1. Transient emission associated with the birth of neutron stars
Xiamen-CUSTIPEN Workshop on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave Astronomy
7 Jan 2018
Transient emission associated with the birth of neutron stars
Yun-Wei Yu / 俞云伟
Central China Normal University / 华中师范大学

2. Neutron stars and supernovae
Superluminous Supernovae
Smith et al. 2007
Gal-Yam 2012

3. Possible energy sources of SLSNe
Pair Instability Supernovae
Nicholl et al. 2013
Smith & McCray 2007
Magnetar engines: Hydrogen-poor SLSNe
(Herger & Woosley 2002)
Gal-Yam 2009
Shock interaction: Hydrogen-rich SLSNe
Smith et al. 2007

4. SLSN magnetars
YY, Zhu, Li et al. 2017, ApJ, 840, 12

5. SLSN magnetars Why? Does this mean something?
The rapid and slow classification of SLSN light curves in observation is a natural result of the distribution of the NS magnetic fields.
The rotational energy of SLSN magnetars seems correlated with the masses of SLSN ejecta.
Why?
The magnetic fields of SLSN magnetars are just higher than the Landau critical field strength of electrons.
Does this mean something?
YY, Zhu, Li et al. 2017, ApJ, 840, 12

6. Spinning-down magnetars and GRB afterglows
Zhang et al. 2006
YY & Dai 2007
GRB afterglow emission should be substantially affected by post-GRB engine activity.

7. Spinning-down magnetars and GRB afterglows
YY, Cheng, Cao 2010
Ultra-high magnetic fields could play a crucial role in driving a relativistic jet to produce GRB emission.
Gravitational wave radiation could sometimes play an important role in spinning down GRB magnetars.
YY, Zhu, Li et al. 2017

8. The remnant of a NS-NS merger could be long-lived massive NS
Short GRBs
Shallow-decay afterglows
Fan & Xu 2006
GRB A
Extended gamma-ray emission
GRB
Barthelmy et al. 2005
X-ray afterglow flares

9. NS-powered mergernovae
YY, Zhang, Gao (2013)
The thermal emission of a merger ejecta could be primarily powered by NS spin-down, rather than by radioactive decays of r-process elements.
Fan, YY, Xu et al. (2013)
GRB B:
A spin-down power can naturally explain the multi-wavelength afterglow emissions and the associated kilonova emission.

10. GW and a post-merger NS
YY, Liu, Dai, 2018
Li, Liu, YY, Zhang 2018
The existence of a post-merger massive NS is beneficial for (1) reducing the high requirement on the ejecta masses and (2) reconciling the opacity values.
Kilonova AT2017gfo could be powered by radioactivity at early phase and by NS spin-down at late phase
In the future, (1) we need more samples, in particular, the more luminous or more faint samples. (2) It is useful to detect the increasing phase of the kilonova emission. (3) On-axis observation is also helpful.
Kilonova AT2017gfo could be powered NS spin-down all the time.

11. The suppression of the EMW emission
The open field lines could be buried by fallback material and also expelled to be within the light cylinder.
AT2017gfo’s luminosity indicates the MDR of the remnant NS is suppressed seriously, if the NS is a magnetar intrinsically.
The serious suppression of the MDR may be indicated by the steep decay after an afterglow plateau.
GW radiation
Magnetic dipole radiation
Troja et al, 2007
Torres-Forné et al. 2016
YY, Liu, Dai, 2018

12. Fast evolving luminous transients
YY, Li, Dai (2015)
Very different from typical supernovae
These FELTs can be explained by a magnetar engine and a low-mass ejecta.
Drout et al. 2014

13. Collapse of white dwarfs
YY, Chen, Wang 2019
Collapse of white dwarfs
Massive WDM remnants could evolve as an AGB star (Schwab et al. 2016).
The collapse of a super-Chand remnant could happen in a dusty wind environment.

14. Fast evolving luminous transients
Margutti et al. 2018
AT2018cow
AT2017gfo
Perntice et al. 2018

15. Summary
NSs in the universe could have very different origins. Different masses? different EOSs?
SLSNe and some long GRBs could have a uniform origin model, whose differences are caused by the different magnetic fields of the magnetar engines.
A long-lived massive NS could exist in some short GRBs/NSMs (e.g. GW170817).
The collapses of super-Chand WDs into a NS will be a very interesting target of transient surveys.
Current and future transient surveys open a new era for researches on newborn NSs.