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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"

21793 results found.

  1. EP251222a: GOTO optical upper limit
  2. GRB 251222A / EP251222b: GOTO optical counterpart detection
  3. GRB 251222A / EP251222b: LCO optical observations
  4. GRB 251222A: 1.3m DFOT optical detection
  5. GRB251221A: 7DT optical upper limits
  6. EP251222a: GSP Optical Counterpart Detection
  7. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  8. EP251221a: Global MASTER-Net observations report
  9. GRB 251222A: PRIME near-infrared detection
  10. EP251221a: NOT optical upper limit
  11. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  12. GRB 251222A: NOT optical observations
  13. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  14. GRB 251222A: Swift ToO observations
  15. SVOM GRB251222A: Global MASTER-Net observations report
  16. EP251220a: PRIME upper limit
  17. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  18. GRB 251221A: PRIME near-infrared observation
  19. EP251220a: NOT optical observations
  20. EP251220a: FTW optical and NIR observations
  21. GRB 251221A: UAFO and Mondy optical upper limit
  22. GRB 251221A: Swift/UVOT Upper Limits
  23. EP251220a: EP-FXT follow-up observation
  24. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  25. EP 251220a: GOTO optical counterpart detection
  26. EP 251220a: COLIBRÍ detection of the optical counterpart
  27. Swift GRB251221A: Global MASTER-Net observations report
  28. EP251220a: Global MASTER-Net observations report
  29. SVOM GRB251220.98: Global MASTER-Net observations report
  30. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  31. GRB 251215A: Swift-XRT afterglow detection
  32. IceCube-251218A: COLIBRÍ optical upper limits
  33. SVOM GRB251219.11: Global MASTER-Net observations report
  34. IceCube Alert 251218.85: Global MASTER-Net observations report
  35. Fermi trigger No 787736968: Global MASTER-Net observations report
  36. Fermi GRB 251217A: Global MASTER-Net observations report
  37. GRB 251215A: Swift/UVOT Upper LImits
  38. Fermi GRB 251216A: Global MASTER-Net observations report
  39. GRB 251215A: COLIBRÍ optical upper limit
  40. GRB 251215A: Swift-XRT observations
  41. Fermi GRB 251215A: Global MASTER-Net observations report
  42. EP251214a: Optical upper limit with Kinder observations
  43. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  44. GRB 251214B: UAFO optical upper limit
  45. GRB 251214B: VLT/X-shooter observations
  46. GRB 251202A: radio detection with the VLA
  47. EP251214b: Global MASTER-Net observations report
  48. GRB 251214B: AbAO optical observations
  49. GRB 251214B: LCO detection of the optical counterpart
  50. GRB 251215A: Swift ToO observations
  51. EP251214b (EP trigger 01709250023): LCO optical limits
  52. GRB 251203B: AbAO optical observations
  53. GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
  54. GRB 251214B: Swift/UVOT Detection
  55. GRB 251214B: COLIBRÍ observations of the afterglow
  56. GRB 251214B: 1.3m DFOT optical detection
  57. EP251214a: Global MASTER-Net observations report
  58. GRB 251214B: Xinglong-2.16m optical observation
  59. GRB 251214B : MASTER optical afterglow detection
  60. Fermi trigger No 787396657: Global MASTER-Net observations report
  61. GRB 251214B: SVOM/C-GFT optical observations
  62. Swift GRB 251214B: Global MASTER-Net observations report
  63. Fermi GRB 251214A: Global MASTER-Net observations report
  64. EP251212a: Global MASTER-Net observations report
  65. EP251212a: KAIT optical upper limit
  66. IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
  67. Fermi-LAT Gamma-ray Observations of IceCube-251210A
  68. Fermi GRB 251211B: Global MASTER-Net observations report
  69. IceCube-251210A: DDOTI Optical Upper Limit
  70. SVOM GRB251211.12: Global MASTER-Net observations report
  71. GRB 251205A: 1.3m DFOT optical upper limit
  72. IceCube Alert 251210.46: Global MASTER-Net observations report
  73. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  74. EP251130a: Mondy and AbAO optical observations
  75. Fermi GBM Sub-Threshold Detection of GRB 251205A
  76. Fermi GRB 251209A: Global MASTER-Net observations report
  77. Fermi GRB 251208C: Global MASTER-Net observations report
  78. GRB 251208B: Swift-XRT afterglow detection
  79. GRB 251208D: LAST optical upper limit
  80. GRB 251208D: LCO analysis of the XRT sources
  81. GRB 251208B: GROWTH-India Telescope optical upper limits
  82. GRB 251205A: J-band detection with WINTER
  83. GRB 251208D: Swift-XRT observations
  84. GRB 251129A: e-MERLIN C-band observations
  85. LAT GRB251208.43: Global MASTER-Net observations report
  86. GRB 251205A: Liverpool Telescope further optical follow-up observations
  87. SVOM GRB251208D: Global MASTER-Net observations report
  88. GRB 251208B: Swift ToO observations
  89. GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
  90. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  91. GRB 251205A: FTW optical and NIR observations
  92. EP-WXT trigger 01709249380: KAIT confirmation of a stellar flare
  93. GRB 251205A: Liverpool Telescope further optical follow-up observations
  94. SVOM GRB251206.86: Global MASTER-Net observations report
  95. GRB 251205A: ZTF and ATLAS optical afterglow detections
  96. GRB 251205A: GROWTH-India Telescope optical observations
  97. GRB 251205A: Swift/UVOT Detection
  98. GRB 251205A: Liverpool Telescope optical follow-up observations
  99. GRB 251203C: Swift/UVOT Upper Limit
  100. GRB 251205A: Zeiss-1000 Koshka observatory optical observations

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