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ABSTRACT: Some of the more illumina/ng discoveries made by the 0.45‐m ROTSE‐III telescopes have come not in response to gamma‐ray bursts but instead during "down /me" between satellite triggers while conduc/ng wide field (>100 square degree) surveys for rare op/cal transients. Here we present the sample of luminous (M < ‐21) supernovae that have so far been captured by the ROTSE‐III telescopes including SN 2006gy, the first candidate to s/r serious discussions of a pair‐instability trigger, and SN 2005ap, the most luminous supernova ever iden/fied. From our modest yet growing sample we es/mate the volumetric rate of such supernovae and explore the proper/es of their host environments. We note the various physical processes that have been employed to explain the high luminosi/es, light curves, and spectra of these supernovae. Finally we address the difficulty in isola/ng these rare events from other signals in the transient sky, perhaps most importantly, the poten/al photometric and even spectroscopic confusion with Blazars. Robert Quimby (Caltech), Fang Yuan (Michigan), Jozsef Vinko (Texas), Manos Chatzopoulos (Texas), J. Craig Wheeler (Texas), & Carl Akerlof (Michigan) Type Ia LSN LSN!IIn Search Limits !50 0 50 100 150 Days After Maximum !18 !19 !20 !21 !22 !23 Absolute Magnitude Object Number Found Rate (events/Mpc 3 /yr) SNe Ia 45 3 x 10 -5 LSNe-IIn 3 2 x 10 -7 LSN 3 6 x 10 -8 Preliminary 10 100 1000 Luminosity Distance (Mpc) 0.0 0.2 0.4 0.6 0.8 Completeness SN M peak ‐21.7 b redshi[ 0.019 L X (erg/sec) 2 x 10 39(b) Host M i ‐22.2 c g‐r 0.78 c L X (erg/sec) ~10 39(b) SN M peak ‐22.7 a redshi[ 0.2832 a L X (erg/sec) ? Host M i ‐18.4 a g‐r 0.41 f L X (erg/sec) < 10 42 SN M peak ‐22.2 e redshi[ 0.205 e L X (erg/sec) < 2 x 10 42 Host M i < ‐17 c,e g‐r ? L X (erg/sec) < 2 x 10 42 SN M peak ‐22.7 redshi[ 0.195 L X (erg/sec) < 10 42 Host M i ‐20.6 c g‐r 0.78 c L X (erg/sec) < 10 42 SN M peak ‐21.0 redshi[ 0.074 L X (erg/sec) ? Host M i ‐17.0 c g‐r 0.23 c L X (erg/sec) < 10 43 SN M peak ‐22.3 d redshi[ 0.234 d L X (erg/sec) < 10 ?? Host M i ‐20.6 c g‐r 0.26 c L X (erg/sec) < 10 42 HOST SN 3000 4000 5000 6000 7000 8000 Rest Wavelength (Å) 0.1 1.0 3000 4000 5000 6000 7000 8000 Rest Wavelength (Å) 1 3000 4000 5000 6000 7000 8000 Rest Wavelength (Å) 1 3000 4000 5000 6000 7000 8000 Rest Wavelength (Å) 1 3000 4000 5000 6000 7000 8000 Rest Wavelength (Å) 1 3000 4000 5000 6000 7000 8000 Rest Wavelength (Å) 1 NOTES: a) Quimby et al., 2007; b) Smith et al., 2007; see also Ofek et al., 2007; c) Blanton et al., 2007 and the SDSS Collaboration; d) Yuan et al., 2008; e) Gezari et al., 2009; see also Miller et al., 2009; f) Adami et al. 2006 Color Magnitude Diagram: Here the rest frame g‐r colors of the host galaxies are ploded against the host absolute i‐band magnitudes. The background image shows the volume corrected frequency distribu/on of galaxies from the Sloan Digital Sky Survey (Blanton, Hogg, and the SDSS Collabora/on, 2003). The image cuts off at M i > ‐17 due to incompleteness in the SDSS. RATES: To calculate the volumetric rate of luminous supernovae, we first construct light curve templates as shown in the figure to the le[. The LSN‐IIn light curve is based on SN 2006gy (Smith et al. 2007). For the LSN light curve, we fit a polynomial to the observa/ons of SN 2008es (Gezari et al. 2009) and compressed the /me axis to represent a compromise with the more narrow SN 2005ap. The peak absolute magnitude for the LSN‐IIn template was fixed at ‐21, which is intended to reflect an average of the popula/on assuming significant line of sight absorp/on as was observed for SN 2006gy. The LSN template was fixed at an absolute magnitude of ‐22. For each of our ROTSE‐IIIb fields, we simulate 100000 events of each type. The dates of maximum light and luminosity distances are chosen randomly and the templates are shi[ed accordingly. We compare the predicted magnitudes of each simulated event to the limi/ng magnitudes recorded by ROTSE‐IIIb between November 2004 and May 2009. An event is considered detected if it is brighter than two of the limi/ng magnitudes on a given night and two observa/ons on a subsequent night. The resul/ng survey completeness for each event type is shown to the le[ over a histogram of our actual discoveries. Although fainter, the broad light curve assumed for the LSNe‐IIn allows for a greater frac/on of nearby off‐season events (those which reach maximum light in months the fields are not observable) to be recovered a[er the seasonal gaps. The derived volumetric rates are listed in the table below. For comparison, we also calculate the rate of Type Ia supernovae, for which independent measurements at low redshi[ exist in the literature (see Dilday et al. 2008 an references therein). The derived Type Ia rate is in agreement with the Dilday et al. value, sugges/ng that we have reasonably accounted for our selec/on biases, at least for this popula/on. The LSNe were all found at the cusp of our distance limit. Here the volume elements reach a maximum, so this clustering adests to the rareness of LSNe. The LSN‐IIn, however, appear to be evenly distributed throughout the observable distance range. This may point to an uncorrected selec/on bias: at even modest distances, events that occur near the cores of ac/ve galaxies such as SN 2006gy (Smith et al., 2007) would be extremely difficult to classify as SNe and not AGN ac/vity. 2005ap 2006gy 2006tf 2008am Dougie 2008es !0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Rest Frame g!r Color !16 !17 !18 !19 !20 !21 !22 !23 Absolute i!band Magnitude Host Galaxies Imposters: Filippenko (1989) discussed the spectroscopic confusion of Type IIn supernovae to certain low luminosity, radio quiet AGN. The similari/es can be quite striking and it is en/rely possible that centrally located SNe IIn can be (and likely have been) mistaken for AGN. Here we show that confusion can extend to the more extreme members of each class, LSN and blazars. The figure to the le[ shows the near maximum light spectra of the confirmed supernova 2008es as compared to the x‐ray detected blazar candidate SDSS J003514.72+151504.1 (Anderson et al., 2007). Both objects show nearly featureless, blue con/nua. SN 2008es was first misiden/fied as a QSO (Yuan et al. 2008), then a /dal disrup/on (Gezari et al. 2008), before the spectra evolved to show more SN‐like features (Miller et al. 2009, Gezari et al. 2009). 4000 5000 6000 7000 8000 9000 Observed Wavelength (Å) 0.1 1.0 Scaled Flux SN 2008es SDSS J003514.72+151504.1 (Blazar) Power Sources: The light curves of 08am (LSN‐IIn) and 08es (LSN) are shown (right) with the best fipng radioac/ve decay diffusion models (Valen/ et al, 2008). These simple models account only for the diffusion of energy generated by the radioac/ve decay of 56 Ni and 56 Co. If the peak of the light curves are powered solely by this process, then the best fipng models give us an es/mate of the mass of the radioac/ve nickel. The best fipng diffusion /me can also give us an es/mate of the mass of the ejecta of the explosion. For those ultra‐luminous events, the implied nickel masses are unrealis/c (larger than the ejecta masses) and thus further energy genera/on mechanisms should be invoked to account for their excep/onal peak luminosity. For the LSN‐IIn cases the best candidate for addi/onal energy is the interac/on between the ejecta and the circumstellar mader shed by the progenitor star in the years prior to the explosion (Immler et al. 2002; Chevalier & Fransson 2003). However, there are other mechanisms that can account for the large luminosity: interac/on between shells (Woosley et al. 2007), shell shocked diffusion (proposed for SN 2006gy by Smith & McCray, 2007) or interac/on between a GRB jet and the progenitor envelope (Young et al. 2005; proposed for SN 2008es in Gezari et al. 2009). 0 50 100 150 200 Phase (days) 10 10 Luminosity (L sun ) SN 2008am 0 20 40 60 80 100 Phase (days) 10 10 Luminosity (L sun ) SN 2008es
