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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 240529A: AstroSat CZTI detection
  2. GRB 240529A: GOTO optical afterglow detection
  3. GRB 240527B: Swift-XRT afterglow detection
  4. GRB 240529A: Enhanced Swift-XRT position
  5. GRB 240529A: Swift detection of a burst with an optical counterpart
  6. Swift GRB240529.12: Global MASTER-Net observations report
  7. LIGO/Virgo/KAGRA S240527fv: Updated Sky localization
  8. GRB 240527B: Fermi GBM Observation
  9. Fermi GRB 240527A: Global MASTER-Net observations report
  10. LIGO/Virgo/KAGRA S240527fv: Identification of a GW compact binary merger candidate
  11. GRB 240527B: Fermi-LAT detection
  12. LAT GRB240527.59: Global MASTER-Net observations report
  13. LIGO/Virgo/KAGRA S240527en: Identification of a GW compact binary merger candidate
  14. Fermi GRB 240527B: Global MASTER-Net observations report
  15. GRB 240527B: Fermi GBM Final Localization
  16. GRB 240527B: BALROG localization (Fermi Trigger 738511436 / GRB 240527586)
  17. GRB 240527A: Fermi GBM Final Real-time Localization
  18. GRB 240523A: Swift-BAT refined analysis
  19. Fermi trigger No 738348224: Global MASTER-Net observations report
  20. Fermi trigger No 738330463: Global MASTER-Net observations report
  21. LIGO/Virgo/KAGRA S240525p: Updated Sky localization
  22. LIGO/Virgo/KAGRA S240525p: Identification of a GW compact binary merger candidate
  23. GRB 240523A: Swift-XRT refined Analysis
  24. GRB 240523A: Enhanced Swift-XRT position
  25. GRB 240523A: Swift detection of a burst
  26. GRB 240521B: Fermi GBM Observation
  27. Fermi GBM Sub-Threshold Detection of GRB 240516B
  28. GRB 240513A: Swift-XRT afterglow detection
  29. GRB 240521B: Swift/BAT-GUANO arcminute localization of a long burst
  30. Fermi trigger No 737996942: Global MASTER-Net observations report
  31. LIGO/Virgo/KAGRA S240520cv: Updated Sky localization and EM Bright Classification
  32. EP240518a: GSP optical upper limit
  33. GRB 240521A: GECAM-B detection of a long burst
  34. GRB 240516B: AstroSat CZTI detection
  35. LIGO/Virgo/KAGRA S240515m: Upper limits from Swift/BAT-GUANO
  36. LIGO/Virgo/KAGRA S240514x: Upper limits from Swift/BAT-GUANO
  37. LIGO/Virgo/KAGRA S240513ei: Upper limits from Swift/BAT-GUANO
  38. LIGO/Virgo/KAGRA S240520cv: Identification of a GW compact binary merger candidate
  39. IceCube-Cascade 240518A: Upper limits from a search for additional neutrino events in IceCube
  40. GRB 240514B: VZLUSAT-2 detection
  41. GRB 240504A: VZLUSAT-2 detection
  42. GRB 240502A: VZLUSAT-2 detection
  43. GRB 240519A: GRBAlpha detection
  44. GRB 240516A: Swift/UVOT Upper Limits
  45. GRB 240519A: AstroSat CZTI detection
  46. Fermi trigger No 737788024: Global MASTER-Net observations report
  47. EP240518a: possibly identified with a flare star by EP-FXT
  48. GRB 240519A: BALROG localization (Fermi Trigger 737788024 / GRB 240519213)
  49. EP240518a: EP-WXT detection of a new X-ray transient
  50. LIGO/Virgo/KAGRA S240514c: Updated Sky localization
  51. GRB 240516A: Swift-BAT refined analysis
  52. Fermi GRB 240517A: Global MASTER-Net observations report
  53. GRB 240516A ATCA radio observations
  54. IPN triangulation of GRB 240514B (short)
  55. GRB 240513A: Swift ToO observations
  56. GRB 240517A: Fermi GBM Final Real-time Localization
  57. Konus-Wind detection of GRB 240513A
  58. GRB 240516A: AstroSat CZTI detection
  59. GRB 240516A: Swift-XRT refined Analysis
  60. GRB 240514E: A possible candidate BD-21 1074
  61. Fermi trigger No 737559855: Global MASTER-Net observations report
  62. GRB 240516A: Fermi GBM Observation
  63. GRB 240511A: Observations from GTC/OSIRIS+
  64. GRB 240502C: Zeiss-1000 at Koshka observations of GOTO24bao optical counterpart candidate
  65. GRB 240516A: GOTO optical upper limit
  66. LIGO/Virgo/KAGRA S240422ed: GRID non-detection and upper limits
  67. Fermi trigger No 737523389: Global MASTER-Net observations report
  68. GRB 240516A: Swift detection of a burst
  69. Swift GRB240516.15: Global MASTER-Net observations report
  70. GRB 240514B: AT2024ixa/GOTO24bph is not consistent with the Fermi localisation
  71. Fermi trigger No 737476171: Global MASTER-Net observations report
  72. GRB 240511A: radio detection of afterglow candidate
  73. GRB 240514B: GOTO candidate optical counterpart
  74. MAXI GRB240514.78: Global MASTER-Net observations report
  75. Fermi Gamma-ray Burst Monitor list of triggers that are not a GRB
  76. GRB 240514E: MAXI/GSC detection of a probable afterglow
  77. GRB 240514B: GRBAlpha detection
  78. LIGO/Virgo/KAGRA S240514x: Updated Sky localization
  79. LIGO/Virgo/KAGRA S240515m: Identification of a GW compact binary merger candidate
  80. GRB 240514B: Fermi GBM Detection
  81. LIGO/Virgo/KAGRA S240422ed: Las Cumbres Observatory Follow-up Observations of the Localization Region
  82. GRB 240513A: Fermi GBM observation
  83. GRB 240513A: Swift-XRT observations
  84. LIGO/Virgo/KAGRA S240513ei: Updated Sky localization
  85. LIGO/Virgo/KAGRA S240514x: Identification of a GW compact binary merger candidate
  86. GRB 240514D: AstroSat CZTI detection
  87. GRB 240514C: Fermi GBM Final Real-time Localization
  88. LIGO/Virgo/KAGRA S240514c: Identification of a GW compact binary merger candidate
  89. Fermi GRB 240514B: Global MASTER-Net observations report
  90. transient: Xinglong Nearby Galaxy Supernova Survey detection of AT2024iss
  91. Fermi Gamma-ray Burst Monitor triggers 737345659/240514093 and GRB240514A are not GRBs
  92. GRB 240514B: Fermi GBM Final Real-time Localization
  93. LIGO/Virgo/KAGRA S240507p: Upper limits from Swift/BAT-GUANO
  94. LIGO/Virgo/KAGRA S240505av: Upper limits from Swift/BAT-GUANO
  95. LIGO/Virgo/KAGRA S240505av: Upper limits from Swift/BAT-GUANO
  96. GRB 240514A: Fermi GBM Final Real-time Localization
  97. GRB 240513A: Tiled Swift observations
  98. LAT GRB240513.31: Global MASTER-Net observations report
  99. GRB 240513A: Fermi-LAT detection
  100. LIGO/Virgo/KAGRA S240513ei: Identification of a GW compact binary merger candidate

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