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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
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To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

2803 results found.

  1. LIGO/Virgo S200128d: No counterpart candidates in Fermi-LAT observations
  2. Fermi-LAT ANTARES 200127.79 coincidence: MASTER alert observation and presence of young pulsar close to error-box
  3. IceCube-200120A: IceCube observation of a high-energy neutrino candidate event
  4. LIGO/Virgo S200114f: SOAR spectroscopy of AT2020zf, AT2020ace and AT2020ach
  5. LIGO/Virgo S200115j: No counterpart detection within possible host galaxies observed by the GRAWITA-Savelli telescope
  6. GRB 200115A: Mondy optical observations and correction to GCN 26790
  7. LIGO/Virgo S200105ae: More candidates from the Zwicky Transient Facility
  8. LIGO/Virgo S200115j: Updated Sky Localization and source properties
  9. LIGO/Virgo S200114f: More candidates from the Zwicky Transient Facility
  10. IceCube-200117A: IceCube observation of a high-energy neutrino candidate event
  11. LIGO/Virgo S200114f: ZTF Forced Photometry of the Swift Source S200114f_X2
  12. LIGO/Virgo S200114f: Possible X-ray transient
  13. LIGO/Virgo S200115j High Rank XRT sources are spurious
  14. LIGO/Virgo S200115j: No counterpart candidates in Fermi-LAT observations
  15. LIGO/Virgo S200115j: Candidates from the Zwicky Transient Facility
  16. LIGO/Virgo S200115j: Revised list of possible host galaxies with the new skymap
  17. LIGO/Virgo trigger S200115j: Possible host galaxies
  18. LIGO/Virgo S200114f: Candidates from SAGUARO observations
  19. LIGO/Virgo S200114f: No counterpart candidates in Fermi-LAT observations
  20. LIGO/Virgo S200114f: Candidates from the Zwicky Transient Facility
  21. Fermi-LAT Gamma-ray Observations of IceCube-200109A and detection of a possible new gamma-ray source, Fermi J1055.8+1034
  22. LIGO/Virgo 200112r: No counterpart candidates in Fermi-LAT observations
  23. IceCube-200109A: IceCube observation of a high-energy neutrino candidate event
  24. IceCube-200107A: IceCube observation of a high-energy neutrino candidate event
  25. LIGO/Virgo 200105ae: No counterpart candidates in Fermi-LAT observations
  26. LIGO/Virgo S200105ae: A subthreshold GW compact binary merger candidate
  27. IceCube-191231A: IceCube observation of a high-energy neutrino candidate event
  28. LIGO/Virgo S191216ap: Two candidate counterparts from UKIRT/WFCAM z-band observations
  29. LIGO/Virgo S191213g: Pan-STARRS monitoring shows PS19hgw (AT2019wxt) to be fading quickly
  30. LIGO/Virgo S191222n: No counterpart candidates in Fermi-LAT observations
  31. GRB 191220A: SAO RAS possible OT detection
  32. LIGO/Virgo S191216ap: Subaru/Hyper Suprime-Cam observations of GW+IceCube+HAWC error region
  33. LIGO/Virgo S191213g: VLT spectrum of AT2019wxt (PS19hgw) - a probable Ib supernova
  34. LIGO/Virgo G191216ap: No counterpart candidates in Fermi-LAT observations
  35. LIGO/Virgo S191215w: No counterpart candidates in Fermi-LAT observations
  36. IceCube-191215A - IceCube observation of a high-energy neutrino candidate event
  37. LIGO/Virgo S191213g: No counterpart candidates in Fermi-LAT observations
  38. Possible HAWC-detected GRB 191210A: Fermi-LAT Upper Limits
  39. Possible HAWC-detected GRB 191210A: no neutrino counterpart candidate in ANTARES search
  40. Possible HAWC-detected GRB 191210A: Swift-XRT observations
  41. GRB 191207A: Possible GRB detected in Fermi-LAT blind search
  42. LIGO/Virgo S191205ah: GMG detection of SAGUARO transient
  43. LIGO/Virgo S191205ah: No counterpart candidates in Fermi-LAT observations
  44. LIGO/Virgo S191204r: No counterpart candidates in Fermi-LAT observations
  45. IceCube-191204A - IceCube observation of a high-energy neutrino candidate event
  46. LIGO/Virgo S191129u: No counterpart candidates in Fermi-LAT observations
  47. IceCube-191122A - IceCube observation of a high-energy neutrino candidate event
  48. IceCube-191119A - IceCube observation of a high-energy neutrino candidate event
  49. Announcing the GW Treasure Map
  50. LIGO/Virgo S191110af: Potential pulsar counterparts
  51. LIGO/Virgo S191110af: No counterpart candidates in Fermi-LAT observations
  52. LIGO/Virgo S191109d: No counterpart candidates in Fermi-LAT observations
  53. LIGO/Virgo S191105e: No counterpart candidates in Fermi-LAT observations
  54. Konus-Wind observation of GRB 191031D: correction to GCN 26126
  55. Possible GRB 191025A: FRAM-Auger optical limit
  56. Swift Trigger 931384: possible GRB 191025A
  57. GRB 191024A: Afterglow Upper Limits with LCO
  58. GRB 19011A: Optical Afterglow Detection with LCO
  59. TESS Detection of the Optical Emission from the Possible Untriggered GRB Associated with ZTF19abvizsw
  60. GRB 191004B: Continued Optical Afterglow Monitoring with LCO
  61. GRB 191004B: Correction to Konus-Wind GCN 25974
  62. GRB 191004A: Optical Detection with LCO
  63. LIGO/Virgo S190930t: SALT optical spectroscopy of Swift J221951-484240
  64. GRB 191004B: Optical Afterglow Detection with LCO
  65. GRB 191001B: Optical Upper Limits with LCO
  66. LIGO/Virgo S190930t: Candidates from ATLAS observations and constraints on AT2019rpr and AT2019rpn
  67. IceCube-191001A - IceCube observation of a high-energy neutrino candidate event
  68. LIGO/Virgo S190930t: Upper limits on the two of the ZTF/GROWTH candidates
  69. LIGO/Virgo S190930t: Candidates from the Zwicky Transient Facility
  70. LIGO/Virgo S190930t: No counterpart candidates in Fermi-LAT observations
  71. LIGO/Virgo S190930s: No counterpart candidates in Fermi-LAT observations
  72. LIGO/Virgo S190930t: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo S190924h: No counterpart candidates in Fermi-LAT observations
  74. LIGO/Virgo S190923y: No counterpart candidates in Fermi-LAT observations
  75. IceCube-190922B - IceCube observation of a high-energy neutrino candidate event
  76. GRB 190919B: LCO Optical Afterglow Detection
  77. LIGO/Virgo S190814bv: SOAR spectroscopy of AT2019nte host galaxy
  78. LIGO/Virgo S190915ak: No counterpart candidates in Fermi-LAT observations
  79. LIGO/Virgo S190910h: No counterpart candidates in Fermi-LAT observations
  80. LIGO/Virgo S190910d: No counterpart candidates in Fermi-LAT observations
  81. ZTF19abvizsw/AT2019pim, search for GRB in SPI-ACS/INTEGRAL data
  82. GRB 190829A: Liverpool Telescope observations of a slow supernova rise
  83. GRB 190829A: LCO Optical Afterglow Detection
  84. LIGO/Virgo S190901ap : SVOM/GWAC-F60A observation of transient ZTFabvizsw
  85. LIGO/Virgo S190901ap: Keck I LRIS spectroscopy of ZTF19abvizsw
  86. Chandra observations of GW170817 ~740-743 days since merger
  87. GRB 190829A: Detection of radio afterglow with the uGMRT
  88. LIGO/Virgo S190901ap: No counterpart candidates in Fermi-LAT observations
  89. LIGO/Virgo S190814bv : No significant candidates in TAROT-GRANDMA observations
  90. LIGO/Virgo S190814bv: SOAR spectroscopy of DECam candidate AT2019ntp
  91. GRB 190829A:: Global MASTER-net optical clear and polarization observations scheduler and some spiculations
  92. LIGO/Virgo S190814bv: SOAR spectroscopy of DECam candidates AT2019ntr and AT2019omx
  93. LIGO/Virgo S190814bv: VLA observation of ASKAP J005547-270433/AT2019osy
  94. LIGO/Virgo S190828l: No counterpart candidates in Fermi-LAT observations
  95. LIGO/Virgo S190828j: No counterpart candidates in Fermi-LAT observations
  96. LIGO/Virgo S190814bv: SOAR spectroscopy of DECam candidates AT2019npw and AT2019num
  97. LIGO/Virgo S190814bv: SALT optical spectrum of candidate DG19aqbkc
  98. Fermi GBM-190816: Updated localization of subthreshold GRB-GW candidate
  99. LIGO/Virgo S190814bv: Keck NIRES spectroscopy of DG19wxnjc/AT2019npv
  100. LIGO/Virgo S190814bv: Further Pan-STARRS z-band observations and AT2019npv photometry

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