ABSTRACT: Someof themore illumina/ngdiscoveriesmadeby the0.45‐mROTSE‐III telescopeshavecomenotinresponsetogamma‐rayburstsbutinsteadduring"down/me"betweensatellitetriggerswhileconduc/ngwidefield(>100squaredegree)surveysforrareop/caltransients.Herewepresentthesampleofluminous(M<‐21)supernovaethathavesofarbeencapturedbytheROTSE‐IIItelescopesincludingSN2006gy,thefirstcandidatetos/rseriousdiscussionsofapair‐instabilitytrigger,andSN2005ap,themostluminoussupernovaeveriden/fied.Fromourmodestyetgrowingsamplewees/matethevolumetricrateofsuchsupernovaeandexploretheproper/esoftheirhostenvironments.Wenotethevariousphysicalprocessesthathavebeenemployedtoexplainthehighluminosi/es,lightcurves,andspectraofthesesupernovae.Finallyweaddressthedifficultyinisola/ngtheserareeventsfromothersignals in the transient sky, perhapsmost importantly, thepoten/alphotometric andeven spectroscopic confusionwithBlazars.

RobertQuimby(Caltech),FangYuan(Michigan),JozsefVinko(Texas),ManosChatzopoulos(Texas),J.CraigWheeler(Texas),&CarlAkerlof(Michigan)

Type Ia

LSN

LSN!IIn

Search Limits

!50 0 50 100 150Days After Maximum

!18

!19

!20

!21

!22

!23

Abs

olut

e M

agni

tude

Object Number Found Rate (events/Mpc3/yr) SNe Ia 45 3 x 10-5

LSNe-IIn 3 2 x 10-7

LSN 3 6 x 10-8 Preliminary

10 100 1000Luminosity Distance (Mpc)

0.0

0.2

0.4

0.6

0.8

Com

plet

enes

s

SN

Mpeak ‐21.7b

redshi[ 0.019

LX(erg/sec) 2x1039(b)

Host

Mi ‐22.2c

g‐r 0.78c

LX(erg/sec) ~1039(b)

SN

Mpeak ‐22.7a

redshi[ 0.2832a

LX(erg/sec) ?

Host

Mi ‐18.4a

g‐r 0.41f

LX(erg/sec) <1042

SN

Mpeak ‐22.2e

redshi[ 0.205e

LX(erg/sec) <2x1042

Host

Mi <‐17c,e

g‐r ?

LX(erg/sec) <2x1042

SN

Mpeak ‐22.7

redshi[ 0.195

LX(erg/sec) <1042

Host

Mi ‐20.6c

g‐r 0.78c

LX(erg/sec) <1042

SN

Mpeak ‐21.0

redshi[ 0.074

LX(erg/sec) ?

Host

Mi ‐17.0c

g‐r 0.23c

LX(erg/sec) <1043

SN

Mpeak ‐22.3d

redshi[ 0.234d

LX(erg/sec) <10??

Host

Mi ‐20.6c

g‐r 0.26c

LX(erg/sec) <1042

HOST SN

3000 4000 5000 6000 7000 8000Rest Wavelength (Å)

0.1

1.0

3000 4000 5000 6000 7000 8000Rest Wavelength (Å)

1

3000 4000 5000 6000 7000 8000Rest Wavelength (Å)

1

3000 4000 5000 6000 7000 8000Rest Wavelength (Å)

1

3000 4000 5000 6000 7000 8000Rest Wavelength (Å)

1

3000 4000 5000 6000 7000 8000Rest 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‐rcolors of the host galaxies are ploded against the hostabsolute i‐band magnitudes. The background imageshows the volume corrected frequency distribu/on ofgalaxies from the Sloan Digital Sky Survey (Blanton,Hogg,andtheSDSSCollabora/on,2003).TheimagecutsoffatMi>‐17duetoincompletenessintheSDSS.

RATES: To calculate the volumetric rate of luminoussupernovae, we first construct light curve templates as shown in thefiguretothele[.TheLSN‐IInlightcurveisbasedonSN2006gy(Smithetal.2007).FortheLSNlightcurve,wefitapolynomialtotheobserva/onsof SN 2008es (Gezari et al. 2009) and compressed the /me axis torepresent a compromise with the more narrow SN 2005ap. The peakabsolutemagnitude for the LSN‐IIn templatewasfixedat ‐21,which isintendedtoreflectanaverageofthepopula/onassumingsignificantlineof sight absorp/on aswas observed for SN 2006gy. The LSN templatewasfixedatanabsolutemagnitudeof‐22.

For each of our ROTSE‐IIIb fields, we simulate 100000 events of each type.Thedatesofmaximum lightand luminositydistancesarechosen

randomly and the templates are shi[ed accordingly.We compare thepredictedmagnitudesof each simulated event to thelimi/ngmagnitudes recordedbyROTSE‐IIIbbetweenNovember2004andMay2009.Anevent is considereddetected if it isbrighterthantwoofthelimi/ngmagnitudesonagivennightandtwoobserva/onsonasubsequentnight.

The resul/ngsurveycompleteness foreachevent type is shownto thele[ over a histogram of our actual discoveries. Although fainter, thebroad lightcurveassumedfortheLSNe‐IInallowsforagreaterfrac/onof nearby off‐season events (those which reach maximum light inmonthsthefieldsarenotobservable)toberecovereda[ertheseasonalgaps. The derived volumetric rates are listed in the table below. Forcomparison,wealsocalculatetherateofTypeIasupernovae,forwhichindependent measurements at low redshi[ exist in the literature (seeDildayetal.2008anreferencestherein).

The derived Type Ia rate is in agreementwith the Dilday et al. value,sugges/ngthatwehavereasonablyaccountedforourselec/onbiases,at leastforthispopula/on.TheLSNewereallfoundatthecuspofour

distance limit. Here the volume elements reach amaximum, so this clustering adests to the rareness of LSNe. The LSN‐IIn,however,appeartobeevenlydistributedthroughouttheobservabledistancerange.Thismaypointtoanuncorrectedselec/onbias:atevenmodestdistances,eventsthatoccurnearthecoresofac/vegalaxiessuchasSN2006gy(Smithetal.,2007)wouldbeextremelydifficulttoclassifyasSNeandnotAGNac/vity.

2005ap

2006gy

2006tf

2008am Dougie

2008es

!0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2Rest Frame g!r Color

!16

!17

!18

!19

!20

!21

!22

!23

Abs

olut

e i!

band

Mag

nitu

de

Host Galaxies

Imposters: Filippenko(1989)discussedthespectroscopicconfusionofTypeIInsupernovaetocertainlowluminosity,radioquietAGN.Thesimilari/escanbequitestrikinganditisen/relypossiblethatcentrallylocatedSNeIIncanbe(andlikelyhave

been)mistaken forAGN.Herewe show that confusion canextend to themoreextrememembersofeachclass,LSNandblazars.Thefiguretothele[showsthenearmaximumlightspectraoftheconfirmedsupernova2008esascomparedtothex‐raydetectedblazarcandidateSDSSJ003514.72+151504.1(Andersonetal., 2007).Bothobjects shownearly featureless,bluecon/nua.SN2008eswasfirstmisiden/fied as a QSO (Yuan et al. 2008), then a /dal disrup/on (Gezari et al. 2008), before the spectra evolved to showmore SN‐like features (Miller et al.2009,Gezarietal.2009).

4000 5000 6000 7000 8000 9000Observed Wavelength (Å)

0.1

1.0

Scal

ed F

lux SN 2008es

SDSS J003514.72+151504.1 (Blazar)

Power Sources: Thelightcurvesof08am(LSN‐IIn)and08es(LSN)areshown(right)withthebestfipngradioac/vedecaydiffusionmodels(Valen/etal,2008).Thesesimplemodelsaccountonlyforthediffusionofenergygeneratedbytheradioac/vedecayof56Niand56Co.Ifthepeakofthelightcurvesarepoweredsolelybythis process, then the best fipng models give us an es/mate of the mass of theradioac/ve nickel. The best fipng diffusion /me can also give us an es/mate of themassoftheejectaoftheexplosion.Forthoseultra‐luminousevents,theimpliednickelmasses are unrealis/c (larger than the ejecta masses) and thus further energygenera/on mechanisms should be invoked to account for their excep/onal peakluminosity. For the LSN‐IIn cases the best candidate for addi/onal energy is theinterac/onbetweentheejectaandthecircumstellarmadershedbytheprogenitorstarin 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/onbetweenshells(Woosleyetal.2007),shellshockeddiffusion(proposedforSN 2006gy by Smith & McCray, 2007) or interac/on between a GRB jet and theprogenitorenvelope(Youngetal.2005;proposedforSN2008esinGezarietal.2009).

0 50 100 150 200Phase (days)

1010

Lum

inos

ity (L

sun)

SN 2008am

0 20 40 60 80 100Phase (days)

1010

Lum

inos

ity (L

sun)

SN 2008es