On Extreme Transient Events from Rotating Black Holes and Their Gravitational Wave Emission 3

arXiv:1610.00535v1 [astro-ph.HE] 3 Oct 2016 cetdXX eevdYY noiia omZZZ form original in YYY; Received XXX. Accepted MNRAS (

uenve(LN-)( super-luminou (SLSNe-I) hydrogen-poor supernovae among far so object brightest ( ( radio on wantin appear based environment circumstellar a with teractions do SNe of these decay of 2016 nuclear curves by light powered the seem not because question, open an 2011 ⋆ ytrigcneto nisha with head its on convention turning by arc ...vnPutten van H.P.M. Maurice and holes emission black wave rotating gravitational from their events transient extreme On yattlenergy total a By INTRODUCTION 1 aito,AAS-5h(SN2015L ASASSN-15lh radiation, c 4 3 2 1 iialei ta.2015 al. et Milisavljevic 2010 al. et Pastorello al nttt o hoeia hsc,Uiest fCal of University Physics, Seo Theoretical Gwangin-gu, for Gunja-Dong Institute 98 Kavli University, Sejong 614, Room -al [email protected] E-mail: nentoa etrfrRltvsi srpyis Piaz Astrophysics, Relativistic for Center International nttt ainl iAtoscOsraoi Astronomi AstrofisicaOsservatorio di Nazionale Instituto 06TeAuthors The 2016 N05 a ersn aial e ls fSLSNe of class new radically a represent may SN2015L ,cmo ocnetoa oeclas supernovae core-collapse conventional to common ), ; a-a ta.2012 al. et Gal-Yam 000 , 1 – 10 ole l 2015 al. et Kool E 21)Pern 6Jl 08Cmie sn NA L MNRAS using Compiled 2018 July 16 Preprint (2016) rad E ; atrloe l 2007 al. et Pastorello rad ≃ age l 2015 al. et Wang ). 1 .Teoii fislmnst is luminosity its of origin The ). ≃ . 1 × E k 10 , h ue-uiosojc SSN1l S21L sa xrm e extreme an is (SN2015L) energy ASASSN-15lh object super-luminous The ABSTRACT E msinadn -ihevrnetw rps oidentify to propose we environment H-rich no super hydrogen-deprived and for emission mechanism explosion new a presents osi lńwvst atra h ne otSal iclrOrbit Circular angular Stable during Most spin, Inner by hole the determined black at e is of matter this duration evolution to of Alvén the waves evolution in by radiative the curve loss and tracks light crossing its closely light curve model envelope of light stellar scales remnant SN2015L’s time thick envelope, negligible optically By the engine. in central outflow baryon-poor a fmass of bevdeetoantcrdainhri ersnsamnrout minor a represents energy herein radiation electromagnetic observed h enn ftoC-N na nr-a iayo w asv sta massive two of GWB ∆ binary magnitude of intra-day in progenitor an change a in binary predicts CC-SNe slow-spin rigorously two high-mass of remnant the the explains model This gemn ihtelgtcreo N05 ihn fine-tuning. no with words: SN2015L Key of curve light the with agreement n pia spectroscopy optical and ) 52 k oge l 2016 al. et Dong r nbakbd (BB) body black in erg neet n aetm lta nteU,ta ee ula origin. nuclear a defies that UV, the in plateau time late a and ejecta in 56 i( Ni E E .Ipraty in- Importantly, ). M rot 1 rad , oyeae al. et Kozyreva : ; 2 umye al. et Quimby σ ftebakhl,wiems srdae neni rvttoa radiat gravitational in unseen radiated is most while hole, black the of ≃ n asm el Valle Della Massimo and ∼ tr:supernovae stars: 1 10 . 1 sthe is ) − × aedlaRpblc ,612Psaa Italy Pescara, 65122 2, Repubblica della zale fri,SnaBraa A91643 USA 93106-4030 CA Barbara, Santa ifornia, 7 od aoiot,Slt oailo1,811Napoli 80131 16, Moiariello Salita Capodimonte, di co 10 (1) and g, 52 s l1377 Korea 143-747, ul r nbakbd aito nprwt t iei energy kinetic its with par on radiation body black in erg σ σ ∼ = osdrda addt ne nie fln gamma-ray long of engines inner candidate as a considered by envelope stellar (BPJ). remnant interest- jet the an baryon-poor evolv heating an offers of engine, SN2015L tracking central day, real-time essentially one for prospect merely ing are time ing 1970 ner ta.2013 al. et Inserra where ih uv etrsalt iepaeuaottomonths two magnitude about in plateau change time a late with post-peak a it features envelope Furthermore, alone. curve expanding engine light inner an long-lived that in a light, by of dissipation powered velocity energy the of from percent derived few a at expanding lope xlso ybro orotos(e.g. outflows poor baryon by explosion neoeo radius of envelope ne nieaea nua oetmrc antr(e.g. magnetar momentum-rich angular an are engine inner 10 M − T antr n oaigbakhlshv enwidely been have holes black rotating and Magnetars oepanS21L aua addtsfralong-lived a for candidates natural SN2015L, explain To .Snetelgtcosn iesaeo h expanding the of scale time crossing light the Since ). 2 /M E o N05 n,rsetvl,aln R.The GRB. long a respectively, and, SN2015L for k ∼ ftetrsmass torus the of 10 52 m ∆ r eoe h iei nryi h enve- the in energy kinetic the denotes erg m ; ≃ 3 ? ∼ ≡ , rbakhl-iksse rvn the driving system hole-disk black or ) 1 4 . m ⋆ 5 5i h ih uv otpa,in post-peak, curve light the in 15 × pl − 10 m 15 M p madisrdaincool- radiation its and cm ≃ T E rad 1 rudtebakhole black the around . oa.Wt oradio no With novae. 2 u fterotational the of put . ihdsiainof dissipation with etwt total a with vent A Bisnovatyi-Kogan T gn.W here We ngine. s hsmodel This rs. rdcdb a by produced E oln fthe of cooling tl l v3.0 file style X IC) The (ISCO). momentum 594 as 150914, tlikely It ion. ing (2) s 2 van Putten and Della Valle

bursts (LGRBs). While there durations T90 of tens of sec- events exist satisfying Erad > Ec. It is not without prece- onds associated with relativistic core-collapse supernovae dent that events discovered in our “local” universe represent (e.g. Woosley & Bloom 2006; Fryer et al. 2015) are shorter the faint tail of a broader class of astrophysical objects. For than the light curve of SN2015L by a factor of about instance, SN1987A (Burrows & Lattimer 1987), SN1885A 5 51 10 , their true output in gamma-rays Eγ ≃ 9 × 10 erg (de Vaucouleurs & Gorwin 1985) or GRB980425 (but not (Frail et al. 2001; Ghirlanda et al. 2006, 2013) is essentially the accompanying SN1998bw; Galama et al. 1998) are cer- equal to Erad. This points to a possibly common energy tainly not the brightest members in their respective classes. reservoir, operating across a broad range of time scales with In light of the qualitative and quantitative considera- different modes of dissipation. While Eγ is largely non- tions above, we here consider the possibility that SN2015L is thermal and probably derives from internal shocks in ultra- powered by black hole-disk system, whose light curve tracks relativistic baryon poor jets (BPJ) (Rees & Mészáros 1992, the evolution and state of accretion of the latter. According 1994; Eichler & Levinson 1993; Eichler 2011), SN2015L fea- to the Kerr metric (Kerr 1963), the rotational energy Erot tures essentially thermal electromagnetic radiation satisfy- can reach up to 29% of its total mass, which exceeds that of ing neutron stars by well over an order of magnitude. A rotating black holes of mass M hereby possess rotational energies up E ≃ E . (3) rad γ to

Attributing Erad to dissipation of a BPJ in the optically 54 M Erot ≃ 6 × 10 erg. (5) thick remnant stellar envelope, SN2015L represents a “failed 10M⊙ GRB” scaled down in luminosity and inverse duration. in the limit as the dimensionless Kerr parameter a/M, A one-parameter scaling across a broad range of lumi- defined by the ratio of specific angular momentum a to nosites and time scales exists in shedding Alvén waves in black hole mass, approaches unity. Near-extremal black holes relativistic outfows from a common energy reservoir in angu- with a/M = 0.9 hereby have about one-half the max- lar momentum, operating at like efficiencies in conversion to ima rotational energy of a black hole with the same mass electromagnetic radiation. For SN2015L, L = E /T ≃ rad rad energy-at-infinity M. Rapidly rotating stellar mass black 2 × 1045 erg s−1 and the duration T of about two months holes hereby provide ample energies for SN2015L and even post-peak to aforementioned plateau satisfy brighter events. Lrad T90 −5 E in SN2015L and E in LGRBs represent about 1% α = ≃ ≃ 10 , (4) rad γ Lγ T of Erot - a very minor fraction of the total energy reservoir of a Kerr black hole. Attributing it to a fraction of hori- where L ≃ E /T ≃ 3 × 1050 erg s−1 for LGRBs of du- γ γ 90 zon magnetic flux, E derives from the total energy E rations T of tens of seconds. Even though SN2015L and rad BPJ 90 along an open magnetic flux tube subtended by a horizon LGRBs have principally different spectra, they may be op- half-opening angle θ satisfying erating at radiation efficiencies that are not too different. H Various authors attribute SN2015L to magnetars EBPJ 1 4 = θH << 1, (6) (Bersten et al. 2016; Dong et al. 2016; Dai et al. 2016; Erot 4 Sukhbold & Woosley 2016; Chatzopoulos et al. 2016) as a supported by an equilibrium magnetic moment of the black variant to magnetar powered luminous type Ic supernovae hole (§4, below). Should a major fraction of (5) be released, (Wang et al. 2015), whose energy budget approaches the ex- it must be largely so in channels unseen, i.e., gravitational 52 tremal value Ec ≃ 7.5 × 10 (Haensel et al. 2009) (but see radiation and MeV neutrinos. These fractions are deter- Metzger et al. (2015)) at high efficiency (e.g. Dong et al. mined by the partition of Alfvén waves around the black hole 2016). This scenario is challenged by some properties ex- (van Putten 2008b, 2015b), producing a BPJ along the black hibited by the SN2015L event. Firstly, the similarity be- hole spin axis and interactions with nearby matter at thet tween the energy budget (Erad+Ek) of SN 2015L and the the Inner Most Stable Circular Orbit (ISCO) (van Putten extremal energy value provided by a rotating neutron star 1999; van Putten & Levinson 2003). These Alfvén waves are implies values for the energy conversion factors, close to induced by relativistic frame dragging. The existence of 100%, which appears unlikely. Secondly, SN2015L shows a frame dragging is not in doubt: recent measurements of non- late time plateau, not seen in conventional core-collapse su- relativistic frame dragging around the Earth are in excellent pernovae (e.g. Turatto et al. 1990) nor in broad lined SNe Ic agreement with general relativity (Ciufolini & Pavlis 2004; −2 (Bufano et al. 2012). The algebraic time decay ∝ (1+t/ts) Ciufolini 2007; Ciufolini et al. 2009; Everitt et al. 2011). of magnetar light curves with characteristic spindown time This partition (6) applies to a state of suspended ts is woefully at odds with aforementioned unconventional accretion. Earlier models envision outflows from accret- temporal behavior. Thirdly, versions of this model that ad- ing black holes (Ruffini & Wilson 1975; Blandford & Znajek dress the UV plateau invoke interaction of the envelope with 1977). It has been suggested that the BPJ represents the the circumstellar environment, which is at odds with above major energetic output from the black hole in the form cited radio non-detection and optical non-detection of Hα of a Poynting flux (Blandford & Znajek 1977). Below a emission. Being hydrogen deficient deprives the expanding critical accretion rate (Globus & Levinson 2014), however, envelope in SN2015L to interact energetically with a dense the black hole may act back onto matter at the ISCO pre-supernova wind (cf. super bright SNe hydrogen rich ex- and sufficiently so to suspend accretion (van Putten 1999; plosions). SN2015L hereby points to a long-lived central en- van Putten & Levinson 2003). Thus, different evolutions of gine with inherent decay to a late-time plateau. the black hole ensue depending on the state of accretion: spin Moreover, amongst the SLSNe-I class, SN2015L is the up, described by modified Bardeen accretion (van Putten brightest observed thus far. It is likely that even brighter 2015b), and spin down, by equations of suspended accretion

MNRAS 000, 1–10 (2016) On extreme transient events from rotating black holes and their gravitational wave emission 3

(van Putten & Levinson 2003). The latter introduces a rad- hole birth remain uncertain. It may form by prompt col- ically new secular time scale, defined by the lifetime of rapid lapse. For instance, at the onset of core-collapse, fall back spin of the black hole (van Putten & Levinson 2003) matter can form highly asymmetric distributions at centrifu- gal hang-up, producing a brief flash of gravitational waves σ −1 T ≃ 100 day, (7) (Duez et al. 2004). By gravitational radiation and diluting s 10−7 angular momentum during continuing fallback, this state defined by the ratio σ = MT /M of the mass MT of a torus should be short-lived. If not, rather exotic objects might at the ISCO to M. This process features a minor output (6) form (Lipunov 1983; Lipunovaet al. 2009). Alternatively, it in a BPJ accompanied by a major output in gravitational forms through core-collapse of a neutron star, and similar radiation from matter at the ISCO. The latter features a flash in gravitational waves might be produced (Rees et al. distinctive descending chirp (van Putten 2008a). 1974). By (6-7), our model is different from others aforemen- Regardless of details at birth, the newly formed black tioned in the partition of energy output - mostly into sur- hole must satisfy the Kerr constraint rounding matter accompanied by minor emisison in open a ≤ 1, (8) outflows - and a new secular timescale in the lifetime of black M hole spin, that may extend well beyond canonical time scales of accretion. where a = J/M denotes the specific angular momentum of a Different modes of accretion naturally appear in black hole of mass M. Here, we use geometric units in which black hole evolution, marked by distinct total en- Newton’s constant G and the velocity of light c are set equal ergies and light curves for frame-dragging induced to 1. In a uniformly rotating core, a newly formed black BPJs. They same applies to any accompanying emis- hole form near-extremal and of small mass (e.g. van Putten sions unseen in gravitational waves from matter at the 2004). It then enters the following three phases in evolution. ISCO, that may be probed by LIGO-Virgo and KA- (i) Phase I. Surge to a non-extremal black hole. The black GRA (Abramovici et al. 1992; Acernese et al. 2006, 2007; hole increases its mass in direct accretion of a fraction of the Somiya et al. 2012; LIGO & Virgo 2016). For LGRBs, a inner region of the core, whose specific angular momentum model light curve for BPJ during the final phase of spin down is insufficient to stall at the ISCO. The dimensionless Kerr (van Putten & Levinson 2003) is supported by spectral- parameter a/M hereby decreases on the free fall time scale energy and temporal properties on long and short time of tens of seconds of the progenitor; scales (summarized in van Putten 2016) in GRBs detected (ii) Phase II. Growth to a near-extremal black hole. Ac- by HETE-II and Swift (Swift 2004, 2014), Burst and Tran- cretion continues from the ISCO on the viscous time time sient Source Experiment (BATSE) (Kouveliotou et al. 1993) scale of a newly formed accretion disk, increasing M and and BeppoSAX (Frontera et al. 2009), whose durations of a/M (Bardeen 1970), also in the presence of outflows at tens of seconds has been association with high density ac- typical efficiencies (van Putten 2015b). The black hole be- cretion flows (Woosley 1993; MacFadyen & Woosley 1999; comes near-extremal (a/M ≃ 1) provided there is sufficient Woosley & Bloom 2006; Woosley 2010). Conceivably, this fall back matter and/or the progenitor rotates sufficiently light curve also has relevance to failed GRBs, i.e., when the rapidly; BPJ fails to break out of the progenitor stellar envelope. (iii) Phase III. Spin down to slow spin. The black hole By the above, we associate SN2015L and long GRBs looses decreases in a/M by angular momentum loss against to scaling (4) with the torus to black hole mass ratio σ matter at the ISCO mediated by an inner torus magneto- −7 −2 according to σ ≃ 10 and, respectively, σ ≃ 10 in sphere supported by a torus about the ISCO, provided that (7). Our σ in (7) is intermediate in being a geometric of (a) there is continuing fall back matter (a near-extremal −2 −12 σ ≃ 10 , which is typical for GRBs, and σ ≃ 10 black hole formed in Phase II) and (b) the accretion rate in the micro-quasar GRS1915+105 (Mirabel & Rodr´ıguez is subcritical (Globus & Levinson 2014; van Putten 2015b). 1994; Miller et al. 2016) and long GRBs. The duration of this suspended accretion state depends on To model the associated transient emission, we first con- the energy in the poloidal magnetic field, bounded by of a sider the phases of black hole evolution by fallback matter torus at the ISCO (van Putten & Levinson 2003). from a rotating progenitor following birth in core-collapse (§2) and their association with supernovae (§3). We then Phase I, considers direct accretion of low angular mo- revisit model light curve for transient emission during ac- mentum from the inner region of a progenitor rotating with cretion and and spin down (§4). In §5-6 we give a detailed period P = Pd day. P may be short, as when in cororation confrontation of our model light curves with LGRBs and with a companion star in a compact stellar binary. We define SN2015L, the former against data from BATSE, BeppoSAX, the dimensionless reciprocal period β (van Putten 2004) Swift and HETE-II. A summary and an outlook on accom- β = 4.22 P −1R−1M −1/3 , (9) panying gravitational wave emission is given in §7. d 1 He,10 5 where R = R1R⊙ (R⊙ = 7 × 10 km) and M0 = MHe,1010M⊙ denotes the progenitor He mass. Direct ac- 2 BLACK HOLE EVOLUTION IN cretion of fallback matter falls occurs provided that its CORE-COLLAPSE specific angular momentum is less than that at the ISCO, defined by the Kerr metric (Bardeen et al. 1972; By core-collapse, massive stars are believed to be factories of MacFadyen & Woosley 1999; Bethe et al. 2003; van Putten neutrons stars and black holes. In the absence of any direct 2004). This condition is satisfied by a finite fraction of the observation by gravitational radiation, the details of black core of the progenitor star, and defines an accretion time

MNRAS 000, 1–10 (2016) 4 van Putten and Della Valle

100 100 1

10-1 10-1 0 Black hole birth ↑ 0.5 Direct accretion 0 Bardeen accretion max rot -2 -2 M/M Spin down against ISCO 10 /E 10 ↑ Black hole remnant M/M rot 0

E 0 1 2 10-3 10-3 10 10 10 Disk first forms Disk first forms Black hole at birth Black hole at birth 1 10-4 10-4 0 0.1 0.2 0.3 0.4 0 0.1 0.2 0.3 0.4 0.8

1/β 1/β 0.6 a/M 1 0.4

0.2 0.8 100 101 102 0.6 ↓ 1 f a/M GW,0 0.4 0.8 f

ISCO GW,2 0.6 0.2 Ω f 0 0.4 GW,1 f M 0.2 GW,3 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0 1 2 β 10 10 10 1/ time (scaled) Figure 1. Formation of initially extremal black hole in prompt Figure 2. Evolution of a rotating black hole following birth in core-collapse from a rotating progenitor, satisfying the Kerr limit a progenitor of mass M0 in three phases of accretion: surge in a/M = 1 and its subsequent surge by direct accretion of fall back direct accretion (dashed), growth by Bardeen accretion (contin- matter to a non-extremal black hole, until a disk ﬁrst forms. The uous) followed by spin down against matter at the ISCO when results depend strongly on the angular velocity of the progen- accretion becomes subcritical (top and middle panels). Shown is itor, here parameterized by the dimensionless period β in (9). further the associated evolution of any quadrupole gravitational (Adapted from (van Putten 2004)). wave signature from matter at the ISCO, marked by frequencies

fGW0 at birth, fGW 1, at the onset of Bardeen accretion, fGW,2 at the onset of spin down and f at late times, when the black scale of at most the free fall time scale GW,3 1 hole is slowly rotating in approximate corotation with matter at − 2 3 M r 2 the ISCO (lower panel.) ≃ 0 tff 30 s 10 . (10) 10M⊙ 10 cm M hereby surges rapidly to a fraction of order unity of the 1.5 progenitor mass M0, until an accretion disk ﬁrst forms. At this moment, the black hole is non-extremal with a typically 1 moderate Kerr parameter a/M shown in Fig. 1.

In Phase II, the black hole evolves by matter 0.5 M a/M plunging in gradually from the ISCO Bardeen (1970); Ω /Ω H ISCO Bardeen et al. (1972); Bethe et al. (2003); van Putten 0 (2004); King & Pringle (2006). Matter is envisioned to 0 10 20 30 40 50 60 70 80 time [s] migrates to the ISCO by large eddy turbulent viscosity Shakura & Sunyaev (1973) in magneto-hydrodyamical stresses, such as may arise from a magneto-rotational in- 0.6 stability (MRI Balbus & Hawley (1991); Hawley & Balbus 0.5 0.4 (1991)). Accretion hereby advects magnetic ﬂux onto the 0.3

event horizon, that may lead to the formation of a BPJ Efficiency 0.2

(Blandford & Znajek 1977). If so, the black hole evolves 0.1 by modified Bardeen accretion (van Putten 2015b), increas- 0 ing M and a/M at canonical efficiencies. In hyper-accretion 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 initial a/M flows dominated by Reynolds stresses, the black hole satisfies the Bardeen integral (Bardeen 1970) Figure 3. In Phase III, spin down of a near-extremal black hole 2 (top), formed in a prior phase of Bardeen accretion, represents zM = const. (11) catalytic conversion of spin energy into various emission channels for the idealized limit of no outflows, shown in Fig. 2. The by matter at the ISCO. Shown are the evolution of total mass M outcome is a high mass near-extremal Kerr black hole that (solid curve), the dimensionless specific angular momentum a/M may reach the Thorne limit Thorne (1974); Sadowski et al. (dashed curve) and ratio of angular velocities of the black hole event horizon to test particles at the ISCO (dot-dashed curve). (2011). In attributing the accretion rate to an MRI induced The efficiency (bottom) in energy extracted over initial rotational viscosity, duration of phase II is expected to scale with the spin can reach 60%. density of the accretion flow. In Phase III (Figs. 2-3), the black hole evolves by an interaction with matter at the ISCO dominated by Maxwell stresses in Alfvén waves, defined by a system of two ordinary differential equations representing conservation of total energy and angular momentum. The system describes a black

MNRAS 000, 1–10 (2016) On extreme transient events from rotating black holes and their gravitational wave emission 5 hole luminosity LH = −M˙ and torque τ = −J˙ on the in- However, growth to a rapidly spinning black hole by ner face of matter at the ISCO (van Putten 1999, 2016), Bardeen accretion is rather insensitive to β, unless β is so satisfying low such that an accretion disk never forms. Figs. 1-2 show the following two cases. M˙ = Ω J,˙ J˙ = −κe (Ω − Ω ) , (12) T k H T Rapidly rotation progenitors limit the initial mass M where κ is the net (variance) in (turbulent) poloidal mag- of the black hole, so that all three phases of accretion can netic field and kinetic energy ek. Matter at the ISCO is proceed. Rapid rotation, e.g., in intra-day stellar binaries, hereby heated, driving non-axisymmetric instabilities giv- allows the formation of an extremal black hole (a/M = 1) ing rise to a dominant output in gravitational radiation at a mass M that may be appreciably below the mass M0 (van Putten & Levinson 2003). The system (12) features of the progenitor at the end of Bardeen accretion. This case two fixed points ΩH = ΩT when the angular velocity of leaves a finite amount of fallback matter to initiate black the black hole ΩH equals that of matter at the ISCO: unsta- hole spin down, after accretion becomes sub-critical. ble at maximal spin (ΩH = 1/2M) and stable at slow spin Slowly rotating progenitors (e.g. Hirsch et al. 2004; (ΩH << 1/2M). It points to a gradual evolution from fast Yoon et al. 2015) imply long-duration direct accretion that to slow spin, i.e., a relaxation of the black hole spacetime may be followed by Bardeen accretion, leading to a high to that of a slowly rotating black hole. Given a stability mass non-extremal black hole (a/M < 1) with M relatively bound on the total energy in the poloidal magnetic field, close or equal to M0. In this event, spindown in a suspended κ proportional to the mass MT of a torus at the ISCO, accretion phase is unlikely, as essentially all fallback has been we have (van Putten & Levinson 2003; van Putten 2015b), exhausted. more specifically than (7), The case of rapid rotation is particularly likely to pro- duce powerful winds and jets driving a supernova, more so 0.01 M z 4 Ts ≃ 30 s , (13) than during direct and Bardeen accretion only for slowly ro- σ 7M⊙ 6 tating progenitors. SN2015L likely occured in a short period where z = rISCO/M denotes the radius of the ISCO relative stellar binary, giving rise to high β and a stripped hydrogen −1 to the gravitational radius M of the black hole. Ts ∝ σ envelope (cf. (Paczyński 1998)). In this event, dependence on shows that dilute mass concentrations at the ISCO result in metallicity is expected to be minor, in contrast to the same lifetimes of the engine much longer than that of long GRBs, by stellar winds from isolated stars (Heger et al. 2003). and hence

−1 α ∝ σ . (14) 4 MODEL LIGHT CURVES IN PHASE II–III At constant poloidal magnetic field energy-to-kinetic en- The short time scale of direct accretion falls outside the ergy in matter at the ISCO (van Putten & Levinson 2003; scope of the months-long light curve of SN2015L. We there- Bromberg et al. 2006), (14) defines a scaling of LH and Ts fore focus on Phase II and III, that, if present, can have long conform (4). Phase II and III hereby satisfy similar scalings durations on secular time scales set by the density of accre- of durations with density in accretion flows. tion flow. Their different modes introduce distinct magnetic Illustrating the above, Fig. 3 shows a black hole evolu- field topologies and black hole evolution associated with spin tion to a high mass near-extremal state through the three up and, respectively, spin down, expressed in distinct light phases of direct and Bardeen accretion followed by spin curves. down, according to (11-12). In this example, the angular In Phase II, the outflow tracks a black hole spinning up velocity of the progenitor is relatively slow, giving rise to according to (11) using canonical scaling relations for BPJs black hole mass close to but still less than the mass M0 of based on total black hole horizon flux (Blandford & Znajek the progenitor at the end of Phase II. Faster angular velocity 1977; Nathanail & Strantzalis 2015a,b). At quipartition val- give an earlier transition to Phase III of a lower mass M of ues of magnetic field and mass density, the latter scales with the black hole, yet still near-extremal in a/M. mass accretion ratem ˙ . Model light curve of during Phase II hereby trackm ˙ , commonly considered as power laws in time, ∝ −n 3 SUPERNOVAE FROM ROTATING LBPJ(t) t , (15) PROGENITORS e.g., at early high accretion rates (n = 1/2) or low accretion rates (n ≥ 1) (Kumar et al. 2008a; Kumer at al. 2008b; Figs. 1-3 show the initial black hole mass and its subsequent Dexter & Kasen 2013). evolution by direct accretion to strongly depend on rota- In Phase III, the outflow tracks a black hole spin- tion of the progenitor star. In attributing an accompanying ning down according to (12), wherein E represent aspherical supernova explosion to winds or jets coming of BPJ a minor fraction of E resulting in a FRED-like light the newly formed rotating inner engine (Bisnovatyi-Kogan rot curve (van Putten & Levinson 2003). A split magnetic field 1970; MacFadyen & Woosley 1999), a successful explosion topology about the black hole in its lowest energy state may ensue during the subsequent Bardeen phase and final (van Putten & Levinson 2003; van Putten 2015b) gives (6) spin down, but less likely so during the first phase of direct by relativistic frame dragging along an open magnetic flux accretion. According to Figs. 1-2, the outcome of direct ac- tube along the spin axis subtended by half-opening angle θ cretion critically depends on the dimensionless angular velic- H on the event horizon. ity β. Our treatment is hereby completely different black To be specific, we consider (van Putten 2012) hole mass estimates in core-collapse of non-rotating isolated ˆ4 2 n stars (our limit of β = 0), see, e.g., (Heger et al. 2003). LBPJ ∝ θH ΩH z Ek, (16)

MNRAS 000, 1–10 (2016) 6 van Putten and Della Valle

1 1 β a/M = 0.8394 proved correlation Eγ ∝ T90Ep β ≃ 0.5) between the 0.9 0.8 true energy in gamma-rays Eγ (corrected for beaming) and )

H 0.8

θ the peak energy Ep in gamma-rays (van Putten 2008b;

(a.u.) 0.6 0.7 Shahmoradi & Nemiroﬀ 2015). /max( BPJ

H 0.6

L Universality.

θ (ii) The dichotomy of long and short GRBs 0.4 0.5 can be identiﬁed with hyper- and suspended accretion onto

0.2 0.4 initially slowly and, respectively, rapidly spinning black 0 20 40 60 80 0 20 40 60 80 time [s] time [s] holes (van Putten & Ostriker 2001). It implies various common emission features. First, SGRBs are expected to pro- 1 1 duce X-ray afterglows similar to LGRBs, albeit less luminous in host environments typical for mergers. This 0.8 0.8 prediction (van Putten & Ostriker 2001) is confirmed by (a.u.) (a.u.) 0.6 0.6 the Swift and HETE-II events GRB050509B (Gehrels et al. BPJ GRB 2005) and GRB050709 (Fox et al. 2005; Hjörth et al. 2005; L 0.4 L 0.4 Villasenor et al. 2005). Second, mergers involving black holes with rapid spin may feature soft Extended Emission 0.2 0.2 0.2 0.4 0.6 0.8 1 0.4 0.6 0.8 1 (EE) in suspended accretion, that bears out in GRBEEs a/M (θ /max(θ ) H H such as GRB 060614 (Della Valle et al. 2006) satisfying the same Amati relation of long GRBs (recently reviewed in Figure 4. Model light curve LBPJ of Phase III, produced along an open magnetic flux tube in a split field topology. It features a (van Putten et al. 2014b)). Third, remnants of GRBs are all near-exponential decay post-peak at a/M = 0.8394 to a plateau slowly spinning black holes with a/M ≃ 0.36 representing with change in magnitude ∆m = 1.154. The horizon half-opening the late-time fixed point ΩH ≃ ΩISCO. With no memory of angle θH evolves to a constant. the initial spin of the black hole it predicts common features from late time accretion or fall back matter. Notably, the Swift discovery of X-ray tails (XRTs) may result, in merg- where RT = zM denotes the radius of the torus, Ek ∝ 2 ers, from messy break-up of a neutron star (Lee & Kluzniak (ΩT RT ) e(z) is the kinetic energy of the torus, and e(z) = 1998, 1999; Rosswog 2007), e.g., in GRB060614 involving a 1 − 2/3/z is the specific energy of matter in an or- rapidly rotating black hole (van Putten 2008a). bitp at angular velocity ΩT at the ISCO (Bardeen et al. (iii) Spin down in BATSE. BATSE light curves of LGRBs 1972). With n = 2, L scales with the surface area BPJ have been analyzed by matched filtering. Figs. 5-6 shows re- within the torus and E is defined by a stability limit k sults matched filtering analysis for Phase II and III, given on poloidal magnetic field energy that the torus can sup- by (15) and, respectively, Fig. 4. Included in Fig. 6 is further port (van Putten & Levinson 2003). In a split magnetic flux a light curve from spin down of a magnetar. The normalized topology, a maximal half-opening angle θˆ ≃ 0.15 rad ac- H light curves (nLC) extracted from BATSE represent aver- counts for a fraction of about 0.1% of L to be emitted along H ages of 960 individually normalized BATSE light curves with the spin axis of the black hole, the remaining 99.9% being T > 20 s and 531 light curves with T < 20 s. The nLC deposited into the torus for conversion into other radiation 90 90 attains a peak at about 16% of its duration. The different channels. matches in Figs. 5-6 show that long GRBs have a gradual While at high spin θ appears to be correlated to z H switch-on as in spin down away from the unstable fixed point (van Putten 2015b), θ rises to a constant post-peak in the H Ω = Ω = 1/2M in (12), rather than prompt switch-on model light curve L (t). The outflow hereby effectively H T BPJ implied by (15) or the light curve of a newly formed mag- satisfies (4). Post-peak, L (t) evolves by near-exponential BPJ netar. Also, very long duration events (T > 20 s) show decay in time to a plateau with a change in magnitude in 90 a remarkably good match to the model template of Fig. 4) L (t) satisfying BPJ for all time. On average, LGRBs appear more likely to de- ∆m ≡ mpl − mp = 1.154, (17) rive from a spin down Phase III rather than Phase II or a magnetar. whose duration scales with σ−1. This dimensionless num- No proto-pulsars. ber is a key model prediction, that we shall compare with (iv) There is a non-detection of proto- Bep- SN2015L (§6 below). pulsars in broadband Kolmogorov spectra of the 2kHz poSAX spectra of long GRBs, extracted by a novel butterfly fliter by matched filtering against a large number of chirp templates (van Putten et al. 2014a). 5 OBSERVATIONAL TESTS ON GRBS (v) Bright is variable. LGRBs show a positive correlation Our light curve of Fig. 2 has been vigorously confronted between luminosity and variability (Reichert et al. 2001). In with data from BATSE, BeppoSAX, Swift and HETE-II. We our model, black hole feedback on accretion flow provides a mention the following. novel channel for instabilities that gives rise to a luminosity proportional to the inverse of the duty cicle (van Putten (i) Long durations. T in (13) defines a secular time spin 2015a). scale of tens of seconds for poloidal magnetic field energies at the limit of stability, defined by the kinetic energy in a torus at the ISCO (van Putten 1999; van Putten & Levinson 2003). For LGRBs, T90 ≃ Tsp of initially rapidly ro- We next confront our model with the light curve of tating black holes with σ ≃ 1%. It also gives an im- ASASSN-15lh.

MNRAS 000, 1–10 (2016) On extreme transient events from rotating black holes and their gravitational wave emission 7

2 s < T < 20 s T > 20 s 90 90 0.5 0.5 1 nLC deviation 1 nLC deviation Template t−1/2 ± 3σ Template t−1/2 ± 3σ 0.8 0.8

0.6 0.6 0 0

0.4 0.4

count rate (a.u.) 0.2 count rate (a.u.) 0.2

0 −0.5 0 −0.5 −1 0 1 2 3 −1 0 1 2 3 −1 0 1 2 3 −1 0 1 2 3

0.5 0.5 1 nLC deviation 1 nLC deviation Template t−1 ± 3σ Template t−1 ± 3σ 0.8 0.8

0.6 0.6 0 0

0.4 0.4

count rate (a.u.) 0.2 count rate (a.u.) 0.2

0 −0.5 0 −0.5 −1 0 1 2 3 −1 0 1 2 3 −1 0 1 2 3 −1 0 1 2 3 normalized time normalized time normalized time normalized time

Figure 5. Phase II matched ﬁltering analysis of BATSE against accretion proﬁles (15). Shown are normalized light curves (thick lines) extracted from the BATSE catalog and model llight curves (thin lines) for accretion rates ∝ t−n at early time high accretion rates 1 (n = 2 ) or at low accretion rates (n = 1) (top panels) and n = 2.5 and n = 2.75 (lower panels). All results show a mismatch to the prompt switch-on in model templates.

2 s < T < 20 s T > 20 s 90 90 0.5 0.5 1 nLC deviation 1 nLC deviation BHS ± 3σ BHS ± 3σ 0.8 0.8

0.6 0.6 0 0

0.4 0.4

count rate (a.u.) 0.2 count rate (a.u.) 0.2

0 −0.5 0 −0.5 −1 0 1 2 3 −1 0 1 2 3 −1 0 1 2 3 −1 0 1 2 3

0.5 0.5 1 nLC deviation 1 nLC deviation PNS ± 3σ PNS ± 3σ 0.8 0.8

0.6 0.6 0 0

0.4 0.4

count rate (a.u.) 0.2 count rate (a.u.) 0.2

0 −0.5 0 −0.5 −1 0 1 2 3 −1 0 1 2 3 −1 0 1 2 3 −1 0 1 2 3 normalized time normalized time normalized time normalized time

Figure 6. Phase III matched ﬁltering analysis of BATSE against the model light curve of Fig. 4 (top panels) and that of a proto-neutron star (PNS, lower panels). Consistency is relatively better for the former, especially so for durations greater than 20 s. We attribute this time scale to that of jet breakout of a stellar remnant envelope. (Adapted from (van Putten 2012).)

6 CONFRONTATION WITH SN2015L post-peak to a plateau is speciﬁc to spindown of black holes with no counterpart to magnetars, since the latter continue Fig. 7 shows a match to the bolometric luminosity of to spin down freely to essentially zero angular velocity at late SN2015L of our light curve LBPJ )(t) with dissipation largely times (e.g. Dai et al. 2016). Our value (17) is in remarkable into heat in the optically thick remnant stellar envelope. On agreement with the observed change ∆m = 1.2. this basis, we identify SN2015L with the relaxation of a Kerr A 120-day UV rebrightening to SN2015L 90 days after spacetime to that of a slowly spinning black hole, featuring its onset (Godoy-Rivera et al. 2016) is a further striking fea- a late time plateau ΩH ≃ ΩT << 1/2M. According to Fig. ture in SN2015L. We interpret it as late-time activity of the 2, the magnitude of LBPJ rises by about one magnitude inner engine, again by virtue of aforementioned short light post-peak peak. A prior onset to peak is associated with the crossing and cooling time scale of the expanding envelope. In formation of a rapidly rotating black hole in prior epoch of our model, the remnant inner engine of the 90-day “prompt” hyper-accretion (van Putten 2015b). SN2015L light curve is a slowly spinning black hole, in com- We emphasize that only one scale factor (14) is applied mon with the remnant of SGRBs and LGRBs. Any late time to LBPJ (t) to match SN2015L, here scaled down by (4) from accretion on these engines produces a latent emission at a the same applied to long GRBs. The predicted transition luminosity essentially set by the accretion rate. In the case

MNRAS 000, 1–10 (2016) 8 van Putten and Della Valle

[h] -24 SN2015L (Dong et al. 2016) m(t) black hole -23.8 m(t) magnetar

-23.6

-23.4

-23.2

-23

-22.8

-22.6 (A) (B) -22.4 Absolute rest frame magnitude

-22.2

-22 -40 -20 0 20 40 60 80 Rest frame time [days]

Figure 7. Shown is a confrontation of the model light curve of black hole spin down in Phase III and that of magnetars to the bolometric light curve of SN2015L (Table S2 in (Dong et al. 2016)) by scaling of peak magnitude and duration (B). The theoretical change in magnitude mpl − mp = 1.15 post-peak agrees with the observed change ∆m ≃ 1.2. Prior to peak luminosity (A), a near-extremal black hole forms during a Bardeen accretion Phase II. of GRBs, we hereby explain the XRTs, common to both scaled in time for consideration to SN2015L based on (3) short and long GRBs discovered by Swift. In the case of and LGRBs according to (4). In our model, the light curve SN2015L, we attribute the UV rebrightening analogously, of SN2015L and prompt GRB-emission are associated with by late time accretion onto the slowly rotating remnant. A black hole spin down. Durations hereof are defined by the further illustration hereof is the decade-long X-ray emission lifetime of spin (13). Scaling of Ts is represented by different in the supernova remnant of SN1979C by accretion onto a ratios σ of torus to black hole mass. Our model hereby con- remant black hole (Patnaude et al. 2011). According to the tains essentially one parameter, assuming stellar mass black Bardeen accretion Phase II, this can lead to spin up, whereby hole masses to vary by at most a factor of a few. the plateau - XRT in case of GRBs and UV rebrightening In light of scaling by σ, we confront our theoretical in case of SN2015 - may fluctuate slightly in luminosity. model light curves with both LGRBs from BATSE and SN2015L. Results on normalized light curves shows satisfactory agreement with black holes loosing angular momentum to matter at the ISCO, more so that a prior accretion 7 CONCLUSIONS AND OUTLOOK powered phase or spin down of magnetars. SN2015L presents a significant addition to the class of The model light curve of Fig. 4 shows a satisfactory extreme transient events, typically associated with core- match to the bolometric luminosity light curve of SN2015L, collapse supernovae and GRBs. By its large amount of radi- here attributed to effective dissipation in the remnant stel- ation Erad satisfying (1) with a light curve featuring a late lar envelope. The late-time plateau is identified with gradual time plateau satisfying (2), SN2015L may present a major spin down of an initially near-extremal Kerr black hole to a new class of SLSNe. If so, we expect to see even brighter slowly rotating black hole, whose angular velocity has set- events in future surveys. tled down to that of matter at the ISCO. This scenario is Core-collapse of massive stars are believed to be facto- exactly the same as identified for LGRBs in BASTSE. The ries of neutron stars and black holes, that may be powering late-time state of ΩH ≃ ΩISCO defines a plateau in the light aspherical explosions by outflows derived from their energy curve unique to black hole-torus system, which is absent in reservoir in angular momentum. These alternatives give rise magnetars. (Their spin decays all the way to zero.) Quanti- to different model light curves in electromagnetic radiation tative agreement is found in the change in magnitude ∆m from dissipation of magnetized outflows, further in light of post-peak in our model light curve and the light curve of different phases in black hole evolution in three consecutive SN2015L. steps shown in Fig. 2. It appears that SN2015L is genuinely powered by the As universal inner engines, black hole outflows can be spin energy of a rotating black hole interacting by frame

MNRAS 000, 1–10 (2016) On extreme transient events from rotating black holes and their gravitational wave emission 9 dragging induced Alfvén waves with surrounding matter at longer durations up to the time scale of months revealed the ISCO, delivering a total energy output typical for normal by the light curve of SN2015L shown in Fig. 7. Based on long GRBs (3) defined by Erot of stellar mass near-extremal Quimby et al. (2013), we anticipate an approximate event black holes. The long duration of months is here identified rate of a few such extreme SN2015L type events Gpc−3 yr−1, with the lifetime of black hole spin, subject to spin down i.e., up to a dozen of SLSN-I per year within a few hundred against relatively low density accretion flow. The commen- Mpc. It therefore seems worthwhile to pursue a multimes- surably lower luminosity is readily radiated off by the en- senger view on these remarkable events. velope in optical emission, whereby the BPJ from the black hole fails to reach successful stellar break-out. A principle outcome of the present model is an accompanying major output EGW >> Erad in gravitational waves 8 SUPPORTING INFORMATION and a slowly rotating black hole remnant, where E is GW Additional supporting information may be found in the emitted over the course of spin down (tens of seconds for online version of this article: LGRBs, months for SN2015L type events) and the final remnant satisfies a relatively high mass low spin black hole (Fig. BHGROWTH: MatLab program of Figs. 1-3. 2) BATSENLC: Fortran program of BATSE analysis in Fig. M ≃ M0, a/M ≃ 0.36, (18) 6. defined by the outcome of black hole growth in spin-up by Acknowledgments. The authors thank A. Levinson Bardeen accretion and subsequent spin-down to the stable and D. Eardley for stimulating discussions and the referee fixed point Ω = Ω (in the approximation Ω ≃ Ω ). T H T ISCO for her/his constructive comments on the manuscript. MVP This outcome should be contrasted with moderate mass thanks the Kavli Instiute for Theoretical Physics, UCSB, black holes at slow spin produced by direct accretion alone, were some of the work has been performed. BATSE data immediately following black hole birth. The outcome (18) are from the NASA GRO archive at Goddard. This research explains the estimated mass and spin parameters of the re- NSF-KITP-16-015 was supported in part by the National cent black hole binary merger GRB150914 (LIGO & Virgo Research Foundation of Korea (2015R1D1A1A01059793, 2016) 2016R1A5A1013277) and the National Science Foundation 5.4 +0.48 M1 = 35.7−3.8M⊙, a1/M1 = 0.31−0.28, (19) under Grant No. NSF PHY11-25915. 3.8 +0.48 M2 = 29.1−4.4 M⊙, a2/M2 = 0.46−0.42 (20) We speculate that the progenitor binary of GWB1509 is a merger of SN2015L type remnants from stars of mass M0 ≤ REFERENCES 50M⊙. The final spin down evolution leading to (18) represents Abramovici, A., Althouse, W.E., Drever, R.W.P., et al., 1992, Science, 256, 325 the liberation of an appreciable fraction of black hole spin Acernese, F. et al. (Virgo Collaboration), 2006, Class. Quantum energy Erot into and output EGW in gravitational waves. Grav., 23, S635 According to Fig. 3, the efficiency η of converting Erot to Acernese, F. et al. (Virgo Collaboration), 2007, Class. Quantum radiation can reach up to 60%. Since EGW is expected to Grav., 24, S381 be the dominant output channel (over, e.g., magnetic winds Balbus, S.A., & Hawley, J.F., 1991, ApJ, 376, 214 (van Putten & Levinson 2003); in the application to long Bardeen, J. M. 1970, Nature, 226, 64 GRBs, the latter further includes MeV neutrino emission in Bardeen, J. M., Press, W. M., & Teukolsky, S. A. 1972, ApJ, 178, a time scale of tens of seconds), an energetic output 347 Bersten, M., Benvenuto, O.G., Orellana, M., & Nomoto, K., 2016, 54 η M ApJ, 817, 1 EGW ≃ 2 × 10 erg (21) 50% 10M⊙ Bethe, H.A., Brown, G.E., & Lee, C.-H., eds., 2003, Formation and Evolution of Black Holes in the Galaxy (Springer-Verlag) from spin down of rapidly rotating stellar mass Kerr Bisnovatyi-Kogan, G. S., 1970, Astron. Zh., 47, 813 black holes in core-collapse such as described in Figs. 2-3 Blandford, R.D., & Znajek, R.L., 1977, MNRAS, 179, 433 (van Putten 2016). Emitted during spin down, this creates Bromberg, O., Levinson, A., & van Putten, M.H.P.M., 2006, a descending chirp in the time-frequency domain, by expan- NewA, 619, 627 sion of the ISCO during black hole spin down. At late time, Bufano, F. et al. 2012, ApJ, 753, 67 it assymptotes to a late time quadrupole frequency indicated Burrows, A., & Lattimer, J.M., 1987, ApJ, 318, L63 in Fig. 3, satisfying (van Putten et al. 2011a) Chatzopoulos, E., Wheeler, J.C., Vinko, J., et al., 2016, arXiv:1603.06926v2 fGW,3 ≃ 600 − 700 Hz (10M⊙/M) . (22) Ciufolini, I., & Pavlis, E.C., 2004, Nature, 431, 958 Continuing emission may ensue by late time accretion in Ciufolini, I., 2007, Nature 449, 41 a subsequent plateau at these frequencies, defined by the Ciufolini, I., Paolozzi, A., Pavlis, E.C., et al., 2009, Space Sci Rev., 148, 71 stable fixed point Ω = Ω . If detected, (22) provides H ISCO Dai, Z.G., Wang, S.Q., Wang, J.S., Wang, L.J., & Yu, Y.W., 2016, a rigorous measurement of the mass of the putative black ApJ, 817, 132 hole, that may be searched for by chirp-based spectrograms Della Valle, M., Chincarini, G.. Panagia, N., et al., Nature, 444, (van Putten 2016). 1050 Our scaling to superluminous SNe of (22) originally de- de Vaucouleurs, G., & Gorwin, H.G., 1985, ApJ, 295, 287 veloped for long GRBs points to simular frequencies at much Dexter, J., & Kasen, D., 2013, ApJ, 772, 30

MNRAS 000, 1–10 (2016) 10 van Putten and Della Valle

Dong, S., et al., 2016, Science, 351, 257; ibid. Supplementary Ma- Quimby, R.M., & Yuan, F., Akerlof, C., & Wheeler, J.C., 2013, terial, Table S2 MNRAS, 431, 912 Duez, M. D., Shapiro, S. L., & Yo, H.-J. 2004, Phys. Rev. D, 69, Rees, M. J., Ruffini, R., & Wheeler, J. A. 1974, Black Holes, Grav- 104016 itational Waves and Cosmology: An Introduction to Current Levinson, A., & Eichler, D., 1993, Astrophys. J. 418, 386 Research (New York: Gordon & Breach), Ch.7 Eichler, D., 2011, Astrophys. J. 730, 41 Rees, M.J. & Mészáros, P., 1992, MNRAS, 258, P41 Everitt, C.W.F., et al., 2011, Phys. Rev. Lett. 106, 221101 Rees, M.J., & Mészáros, P., 1994, ApJ, 430, L93 Fox, D. B., Frail, D. A., Price, P. A., et al. 2005, Natur, 437, 845 Reichert D. E., Lamb D. Q., Fenimore E. E., Ramirez-Ruiz E., Frail, D.A., et al., 2001, ApJ, 567, L41 Cline T. L., & Hurley K., 2001, ApJ, 552, 57 Frontera, F., Guidorzi, C., Montanari, E., et al. 2009, ApJS, 180, Rosswog, S., 2007, MNRAS, 376, 48 192 Ruffini, R., & Wilson, J.R., 1975, Phys. Rev. D 12, 2959 Fryer, C.L., Oliveira, F.G., Rueda, J.A., & Ruffini, R., 2015, Phys. Sadowski, A., Bursa, M., Abramowicz, M., et al., 2011, A&A, 532, Rev. Lett., 115, 231102 A41 Galama, T.J., Vreeswijk, P.M., van Paradijs, J., et al. 1998, Na- Shahmoradi, A., & Nemiroff, R.J., 2015, MNRAS, 451, 126 ture, 395, 670 Shakura, N.I., & Sunyaev, R.A., 1973, Astron. Asto- phys., 24, Gal-Yam, A., et al., 2012, Science, 337, 927 337. Gehrels, N., et al., 2005, Natur, 437, 851 Somiya, K., (for the KAGRA Collaboration), 2012, Class. Quan- Ghirlanda, G., Ghisillini, G., & Firmani, C., 2006, New J. Phys., tum Grav., 29, 124007 8, 123 Sukhbold, T., & Woosley, S.E., 2016, 820, L38; Ghirlanda, G., Ghisillini, G., Salvaterra, R., et al., 2013, MNRAS, arXiv:1602.04865v1 428, 123 Gehrels, N., Chincarini, G., Giommi, P., et al., 2004, ApJ, 611, Globus, N., & Levinson, A. 2014, ApJ, 796, 26 1005 Swift/BAT, 2014, http://swift.gsfc.nasa.gov/analysis/ Godoy-Rivera, D., Stanek, K.Z., Kochanek, C.S., Chen, P., Dong, threads/batâ´LSthreads.htmlˇ Subo, et al., 2016, arXiv:1605.00645v1 Turatto, M., Cappellaro, E., Baron, R., Della Valle, M., Ortelani, Haensel, P., Zdunik, J. L., Bejger, M., et al. 2009, A&A, 502, 605 S., & Rosino, L., 1990, AJ, 100, 771 Hawley, J.F., & Balbus, S.A., 1991, ApJ, 376, 223 Thorne, K.S., 1974, ApJ, 191, 507 Heger, A., Fryer, C.L., Woosley, S.E., Langer, N., & Hartman, van Putten, M.H.P.M., 1999, Science, 284, 115 D.H., 2003, ApJ, 591, 288 van Putten, M.H.P.M., & Ostriker, E.C., 2001, ApJ, 552, L31 Hirsch, R., Mynet, G., & Maeder, A., 2004, A&A, 425, 649 van Putten, M.H.P.M., 2004, ApJ, 611, L81 Hjorth, J., Watson, D., Fynbo, J. P. U., et al. 2005, Natur, 437, ¨ van Putten, M.H.P.M., 2008a, ApJ, 684, L91 859 van Putten, M.H.P.M., 2008b, ApJ, 685, L63 Inserra, C., Smartt, S.J., Jerkstrand, A., et al., 2013, ApJ, 770, van Putten, M.H.P.M., & Levinson, A., 584, 937 128 van Putten, M.H.P.M., Kanda, N., Tagoshi, H., Tat- sumi, D., Kerr, R.P., 1963, Phys. Rev. Lett., 11, 237 Masa-Katsu, F., & Della Valle, M., 2011, Phys. Rev. D 83, King, A.R., & Pringle, J.E., 2006, MNRAS, 373, L90 044046 Kool, E.C., Ryder, S.D., Stockdale, C.J., et al., 2015, ATel #8388 van Putten, M.H.P.M., 2012, Prog. Theor. Phys., 2012, 127, 331 Kouveliotou, C., et al., 1993, Astrophys. J., 413, L101 van Putten, M.H.P.M., Guidorzi, C., & Frontera, F. 2014, ApJ, Kozyreva, A., Hirschi, R., H., Blinnikov, S., & den Hartogh, J., 786, 146 2016, MNRAS, 459, L21 van Putten, M.H.P.M., Gyeong-Min, Lee, Della Valle, M., Amati, Kumar, P., Narayan, R., & Johnson, J. L., 2008, Science, 321, 376 L., & Levinson, A., 2014, MNRASL, 444, L58 Kumar, P., Narayan, R., & Johnson, J. L., 2008, MNRAS, 388, van Putten, M.H.P.M., 2015, MNRAS, 447, L11 1729 van Putten, M.H.P.M., 2015, ApJ, 810, 7 Lee, W.H., & Kluzniak, W., 1998, ApJ, 494, 153 van Putten, M.H.P.M., 2016, ApJ, 819, 169 Lee, W.H., & Kluzniak, W., 1999, ApJ, 526, 178 Villasenor, J. S., Lamb, D. Q., Ricker, G. R., et al. 2005, Natur, LIGO Virgo collaboration 2016, arXiv:1602.03840 437, 855 Lipunov, V.M., 1983, Ap&SS, 97, 121 Wang, S.Q., Wang, L.J., Dai, Z.G., & Wu, X.F., 2015, ApJ, 807, Lipunov, G.V., Gorbovskoy, E.S., Bogomazov, A.I., & Liponov, 147 V.M., 2009, MNRAS, 397, 1695 Woosley, S.L., 1993, ApJ, 405, 273 MacFadyen A. I., & Woosley S. E., 1999, ApJ, 524, 262 Woosley, S.E., 2010, ApJ, 719, L204 Metzger, B.D., Margalit, B., Kasen, D., & Quataert, E., 2015, Woosley, S.E., & Bloom, J.S., 2006, ARA&A., 44, 507 MNRAS 454, 3311 Yoon, S.-C., Kang, J., & Kozyreva, A., 2015, ApJ, 802, 16 Mazzalli, P.A., McFadyen, A.I., Woosley, S.E., Pian, E., & Tanaka, 2014, MNRAS, 443, 67 This paper has been typeset from a TEX/LATEX file prepared by Milisavljev, D., James, D.J., Patnaude, D., et al., 2015, ATel # the author. 8216 Miller,J.M., Raymond, J., Fabian, A.C., et al., 2016, ApJ, 821, L9 Mirabel, I.F., & Rodr´ıguez, L.F., 1994, Nature, 371, 46 Nathanail, A., Strantzalis, A., & Contopoulos, I. 2015, MNRAS, 453, L1 Nathanail, A., Strantzalis, A., & Contopoulos, I. 2015, MNRAS, 455, 4479 Paczyński, B. P. 1998, ApJL, 494, L45 Pastorello, A., et al. 2007, Nature, 447, 829 Pastorello, A., et al. 2010, ApJ, 724, L16 Patnaude, D.J., Loeb, A., & Jones, C., 2011, NewA, 16, 187 Quimby, R.M., et al., 2011, Nature, 474, 487

MNRAS 000, 1–10 (2016)