Search

Since the LP-Nova models were proposed, and the short gamma-ray burst (SGRB) afterglows were confirmed, people have actively made searches for the evidence of the existence of LP-Novae among the optical (or near-infrared) counterparts of SGRBs. In this paper, we first summarize these observational progresses before 2012 in Section 2. In Section 3 and 4, we respectively introduce the basic properties of GRBs 130603B and 060614, as well as the theoretical interpretation for their near-infrared (NIR) counterparts, and their NIR excess may be the signature of the existence of LP-Novae. In Section 5, we describe the basic properties of GRB 080503, and the theoretical interpretation for its optical and X-ray counterparts, and the later re-brightening of its optical and X-ray light curves is explained as the ejecta radiation (merger-nova radiation) of magnetar heating after the neutron star merging. If the interpretations for the SGRB-associated optical and infrared counterparts are correct, they may provide the first series of direct evidence to show that SGRBs and some special LGRBs are originated from the compact star mergers. Besides LP-novae (and merger-novae), the high-speed orbital motion before the compact star merging and the merger itself will produce strong gravitational-wave bursts (GWBs). In the coming era of gravitational wave detection, the theoretical and observational studies on the electromagnetic counterparts of compact star mergers will receive more and more attentions. Due to the larger uncertainty of GWB's location, the LP-Novae associated with GWBs can serve as the best candidates for the precise location of GWBs. The fast developing high-cadence and wide-field optical-NIR surveys will make effective explorations on the LP-Novae and similar phenomena, and interact the detection and research of gravitational waves. Therefore, in the last section we present the methods for the future detections of LP-Novae, and the prospect of their multi-messenger detections.

The neutron-rich matter ejected by compact object mergers (neutron star-neutron star merger and neutron star-black hole merger) provides one of the most important environments for the syntheses of r-process elements. In recent seventeen years, theoretical studies suggested that the energy produced during the decay of r-process elements will form optical/near infrared (NIR) radiations after thermalization. This type of optical/NIR transients are called Li-Paczynski novae, or LP-novae for short. Since the typical peak brightness of LP-novae is ∼1000 times brighter than that of a typical nova, they are also called Kilonovae. Besides, both theoretical and observational studies have showed, directly or indirectly, that under certain conditions, the compact object mergers can produce the gamma-ray bursts with a rather short duration of T90 ≤ 2s (SGRBs for short), and most SGRBs may come from compact object mergers. After the identification of SGRB afterglows, dedicated searches of the LP-novae associated with SGRBs have been taken. In this review we present the theoretical progress of LP-novae in recent seventeen years, and the observational aspect will appear in a upcoming paper.

Neutron star-neutron star, neutron star-black hole, and black hole-black hole mergers are the most promising sources of high-frequency gravitational waves (GWs) in the universe. Simultaneously, these compact binary mergers can also produce various electromagnetic emission represented by short gamma-ray burst (SGRB) phenomena, which had been confirmed by the discoveries in the GW170817/GRB 170817A event. Therefore, these merger events are undoubtedly one of the most important targets of the multi-messenger astronomical researches. We provide a brief review on the state of art of the SGRB studies. First of all, the emission properties during the prompt, precursor, extended, and afterglow phases of SGRBs are described subsequently by following a theoretical understanding for relativistic jets. For completeness, we also pay many attentions to the associated kilonova/mergernova emission from a quasi-isotropic merger ejecta, the potential neutrino production, and the host galaxies of SGRBs, which can provide independent constraints on the origin of SGRBs. The observations in the GW170817/GRB 170817A event are specially introduced, in particular, focusing on the implications for the merger product and the jet structure. Finally, by considering of the viewing angle-dependence of SGRB emission, we discuss a new understanding of the luminosity function of SGRBs. Then, we can prospect the future observation by the GECAM satellites, which are specially designed to monitor the GW-associated SGRBs and planned to be launched in 2020.

We present a detailed report of the connection between long-duration gamma-ray bursts (GRBs) and their accompanying supernovae (SNe). The discussion presented here places emphasis on how observations, and the modelling of observations, have constrained what we know about GRB-SNe. We discuss their photometric and spectroscopic properties, their role as cosmological probes, including their measured luminosity–decline relationships, and how they can be used to measure the Hubble constant. We present a statistical summary of their bolometric properties and use this to determine the properties of the “average” GRB-SN. We discuss their geometry and consider the various physical processes that are thought to power the luminosity of GRB-SNe and whether differences exist between GRB-SNe and the SNe associated with ultra-long-duration GRBs. We discuss how observations of their environments further constrain the physical properties of their progenitor stars and give a brief overview of the current theoretical paradigms of their central engines. We then present an overview of the radioactively powered transients that have been photometrically associated with short-duration GRBs, and we conclude by discussing what additional research is needed to further our understanding of GRB-SNe, in particular the role of binary-formation channels and the connection of GRB-SNe with superluminous SNe.

We propose to construct a 2.5 m wide-field and high-resolution telescope (WeHiT).It will be the first facility in the world with a special innovative design and can conduct bothhigh-resolution solar observations and the wide-field night sky survey. Its scientific objectivescover solar physics, time-domain astronomy, galactic astrophysics, and exoplanet science, all ofwhich are recent hot topics in astronomy. The telescope can provide top-ranked data for Chineseastronomers. In particular, as the largest on-axis solar telescope in the world with wide-field thanall large solar telescopes operating at present, it can provide unprecedented high-resolution solardata, which can help us obtain breakthrough achievements in the study of solar active regionsand solar eruptions, such as solar flares and coronal mass ejections (CMEs). The data are also veryuseful for the study of space weather. As a large telescope in the China time-zone, the telescopeis very unique in continuously monitoring short-time transient events by filling the gap in thetime-zone. Furthermore, it can provide valuable high-quality data of the narrow-band extragalacticsurvey, nearby galaxy study and exoplanet survey. Moreover, the telescope is a top-level one whichcan make essential contribution to training the graduate and undergraduate students majoring inobservational astronomy.

The “strange star - NDAF” model (NDAF: Neutrino Dominated Accretion Flow) is proposed as an alternative central engine of gamma-ray bursts for unifying the interpretation of the prompt emission and postburst activities of gamma-ray bursts. The structure of NDAF around a strange star is calculated. Different from other central compact objects, the strange star will feed back the phase transition energy of strangization on the accretion flow, with neutrinos as energy carriers. The friction between NDAF and strange star is ignored in this paper. The results indicate: firstly, the structure of NDAF around a strange star is sensitive to accretion rate; secondly, if accretion rate is larger than 0.18 Mʘ s-1, the “strange star - NDAF” model can unify the explanation on the prompt emission and postburst activities of gamma-ray bursts, and the range of allowable accretion rates is wider than that in frictionless “neutron star - NDAF” models; thirdly, the range of annihilation energy of “strange star - NDAF” model is very wide, when the accretion rate is higher than 0.3 Mʘ s-1, the annihilation energy is greater than 1051 erg; finally, if the accretion rate is greater than 0.3 Mʘ s-1, the annihilation energy of “strange star - NDAF” model is larger than what of “black hole - NDAF” model at the same accretion rate by more than one order of magnitude, it is favorable to explaining some extremely energetic gamma-ray bursts.

The gravitational wave (GW) signal from a binary neutron star (NS) merger wasdetected by the LIGO/virgo detectors on August 17th 2017 for the first time.A short gamma-ray burst (GRB) and a kilonova were detected 1.74 s andlinebreak 10.9 h after the GW signal, respectively.These detections confirm the hypothesis that at least some short gamma-ray bursts (GRB)originate from binary neutron star mergers.Furthermore, it is clear that r-process nucleosynthesis should occur in NS-NS mergers and then power a kilonova.Observations on its multi-wavelength counterparts (including the prompt gamma-ray emission, kilonova, and afterglow) make us be ableto investigate their physical origins as a whole for the first time.Comparisons between the theories and observations would greatly help answerquestions such as the binary NS merger remnant, the characteristics of the GRB jet,and the characteristics of the ejecta. This paper summarizes these electromagnetic counterparts to GW170817 from the NS-NS merger and provides theoretical interpretations for them.

Gamma-ray bursts (GRBs) are the most violent explosions in the universe. Thanks totheir extreme brightness, GRBs can be detected up to the edge of the visible universe.As bright beacons in the deep universe, high-redshift GRBs have been considered as an ideal tool toexplore the properties of the early universe: including the dark energy and cosmological parameters,star formation rate, first stars, the reionization and metal enrichment history of the universe.So the detection of high-$z$ GRBs has important scientific significance. Compared to currentmissions, Einstein Probe has a higher sensitivity and a wider field-of-view, operating the softX-ray band (0.5–4 keV), which would be suitable for the detection of high-$z$ GRBs. With itsobservational mode and ability, we compute the expected detection rate of high-$z$ GRBs byEinstein Probe by means of a observational tested population synthesis model of Swift GRBs.Our results show that the detection rates are expected to be about 20 events $\\rm~yr^{-1}$ $\\rm~sr^{-1}$for $z>6$ bursts, 6 events $\\rm~yr^{-1}$ $\\rm~sr^{-1}$ for $z>8$ bursts, and 1 events $\\rm~yr^{-1}$$\\rm~sr^{-1}$ for $z>12$ bursts, respectively. Over the 3 yr lifetime of the mission,Einstein Probe will able to detect about 65 GRBs at $z>6$, including $\\sim20$ GRBs at $z>8$ and$\\sim3$ GRBs at $z>12$. In sum, Einstein Probe would significantly improve the detection of high-$z$GRBs, and these abundant observational information would probably reveal some scientific mysteries ofthe early universe.