Types seen and/or expected theoretically from stars

Table of Contents

1 Merging white dwarfs    CHARLES

  • Phinney KITP review of WD+WD (q<.6 stable;He+He->sdB (ex.: sdB ejected from Gal.C.; Hirsh+ 2005A&A…444L..61H; AIC; magnetars, spec.) (merger -> accretion at Ledd? Or faster with strong winds? -> might have M~-11 source for ~1yr before Ia)
  • Further considerations of stability: Han+Webbink 1999A&A…349L..17H, Motl+ 2007ApJ…670.1314M
  • WD merger simulations, Loren-Aguilar+ 2009A&A…500.1193L; equal mass has peak T at centre
  • WD mergers should not be in corotation (tides too slow; check); if they are, tidal dissipation makes them very hot (check)

1.1 H WD = BD: stable ignition (if any)?

1.2 He WD

1.3 CO WD

1.4 ONe WD

For some references, see discussion about e- cap models in Foley+ 2009AJ….138..376F (their S6.2)

  • ONe+He -> always stable? Or make R CrB like object? AIC at end?
  • ONe+CO -> CO ignition? Sim. to Ia? Also AIC?
  • ONe+ONe -> AIC? BH? but will have disk; e- cap fast enough? Or Ne burning?

2 Accreting WDs    KELLY

Below is all for slow accretion; does "hypercritical" exists for WDs? Also, for some WDs in very close binaries, accretion is not via a disk, but via direct impact. The prime example is HM Cancri, with a 5.4-minute orbital period; see Roelofs+ 2010ApJ…711L.138R. The system is also interesting in showing hydrogen in its spectrum, likely because the donor had a thick, non-degenerate hydrogen envelope (D'Antona+ 2006ApJ…653.1429D). As a result, its radius shrinks upon mass loss and the orbit shrinks as well (rather than expands as expected for a cold WD). Finally, for symbiotics, only small, temporary disks may form (but see tidally enhanced winds, Chen+ arXiv:1106.1252

2.1 H WD = BD: ???

2.2 He WD

  • Nova explosions very long/strong, followed by ~1000yr SSS phase; Shen+ 2009ApJ…705..693S. This is for very slow accretion rates, expected for Roche-lobe filling systems (where, to have stable mass transfer, the donor much be very low mass).
  • Higher mass transfer rates may be possible accreting from winds (as happens in symbiotics).

2.3 ONe & CO WD

  • normal novae; for theory of long-term state, see Townsley&Bildsten 2004ApJ…600..390T; for rapid accretion Nomoto+ 2007ApJ…663.1269N; stable state may not really exist, and should still have He novae that remove most mass, Idan+ 2012arXiv1207.5575I.
  • typing the WD from nebular spectra; e.g., Helton+ 2012arXiv1206.4005H
  • novae on low-mass WD => luminous red novae? For M31-RV: Shara+ 2010ApJ…725..824S (note: their UV ctpt is not real; see Bond arXiv:1105.4595); models in Shara+ 2010ApJ…725..831S
  • What if generally accreting He (from sdOB or He Ms or He giant)? Some preliminary work in Piersanti+ 2011arXiv1109.4786P; also HM Can and AM CVn systems, see Kaplan+ 2012arXiv1208.6320K for discussion of evolution.
  • He novae, an example perhaps V445 Pup; see Iijima&Nakanishi 2008A&A…482..865I; theory: Kato+ 2008ApJ…684.1366K
  • Rapid He accretion: Saio&Nomoto 1998ApJ…500..388S; Saio&Jeffery 2002MNRAS.333..121S
  • .Ia supernovae Bildsten+ 2007ApJ…662L..95B; LC in Fryer et al., 2009ApJ…707..193F; possible observed example=SN 2010X: Kasliwal+ 2010ApJ…723L..98K (or AIC?)
  • C novae (Phil: for high enough Mdot, accreted layer ignites before core, possibly leading to Ia, but perhaps not). Relevant sources could be the L~Ledd supersoft sources. If indeed in a thin, Roche-lobe filling envelope, would get shock break-out, etc. (But: Falk Herwig said one should not expect C "pulses" -- does not ignite).
  • Considerations of fast accretion and rapid rotation of CO WD accreting from another CO WD: Nomoto+Iben 1985ApJ…297..531N; Piersanti+ 2003ApJ…583..885P and 2003ApJ…598.1229P.
  • consideration of how to get strongly superchandrasekhar mass, Hachisu+ arXiv:1106.3510
  • observational evidence on whether or not mass increases: Zorotovic+ arXiv:1108.4600: Post-common-envelope binaries from SDSS. XI: The white dwarf mass distributions of CVs and pre-CVs
  • Theoretical arguments against mass growth (Falk Herwig, pers.comm.):
    • If SSS SD, should have many thermal pulses for each Ia can be 50-100year if already AGB-ish, few years if started as "WD" yet see only few born-again AGB. For recurrent novae has to go eventually.
    • As thermal pulse causes expansion, would disrupt disk, rapid mass loss due to companion (reverse CE)
    • Existence of ONe novae evidence that WDs do not grow -> need to dig through few 0.01 M⊙ of CO to get to ONe core.
  • Alexander+ arXiv:1108.3837 argue recurrent outbursts of RS Oph are not novae but rather disc instabilities plus nuclear burning; Williams arXiv:1108.4917 makes the argument more generally (triggered by episodic mass transfer?); but this may be more like the strange object DASCH J075731.1+201735 (Tang+ 2011arXiv1110.0019T, discovery of a peculiar slow nova in a peculiar symbiotic binary).
  • Sokoloski+ 2006ApJ…636.1002S: Could also have "combination novae", accretion plus nuclear (Z And)

2.4 ONe WD

  • likely cannot accrete stably from another ONe WD

3 End points of accreting WDs    YEVGENI

  • what's below mostly assumes increase in mass, but also think through if anything special happens if novae reduce mass (e.g., could accretor decrease in mass faster than donor, thus bringing mass ratio closer to unity and to unstable mass transfer?). A shrinking accretor may be the more common case (theoretical expectations: Yaron+ 2005ApJ…623..398Y, their Fig. 6). He novae are supposed to give lower mass loss (Kato+ 1989ApJ…340..509K). Observational data scarce; Schaefer 2010ApJS..187..275S should have references; according to Selvelli+ 2008A&A…492..787S, T Pyx ejected far more than it accreted. On the other hand, a study of eclipsing cataclysmic variables finds rather high WD masses, see Savoury+ arXiv:1103.2713.

3.1 H WD = BD

  • BD pushed to ignition? slow given H fusion? (yes, Salpeter 1992ApJ…393..258S Might some "free-floating" planets experience this? Likely accretion rates probably too low (need to accrete at ~1e-11 Msun/yr to accrete 0.1 Msun in a hubble time).

3.2 He WD

  • He core WD pushed to ~0.45 Msun: visible He flash?

3.3 CO WD

3.4 ONe WD

  • AIC unavoidable for ONe WDs? AIC conditions in Nomoto&Kondo 1991ApJ…367L..19N; but see Gutiérrez+ 2005A&A…435..231G, who argue that just 1.5% of leftover C is enough to explode instead of collapse.
  • AIC LC predictions in Darbha+ 2010MNRAS.409..846D; Fryer+ 2009ApJ…707..193F Possible example (more likely .Ia?) SN 2010X: Kasliwal+ 2010ApJ…723L..98K (or AIC?) End point might be magnetar, Levan+ 2006MNRAS.368L…1L, if so, could boost fireworks; for radio afterglow, Piro+Kulkarni 2012arXiv1211.0547P
  • Could one have double detonation – Ne detonation triggered by He or C nova?
  • More strangely, Falk Herwig mentioned it may make hybrid CONe WDs, with CO core and ONe layer on top Off-center C ignition: if close to no ignition, neutrino cooling is too fast to allow burning to go to core; form layer of ash. Reality: maybe convective down-mixing would remove this (1-d stellar evolution often gives abundance gradients that are too sharp)

4 Accreting neutron stars    MATT

4.1 slow accretion (low priority)

  • accretion instabilities: well-known, no real need to investigate.
  • X-ray bursts, superbursts: well-known, no real need to investigate.
  • Differences for He accretion? (WD or Helium star): fairly well-known, low priority.
  • CO or ONe WD? May be stable; estimate Mdot using GR Porb decay.

4.2 fast accretion

5 End point of accreting neutron stars    MATT

6 Merging neutron stars (and black holes)    RONGFENG

7 Accreting black holes    RONGFENG

7.1 slow accretion (lower priority)

  • from lower mass MS/Giant: soft X-ray transients
  • optical flashes from short-P BH transient? Rea+ 2011arXiv1101.3483R: Swift J195509.6+261406: an optical bursting X-ray binary?

7.2 fast accretion

E.g., in merger with more normal star, perhaps WD or NS

  • hypercritical accretion in neutrino-cooled disk; e.g., Beloborodov 2008AIPC.1054…51B. Leads to long GRB?

8 Mergers of main sequence stars and giants    DANIELA

See CEE review: Ivanova+ ~/literature/ivan+12.pdf Focus here on the merger proper: envelope ejection and lightcurve. Recent review: Taam+Ricker 2010NewAR..54…65T; classic paper (with good description): Meyer+Meyer-Hofmeister 1979A&A….78..167M. Review for massive stars, Taam+Sandquist 2000ARA&A..38..113T. Nice very recent Letter on best criterion for common envelope: Ivanova+Chaichenets arXiv:1103.2790; also a critique on stability (more stable than one thinks): Woods+Ivanova arXiv:1108.2752; similarly, Passy+ 2012ApJ…760…90P argue that giants do not always expand upon rapid mass loss (visit Falk: do not yet know qcrit). Interesting details such as that CE may end by mass transfer from a MS to a giant core, leading to explosive H burning (see 3.3.4 in review)

8.1 Merger in main-sequence star

8.2 Merger in giant

8.3 Envelope ejection/lightcurve details

  • For many systems, ejection very asymmetric (but axisymmetric); SN 1987A? See Morris&Podsiadlowki 2006MNRAS.365….2M
  • Lightcurve dominated by recombination front; Ivanova+ arXiv:1104.5026
  • He WD with giant leads to R, J stars? Zhang+Jeffery 2013arXiv1301.0766Z
  • Any predictions for mergers in sdB or helium stars/giants? Differences?

9 Further evolution of merger products    SANTIAGO

Need to think whether these different products lead to new types of transients Some expected merger products

  • MS+MS result in blue stragglers; e.g., SX Phe=pulsating blue stragglers.
  • Also may result in FK Comae stars=rapidly rotating supergiants; e.g., Podsiadlowski 2001ASPC..229..239P. More massive stars could form sgB[e] stars, or stars like the progenitor of SN 1987A; Podsiadloski+ 2006ASPC..355..259P
  • CE in giant can leave sdB (Heber 2009ARA&A..47..211H) or helium star
  • For He WD + He core, the resulting core would be more massive than typical, which might make an overluminous, weird, horizontal branch or red clump star
  • He core merger with A* -> CE leading to rapidly rotating red-clump/HB star?
  • ONe merger w/ MS -> "Born-again star?" (PN w/ ONe rich inner ejecta; Lau+ 2011MNRAS.410.1870L
  • Perhaps make C-rich R stars? No acc. to Piersanti+ 2010A&A…522A..80P
  • For giants, high-B WDs as CE products? Nordhaus+ 2010arXiv1010.1529N; see also Tout+ 2008MNRAS.387..897T for a broader perspective.
  • Look at stranger possibilities, such as HeWD+sdB merger -> sdO (Justham+ 2011MNRAS.410..984J); is final fate interesting?

9.1 Events when core of giant merges during CE

This has overlap with merging white dwarfs and end points of accreting white dwarfs. A complete merger would typically be of a relatively unevolved giant, with, therefore, a relatively low-mass core. Thus, eg., CO-WD plus CO-core may be difficult. Though one can have two CE phases, with the first leaving a He star (a common occurrence), which later becomes a He giant, leading to a second CE. For general considerations, see Kashi+Soker arXiv:1105.5698

  • With WD, just like WD+WD, but in envelope? Or does giant core have substantially different M(R), so that core is disrupted rather than WD even if core is more massive?
  • Suggestion that ONe core plus CO WD leads to AIC and later long GRB; Tout+ 2011MNRAS.410.2458T
  • Could this be related to enshrouded SN (see reference section)?
  • Maybe generally think through what, e.g., a SN Ia inside a envelope would look like. Possible observational examples are SN 2005gj (Aldering+ 2006ApJ…650..510A, Prieto+ 2007arXiv0706.4088P) and SN 2002ic (Hamuy+ 2003Natur.424..651H). Chugai&Yungelson 2004AstL…30…65C argue that CO core + CO WD merger could not lead to this scenario, because it takes too long for GR to have the cores merge. If they merge immediately, the Ia may be too soon. At least for 2002ic, there must be some delay between envelope ejection and SN Ia to ensure the envelope is far enough out (interaction is still strong at 256d; the SN Ia ejecta travel at ~2000 km/s at that time (so have gone out to ~4e15 cm=300 AU), while the ejecta travel at 100 km/s, so must be emitted at least 20*256 d ~ 14 year earlier). See Kotak+ 2004MNRAS.354L..13K for obs., Chugai+ 2004MNRAS.355..627C for the inferred CSM density structure, and Benetti+ 2006ApJ…653L.129B for an interpretation as a Ic inside a thick envelope (but Prieto+ say it has to be a Ia).
  • For more massive stars, could CE trigger core collapse and could this in turn be responsible for ultraluminous supernovae? (see also Magnetar-assisted SNe). Timing seems difficult; maybe via electron-capture?
  • For more massive stars, injection of H in He burning shell could help eject envelope and leave CO star with a low-mass companion, possibly later making long GRB; Podsiadlowski+ 2010MNRAS.406..840P.

9.2 Later events

Following CE, there may be a mass-transfer phase in which the remainder of the donor is adjusting to regain thermal equilibrium; this can cause more accretion than the CE; Ivanova 2011ApJ…730…76I.

  • Merger of sdB (or more massive helium star) with WD

10 Stable mass transfer between MS/Giant    RENE

Generally, this would seem not to lead to transient events, so much lower priority than the changed evolution. Main thing to do is to think what systems can be produced.

10.1 Weirder combinations

  • accretion of H onto sdB (or Helium star)? Shell flashes?

11 Changed evolution of one of the components    RENE

11.1 Companion triggering of evolution

11.2 Due to stripping

11.3 Different evolution due to accretion

11.4 Likely related

12 Not in binaries (globular clusters, massive black holes)

  • In GC, HB+MS -> low-M HeMS + MS?? -> how would these look like? (Stephen) Find in GC via odd position in CMD? (look up low-mass He evol. tracks)
  • In GC, WD collissions: if sufficiently head-on, sublum SN Ia (perhaps; arXiv:0907.3915 and something the day before or so)
  • Radiation from tidal disruption debris that's thrown out; arXiv:0911.5358
  • stellar disruption by super-massive black hole; eg., arXiv:1001.2991

13 For reference

Date: 2013-03-27T12:46-0400

Author: Marten van Kerkwijk

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