Paul T O'Brien

GOTO Transient Discovery Report for 2024-02-16 - NASA/ADS Now on home page ads icon ads Enable full ADS view NASA/ADS GOTO Transient Discovery Report for 2024-02-16 Ramsay, G. ; Ackley, K. ; Dyer, M. ; Jiménez-Ibarra, F. ; Lyman, J. ; Ulaczyk, K. ; Steeghs, D. ; Galloway, D. ; Dhillon, V. ; O'Brien, P. ; Noysena, K. ; Kotak, R. ; Breton, R. ; Nuttall, L. ; Pallé, E. ; Pollacco, D. ; Killestein, T. ; Kumar, A. ; O'Neill, D. Abstract Publication: Transient Name Server Discovery Report Pub Date: February 2024 Bibcode: 2024TNSTR.472....1R Keywords: Transient; 2024cvb; AT2024cvb; AT 2024cvb; GOTO24rw full text sources Publisher | data products TNS (1) © The SAO/NASA Astrophysics Data System adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A NASA logo Smithsonian logo Resources About ADS ADS Help What's …

The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs), sources of high-frequency gravitational waves (GWs) and likely production sites for heavy-element nucleosynthesis by means of rapid neutron capture (the r-process). Here we present observations of the exceptionally bright GRB 230307A. We show that GRB 230307A belongs to the class of long-duration GRBs associated with compact object mergers, – and contains a kilonova similar to AT2017gfo, associated with the GW merger GW170817 (refs. , , , , –). We obtained James Webb Space Telescope (JWST) mid-infrared imaging and spectroscopy 29 and 61 days after the burst. The spectroscopy shows an emission line at 2.15 microns, which we interpret as tellurium (atomic mass A = 130) and a very red source …

GOTO Transient Discovery Report for 2024-01-23 - NASA/ADS Now on home page ads icon ads Enable full ADS view NASA/ADS GOTO Transient Discovery Report for 2024-01-23 Godson, B. ; Ulaczyk, K. ; Ackley, K. ; Dyer, M. ; Jiménez-Ibarra, F. ; Lyman, J. ; Steeghs, D. ; Galloway, D. ; Dhillon, V. ; O'Brien, P. ; Ramsay, G. ; Noysena, K. ; Kotak, R. ; Breton, R. ; Nuttall, L. ; Pallé, E. ; Pollacco, D. ; Killestein, T. ; Kumar, A. ; O'Neill, D. Abstract Publication: Transient Name Server Discovery Report Pub Date: January 2024 Bibcode: 2024TNSTR.236....1G Keywords: Transient; 2024arr; AT2024arr; AT 2024arr; GOTO24ft full text sources Publisher | data products TNS (1) © The SAO/NASA Astrophysics Data System adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A NASA logo Smithsonian logo Resources About ADS ADS Help …

We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022) in response to the LIGO/Virgo/KAGRA candidate NSBH event S240422ed (The LIGO-Virgo-KAGRA Collaboration, GCN 36236). Targeted observations covering 260 sqr. degrees or 96.2% of the localisation probability of the Bilby skymap (The LIGO-Virgo-KAGRA Collaboration, GCN 36240) were performed between 21: 38 UT and 23: 09 UT April 22 2024 (starting 2.7 minutes after trigger) with GOTO-N and 08: 33 UT and 12: 47 UT on April 23 2024 (starting 10.96 hours after trigger) with GOTO-S. Exposures were taken in L-band (400-700 nm passband) and the median 5 sigma depth was L= 18.84 AB magnitudes with GOTO-N and 19.56 with GOTO-S, under bright moon and partly cloudy conditions. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and not corrected for …

We report on the detection of a fast X-ray transient EP240315a at 2024-03-15T20: 10: 44 (UTC) by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission during a calibration observation. The position of the source is RA= 141.644 deg, DEC=-9.547 deg (J2000) with an uncertainty of 3 arcmin (radius, 90% CL statistical and systematic). The light curve of the source shows a multi-peak profile. The transient event lasts for~ 1600 seconds and has a peak flux of~ 3e-9 erg/s/cm^ 2 in the 0.5-4 keV band. The averaged spectrum can be fitted by an absorbed power-law with NH= 1.5 (-0.9/+ 1.0) x 10^ 21 cm^-2 and a photon index of 1.7 (-0.4/+ 0.4). The derived average unabsorbed 0.5-4.0 keV flux is 5.3 (-0.7/+ 1.0) x 10^-10 erg/s/cm^ 2. However, we note that the derived source parameters may be subject to larger uncertainties than those quoted here since in-orbit calibration of the instrument is still …

HESS J1813178 is a very-high-energy -ray source spatially coincident with the young and energetic pulsar PSR J18131749 and thought to be associated with its pulsar wind nebula (PWN). Recently, evidence for extended high-energy emission in the vicinity of the pulsar has been revealed in the Fermi Large Area Telescope (LAT) data. This motivates revisiting the HESS J1813178 region, taking advantage of improved analysis methods and an extended data set. Using data taken by the High Energy Stereoscopic System (H.E.S.S.) experiment and the Fermi-LAT, we aim to describe the -ray emission in the region with a consistent model, to provide insights into its origin. We performed a likelihood-based analysis on 32 hours of H.E.S.S. data and 12 years of Fermi-LAT data and fit a spectro-morphological model to the combined datasets. These results allowed us to develop a physical model for the origin of the observed -ray emission in the region. In addition to the compact very-high-energy -ray emission centered on the pulsar, we find a significant yet previously undetected component along the Galactic plane. With Fermi-LAT data, we confirm extended high-energy emission consistent with the position and elongation of the extended emission observed with H.E.S.S. These results establish a consistent description of the emission in the region from GeV energies to several tens of TeV. This study suggests that HESS J1813178 is associated with a -ray PWN powered by PSR J18131749. A possible origin of the extended emission component is inverse Compton emission from electrons and positrons that have escaped the confines …

We present the first release of the Gravitational Wave AfterglowPy Analysis (GWAPA) webtool (Available at https://gwapa.web.roma2.infn.it/). GWAPA is designed to provide the community with an interactive tool for rapid analysis of gravitational wave afterglow counterparts and can be extended to the general case of gamma-ray burst afterglows seen at different angles. It is based on the afterglowpy package and allows users to upload observational data and vary afterglow parameters to infer the properties of the explosion. Multiple jet structures, including top hat, Gaussian and power laws, in addition to a spherical outflow model are implemented. A Python script for MCMC fitting is also available to download, with initial guesses taken from GWAPA.

Since their first discovery in the late 1960s, gamma-ray bursts have attracted an exponentially growing interest from the international community due to their central role in the most highly debated open questions of the modern research of astronomy, astrophysics, cosmology, and fundamental physics. These range from the intimate nuclear composition of high-density material within the core of ultra-dense neuron stars, to stellar evolution via the collapse of massive stars, the production and propagation of gravitational waves, as well as the exploration of the early universe by unveiling the first stars and galaxies (assessing also their evolution and cosmic re-ionization). GRBs in the past ∼50 years have stimulated the development of cutting-edge technological instruments for observations of high-energy celestial sources from space, leading to the launch and successful operations of many different scientific missions (several of them still in data-taking mode currently). In this review, we provide a brief description of the GRB-dedicated missions from space being designed and developed for the future. The list of these projects, not meant to be exhaustive, shall serve as a reference to interested readers to understand what is likely to come next to lead the further development of GRB research and the associated phenomenology.

GOTO Transient Classification Report for 2024-02-12 - NASA/ADS Now on home page ads icon ads Enable full ADS view NASA/ADS GOTO Transient Classification Report for 2024-02-12 Godson, B. ; Warwick, B. ; Pursiainen, M. ; Dyer, MJ ; Mitchell, M. ; Lyman, J. ; Killestein, T. ; Sahu, A. ; Charalampopoulos, P. ; O'Neill, D. ; Kumar, A. ; Coppejans, D. ; Ramsay, G. ; Kotak, R. ; Gompertz, B. ; Ulaczyk, KAK ; Jiminez-Ibarra, F. ; Kumar, A. ; Steeghs, D. ; Galloway, DK ; Dhillon, V. ; O'Brien, P. ; Noysena, K. ; Breton, RP ; Nuttall, LK ; Pall'e, E. ; Pollacco, D. Abstract Publication: Transient Name Server Classification Report Pub Date: February 2024 Bibcode: 2024TNSCR.414....1G Keywords: Transient; Supernova; 2024brg; SN2024brg; SN 2024brg full text sources Publisher | data products TNS (1) © The SAO/NASA Astrophysics Data System adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical …

GOTO Transient Discovery Report for 2024-02-07 - NASA/ADS Now on home page ads icon ads Enable full ADS view NASA/ADS GOTO Transient Discovery Report for 2024-02-07 O'Neill, D. ; Gompertz, B. ; Ackley, K. ; Dyer, M. ; Jiménez-Ibarra, F. ; Lyman, J. ; Ulaczyk, K. ; Steeghs, D. ; Galloway, D. ; Dhillon, V. ; O'Brien, P. ; Ramsay, G. ; Noysena, K. ; Kotak, R. ; Breton, R. ; Nuttall, L. ; Pallé, E. ; Pollacco, D. ; Killestein, T. ; Kumar, A. Abstract Publication: Transient Name Server Discovery Report Pub Date: February 2024 Bibcode: 2024TNSTR.367....1O Keywords: Transient; 2024bww; AT2024bww; AT 2024bww; GOTO24oj full text sources Publisher | data products TNS (1) © The SAO/NASA Astrophysics Data System adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A NASA logo Smithsonian logo Resources About ADS …

GOTO Transient Discovery Report for 2024-02-11 - NASA/ADS Now on home page ads icon ads Enable full ADS view NASA/ADS GOTO Transient Discovery Report for 2024-02-11 Belkin, S. ; Gompertz, B. ; Ackley, K. ; Dyer, M. ; Jiménez-Ibarra, F. ; Lyman, J. ; Ulaczyk, K. ; Steeghs, D. ; Galloway, D. ; Dhillon, V. ; O'Brien, P. ; Ramsay, G. ; Noysena, K. ; Kotak, R. ; Breton, R. ; Nuttall, L. ; Pallé, E. ; Pollacco, D. ; Killestein, T. ; Kumar, A. ; O'Neill, D. Abstract Publication: Transient Name Server Discovery Report Pub Date: February 2024 Bibcode: 2024TNSTR.395....1B Keywords: Transient; 2024cew; AT2024cew; AT 2024cew; GOTO24pw full text sources Publisher | data products TNS (1) © The SAO/NASA Astrophysics Data System adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A NASA logo Smithsonian logo Resources …

GOTO Transient Discovery Report for 2024-01-30 - NASA/ADS Now on home page ads icon ads Enable full ADS view NASA/ADS GOTO Transient Discovery Report for 2024-01-30 Killestein, T. ; Ackley, K. ; Dyer, M. ; Jiménez-Ibarra, F. ; Lyman, J. ; Ulaczyk, K. ; Steeghs, D. ; Galloway, D. ; Dhillon, V. ; O'Brien, P. ; Ramsay, G. ; Noysena, K. ; Kotak, R. ; Breton, R. ; Nuttall, L. ; Pallé, E. ; Pollacco, D. ; Kumar, A. ; O'Neill, D. Abstract Publication: Transient Name Server Discovery Report Pub Date: January 2024 Bibcode: 2024TNSTR.291....1K Keywords: Transient; 2024bdx; AT2024bdx; AT 2024bdx; GOTO24hp full text sources Publisher | data products TNS (1) © The SAO/NASA Astrophysics Data System adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A NASA logo Smithsonian logo Resources About ADS ADS Help What's …

GOTO Transient Discovery Report for 2024-04-03 - NASA/ADS Now on home page ads icon ads Enable full ADS view NASA/ADS GOTO Transient Discovery Report for 2024-04-03 Steeghs, D. ; Ackley, K. ; Dyer, M. ; Jiménez-Ibarra, F. ; Lyman, J. ; Ulaczyk, K. ; Galloway, D. ; Dhillon, V. ; O'Brien, P. ; Ramsay, G. ; Noysena, K. ; Kotak, R. ; Breton, R. ; Nuttall, L. ; Pallé, E. ; Pollacco, D. ; Killestein, T. ; Kumar, A. ; O'Neill, D. Abstract Publication: Transient Name Server Discovery Report Pub Date: April 2024 Bibcode: 2024TNSTR.910....1S Keywords: Transient; 2024fld; AT2024fld; AT 2024fld; GOTO24aft full text sources Publisher | data products TNS (1) © The SAO/NASA Astrophysics Data System adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A NASA logo Smithsonian logo Resources About ADS ADS Help What's New …

GOTO Transient Discovery Report for 2024-03-08 - NASA/ADS Now on home page ads icon ads Enable full ADS view NASA/ADS GOTO Transient Discovery Report for 2024-03-08 Lyman, J. ; Ackley, K. ; Dyer, M. ; Jiménez-Ibarra, F. ; Ulaczyk, K. ; Steeghs, D. ; Galloway, D. ; Dhillon, V. ; O'Brien, P. ; Ramsay, G. ; Noysena, K. ; Kotak, R. ; Breton, R. ; Nuttall, L. ; Pallé, E. ; Pollacco, D. ; Killestein, T. ; Kumar, A. ; O'Neill, D. Abstract Publication: Transient Name Server Discovery Report Pub Date: March 2024 Bibcode: 2024TNSTR.630....1L Keywords: Transient; 2024eaj; AT2024eaj; AT 2024eaj; GOTO24xc full text sources Publisher | © The SAO/NASA Astrophysics Data System adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A NASA logo Smithsonian logo Resources About ADS ADS Help What's New Careers@ADS Social …

Most -ray detected active galactic nuclei are blazars with one of their relativistic jets pointing towards the Earth. Only a few objects belong to the class of radio galaxies or misaligned blazars. Here, we investigate the nature of the object PKS 0625-354, its -ray flux and spectral variability and its broad-band spectral emission with observations from H.E.S.S., Fermi-LAT, Swift-XRT, and UVOT taken in November 2018. The H.E.S.S. light curve above 200 GeV shows an outburst in the first night of observations followed by a declining flux with a halving time scale of 5.9h. The -opacity constrains the upper limit of the angle between the jet and the line of sight to . The broad-band spectral energy distribution shows two humps and can be well fitted with a single-zone synchrotron self Compton emission model. We conclude that PKS 0625-354, as an object showing clear features of both blazars and radio galaxies, can be classified as an intermediate active galactic nuclei. Multi-wavelength studies of such intermediate objects exhibiting features of both blazars and radio galaxies are sparse but crucial for the understanding of the broad-band emission of -ray detected active galactic nuclei in general.

Gamma-ray bursts (GRBs) are traditionally classified as either short GRBs with durations≲ 2 s that are powered by compact object mergers or long GRBs with durations≳ 2 s that are powered by the deaths of massive stars. Recent results, however, have challenged this dichotomy and suggest that there exists a population of merger-driven long bursts. One such example, GRB 191019A, has a t 90≈ 64 s, but many of its other properties—including its host galaxy, afterglow luminosity and lack of associated supernova—are more consistent with a short GRB. Here we propose an alternative interpretation: that GRB 191019A (which is located in the nucleus of its host) is an atypical jetted tidal disruption event (TDE). In particular, we suggest the short timescale and rapid decline, not expected for standard TDEs, are the result of an" ultradeep" encounter, in which the star came well within the tidal radius of the black hole …

The Crab Nebula is a unique laboratory for studying the acceleration of electrons and positrons through their non-thermal radiation. Observations of very-high-energy rays from the Crab Nebula have provided important constraints for modelling its broadband emission. We present the first fully self-consistent analysis of the Crab Nebula's -ray emission between 1 GeV and 100 TeV, that is over five orders of magnitude in energy. Using the open-source software package Gammapy, we combine 11.4 yr of data from the Fermi Large Area Telescope and 80 h of High Energy Stereoscopic System (H.E.S.S.) data at the event level and provide a measurement of the spatial extension of the nebula and its energy spectrum. We find evidence for a shrinking of the nebula with increasing -ray energy. Furthermore, we fit several phenomenological models to the measured data, finding that none of them can fully describe the spatial extension and the spectral energy distribution at the same time. Especially the extension measured at TeV energies appears too large when compared to the X-ray emission. Our measurements probe the structure of the magnetic field between the pulsar wind termination shock and the dust torus, and we conclude that the magnetic field strength decreases with increasing distance from the pulsar. We complement our study with a careful assessment of systematic uncertainties.

GOTO-FAST classification of AT2024cew - NASA/ADS Now on home page ads icon ads Enable full ADS view NASA/ADS GOTO-FAST classification of AT2024cew Godson, B. ; Warwick, B. ; O'Neill, D. ; Lyman, J. ; Killestein, T. ; Pursiainen, M. ; Ackley, K. ; Kumar, A. ; Coppejans, D. ; Ramsay, G. ; Kotak, R. ; Gompertz, B. ; Dyer, MJ ; Ulaczyk, K. ; Jiminez-Ibarra, F. ; Kumar, A. ; Steeghs, D. ; Galloway, DK ; Dhillon, V. ; O'Brien, P. ; Noysena, K. ; Breton, RP ; Nuttall, LK ; Pall'e, E. ; Pollacco, D. Abstract This report includes the classification of 1 Type Ia SN. Publication: Transient Name Server AstroNote Pub Date: February 2024 Bibcode: 2024TNSAN..52....1G Keywords: Transient; Supernova; Optical; Spectroscopy; GOTO24pw; 2024cew; SN2024cew; SN 2024cew No Sources Found data products TNS (1) © The SAO/NASA Astrophysics Data System adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian …

We report on the classification of AT2024cew/GOTO24pw as part of the GOTO-FAST program (Godson et al., https://www. wis-tns. org/astronotes/astronote/2023-224). The source was first reported by GOTO (Belkin et al, GCN 35715) as a possible optical counterpart to GRB 240209A (Fermi GBM team, GCN 35712). It showed an initial decline across the GOTO epochs which was consistent with the ZTF photometry obtained through the Lasair broker (Smith et al. 2019). Following the reported brightening of the source (de Ugarte Postigo et al., GCN 35716) we obtained spectroscopic observations on the night of 2024-02-13 with the Isaac Newton Telescope (INT) using the IDS spectrograph with R150V grating (3950-7900 A, R~ 600). The INT spectrum is consistent with a Type Ia-pec SN at a redshift of z= 0.15 (Godson et al. 2024, https://www. wis-tns. org/astronotes/astronote/2024-52). AT2024cew is therefore …

GOTO Transient Discovery Report for 2024-02-13 - NASA/ADS Now on home page ads icon ads Enable full ADS view NASA/ADS GOTO Transient Discovery Report for 2024-02-13 Pursiainen, M. ; Godson, B. ; Dyer, M. ; Warwick, B. ; Mitchell, M. ; Ackley, K. ; Jiménez-Ibarra, F. ; Lyman, J. ; Ulaczyk, K. ; Steeghs, D. ; Galloway, D. ; Dhillon, V. ; O'Brien, P. ; Ramsay, G. ; Noysena, K. ; Kotak, R. ; Breton, R. ; Nuttall, L. ; Pallé, E. ; Pollacco, D. ; Killestein, T. ; Kumar, A. ; O'Neill, D. Abstract Publication: Transient Name Server Discovery Report Pub Date: February 2024 Bibcode: 2024TNSTR.422....1P Keywords: Transient; Supernova; 2024cld; SN2024cld; SN 2024cld; GOTO24ql full text sources Publisher | data products TNS (1) © The SAO/NASA Astrophysics Data System adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A NASA …