Early Supernova Light Curves: Now and in the Future

Transcription

1 Early Supernova Light Curves: Now and in the Future Anthony Piro George Ellery Hale Distinguished Scholar in Theoretical Astrophysics (Carnegie Observatories, Pasadena) Supernovae: The LSST Revolution - Northwestern June 1, 2017

2 Why Early Light Curves? Observations of early light curves during the first ~days to weeks after explosion provide key information about SNe and their progenitors 1. Shock cooling measures the radius of the exploding star 2. Interaction with a companion constrains progenitors models 3. Probes circumstellar material reflecting activity of the progenitor right before death What kind of observing strategies will allow LSST to address these issues?

3 The first signature of a supernova Shock propagating through star tsh ~ δr/v tdif ~ τ δr/c tdif < tsh τ < c/v ~ 30 Shock breakout!

4 Following Breakout is Shock Cooling Early UV/optical dominated by cooling of shock-heated material Luminosity proportional to initial radius Piro, Chang, & Weinberg (2010) L R 0c apple E M

5 Core-Collapse Shock Cooling Emission Nakar & Sari 10 (also see Chevalier 92)

6 Shock Cooling Proportional to R0 Expands and cools Expands and cools but not as much

7 Rising Light Curve of SN 2011fe No detection of shock cooling Upper limit constrains progenitor radius <0.02 R sun 1 st direct evidence that Type Ia SNe are from white dwarfs Bloom et al. (2011)

8 Companion interaction in Type Ia LCs? Early light curve also provides constraints on companion radius (Kasen 10) Shappee, Piro, et al. (2015) Constraints depend on explosion time!

9 Companion constraints from Kepler Three exquisite light curves from Kepler by Olling et al (only 2 shown here) No evidence of interaction with a companion

10 Evidence for companion interactions? Cao et al. (2015) Marion et al. (2016) If true, this would be support for single degenerate scenario. Not a normal SN Ia (see McCully et al; Foley et al) Although see Shappee, Piro, et al. (2016) for a contrary opinion

11 Radius Upper Limits for Stripped SNe Corsi et al. (2012) Piro & Nakar (2013) Cao et al. (2013) using Piro & Nakar (2013) R * =4R sun R * =1.5R sun R * =0.3R sun PTF 10vgv, SN Ic R * < 3R sun PTF 13bvn, SN Ib R * < few R sun

12 Shock Cooling from Type IIb SNe Tenuous, extended envelope (~300R sun ) leads to distinct shock cooling signature (Woosley et al. 94, Shigeyama et al. 94, Blinnikov et al. 98) Consistent with yellow supergiant progenitors (e.g., Van Dyk) SN 2011dh by Bersten et al. (2012) SN 1993J, Piro ( 15), Nakar & Piro ( 14)

13 Recent Results on Superluminous SNe Type I Superluminous SN with peak at M = -22 (powering source still controversial, see Kasen & Bildsten, etc) Nicholl et al. (2015) First peak at M = -20, brighter than a Type Ia! What is it?

14 Another Double-peaked SLSN Multi-band light curve well fit by extended material (Piro 2015): ~ 400 R sun ~ 3 M sun ~ 6x10 51 erg Magnetar model might work as well (Kasen, Metzger, & Bildsten 16) Smith, Sullivan, et al (2016)

15 Are all SLSNe double peaked? LSST well-suited to find more SLSNe (low rate and bright) First peak is not that short lived for LSST Nicholl & Smartt (2016) Understanding the first peak s occurrence rate and diversity is key for unraveling this mystery

16 SuperNova Explosion Code (SNEC) Led by Viktoriya Morozova Morozova, Piro, et al. (2015) 1D Lagrangian hydrodynamics and radiative diffusion Bolometric light curves and specific wave bands Open source with growing usage (Taddia et al 16; Nagy & Vinko 16; Szalai et al. 16; Eldridge, Wheeler; Petcha; and more)

17 Type IIb SN 2016gkg Detailed modeling of first peak to constrain circumstellar structure Need ~0.02 M sun spread out to a radius of ~200 R sun around a helium core Consistent with preexplosion imaging and temperature evolution (Kilpatrick, Foley, et al. 17; Tartaglia et al. 17; Arcavi et al. 17) Piro, Muhleisen, et al. (2017)

18 What about boring Type II SNe? Morozova, Piro, & Valenti (2017)

19 How do we solve this? Expands and cools Expands and cools but not as much

20 What if... there s extra stuff around the star?

21 Maybe not so boring after all? Morozova, Piro, & Valenti (2017)

22 Further Evidence of Dense CSM Yaron et al. (2017) Emission lines seen in early Type II spectra indicate dense CSM Lower-density, larger-radius material than what we infer

23 Constraining the CSM Structure Moriya et al. (2017) What s causing this? Wind acceleration? Additional energy input? (see Fuller 17 and refs therein) Something exciting is happening at the end of these stars lives!

24 e R-band magnitude R-band magnitude R-band magnitude R-band magnitude R-band magnitude 19 Detailed Modeling of a Larger Population ecm 10gva 10osr 10uqg 11cwi Morozova, Piro, & Valenti, in preparation E fin = 1.00 foe M ZAMS = 11.0 M E fin = 2.25 foe M ZAMS = 11.0 M E fin = 0.75 foe M ZAMS = 11.0 M E fin = 1.25 foe M ZAMS = 11.0 M E fin = 0.75 foe M ZAMS = 11.0 M 09fma 10gxi 10rem E fin = 1.25 foe M ZAMS = 11.0 M E fin = 0.50 foe M ZAMS = 19.0 M E fin = 0.50 foe M ZAMS = 11.0 M 10abyy 10jwr 10uls E fin = 3.00 foe M ZAMS = 21.0 M E fin = 1.50 foe M ZAMS = 20.0 M E fin = 0.75 foe M ZAMS = 20.0 M Once these tools are in place, they will be a E fin = 0.75 foe E fin = 2.50 foe 10uqn M ZAMS useful for applying = 11.0 M 10xtq M ZAMS = 11.0 M to the larger LSST samples 11hsj E fin = 1.00 foe M ZAMS = 11.0 M 11htj E fin = 0.50 foe M ZAMS = 11.5 M 10bgl 10mug 10umz 11ajz 11iqb E fin = 2.25 foe M ZAMS = 20.0 M E fin = 1.75 foe M ZAMS = 11.0 M E fin = 0.75 foe M ZAMS = 11.0 M E fin = 1.25 foe M ZAMS = 11.0 M E fin = 2.75 foe M ZAMS = 11.0 M

25 Black Hole Formation Unnova

26 Deep Inside the Star Hot, young neutron star produces neutrinos Neutrinos carry away energy and mass (~0.1Msun) from the neutron star This decreases the neutron star s gravitational pull, causing the envelope to expand slightly

27 Birth of a black hole (Piro 13) Followed by ~yr long, dim, plateau-like light curve (Lovegrove & Woosley 13)

28 Observation of a BH birth? Adams et al. (2017) ~25 M sun RSG, increased from ~10 5 L sun to ~10 6 L sun, and then disappeared

29 LSST as a Discovery Machine Amazing sky coverage & depth is potentially ideal for catching early light curves, and rare and/or dim events Need high cadence! (between days to ~hrs depending on science) Color critical for identification (young and hot!) Quick communication (<hrs) key for crucial follow up Need to think about landscape (ZTF, ASAS-SN, ELTs, etc) during LSST era These are hard problems!

30 LSST as a Time Machine Exquisite record over a lot of the sky with a large time baseline After SNe discovered by others, search LSST records for early LCs ~hr to day cadence needed LC features Longer cadence may still be exciting for preexplosion activity (see Type II light curves!) and early SLSNe

31 General LSST Cadence Thoughts What is the main transient science we want to address? (not now, but when LSST is operating!) What will be the landscape when LSST is operating? (ASAS-SN, ZTF, GMT, TMT, ELT, etc) There s cadence AND color AND targeting. What is the correct balance? What is the best way to make data useful for transient scientists? Is there a way to build in flexibility? How much?

32 Conclusions Early light curves provide new and valuable information about exploding stars Shock cooling non-detections provide radius constraints for SN Ia progenitors (< 0.02 R sun ) and stripped-envelope SNe (< 5 R sun ) Evidence (or not) for non-degenerate companions in SNe Ia Direct measurements of the radius of extended material around SNe IIb (~300 R sun ), SLSNe (~ R sun ) Surprisingly, boring Type II SNe show signs of dense CSM LSST is a Discovery Machine but is also a Time Machine, providing a record of early LCs and pre-explosion activity