lines with narrow P-Cygni profiles are detected. We also identify weak Fe III and N II features. All these lines show an absorption component which is blue-shifted by about 900-1000 km/s. The spectra also show relatively broad He I line wings with low contrast, which extend to above 3000 km/s. From about 2 weeks past maximum, broad lines of O I, Mg II and the Ca II near-infrared triplet are identified. The composition and the expansion velocity of the circumstellar material, and the presence of He I and alpha-elements in the SN ejecta indicate that PSN J07285387+3349106 was produced by the core-collapse of a stripped-envelope star. We suggest that the precursor was WNE-type Wolf-Rayet star in its dense, He-rich circumstellar cocoon.
We present near- and mid-infrared (IR) photometric data of the Type Ibn supernova (SN) 2006jc obtained with the United Kingdom Infrared Telescope (UKIRT), the Gemini North Telescope, and the Spitzer Space Telescope between days 86 and 493 post-explos
ion. We find that the IR behaviour of SN 2006jc can be explained as a combination of IR echoes from two manifestations of circumstellar material. The bulk of the near-IR emission arises from an IR echo from newly-condensed dust in a cool dense shell (CDS) produced by the interaction of the ejecta outward shock with a dense shell of circumstellar material ejected by the progenitor in a luminous blue variable (LBV) like outburst about two years prior to the SN explosion. The CDS dust mass reaches a modest 3.0 x 10^(-4) M(solar) by day 230. While dust condensation within a CDS formed behind the ejecta inward shock has been proposed before for one event (SN 1998S), SN 2006jc is the first one showing evidence for dust condensation in a CDS formed behind the ejecta outward shock in the circumstellar material. At later epochs, a substantial and growing contribution to the IR fluxes arises from an IR echo from pre-existing dust in the progenitor wind. The mass of the pre-existing CSM dust is at least ~8 x 10^(-3) M(solar). This work therefore adds to the evidence that mass-loss from the progenitors of core-collapse supernovae could be a major source of dust in the universe. However, yet again, we see no direct evidence that the explosion of a supernova produces anything other than a very modest amount of dust.
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