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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 S191110af: Upper limits from KM3NeT MeV neutrino search.
  2. LIGO/Virgo S191110af: Upper limits from Konus-Wind observations
  3. GRB 191111A: Insight-HXMT/HE detection
  4. GRB 191027A: CALET Gamma-Ray Burst Monitor detection
  5. LIGO/Virgo S191105e: Updated Sky Localization
  6. Announcing the GW Treasure Map
  7. LIGO/Virgo S191110af: Potential pulsar counterparts
  8. Konus-Wind observation of the recent SGR 1935+2154 activity
  9. GRB 191113A: Fermi GBM Final Real-time Localization
  10. GRB 191031D: CALET Gamma-Ray Burst Monitor detection
  11. GRB 191112A: Fermi GBM Final Real-time Localization
  12. LIGO/Virgo S191110af: Swift XRT observations, no secure afterglow found
  13. LIGO/Virgo S191110af: Upper limits from CALET observations.
  14. LIGO/Virgo S191109d: Not observable by CALET
  15. LIGO/Virgo S191110af: Upper limits from IceCube MeV neutrino searches
  16. LIGO/Virgo S191110af: no counterpart candidates in the Swift/BAT observations
  17. GRB 191111B: BALROG localization (Fermi Trigger 595170435 / GRB 191111547)
  18. LIGO/Virgo S191110af: No counterpart candidates in INTEGRAL SPI-ACS, and IBIS prompt observation
  19. GRB 191111B: Fermi GBM Final Real-time Localization
  20. LIGO/Virgo S191110af: No neutrino counterpart candidate in ANTARES search
  21. LIGO/Virgo S191110af: No counterpart candidates in Fermi-LAT observations
  22. LIGO/Virgo S191110af: upper limits from AGILE/MCAL observations
  23. LIGO/Virgo S191110af: Evryscope observation report, no counterpart candidates
  24. GRB 191111A: Fermi GBM Final Real-time Localization
  25. LIGO/Virgo S191110af: No counterpart candidates in INTEGRAL SPI-ACS, prompt observation
  26. LIGO/Virgo S191110af: Upper limits from Fermi-GBM Observations
  27. LIGO/Virgo S191110af: Coverage and upper limits from MAXI/GSC observations
  28. LIGO/Virgo S191110af: Identification of a GW unmodeled transient candidate
  29. LIGO/Virgo S191110af: Upper limits from IceCube neutrino searches
  30. LIGO/Virgo S191110af: Global MASTER-Net observations report
  31. LIGO/Virgo S191109d: No significant candidates in FRAM-TAROT-GRANDMA observations
  32. LIGO/Virgo S191110x: Retraction of GW compact binary merger candidate
  33. LIGO/Virgo S191110x: Global MASTER-Net observations report
  34. LIGO/Virgo S191109d: No counterpart candidates in Fermi-LAT observations
  35. LIGO/Virgo S191105e: No significant candidates in FRAM-TAROT-GRANDMA observations
  36. GRB 191110A: Fermi GBM Final Real-time Localization
  37. LIGO/Virgo S191105e: Upper limits from Insight-HXMT/HE observations
  38. LIGO/Virgo S191109d: AstroSat CZTI upper limits
  39. LIGO/Virgo S191109d: no counterpart candidates in the Swift/BAT observations
  40. LIGO/Virgo S191109d : no neutrino counterpart candidate in ANTARES search
  41. LIGO/Virgo S191109d: Global MASTER-Net observations report
  42. LIGO/Virgo S191109d: upper limits from AGILE-GRID observations mailed-by:
  43. LIGO/Virgo S191109d: No counterpart candidates in INTEGRAL SPI-ACS,prompt observation
  44. LIGO/Virgo S191109d: upper limits from AGILE/MCAL observations
  45. LIGO/Virgo S191109d: Upper limits from Fermi-GBM Observations
  46. LIGO/Virgo S191109d: Coverage and upper limits from MAXI/GSC observations
  47. LIGO/Virgo S191109d: Upper limits from IceCube neutrino searches
  48. LIGO/Virgo S191109d: Identification of a GW compact binary merger candidate
  49. GRB 191106A: AstroSat CZTI detection
  50. GRB 191108A: Fermi GBM Final Real-time Localization
  51. GRB 191106A: Swift/UVOT Upper Limits
  52. GRB 191106A: Swift-BAT refined analysis
  53. ZTF19abvizsw: Upper limits from Konus-Wind observations
  54. LIGO/Virgo S191105e: AstroSat CZTI upper limits
  55. LIGO/Virgo S191105e: Not observable by CALET
  56. LIGO/Virgo S191105e: No counterpart candidates in Fermi-LAT observations
  57. LIGO/Virgo S191105e: Coverage and upper limits from MAXI/GSC observations
  58. LIGO/Virgo S191105e: no counterpart candidates in the Swift/BAT observations
  59. GRB 191106A: NOT optical upper limit
  60. GRB 191106A: Swift-XRT refined Analysis
  61. LIGO/Virgo S191105e : no neutrino counterpart candidate in ANTARES search
  62. LIGO/Virgo S191105e: No counterpart candidates in HAWC observations
  63. LIGO/Virgo S191105e: No counterpart candidates in INTEGRAL SPI-ACS and,IBIS prompt observation
  64. LIGO/Virgo S191105e: upper limits from AGILE/GRID observations
  65. LIGO/Virgo S191105e: Upper limits from Fermi-GBM Observations
  66. LIGO/Virgo S191105e: Global MASTER-Net observations report
  67. LIGO/Virgo S191105e: upper limits from AGILE/MCAL observations
  68. LIGO/Virgo S191105e: Identification of a GW compact binary merger candidate
  69. LIGO/Virgo S191105e: Upper limits from IceCube neutrino searches
  70. GRB 191106A: Mondy optical upper limit
  71. GRB 191106A: BOOTES-4/MET optical limit
  72. GRB 191106A: MASTER optical observation
  73. GRB 191106A: Swift detection of a burst
  74. GRB191016A GROND observations
  75. GRB 191031D: Chandra upper limit
  76. Swift trigger 933276 MASTER observation
  77. Fermi trigger No 594592184: Global MASTER-Net observations report
  78. Fermi trigger No 594523229: Global MASTER-Net observations report
  79. Trigger 933285: Swift detection of the brightest burst so far from SGR 1935+2154
  80. Swift GRB191105.01: Global MASTER-Net observations report
  81. Trigger 933276: Swift detection of further activity from SGR 1935+2154
  82. Swift GRB191105.01: Global MASTER-Net OT detection
  83. GRB 191101A: Swift-BAT refined analysis
  84. Fermi GBM GRB 191104C (trigger 594592184 / 191104854) is not a GRB
  85. GRB 191104C: Fermi GBM Final Real-time Localization
  86. GRB 191101A: Swift/UVOT Upper Limits
  87. Fermi GBM GRBs 191104 A, B, C and triggers 594534420/191104185 and 594563923/191104527 are not GRBs
  88. SGR 1935+2154: Swift-BAT refined analysis
  89. Fermi trigger No 594563923: Global MASTER-Net observations report
  90. GRB 191104B/GRB 191104C are SGR 1935+2154
  91. Fermi trigger No 594557071: Global MASTER-Net observations report
  92. GRB 191104C: BALROG localization (Fermi Trigger 594557071 / GRB 191104448)
  93. GRB 191104C: Fermi GBM Final Real-time Localization
  94. Fermi trigger No 594551878: Global MASTER-Net observations report
  95. Fermi trigger No 594528816: Global MASTER-Net observations report
  96. GRB 191104B: Fermi GBM Final Real-time Localization
  97. Trigger 933083: Swift detection of SGR 1935+2154
  98. Fermi GBM triggers 594523229/191104056 and 594528816/191104120 are not GRBs
  99. GRB 191104A: Fermi GBM Final Real-time Localization
  100. GRB 191031D: Zwicky Transient Facility Follow-Up of a Swift Short GRB (Trigger 594249816/191031891)

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