scholarly journals Unveiling the enigma of ATLAS17aeu

2019 ◽  
Vol 621 ◽  
pp. A81
Author(s):  
A. Melandri ◽  
A. Rossi ◽  
S. Benetti ◽  
V. D’Elia ◽  
S. Piranomonte ◽  
...  

Aims. The unusual transient ATLAS17aeu was serendipitously detected within the sky localisation of the gravitational wave trigger GW 170104. The importance of a possible association with gravitational waves coming from a binary black hole merger led to an extensive follow-up campaign, with the aim of assessing a possible connection with GW 170104. Methods. With several telescopes, we carried out both photometric and spectroscopic observations of ATLAS17aeu, for several epochs, between ∼3 and ∼230 days after the first detection. Results. We studied in detail the temporal and spectroscopic properties of ATLAS17aeu and its host galaxy. Although at low significance and not conclusive, we found similarities to the spectral features of a broad-line supernova superposed onto an otherwise typical long-GRB afterglow. Based on analysis of the optical light curve, spectrum, and host galaxy spectral energy distribution, we conclude that the redshift of the source is probably z ≃ 0.5 ± 0.2. Conclusions. While the redshift range we have determined is marginally compatible with that of the gravitational wave event, the presence of a supernova component and the consistency of this transient with the Ep–Eiso correlation support the conclusion that ATLAS17aeu was associated with the long gamma-ray burst GRB 170105A. This rules out the association of the GRB 170105A/ATLAS17aeu transient with the gravitational wave event GW 170104, which was due to a binary black hole merger.

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Adrian Ka-Wai Chung ◽  
Mairi Sakellariadou

AbstractWe present a method to constrain the temperature of astrophysical black holes through detecting the inspiral phase of binary black hole coalescences. At sufficient separation, inspiraling black holes can be regarded as isolated objects, hence their temperature can still be defined. Due to their intrinsic radiation, inspiraling black holes lose part of their masses during the inspiral phase. As a result, coalescence speeds up, introducing a correction to the orbital phase. We show that this dephasing may allow us to constrain the temperature of inspiraling black holes through gravitational-wave detection. Using the binary black-hole coalescences of the first two observing runs of the Advanced LIGO and Virgo detectors, we constrain the temperature of parental black holes to be less than about $$ 10^9 $$ 10 9  K. Such a constraint corresponds to luminosity of about $$ 10^{-16} M_{\odot }~\mathrm{s}^{-1} $$ 10 - 16 M ⊙ s - 1 for a black hole of $$ 20 M_{\odot } $$ 20 M ⊙ , which is about 20 orders of magnitude below the peak luminosity of the corresponding gravitational-wave event, indicating no evidence for strong quantum-gravity effects through the detection of the inspiral phase.


2018 ◽  
Vol 620 ◽  
pp. A37 ◽  
Author(s):  
M. Contini

We present the spectral detailed modelling of NGC 4993 – the host galaxy of GW 170817 – and other short gamma-ray burst (SGRB) host galaxies. In order to determine their physical conditions and the element abundances, we have gathered spectroscopic and photometric data from the literature. The observation data are sometimes missing, preventing us from fully constraining the model. However, for most of the SGRB hosts the [OIII]5007/Hβ and [NII]6548/Hα line ratios are reported. The analysis of NGC 4993 by a composite model (photoionization+shock) confirms that an active galactic nucleus (AGN), most probably a low-ionization nuclear emission-line region (LINER) or a low-luminosity AGN (LLAGN) is the gas photoionization source. Shock velocities and preshock densities are similar to those found in the narrow line region of AGN. O/H and N/H have solar values. For the other SGRB of the sample, we found that O/H ratios are nearly solar, while N/H covers a much larger range of values at redshifts close to 0.4. In NGC 4993, the relative contribution to the spectral energy distribution of an old stellar population, characterized by a black-body temperature of Tbb = 4000 K, with respect to bremsstrahlung is higher by a factor of >100 than in most of the local AGN and starburst (SB) galaxies. For the other SGRB that compose the sample, Tbb ranges between 2000 K for SGRB 100206A and 8000 K for SGRB 111117A.


2019 ◽  
Vol 488 (4) ◽  
pp. 5029-5041 ◽  
Author(s):  
Tetsuya Hashimoto ◽  
Bunyo Hatsukade ◽  
Tomotsugu Goto ◽  
Seong Jin Kim ◽  
Kouji Ohta ◽  
...  

ABSTRACT The event rate of long gamma-ray bursts (GRBs) is expected to be a useful tracer of cosmic star-formation history. For this purpose, it is necessary to understand what kinds of star formation/galaxies are traced by GRBs. Here we report rest-frame far-infrared (FIR) continuum detections of the GRB 070521 and 080207 host galaxies at z ∼ 2 with Atacama Large Millimeter/submillimeter Array (ALMA) bands 8 and 9. FIR photometry provides reliable star-formation rates (SFRs), because FIR emission is free from dust extinction and possible radio contamination from the long-lived afterglows of GRBs. Spectral energy distribution fitting yields 49.85$^{+72.33}_{-2.86}$ and 123.4$^{+25.19}_{-21.78}$ M⊙ yr−1 for the 070521 and 080207 hosts, respectively. The derived SFRs place them on the ‘main sequence’ of normal star-forming galaxies at z ∼ 2. The derived SFRs are significantly lower than those from radio observations. It is inferred that the observed radio fluxes in a previous study are contaminated by afterglows. ALMA marginally detected the [C ii] 158-μm emission line from the GRB 080207 host galaxy with signal-to-noise ratio (S/N) ∼ 4. This is the first detection of [C ii] 158-μm from a GRB host at z > 2 and the second detection among known GRBs. The luminosity ratio of [C ii] 158 μm to FIR is 7.5 × 10−4, which is one of the smallest values among galaxies at z ∼ 1–2 with the same FIR luminosity. The ‘[C ii] deficit’ could be a new physical property with which to characterize GRB hosts at z ∼ 1–2. Possible parameters controlling the deficit include the metallicity, initial mass function and gas density.


2019 ◽  
Vol 492 (2) ◽  
pp. 1731-1754 ◽  
Author(s):  
A Grado ◽  
E Cappellaro ◽  
S Covino ◽  
F Getman ◽  
G Greco ◽  
...  

ABSTRACT We report on the search for the optical counterpart of the gravitational event GW170814, which was carried out with the VLT Survey Telescope (VST) by the GRAvitational Wave Inaf TeAm. Observations started 17.5 h after the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo alert and we covered an area of 99 deg2 that encloses $\sim 77{{\ \rm per\ cent}}$ and $\sim 59{{\ \rm per\ cent}}$ of the initial and refined localization probability regions, respectively. A total of six epochs were secured over nearly two months. The survey reached an average limiting magnitude of 22 AB mag in the r band. After assuming the model described in Perna, Lazzati & Farr, that derives as possible optical counterpart of a BBH (binary black hole) event a transient source declining in about one day, we have computed a survey efficiency of about $5{{\ \rm per\ cent}}$. This paper describes the VST observational strategy and the results obtained by our analysis pipelines developed to search for optical transients in multi-epoch images. We report the catalogue of the candidates with possible identifications based on light-curve fitting. We have identified two dozens of SNe, nine AGNs, and one QSO. Nineteen transients characterized by a single detection were not classified. We have restricted our analysis only to the candidates that fall into the refined localization map. None out of 39 left candidates could be positively associated with GW170814. This result implies that the possible emission of optical radiation from a BBH merger had to be fainter than r ∼ 22 (Loptical ∼ 1.4 × 1042 erg s−1) on a time interval ranging from a few hours up to two months after the gravitational wave event.


Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 104
Author(s):  
Jie-Shuang Wang ◽  
Liang-Duan Liu

Precursor emissions are found in some short gamma-ray bursts (SGRBs). In this paper, we review the theories and observations of the SGRB precursor and discuss its prospect as an electromagnetic counterpart of the gravitational wave event produced by neutron star (NS) mergers. The observed luminosity, spectrum, and duration of precursors are explained by the magnetospheric interaction model during the inspiral or the cocoon/jet shock breakout model during the jet propagation. In general, these two models predict that the precursor will be weaker than the main GRB, but will be of a larger opening angle, which makes it an advantageous gamma-ray counterpart for NS mergers in the local Universe, especially for NS - black hole mergers with very low mass ratios, in which the main GRBs are not expected. The joint observation of the precursor, SGRB, and gravitational wave will help to reveal the jet launch mechanism and post-merger remnant.


2020 ◽  
Vol 124 (25) ◽  
Author(s):  
M. J. Graham ◽  
K. E. S. Ford ◽  
B. McKernan ◽  
N. P. Ross ◽  
D. Stern ◽  
...  

2018 ◽  
Vol 617 ◽  
pp. A122 ◽  
Author(s):  
D. A. Kann ◽  
P. Schady ◽  
E. F. Olivares ◽  
S. Klose ◽  
A. Rossi ◽  
...  

Context. Afterglows of gamma-ray bursts (GRBs) are simple in the most basic model, but can show many complex features. The ultra-long duration GRB 111209A, one of the longest GRBs ever detected, also has the best-monitored afterglow in this rare class of GRBs. Aims. We want to address the question whether GRB 111209A was a special event beyond its extreme duration alone, and whether it is a classical GRB or another kind of high-energy transient. The afterglow may yield significant clues. Methods. We present afterglow photometry obtained in seven bands with the GROND imager as well as in further seven bands with the Ultraviolet/Optical Telescope (UVOT) on-board the Neil Gehrels Swift Observatory. The light curve is analysed by multi-band modelling and joint fitting with power-laws and broken power-laws, and we use the contemporaneous GROND data to study the evolution of the spectral energy distribution. We compare the optical afterglow to a large ensemble we have analysed in earlier works, and especially to that of another ultra-long event, GRB 130925A. We furthermore undertake a photometric study of the host galaxy. Results. We find a strong, chromatic rebrightening event at ≈0.8 days after the GRB, during which the spectral slope becomes redder. After this, the light curve decays achromatically, with evidence for a break at about 9 days after the trigger. The afterglow luminosity is found to not be exceptional. We find that a double-jet model is able to explain the chromatic rebrightening. The afterglow features have been detected in other events and are not unique. Conclusions. The duration aside, the GRB prompt emission and afterglow parameters of GRB 111209A are in agreement with the known distributions for these parameters. While the central engine of this event may differ from that of classical GRBs, there are multiple lines of evidence pointing to GRB 111209A resulting from the core-collapse of a massive star with a stripped envelope.


2020 ◽  
Vol 498 (3) ◽  
pp. 3395-3402 ◽  
Author(s):  
Otto A Hannuksela ◽  
Thomas E Collett ◽  
Mesut Çalışkan ◽  
Tjonnie G F Li

ABSTRACT The current gravitational-wave (GW) localization methods rely mainly on sources with electromagnetic counterparts. Unfortunately, a binary black hole does not emit light. Due to this, it is generally not possible to localize these objects precisely. However, strongly lensed gravitational waves, which are forecasted in this decade, could allow us to localize the binary by locating its lensed host galaxy. Identifying the correct host galaxy is challenging because there are hundreds to thousands of other lensed galaxies within the sky area spanned by the GW observation. However, we can constrain the lensing galaxy’s physical properties through both GW and electromagnetic observations. We show that these simultaneous constraints allow one to localize quadruply lensed waves to one or at most a few galaxies with the LIGO/Virgo/Kagra network in typical scenarios. Once we identify the host, we can localize the binary to two sub-arcsec regions within the host galaxy. Moreover, we demonstrate how to use the system to measure the Hubble constant as a proof-of-principle application.


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