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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. GRB 191112A: Fermi GBM Final Real-time Localization
  2. LIGO/Virgo S191110af: Swift XRT observations, no secure afterglow found
  3. LIGO/Virgo S191110af: Upper limits from CALET observations.
  4. LIGO/Virgo S191109d: Not observable by CALET
  5. LIGO/Virgo S191110af: Upper limits from IceCube MeV neutrino searches
  6. LIGO/Virgo S191110af: no counterpart candidates in the Swift/BAT observations
  7. GRB 191111B: BALROG localization (Fermi Trigger 595170435 / GRB 191111547)
  8. LIGO/Virgo S191110af: No counterpart candidates in INTEGRAL SPI-ACS, and IBIS prompt observation
  9. GRB 191111B: Fermi GBM Final Real-time Localization
  10. LIGO/Virgo S191110af: No neutrino counterpart candidate in ANTARES search
  11. LIGO/Virgo S191110af: No counterpart candidates in Fermi-LAT observations
  12. LIGO/Virgo S191110af: upper limits from AGILE/MCAL observations
  13. LIGO/Virgo S191110af: Evryscope observation report, no counterpart candidates
  14. GRB 191111A: Fermi GBM Final Real-time Localization
  15. LIGO/Virgo S191110af: No counterpart candidates in INTEGRAL SPI-ACS, prompt observation
  16. LIGO/Virgo S191110af: Upper limits from Fermi-GBM Observations
  17. LIGO/Virgo S191110af: Coverage and upper limits from MAXI/GSC observations
  18. LIGO/Virgo S191110af: Identification of a GW unmodeled transient candidate
  19. LIGO/Virgo S191110af: Upper limits from IceCube neutrino searches
  20. LIGO/Virgo S191110af: Global MASTER-Net observations report
  21. LIGO/Virgo S191109d: No significant candidates in FRAM-TAROT-GRANDMA observations
  22. LIGO/Virgo S191110x: Retraction of GW compact binary merger candidate
  23. LIGO/Virgo S191110x: Global MASTER-Net observations report
  24. LIGO/Virgo S191109d: No counterpart candidates in Fermi-LAT observations
  25. LIGO/Virgo S191105e: No significant candidates in FRAM-TAROT-GRANDMA observations
  26. GRB 191110A: Fermi GBM Final Real-time Localization
  27. LIGO/Virgo S191105e: Upper limits from Insight-HXMT/HE observations
  28. LIGO/Virgo S191109d: AstroSat CZTI upper limits
  29. LIGO/Virgo S191109d: no counterpart candidates in the Swift/BAT observations
  30. LIGO/Virgo S191109d : no neutrino counterpart candidate in ANTARES search
  31. LIGO/Virgo S191109d: Global MASTER-Net observations report
  32. LIGO/Virgo S191109d: upper limits from AGILE-GRID observations mailed-by:
  33. LIGO/Virgo S191109d: No counterpart candidates in INTEGRAL SPI-ACS,prompt observation
  34. LIGO/Virgo S191109d: upper limits from AGILE/MCAL observations
  35. LIGO/Virgo S191109d: Upper limits from Fermi-GBM Observations
  36. LIGO/Virgo S191109d: Coverage and upper limits from MAXI/GSC observations
  37. LIGO/Virgo S191109d: Upper limits from IceCube neutrino searches
  38. LIGO/Virgo S191109d: Identification of a GW compact binary merger candidate
  39. GRB 191106A: AstroSat CZTI detection
  40. GRB 191108A: Fermi GBM Final Real-time Localization
  41. GRB 191106A: Swift/UVOT Upper Limits
  42. GRB 191106A: Swift-BAT refined analysis
  43. ZTF19abvizsw: Upper limits from Konus-Wind observations
  44. LIGO/Virgo S191105e: AstroSat CZTI upper limits
  45. LIGO/Virgo S191105e: Not observable by CALET
  46. LIGO/Virgo S191105e: No counterpart candidates in Fermi-LAT observations
  47. LIGO/Virgo S191105e: Coverage and upper limits from MAXI/GSC observations
  48. LIGO/Virgo S191105e: no counterpart candidates in the Swift/BAT observations
  49. GRB 191106A: NOT optical upper limit
  50. GRB 191106A: Swift-XRT refined Analysis
  51. LIGO/Virgo S191105e : no neutrino counterpart candidate in ANTARES search
  52. LIGO/Virgo S191105e: No counterpart candidates in HAWC observations
  53. LIGO/Virgo S191105e: No counterpart candidates in INTEGRAL SPI-ACS and,IBIS prompt observation
  54. LIGO/Virgo S191105e: upper limits from AGILE/GRID observations
  55. LIGO/Virgo S191105e: Upper limits from Fermi-GBM Observations
  56. LIGO/Virgo S191105e: Global MASTER-Net observations report
  57. LIGO/Virgo S191105e: upper limits from AGILE/MCAL observations
  58. LIGO/Virgo S191105e: Identification of a GW compact binary merger candidate
  59. LIGO/Virgo S191105e: Upper limits from IceCube neutrino searches
  60. GRB 191106A: Mondy optical upper limit
  61. GRB 191106A: BOOTES-4/MET optical limit
  62. GRB 191106A: MASTER optical observation
  63. GRB 191106A: Swift detection of a burst
  64. GRB191016A GROND observations
  65. GRB 191031D: Chandra upper limit
  66. Swift trigger 933276 MASTER observation
  67. Fermi trigger No 594592184: Global MASTER-Net observations report
  68. Fermi trigger No 594523229: Global MASTER-Net observations report
  69. Trigger 933285: Swift detection of the brightest burst so far from SGR 1935+2154
  70. Swift GRB191105.01: Global MASTER-Net observations report
  71. Trigger 933276: Swift detection of further activity from SGR 1935+2154
  72. Swift GRB191105.01: Global MASTER-Net OT detection
  73. GRB 191101A: Swift-BAT refined analysis
  74. Fermi GBM GRB 191104C (trigger 594592184 / 191104854) is not a GRB
  75. GRB 191104C: Fermi GBM Final Real-time Localization
  76. GRB 191101A: Swift/UVOT Upper Limits
  77. Fermi GBM GRBs 191104 A, B, C and triggers 594534420/191104185 and 594563923/191104527 are not GRBs
  78. SGR 1935+2154: Swift-BAT refined analysis
  79. Fermi trigger No 594563923: Global MASTER-Net observations report
  80. GRB 191104B/GRB 191104C are SGR 1935+2154
  81. Fermi trigger No 594557071: Global MASTER-Net observations report
  82. GRB 191104C: BALROG localization (Fermi Trigger 594557071 / GRB 191104448)
  83. GRB 191104C: Fermi GBM Final Real-time Localization
  84. Fermi trigger No 594551878: Global MASTER-Net observations report
  85. Fermi trigger No 594528816: Global MASTER-Net observations report
  86. GRB 191104B: Fermi GBM Final Real-time Localization
  87. Trigger 933083: Swift detection of SGR 1935+2154
  88. Fermi GBM triggers 594523229/191104056 and 594528816/191104120 are not GRBs
  89. GRB 191104A: Fermi GBM Final Real-time Localization
  90. GRB 191031D: Zwicky Transient Facility Follow-Up of a Swift Short GRB (Trigger 594249816/191031891)
  91. Konus-Wind observation of GRB 191031D: correction to GCN 26126
  92. GRB 191031E: Insight-HXMT/HE detection
  93. GRB 191031D: Gemini optical upper limit
  94. GRB 191031C: Insight-HXMT/HE detection
  95. GRB 191101A: iTelescope optical limit
  96. GRB 191101A: Swift-XRT refined Analysis
  97. Baksan Neutrino Observatory Alert 191102.06: Global MASTER-Net observations report
  98. GRB 191101A: VIRT Optical Upper Limits
  99. Fermi trigger No 594336535: Global MASTER-Net observations report
  100. GRB 191101A: Enhanced Swift-XRT position

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