Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userAn r-Process Kilonova Associated with the Short-Hard GRB 130603B
141
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present ground-based optical and Hubble Space Telescope optical and near-IR observations of the short-hard GRB130603B at z=0.356, which demonstrate the presence of excess near-IR emission matching the expected brightness and color of an r-process powered transient (a kilonova). The early afterglow fades rapidly with alpha<-2.6 at t~8-32 hr post-burst and has a spectral index of beta=-1.5 (F_nu t^alpha*nu^beta), leading to an expected near-IR brightness at the time of the first HST observation of m(F160W)>29.3 AB mag. Instead, the detected source has m(F160W)=25.8+/-0.2 AB mag, corresponding to a rest-frame absolute magnitude of M(J)=-15.2 mag. The upper limit in the HST optical observations is m(F606W)>27.7 AB mag (3-sigma), indicating an unusually red color of V-H>1.9 mag. Comparing the observed near-IR luminosity to theoretical models of kilonovae produced by ejecta from the merger of an NS-NS or NS-BH binary, we infer an ejecta mass of M_ej~0.03-0.08 Msun for v_ej=0.1-0.3c. The inferred mass matches the expectations from numerical merger simulations. The presence of a kilonova provides the strongest evidence to date that short GRBs are produced by compact object mergers, and provides initial insight on the ejected mass and the primary role that compact object merger may play in the r-process. Equally important, it demonstrates that gravitational wave sources detected by Advanced LIGO/Virgo will be accompanied by optical/near-IR counterparts with unusually red colors, detectable by existing and upcoming large wide-field facilities (e.g., Pan-STARRS, DECam, Subaru, LSST).
rate research
Read More
GRB 160821B is a short duration gamma-ray burst (GRB) detected and localized by the Neil Gehrels Swift Observatory in the outskirts of a spiral galaxy at z=0.1613, at a projected physical offset of 16 kpc from the galaxys center. We present X-ray, optical/nIR and radio observations of its counterpart and model them with two distinct components of emission: a standard afterglow, arising from the interaction of the relativistic jet with the surrounding medium, and a kilonova, powered by the radioactive decay of the sub-relativistic ejecta. Broadband modeling of the afterglow data reveals a weak reverse shock propagating backward into the jet, and a likely jet-break at 3.5 d. This is consistent with a structured jet seen slightly off-axis while expanding into a low-density medium. Analysis of the kilonova properties suggests a rapid evolution toward red colors, similar to AT2017gfo, and a low nIR luminosity, possibly due to the presence of a long-lived neutron star. The global properties of the environment, the inferred low mass (M_ej < 0.006 Msun) and velocities (v > 0.05 c) of lanthanide-rich ejecta are consistent with a binary neutron star merger progenitor.
We present early optical photometry and spectroscopy of the afterglow and host galaxy of the bright short-duration gamma-ray burst GRB 130603B discovered by the Swift satellite. Using the Gemini South telescope, our prompt optical spectra reveal a strong trace from the afterglow superimposed on continuum and emission lines from the $z = 0.3568 pm 0.0005$ host galaxy. The combination of a relatively bright optical afterglow (r = 21.52 at $Delta_t $= 8.4hr), together with an observed offset of 0farcs9 from the host nucleus (4.8kpc projected distance at z=0.3568), allow us to extract a relatively clean spectrum dominated by afterglow light . The spatially resolved spectrum allows us to constrain the properties of the explosion site directly, and compare these with the host galaxy nucleus, as well as other short-duration GRB host galaxies. We find that while the host is a relatively luminous ($L approx 0.8 L^{*}_{B}$), star-forming galaxy with solar metallicity, the spectrum of the afterglow exhibits weak CaII absorption features but negligible emission features. The explosion site therefore lacks evidence of recent star formation, consistent with the relatively long delay time distribution expected in a compact binary merger scenario. The star formation rate (both in an absolute sense and normalized to the luminosity) and metallicity of the host are both consistent with the known sample of short-duration GRB hosts and with recent results which suggest GRB130603B emission to be the product of the decay of radioactive species produced during the merging process of a NS-NS binary (kilonova). Ultimately, the discovery of more events similar to GRB130603B and their rapid follow-up from 8-m class telescopes will open new opportunities for our understanding of the final stages of compact-objects binary systems.
Short duration gamma-ray bursts (SGRBs) are thought to be related to the violent merger of compact objects, such as neutron stars or black holes, which makes them promising sources of gravitational waves. The detection of a kilonova-like signature associated to the Swift-detected GRB 130603B has suggested that this event is the result of a compact object merger. Our knowledge on SGRB has been, until now, mostly based on the absence of supernova signatures and the analysis of the host galaxies to which they cannot always be securely associated. Further progress has been significantly hampered by the faintness and rapid fading of their optical counterparts (afterglows), which has so far precluded spectroscopy of such events. Afterglow spectroscopy is the key tool to firmly determine the distance at which the burst was produced, crucial to understand its physics, and study its local environment. Here we present the first spectra of a prototypical SGRB afterglow in which both absorption and emission features are clearly detected. Together with multiwavelength photometry we study the host and environment of GRB 130603B. From these spectra we determine the redshift of the burst to be z = 0.3565+/-0.0002, measure rich dynamics both in absorption and emission, and a substantial line of sight extinction of A_V = 0.86+/-0.15 mag. The GRB was located at the edge of a disrupted arm of a moderately star forming galaxy with near-solar metallicity. Unlike for most long GRBs (LGRBs), N_HX / A_V is consistent with the Galactic ratio, indicating that the explosion site differs from those found in LGRBs. The merger is not associated with the most star-forming region of the galaxy; however, it did occur in a dense region, implying a rapid merger or a low natal kick velocity for the compact object binary.
The first detected gravitational wave GW170817 from a binary neutron star merger is associated with an important optical transient AT 2017gfo, which is a direct observation of kilonova. Recent observations suggest that the remnant compact object of the binary neutron star merger associated with GW170817/GRB 170817A may be a stable long-lived magnetized neutron star. In this situation, there would be a pulsar wind nebula (PWN) embedded inside the dynamic ejecta. The PWN emission may be absorbed by the ejecta or leak out of the system. We study the effect of the PWN emission on the observed light curves and radiation spectra. Different from previous works, the absorption and leakage of the PWN emission are all involved in our model, where the absorption of the PWN emission heats up the ejecta and alters its radiation. It is found that the characteristic emission of the embedded PWN quickly evolves. For the multiband and long-term observations of AT 2017gfo, we find that the dynamic ejecta with a PWN emission can fit the observational data very well, especially for the light curves at $tsim 5$ days and those in the late phase. In addition, our model can naturally generate the thermal to nonthermal spectrum evolution of AT 2017gfo. Our fitting result suggests that a PWN is embedded in the AT 2017gfo.
We report our identification of the optical afterglow and host galaxy of the short-duration gamma-ray burst GRB 160821B. The spectroscopic redshift of the host is $z=0.162$, making it one of the lowest redshift sGRBs identified by Swift. Our intensive follow-up campaign using a range of ground-based facilities as well as HST, XMM and Swift, shows evidence for a late-time excess of optical and near-infrared emission in addition to a complex afterglow. The afterglow light-curve at X-ray frequencies reveals a narrow jet, $theta_jsim1.9^{+0.10}_{-0.03}$ deg, that is refreshed at $>1$ day post-burst by a slower outflow with significantly more energy than the initial outflow that produced the main GRB. Observations of the 5 GHz radio afterglow shows a reverse shock into a mildly magnetised shell. The optical and near-infrared excess is fainter than AT2017gfo associated with GW170817, and is well explained by a kilonova with dynamic ejecta mass $M_{rm dyn}=(1.0pm0.6)times10^{-3}$ M$_{odot}$ and a secular (postmerger) ejecta mass with $M_{rm pm}=(1.0pm0.6)times10^{-2}$ M$_odot$, consistent with a binary neutron star merger resulting in a short-lived massive neutron star. This optical and near-infrared dataset provides the best-sampled kilonova light-curve without a gravitational wave trigger to date.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
