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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. IPN triangulation of the initial episode of GRB 240529A
  2. GRB 240529A: SAO RAS optical observations
  3. LIGO/Virgo/KAGRA S240531bp: Updated Sky localization
  4. LIGO/Virgo/KAGRA S240531bp: Identification of a GW compact binary merger candidate
  5. GRB 240529A: MAAO 0.7m telescope optical afterglow detection
  6. GRB 240529A: Insight-HXMT/HE detection
  7. GRB 240529A: optical photometry from Konkoly
  8. GRB 240529A: GROWTH-India optical follow-up
  9. GRB 240529A: T193/MISTRAL observations
  10. GRB 240529A: Redshift from GTC/OSIRIS+
  11. GRB 240529A: AKO Optical Afterglow Detection
  12. LIGO/Virgo/KAGRA S240530a: Identification of a GW compact binary merger candidate
  13. LIGO/Virgo/KAGRA S240527fv: Upper limits from Swift/BAT-GUANO
  14. LIGO/Virgo/KAGRA S240525p: Upper limits from Swift/BAT-GUANO
  15. GRB 240529A: J-band detections with WINTER
  16. GRB 240529A: Skynet Optical Observations
  17. LXT 240528A: LEIA detection of a fast X-ray transient
  18. GRB 240529A: Swift-BAT refined analysis
  19. LIGO/Virgo S240527fv: GRANDMA/FRAM-Auger Optical Observations
  20. GRB 240529A: Swift-XRT refined Analysis
  21. GRB240529A: BOOTES-6/DPRT optical detection
  22. GRB 240529A: Swift/UVOT Detection
  23. GRB 240529A: NOT optical observations
  24. GRB 240529A: AstroSat CZTI detection
  25. GRB 240529A: GOTO optical afterglow detection
  26. GRB 240527B: Swift-XRT afterglow detection
  27. GRB 240529A: Enhanced Swift-XRT position
  28. GRB 240529A: Swift detection of a burst with an optical counterpart
  29. Swift GRB240529.12: Global MASTER-Net observations report
  30. LIGO/Virgo/KAGRA S240527fv: Updated Sky localization
  31. GRB 240527B: Fermi GBM Observation
  32. Fermi GRB 240527A: Global MASTER-Net observations report
  33. LIGO/Virgo/KAGRA S240527fv: Identification of a GW compact binary merger candidate
  34. GRB 240527B: Fermi-LAT detection
  35. LAT GRB240527.59: Global MASTER-Net observations report
  36. LIGO/Virgo/KAGRA S240527en: Identification of a GW compact binary merger candidate
  37. Fermi GRB 240527B: Global MASTER-Net observations report
  38. GRB 240527B: Fermi GBM Final Localization
  39. GRB 240527B: BALROG localization (Fermi Trigger 738511436 / GRB 240527586)
  40. GRB 240527A: Fermi GBM Final Real-time Localization
  41. GRB 240523A: Swift-BAT refined analysis
  42. Fermi trigger No 738348224: Global MASTER-Net observations report
  43. Fermi trigger No 738330463: Global MASTER-Net observations report
  44. LIGO/Virgo/KAGRA S240525p: Updated Sky localization
  45. LIGO/Virgo/KAGRA S240525p: Identification of a GW compact binary merger candidate
  46. GRB 240523A: Swift-XRT refined Analysis
  47. GRB 240523A: Enhanced Swift-XRT position
  48. GRB 240523A: Swift detection of a burst
  49. GRB 240521B: Fermi GBM Observation
  50. Fermi GBM Sub-Threshold Detection of GRB 240516B
  51. GRB 240513A: Swift-XRT afterglow detection
  52. GRB 240521B: Swift/BAT-GUANO arcminute localization of a long burst
  53. Fermi trigger No 737996942: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S240520cv: Updated Sky localization and EM Bright Classification
  55. EP240518a: GSP optical upper limit
  56. GRB 240521A: GECAM-B detection of a long burst
  57. GRB 240516B: AstroSat CZTI detection
  58. LIGO/Virgo/KAGRA S240515m: Upper limits from Swift/BAT-GUANO
  59. LIGO/Virgo/KAGRA S240514x: Upper limits from Swift/BAT-GUANO
  60. LIGO/Virgo/KAGRA S240513ei: Upper limits from Swift/BAT-GUANO
  61. LIGO/Virgo/KAGRA S240520cv: Identification of a GW compact binary merger candidate
  62. IceCube-Cascade 240518A: Upper limits from a search for additional neutrino events in IceCube
  63. GRB 240514B: VZLUSAT-2 detection
  64. GRB 240504A: VZLUSAT-2 detection
  65. GRB 240502A: VZLUSAT-2 detection
  66. GRB 240519A: GRBAlpha detection
  67. GRB 240516A: Swift/UVOT Upper Limits
  68. GRB 240519A: AstroSat CZTI detection
  69. Fermi trigger No 737788024: Global MASTER-Net observations report
  70. EP240518a: possibly identified with a flare star by EP-FXT
  71. GRB 240519A: BALROG localization (Fermi Trigger 737788024 / GRB 240519213)
  72. EP240518a: EP-WXT detection of a new X-ray transient
  73. LIGO/Virgo/KAGRA S240514c: Updated Sky localization
  74. GRB 240516A: Swift-BAT refined analysis
  75. Fermi GRB 240517A: Global MASTER-Net observations report
  76. GRB 240516A ATCA radio observations
  77. IPN triangulation of GRB 240514B (short)
  78. GRB 240513A: Swift ToO observations
  79. GRB 240517A: Fermi GBM Final Real-time Localization
  80. Konus-Wind detection of GRB 240513A
  81. GRB 240516A: AstroSat CZTI detection
  82. GRB 240516A: Swift-XRT refined Analysis
  83. GRB 240514E: A possible candidate BD-21 1074
  84. Fermi trigger No 737559855: Global MASTER-Net observations report
  85. GRB 240516A: Fermi GBM Observation
  86. GRB 240511A: Observations from GTC/OSIRIS+
  87. GRB 240502C: Zeiss-1000 at Koshka observations of GOTO24bao optical counterpart candidate
  88. GRB 240516A: GOTO optical upper limit
  89. LIGO/Virgo/KAGRA S240422ed: GRID non-detection and upper limits
  90. Fermi trigger No 737523389: Global MASTER-Net observations report
  91. GRB 240516A: Swift detection of a burst
  92. Swift GRB240516.15: Global MASTER-Net observations report
  93. GRB 240514B: AT2024ixa/GOTO24bph is not consistent with the Fermi localisation
  94. Fermi trigger No 737476171: Global MASTER-Net observations report
  95. GRB 240511A: radio detection of afterglow candidate
  96. GRB 240514B: GOTO candidate optical counterpart
  97. MAXI GRB240514.78: Global MASTER-Net observations report
  98. Fermi Gamma-ray Burst Monitor list of triggers that are not a GRB
  99. GRB 240514E: MAXI/GSC detection of a probable afterglow
  100. GRB 240514B: GRBAlpha detection

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