اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدEvidence of Asymmetry in SN 2007rt, a Type IIn Supernova
147
0
0.0
(
0
)
تأليف
C. Trundle
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
An optical photometric and spectroscopic analysis of the slowly-evolving Type IIn SN2007rt is presented, covering a duration of 481 days after discovery. Its earliest spectrum, taken approximately 100 days after the explosion epoch, indicates the presence of a dense circumstellar medium, with which the supernova ejecta is interacting. This is supported by the slowly-evolving light curve. A notable feature in the spectrum of SN 2007rt is the presence of a broad He I 5875 line, not usually detected in Type IIn supernovae. This may imply that the progenitor star has a high He/H ratio, having shed a significant portion of its hydrogen shell via mass-loss. An intermediate resolution spectrum reveals a narrow Halpha P-Cygni profile, the absorption component of which has a width of 128 km/s. This slow velocity suggests that the progenitor of SN 2007rt recently underwent mass-loss with wind speeds comparable to the lower limits of those detected in luminous blue variables. Asymmetries in the line profiles of H and He at early phases bears some resemblance to double-peaked features observed in a number of Ib/c spectra. These asymmetries may be indicative of an asymmetric or bipolar outflow or alternatively dust formation in the fast expanding ejecta. In addition, the late time spectrum, at over 240 days post-explosion, shows clear evidence for the presence of newly formed dust.
قيم البحث
اقرأ أيضاً
We present an optical and near-infrared photometric and spectroscopic study of supernova (SN) 2009kn spanning ~1.5 yr from the discovery. The optical spectra are dominated by the narrow (full width at half-maximum ~1000 km s^-1) Balmer lines distinct
ive of a Type IIn SN with P Cygni profiles. Contrarily, the photometric evolution resembles more that of a Type IIP SN with a large drop in luminosity at the end of the plateau phase. These characteristics are similar to those of SN 1994W, whose nature has been explained with two different models with different approaches. The well-sampled data set on SN 2009kn offers the possibility to test these models, in the case of both SN 2009kn and SN 1994W. We associate the narrow P Cygni lines with a swept-up shell composed of circumstellar matter and SN ejecta. The broad emission line wings, seen during the plateau phase, arise from internal electron scattering in this shell. The slope of the light curve after the post-plateau drop is fairly consistent with that expected from the radioactive decay of 56Co, suggesting an SN origin for SN 2009kn. Assuming radioactivity to be the main source powering the light curve of SN 2009kn in the tail phase, we infer an upper limit for 56Ni mass of 0.023 M_sun. This is significantly higher than that estimated for SN 1994W, which also showed a much steeper decline of the light curve after the post-plateau drop. We also observe late-time near-infrared emission which most likely arises from newly formed dust produced by SN 2009kn. As with SN 1994W, no broad lines are observed in the spectra of SN 2009kn, not even in the late-time tail phase.
We present photometry, spectra, and spectropolarimetry of supernova (SN) 2014ab, obtained through $sim 200$ days after peak brightness. SN 2014ab was a luminous Type IIn SN ($M_V < -19.14$ mag) discovered after peak brightness near the nucleus of its
host galaxy, VV 306c. Prediscovery upper limits constrain the time of explosion to within 200 days prior to discovery. While SN 2014ab declined by $sim 1$ mag over the course of our observations, the observed spectrum remained remarkably unchanged. Spectra exhibit an asymmetric emission-line profile with a consistently stronger blueshifted component, suggesting the presence of dust or a lack of symmetry between the far side and near side of the SN. The Pa$beta$ emission line shows a profile very similar to that of H$alpha$, implying that this stronger blueshifted component is caused either through obscuration by large dust grains, occultation by optically thick material, or a lack of symmetry between the far side and near side of the interaction region. Despite these asymmetric line profiles, our spectropolarimetric data show that SN 2014ab has little detected polarization after accounting for the interstellar polarization. This suggests that we are seeing emission from a photosphere that has only small deviation from circular symmetry face-on. We are likely seeing a SN IIn with nearly circular symmetry in the plane normal to our line of sight, but with either large-grain dust or significant asymmetry in the density of circumstellar material or SN ejecta along our line of sight. We suggest that SN 2014ab and SN 2010jl (as well as other SNe IIn) may be similar events viewed from different directions.
In order to understand the contribution of core-collapse supernovae to the dust budget of the early universe, it is important to understand not only the mass of dust that can form in core-collapse supernovae but also the location and rate of dust for
mation. SN 2005ip is of particular interest since dust has been inferred to have formed in both the ejecta and the post-shock region behind the radiative reverse shock. We have collated eight optical archival spectra that span the lifetime of SN 2005ip and we additionally present a new X-shooter optical-near-IR spectrum of SN 2005ip at 4075d post-discovery. Using the Monte Carlo line transfer code DAMOCLES, we have modelled the blueshifted broad and intermediate width H$alpha$, H$beta$ and He I lines from 48d to 4075d post-discovery using an ejecta dust model. We find that dust in the ejecta can account for the asymmetries observed in the broad and intermediate width H$alpha$, H$beta$ and He I line profiles at all epochs and that it is not necessary to invoke post-shock dust formation to explain the blueshifting observed in the intermediate width post-shock lines. Using a Bayesian approach, we have determined the evolution of the ejecta dust mass in SN 2005ip over 10 years presuming an ejecta dust model, with an increasing dust mass from ~10$^{-8}$ M$_{odot}$ at 48d to a current dust mass of $sim$0.1 M$_{odot}$.
We have recently confirmed SN 1996cr as a late-time type IIn supernova (SN) via VLT spectroscopy and isolated its explosion date to ~1 yr using archival optical imaging. We briefly touch upon here the wealth of optical, X-ray, and radio archival obse
rvations available for this enigmatic source. Due to its relative proximity (3.8 +/-0.6 Mpc), SN 1996cr ranks among the brightest X-ray and radio SNe ever detected and, as such, may offer powerful insights into the structure and composition of type IIn SNe. We also find that SN 1996cr is matched to GRB 4B 960202 at a 2-3 sigma confidence level, making it perhaps the third GRB to be significantly associated with a type II SN. We speculate on whether SN 1996cr could be an off-axis or ``failed GRB.
The physical characteristics of dust formed in supernovae is poorly known. In this paper, we investigate the extinction properties of dust formed in the type IIn SN 2005ip. The observed light curves of SN 2005ip all exhibit a sudden drop around 50 da
ys after discovery. This has been attributed to dust formation in the dense circumstellar medium. We modeled the intrinsic light curves in six optical bands, adopting a theoretical model for the luminosity evolution of supernovae interacting with their circumstellar material. From the difference between the observed and intrinsic light curves, we calculated extinction curves as a function of time. The total-to-selective extinction ratio, $R_V$, was determined from the extinction in the B and V bands. The resulting extinction, $A_V$, increases monotonically up to about 1 mag, 150 days after discovery. The inferred $R_V$ value also increases slightly with time, but appears constant in the range 4.5--8, beyond 100 days after discovery. The analysis confirms that dust is likely formed in SN 2005ip, starting about two months after explosion. The high value of $R_V$, that is, gray dust, suggests dust properties different from of the Milky Way. While this result hinges on the assumed theoretical intrinsic light curve evolution, it is encouraging that the fitted light curves are as expected for standard ejecta and circumstellar medium density structures.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
