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Register a new userDetailed Radio View on Two Stellar Explosions and Their Host Galaxy: XRF080109/SN2008D and SN2007uy in NGC2770
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Added by
Alexander J. van der Horst
Publication date
2010
fields
Physics
and research's language is
English
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The galaxy NGC2770 hosted two core-collapse supernova explosions, SN2008D and SN2007uy, within 10 days of each other and 9 years after the first supernova of the same type, SN1999eh, was found in that galaxy. In particular SN2008D attracted a lot of attention due to the detection of an X-ray outburst, which has been hypothesized to be caused by either a (mildly) relativistic jet or the supernova shock breakout. We present an extensive study of the radio emission from SN2008D and SN2007uy: flux measurements with the Westerbork Synthesis Radio Telescope and the Giant Metrewave Radio Telescope, covering ~600 days with observing frequencies ranging from 325 MHz to 8.4 GHz. The results of two epochs of global Very Long Baseline Interferometry observations are also discussed. We have examined the molecular gas in the host galaxy NGC2770 with the Arizona Radio Observatory 12-m telescope, and present the implications of our observations for the star formation and seemingly high SN rate in this galaxy. Furthermore, we discuss the near-future observing possibilities of the two SNe and their host galaxy at low radio frequencies with the Low Frequency Array.
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The host galaxies of nearby (z<0.3) core-collapse supernovae and long-duration gamma-ray bursts offer an excellent means of probing the environments and populations that produce these events varied massive progenitors. These same young stellar progenitors make LGRBs and SNe valuable and potentially powerful tracers of star formation, metallicity, the IMF, and the end phases of stellar evolution. However, properly utilizing these progenitors as tools requires a thorough understanding of their formation and, consequently, the physical properties of their parent host environments. This review looks at some of the recent work on LGRB and SN hosts with resolved environments that allows us to probe the precise explosion sites and surrounding environments of these events in incredible detail.
The only supernovae (SNe) to have shown early gamma-ray or X-ray emission thus far are overenergetic, broad-lined Type Ic SNe (Hypernovae - HNe). Recently, SN 2008D shows several novel features: (i) weak XRF, (ii) an early, narrow optical peak, (iii) disappearance of the broad lines typical of SNIc HNe, (iv) development of He lines as in SNeIb. Detailed analysis shows that SN 2008D was not a normal SN: its explosion energy (KE ~ 6*10^{51} erg) and ejected mass (~7 Msun) are intermediate between normal SNeIbc and HNe. We derive that SN 2008D was originally a ~30Msun star. When it collapsed a black hole formed and a weak, mildly relativistic jet was produced, which caused the XRF. SN 2008D is probably among the weakest explosions that produce relativistic jets. Inner engine activity appears to be present whenever massive stars collapse to black holes.
The possible existence of a continuum encompassing the diversity of explosive stellar deaths,ranging from ordinary SNe to relativistic hypernovae associated with long duration GRBs, is under intense debate. In this context, SN2008D associated with XT080109 could represent a paradigmatic case, since it might exemplify a potential borderline event. The main aim is to infer geometric information of SN2008D through the evolution of its linear optical polarization. We also report the polarization evolution of SN2007uy, and discuss the properties of the host ISM towards the XT. The final goal is to compare the polarization properties, and hence the geometries of both SNe, which shone contemporaneously in NGC2770. This fortunate coincidence brought us the opportunity to observe both SNe simultaneously, and most importantly, with identical instrumental setups. The observations span 74.9 days, starting 3.6 days after the XT and are distributed in 11 visits. In addition we performed observations in the mm range in order to identify the dominant polarization. We report positive linear polarization detections at several epochs for SN2008D at a level of ~1% and at ~1.5% for SN2007uy. SN2007uy shows constant polarization, which could be described by the host interstellar polarization plus a constant eccentricity expansion on the sky plane. A statistical analysis of the distribution of the SN2008D Stokes parametres suggests that it could show an intrinsic variable polarization component. Assuming the SN2007uy polarization is constant, we find that the evolution of the intrinsic SN2008D polarization could be explained by an aspherical axisymmetric expansion with variable eccentricity. We come to the same result even if we make no assumption on SN2007uy, although at a lower significance level. We suggest that at least the projected, if not the intrinsic, geometries of both SNe could differ.
We aim to understand the properties at the locations of supernova (SN) explosion in their host galaxies and compare with the global properties of the host galaxies. We use the integral field spectrograph (IFS) of Mapping Nearby Galaxies (MaNGA) at Apache Point Observatory (APO) to get the 2D maps of the parameter properties for eleven SN host galaxies. The sample galaxies are analyzed one by one in details on their properties of velocity field, star formation rate, oxygen abundance and stellar mass etc. This sample of SN host galaxies have redshifts around $z$ $sim$ 0.03, which is higher than those of the previous related works. The higher redshift distribution allows us to obtain the properties of more distant SN host galaxies. Metallicity (gas-phase oxygen abundance) estimated from integrated spectra could represent the local metallicity at SN explosion sites with small bias. All the host galaxies in our sample are metal-rich galaxies (12+log(O/H) $>$ 8.5) except for NGC 6387, which means supernovae (SNe) may be more inclined to explode in rich-metallicity galaxies. There is a positive relation between global gas-phase oxygen abundance and the stellar mass of host galaxies. We also try to compare the differences of the host galaxies between SN Ia and SN II. In our sample, both SNe Ia and SNe II could explode in normal galaxies, while SNe II also could explode in an interactive or merger system, which has star formation in the galaxy.
Recent arcsecond localizations of Fast Radio Bursts and identifications of their host galaxies confirmed their extragalactic origin.While FRB 121102 resides in the bright region of a dwarf star forming galaxy, other FRBs reside in more massive galaxies and are related to older stellar populations. We compare the host galaxy properties of {nine} FRBs with those of several types of stellar transients: from young to old population, long duration gamma ray bursts (LGRBs), superluminous supernovae (SLSNe), Type Ib/Ic supernovae (SN Ibc), Type II supernovae (SN II), type Ia supernovae (SN Ia), and short duration gamma ray bursts (SGRBs). We find that as a whole sample, the stellar mass and star formation rate of the FRB host galaxies prefer a medium to old population, and are against a young population similar to LGRBs and SLSNe by a null probability 0.02. Individually, the FRB 121102 host is consistent with that of young population objects; the FRB 180924 environment is similar to that of SGRBs; and the FRB 190523 environment is similar to those of SN Ia. These results are consistent with the magnetar engine model for FRBs, if both magnetars produced from extreme explosions (GRBs/SLSNe) and from regular channels (e.g. those producing Galactic magnetars) can produce FRBs.
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