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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').
Advanced Search

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"
  1. LIGO/Virgo S191109d: Upper limits from IceCube neutrino searches
  2. LIGO/Virgo S191109d: Identification of a GW compact binary merger candidate
  3. GRB 191106A: AstroSat CZTI detection
  4. GRB 191108A: Fermi GBM Final Real-time Localization
  5. GRB 191106A: Swift/UVOT Upper Limits
  6. GRB 191106A: Swift-BAT refined analysis
  7. ZTF19abvizsw: Upper limits from Konus-Wind observations
  8. LIGO/Virgo S191105e: AstroSat CZTI upper limits
  9. LIGO/Virgo S191105e: Not observable by CALET
  10. LIGO/Virgo S191105e: No counterpart candidates in Fermi-LAT observations
  11. LIGO/Virgo S191105e: Coverage and upper limits from MAXI/GSC observations
  12. LIGO/Virgo S191105e: no counterpart candidates in the Swift/BAT observations
  13. GRB 191106A: NOT optical upper limit
  14. GRB 191106A: Swift-XRT refined Analysis
  15. LIGO/Virgo S191105e : no neutrino counterpart candidate in ANTARES search
  16. LIGO/Virgo S191105e: No counterpart candidates in HAWC observations
  17. LIGO/Virgo S191105e: No counterpart candidates in INTEGRAL SPI-ACS and,IBIS prompt observation
  18. LIGO/Virgo S191105e: upper limits from AGILE/GRID observations
  19. LIGO/Virgo S191105e: Upper limits from Fermi-GBM Observations
  20. LIGO/Virgo S191105e: Global MASTER-Net observations report
  21. LIGO/Virgo S191105e: upper limits from AGILE/MCAL observations
  22. LIGO/Virgo S191105e: Identification of a GW compact binary merger candidate
  23. LIGO/Virgo S191105e: Upper limits from IceCube neutrino searches
  24. GRB 191106A: Mondy optical upper limit
  25. GRB 191106A: BOOTES-4/MET optical limit
  26. GRB 191106A: MASTER optical observation
  27. GRB 191106A: Swift detection of a burst
  28. GRB191016A GROND observations
  29. GRB 191031D: Chandra upper limit
  30. Swift trigger 933276 MASTER observation
  31. Fermi trigger No 594592184: Global MASTER-Net observations report
  32. Fermi trigger No 594523229: Global MASTER-Net observations report
  33. Trigger 933285: Swift detection of the brightest burst so far from SGR 1935+2154
  34. Swift GRB191105.01: Global MASTER-Net observations report
  35. Trigger 933276: Swift detection of further activity from SGR 1935+2154
  36. Swift GRB191105.01: Global MASTER-Net OT detection
  37. GRB 191101A: Swift-BAT refined analysis
  38. Fermi GBM GRB 191104C (trigger 594592184 / 191104854) is not a GRB
  39. GRB 191104C: Fermi GBM Final Real-time Localization
  40. GRB 191101A: Swift/UVOT Upper Limits
  41. Fermi GBM GRBs 191104 A, B, C and triggers 594534420/191104185 and 594563923/191104527 are not GRBs
  42. SGR 1935+2154: Swift-BAT refined analysis
  43. Fermi trigger No 594563923: Global MASTER-Net observations report
  44. GRB 191104B/GRB 191104C are SGR 1935+2154
  45. Fermi trigger No 594557071: Global MASTER-Net observations report
  46. GRB 191104C: BALROG localization (Fermi Trigger 594557071 / GRB 191104448)
  47. GRB 191104C: Fermi GBM Final Real-time Localization
  48. Fermi trigger No 594551878: Global MASTER-Net observations report
  49. Fermi trigger No 594528816: Global MASTER-Net observations report
  50. GRB 191104B: Fermi GBM Final Real-time Localization
  51. Trigger 933083: Swift detection of SGR 1935+2154
  52. Fermi GBM triggers 594523229/191104056 and 594528816/191104120 are not GRBs
  53. GRB 191104A: Fermi GBM Final Real-time Localization
  54. GRB 191031D: Zwicky Transient Facility Follow-Up of a Swift Short GRB (Trigger 594249816/191031891)
  55. Konus-Wind observation of GRB 191031D: correction to GCN 26126
  56. GRB 191031E: Insight-HXMT/HE detection
  57. GRB 191031D: Gemini optical upper limit
  58. GRB 191031C: Insight-HXMT/HE detection
  59. GRB 191101A: iTelescope optical limit
  60. GRB 191101A: Swift-XRT refined Analysis
  61. Baksan Neutrino Observatory Alert 191102.06: Global MASTER-Net observations report
  62. GRB 191101A: VIRT Optical Upper Limits
  63. Fermi trigger No 594336535: Global MASTER-Net observations report
  64. GRB 191101A: Enhanced Swift-XRT position
  65. Swift GRB191101.88: Global MASTER-Net observations report
  66. Fermi trigger No 594227699: Global MASTER-Net observations report
  67. GRB 191101A: Prompt enhanced Swift-XRT position
  68. GRB 191101B: Fermi GBM Final Real-time Localization
  69. GRB 191101A: Swift detection of a burst
  70. GRB 191031D: MMT Binospec Optical Upper Limit
  71. GRB 191031D: Swift-BAT refined analysis
  72. GRB 191031C: Swift-BAT refined analysis
  73. GRB 191031A: Swift-BAT refined analysis
  74. GRB 191031C: Swift-XRT refined Analysis
  75. GRB 191031D: AstroSat CZTI detection
  76. GRB 191031D: Swift/UVOT Upper Limits
  77. GRB 191031C: Swift/UVOT Detection
  78. Konus-Wind observation of GRB 191031D
  79. GRB 191031D: MITSuME Akeno optical upper limits
  80. GRB 191031D: Swift-XRT refined Analysis
  81. GRB 191031D: AGILE/MCAL observations
  82. GRB 191031D: COATLI Optical Observations
  83. GRB 191031D: RATIR Optical and NIR Observations
  84. GRB 191031D: VLA 9.8 GHz upper limit
  85. GRB 191031C: Fermi GBM detection
  86. GRB 191031D: Fermi GBM detection
  87. GRB 191031D: Enhanced Swift-XRT position
  88. GRB 191031A: Fermi GBM detection
  89. GRB 191031C: Enhanced Swift-XRT position
  90. Correction in name: GRB 191031D (not GRB 191031C)
  91. Swift GRB191031.89: Global MASTER-Net observations report
  92. GRB 191031D: Swift detection of a short hard burst
  93. GRB 191031C: Fermi GBM Final Real-time Localization
  94. GRB 191029A: Swift-BAT refined analysis
  95. GRB 191031C: Prompt enhanced Swift-XRT position
  96. GRB 191031C: Swift detection of a burst
  97. GRB 191031C: Fermi GBM Final Real-time Localization
  98. GRB 191025B: AstroSat CZTI detection
  99. Fermi trigger No 594175000: Global MASTER-Net observations report
  100. GRB 191031B: Fermi GBM Final Real-time Localization

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