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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 S191105e: AstroSat CZTI upper limits
  2. LIGO/Virgo S191105e: Not observable by CALET
  3. LIGO/Virgo S191105e: No counterpart candidates in Fermi-LAT observations
  4. LIGO/Virgo S191105e: Coverage and upper limits from MAXI/GSC observations
  5. LIGO/Virgo S191105e: no counterpart candidates in the Swift/BAT observations
  6. GRB 191106A: NOT optical upper limit
  7. GRB 191106A: Swift-XRT refined Analysis
  8. LIGO/Virgo S191105e : no neutrino counterpart candidate in ANTARES search
  9. LIGO/Virgo S191105e: No counterpart candidates in HAWC observations
  10. LIGO/Virgo S191105e: No counterpart candidates in INTEGRAL SPI-ACS and,IBIS prompt observation
  11. LIGO/Virgo S191105e: upper limits from AGILE/GRID observations
  12. LIGO/Virgo S191105e: Upper limits from Fermi-GBM Observations
  13. LIGO/Virgo S191105e: Global MASTER-Net observations report
  14. LIGO/Virgo S191105e: upper limits from AGILE/MCAL observations
  15. LIGO/Virgo S191105e: Identification of a GW compact binary merger candidate
  16. LIGO/Virgo S191105e: Upper limits from IceCube neutrino searches
  17. GRB 191106A: Mondy optical upper limit
  18. GRB 191106A: BOOTES-4/MET optical limit
  19. GRB 191106A: MASTER optical observation
  20. GRB 191106A: Swift detection of a burst
  21. GRB191016A GROND observations
  22. GRB 191031D: Chandra upper limit
  23. Swift trigger 933276 MASTER observation
  24. Fermi trigger No 594592184: Global MASTER-Net observations report
  25. Fermi trigger No 594523229: Global MASTER-Net observations report
  26. Trigger 933285: Swift detection of the brightest burst so far from SGR 1935+2154
  27. Swift GRB191105.01: Global MASTER-Net observations report
  28. Trigger 933276: Swift detection of further activity from SGR 1935+2154
  29. Swift GRB191105.01: Global MASTER-Net OT detection
  30. GRB 191101A: Swift-BAT refined analysis
  31. Fermi GBM GRB 191104C (trigger 594592184 / 191104854) is not a GRB
  32. GRB 191104C: Fermi GBM Final Real-time Localization
  33. GRB 191101A: Swift/UVOT Upper Limits
  34. Fermi GBM GRBs 191104 A, B, C and triggers 594534420/191104185 and 594563923/191104527 are not GRBs
  35. SGR 1935+2154: Swift-BAT refined analysis
  36. Fermi trigger No 594563923: Global MASTER-Net observations report
  37. GRB 191104B/GRB 191104C are SGR 1935+2154
  38. Fermi trigger No 594557071: Global MASTER-Net observations report
  39. GRB 191104C: BALROG localization (Fermi Trigger 594557071 / GRB 191104448)
  40. GRB 191104C: Fermi GBM Final Real-time Localization
  41. Fermi trigger No 594551878: Global MASTER-Net observations report
  42. Fermi trigger No 594528816: Global MASTER-Net observations report
  43. GRB 191104B: Fermi GBM Final Real-time Localization
  44. Trigger 933083: Swift detection of SGR 1935+2154
  45. Fermi GBM triggers 594523229/191104056 and 594528816/191104120 are not GRBs
  46. GRB 191104A: Fermi GBM Final Real-time Localization
  47. GRB 191031D: Zwicky Transient Facility Follow-Up of a Swift Short GRB (Trigger 594249816/191031891)
  48. Konus-Wind observation of GRB 191031D: correction to GCN 26126
  49. GRB 191031E: Insight-HXMT/HE detection
  50. GRB 191031D: Gemini optical upper limit
  51. GRB 191031C: Insight-HXMT/HE detection
  52. GRB 191101A: iTelescope optical limit
  53. GRB 191101A: Swift-XRT refined Analysis
  54. Baksan Neutrino Observatory Alert 191102.06: Global MASTER-Net observations report
  55. GRB 191101A: VIRT Optical Upper Limits
  56. Fermi trigger No 594336535: Global MASTER-Net observations report
  57. GRB 191101A: Enhanced Swift-XRT position
  58. Swift GRB191101.88: Global MASTER-Net observations report
  59. Fermi trigger No 594227699: Global MASTER-Net observations report
  60. GRB 191101A: Prompt enhanced Swift-XRT position
  61. GRB 191101B: Fermi GBM Final Real-time Localization
  62. GRB 191101A: Swift detection of a burst
  63. GRB 191031D: MMT Binospec Optical Upper Limit
  64. GRB 191031D: Swift-BAT refined analysis
  65. GRB 191031C: Swift-BAT refined analysis
  66. GRB 191031A: Swift-BAT refined analysis
  67. GRB 191031C: Swift-XRT refined Analysis
  68. GRB 191031D: AstroSat CZTI detection
  69. GRB 191031D: Swift/UVOT Upper Limits
  70. GRB 191031C: Swift/UVOT Detection
  71. Konus-Wind observation of GRB 191031D
  72. GRB 191031D: MITSuME Akeno optical upper limits
  73. GRB 191031D: Swift-XRT refined Analysis
  74. GRB 191031D: AGILE/MCAL observations
  75. GRB 191031D: COATLI Optical Observations
  76. GRB 191031D: RATIR Optical and NIR Observations
  77. GRB 191031D: VLA 9.8 GHz upper limit
  78. GRB 191031C: Fermi GBM detection
  79. GRB 191031D: Fermi GBM detection
  80. GRB 191031D: Enhanced Swift-XRT position
  81. GRB 191031A: Fermi GBM detection
  82. GRB 191031C: Enhanced Swift-XRT position
  83. Correction in name: GRB 191031D (not GRB 191031C)
  84. Swift GRB191031.89: Global MASTER-Net observations report
  85. GRB 191031D: Swift detection of a short hard burst
  86. GRB 191031C: Fermi GBM Final Real-time Localization
  87. GRB 191029A: Swift-BAT refined analysis
  88. GRB 191031C: Prompt enhanced Swift-XRT position
  89. GRB 191031C: Swift detection of a burst
  90. GRB 191031C: Fermi GBM Final Real-time Localization
  91. GRB 191025B: AstroSat CZTI detection
  92. Fermi trigger No 594175000: Global MASTER-Net observations report
  93. GRB 191031B: Fermi GBM Final Real-time Localization
  94. GRB 191031A: COATLI Optical Observations
  95. GRB 191031A: Fermi GBM Final Real-time Localization
  96. GRB 191031A: Swift detection of a burst
  97. Konus-Wind observation of GRB 191027A
  98. GRB 191029A: CORRECTED Swift-XRT refined analysis
  99. GRB 191019A: Zadko Telescope optical observations
  100. GRB 191029A: Swift/UVOT Upper Limits

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