The Mysterious Connection between Superluminous Supernovae and Gamma-Ray Bursts STScI Mon, May 23, 2016 2:00 PM Chryssa Kouvelioto: The State of Magnetars The state of magnetars is ... very good! A touch of history X-ray pulsar in Dorado, March 5, 1979 recognized by Florets (sp?) this object is located in a SN remnant in the LMC NS populations with magnetars -- many names Soft Gamma Repeaters Anomalous X-ray Pulars Dim Isolated Neutron Stars Compact central X-ray Objects Rotation powered pulsars but ideally, should call them all MGC XXXX+/-YYYY rate of detection has increased with time now up to about 30 objects discovery rate about 1 per year lately SWIFT and Fermi together work well poor RXTE is now defunct all are in MW plane, except one each in LMC, SMC sources in MW spread out throughout galaxy, a bunch in direction not far from center of MW statistics discovered in optical, gamma, X-rays, radio P = 2-12 seconds, P-dot = 10^(-11) to 10^(-13) s/s t(spindown) = 2 - 36,000 kyrs B-field around 1-10 x 10^(14) G but three are significantly lower Lum approx 10^(32) - 10^(36) erg/s no evidence for binarity massive star progenitors? the Magnetar Conjecture powered by strong mag fields in rapidly rotating object note magnetic energy must be less than grav binding energy of NS max B-field is approx 10^(18) Gauss we calculate a MINIMUM value of magnetic field due to unknown orientations measured B-fields 10^(12) to 10^(15) Gauss with peak 10^(14) pulsar spindown ages big uncertainties compute it via several assumptions: tau = (P / 2*P-dot) Crab: spindown age 1300 years, but real age 950 years problem: real P-dot is not constant distribution is from 2 Kyrs to 36,000 kyrs probably 10 Kyrs is reasonable magnetar states quiescent active bursts of duration few 100 seconds giant flares - 3 sources found so far few tens of bursts from 3 sources < 10 bursts - 11 sources no bursts - 5 sources 5 candidate magnetars Timing P-dot values are higher in SGRs higher B field, shorter spindown ages P-dot values are smaller in AXPs smaller B field, longer spindown ages Magnetars have large Pdot, large P, compared to other classes of sources Pulsar J1846-0258 had magnetar-like bursts rotation powered age 900 years bursts assoc with change in timing behavior Spectra of magnetars best fit with absorbed power law plus blackbody Active state emission properties burst modes: single bursts, storms, forests storms over half-hours, six hours intermediate bursts 10^(42) erg giant flares 10^(44) - 10^(45) erg initial very short burst, then long decay SGR 1806-20 giant flare extended emission lasted over 5 minutes properties of magnetars observed with GBM 10 observed objects have similar properties spectra, fluxes, etc. location of unknown sources are all close to MW plane burst energetics lum range 10^(34) - 10^(41) erg AXPs have lower luminosities Persistent flux when source is bursting, flux goes up SGR 1935+2154 May 2016 outburst currently 18 bursts so far P-dot not constant sometimes decreases by factor 4, by factor 2.6 no assoc between bursts and P-dot change this is very mysterious Pulse profile affected by activity sinusoidal near time of giant flare SGR J1834.9-0846 close to SNR W41, close to HESS source, Fermi source very active region XMM showed pulsar-like wind nebula in 2005 (before active), and 2011 combination of dust-scatting ring and pulsar-wind nebula? nebula has lasted over 9 years why is this source unique? could the rich environment be responsible? could this source evolve from Magnetar Wind Nebula to Pulsar Wind Nebula? 2:30 PM Q: progenitors are massive stars? A: in at least 2 cases: one source behind MW center, in cluster of massive stars source could be runaway star from that cluster in N49 source, cluster of massive stars close to magnetar Q: is there a connection between P-dot and X-ray Lum? A: yes 2:32 PM Dan Kesen: Signatures of Magnetar or BH Powered supernovae what mystery? somewhat oversimplified, can say we know about engines: magnetar(spindown), BH(accretion) GRB last a few hundred seconds ultra-long GRB last few 10,000 seconds Super-luminous Supernovae last a few million seconds observations customary to try to fit magnetar-powered light curve to real light curves of SLSNe SLSN Type I spectra lines of C II, CIII, Mg II, Fe II may be identified so "photosphere" is NOT mostly H or He stripped envelope star other contraints on energy, time, mass-of-ejecta shell structure: magnetar inflates bubble shock breakout: radiation vents when shock reaches surface double-peak light curves shell blowout: can lead to ionization breakout, UV/X-ray rebrightening bipolarity: polarization, observables depend on viewing angle Dynamics of magnetar powered supernova magnetar evacuates cavity, pushes it into a shell accelerates shell outward shows movie of 2-D model when shell reaches photosphere, hot stuff escapes signs in spectra prediction of plateau in velocity of ejecta observed SN 2015bn did sort of have plateau at late times double-peaked light curves initial peak lasts a few days, not as bright as main peak similarity between events had to explain via CSM magnetar-pushed shell may explain should be several days after explosion radius will be approx 10^(14) cm shell is much bigger than original star at breakout time so breakout lasts longish time magnetar may emit energy in bipolar manner opening angle around 25 degrees currently working on simulations in 2-D shock breakout first happens near pole should therefore be brighter if viewed near pole holes in shell open channels for UV/X-rays to escape responsible for "undulations" in SLSN light curves? responsible for rebrightening of 2:47 PM Q: how long can you make the initial peak last? A: depends on properties of magnetar, diffusion time of SN could be many days, but then smears into second peak Q: spectra you showed -- are they mostly early times? A: yes, photospheric times Q: 1987A had a second brightening -- was explained as shock breakout are magnetars different? A: 1987A had ordinary shock breakout, was orders of mag less luminous magnetar shock breakout happens when photosphere is much larger Q: how exactly does magnetar transfer energy to ejecta? A: yes, that's the hard part. we're not sure, has something to do with magnetic reconnection (?) if one can create e-/e+ pairs, the rest is easier but this is indeed a tough question Q: do we know the efficiency? A: no, not very well 2:51 PM: Chris Kochanek: ASASSN 15lh we have an awesome logo! could be a SLSN, or a TDE -- both are way cool ASAS-SN: all-sky survey for bright transients cover entire sky to 17th mag no selection based on host appears less biased against events close to centers of galaxies 18-arcsec FWHM images does well at finding TDEs event ASASSN-15lh spectrum looks like SLSN type I redshift z=0.23 similar to PTF10cwr/SN 2010gx shows light curve of the event declined in luminosity and temperature then rebrightened, plateau now fading again crazy numbers: integrated energy 1.6 x 10^(52) ergs 60% before valley, 40% after more luminous than other SLSNe no X-rays, no radio no hydrogen, no helium, mostly featureless spectra is it a SLSN? it sort of resembles one energetically lack of polarization is it NOT a SLSN? projected position close to center of massive galaxy (not in dwarf galaxy) energetics push the envelope of possible for SN could be a tidal disruption events (TDEs) why not a TDE? other TDEs show evidence of H or He evolution very different TDE should be very asymmetric, perhaps highly polarized could you make it from a TDE? well, it is in a massive galaxy but hard to disrupt a compact object -- must be MS star so how to avoid H and He? lots and lots of ionizing photons, yet no sign of H or He lines .. but this would be the fourth ASASSN TDE SWIFT makes this observation possible need the monitoring in UV from space 3:01 PM Q: ASASSN has not discovered any others SLSNe -- why find a strange one? A: yes, this is a mild statistical embarrasment Q: how massive could a BH be and still make TDEs? A: could be at most 10^8 solar masses Q: how do you explain seeing only one Oxygen line? A: I can't. but it looks sorta like a SLSN Q: does the host galaxy have dust lanes or any signatures of gas? A: no, its pretty smooth Q: at what redshift are you sensitive to SLSN? A: 50% efficient at mag = 17 Q: what are limits on star formation in host? A: there can't be much Q: SN come from massive stars A: I've heard that 3:04 PM: Emmanouil Chatzopoulos: Extreme Supernova Models for ASASSN-15lh I will argue that it is a SLSN shows the light curves and spectra -- reached abs mag -23.5 what powered it? large amounts of 56Ni? decline rates too rapid would require 30 solar masses of 56Ni magnetar spindown energy need B-field 10^(14) G and period 1 ms but could it be efficient enough? circum-stellar interaction? no H or He H-poor CSM? tidal-disruption event near center of host new observations show late-time UV-bright plateau 100-200 days after explosion 10^(44) erg/s maybe use multiple-input models combine several sources of energy 56Ni, plus magnetar, plus H-poor CSM, so, I've tried creating a range of such models some models do reproduce late-time rebrightening models with winds don't work well at late times probably need strong CSM interaction results: interaction with 1/r^2 winds don't work well dense shell interaction works better best-fit models require 40-solar-mass star interacting with 20 solar masses of prev ejected material and magnetar what would progenitor be? rapidly rotating (> 50% breakup speed) 50-60 solar mass star helps produce pulsational pair-instability SN pulsations eject much mass, H/He leaves long before SN rapidly rotating C/O core collapses to form magnetar why not BH instead of magnetar? the limits to magnetar formation still under debate possible models PPISN + magnetar multiple PPISN single PPISN 3:14 PM Q: what do your models predict for future evolution? A: one model predicts decline after 230 days, but others have different properties Q: are you bothered by lack of evidence for star formation in host? A: No. But, well, that's a good question. It's just one star! Q: why is late-time emission in UV, not optical? A: shocks may emit mostly in UV Q: what are timescales for pulses? A: can range widely Q: were there pulses before the current one? are there archival limits? A: we don't know. (A - there are few observational limits) Q: ? A: ? 3:18 PM Ryan Chornock: X_rays obs of SLSN-I we use SWIFT, XMM, Chandra work in progress paper to appear shortly actively monitoring active SNe motivated by SLSN-I SCP06F6 observed X-ray source at 74 days after discovery transient Lx 10^(45) erg/s -- really high peak optical lum 10^(44) erg/s Chandra obs 1 month later shows no detection to Lx approx 10^(44) erg/s so X-ray source short-lived X-ray emission mechanisms inverse Compton: energetic electrons upscatter photons to X-ray normal SN Ic produces 10^(39) erg/s X-rays million times too weak for SCP06F6 depends on density of material circumstellar interaction SNe IIn, Lx 10^(41) erg/s SN 2006gy = SLSN type II showed Lx 10^(39) erg/s off-axis jets? ULGRB 111209A/SN 2011kl GRB-like jet viewed off-axis could look like late-time X-rays ionization breakout? magnetar ionizes from within when ionization front reaches photosphere, breakout and X-rays appear depends sensitively on magnetar spin, mass of ejecta timescale is delayed long after optical peak delayed longer for slow spinning magnetars late-time leakage magnetar fits to SLSN optical light curves overpredict late-time fluxes could be explained by ionization breakout this work 29 SLSN-I (2 in progress) SCP06F6 was really, really luminous! this sample has many upper limits at very late times fills in a region of parameter space which was previously empty SCP06F6 is STILL really, really luminous! how do the obs compare to magnetar models? rule out the most quickly-spinning magnetars (1 ms period) but slower-spinning are okay what about ASASSN-15lh? upper limits of X-rays 10^(42) erg/s during first 250 days after explos we dedicated time on Chandra to this event we have detected photons from its direction but it is spatially coincident with center of big galaxy waiting for next obs to say more a transient source ought to decline by then ... conclusion SCP06F6 is only 10^(45) erg/s source in X-rays so far can still hide magnetars, by varying CSM parameters 3:32 PM Q: would the recently-detected photons .. A: no comment Q: will it help to have HST images of the source? A: it may help a little Q: limits depend on ejecta mass, spindown period of magnetar, etc. don't you have limits from light curve in optical? A: those contraints aren't very useful Q: to explain SCP06F6, do you need 1 ms period magnetar? A: is necessary to push things to extreme Q: you really need to know the duration of the X-ray signal, don't you? A: yes Q: SCP06F6 is clearly an outlier. Real dection, not instrument artifact? really SN? A: the optical spectrum shows SN features Q: but there were reports of issues with X-ray detection, right? A: there were 3 independent channel detections with XMM, not just 1 so less likely to be instrument issue Q: errorbars in X-rays are big. could be viewing angle dependence, same SN could look diff from diff angles Q: can you rule out two events happening close together? A: well, it is at center of big galaxy cluster so plenty of opportunity for overlapping events, I guess but optical shows only one transient 3:39 PM break