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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"

6791 results found.

  1. GRB 260226A: Fermi GBM observation
  2. GRB 260226A: Fermi-LAT refined analysis
  3. GRB 260226A: Fermi-LAT detection of a bright burst
  4. GRB 260223A: Fermi GBM Observation
  5. EP260223a: EP-FXT follow-up observation
  6. EP260221a: Optical upper limit with Kinder observations
  7. EP260221a: Gemini South z-band upper limit
  8. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  9. EP260214b: 1.3m DFOT optical upper limit
  10. EP260214b: Optical upper limit with Kinder observations
  11. EP260214a: Optical upper limits with Kinder observations
  12. EP260214b: EP-FXT follow-up observation
  13. EP260214a: refined analysis of the EP-FXT observation
  14. GRB 260212A: Fermi GBM Observation
  15. EP260213a: Optical upper limits with Kinder observations
  16. EP260213a: NUTTelA-TAO Early Optical Limits
  17. EP260213a: refined analysis of the EP-FXT observation
  18. GRB 260208A: Swift UVOT detection
  19. EP260210a: refined analysis of the EP-FXT observation
  20. GRB 260208A: LCO detection of the optical counterpart
  21. EP260210a: Optical upper limits with Kinder observations
  22. GRB 260208B: refined analysis of the EP-FXT observation
  23. GRB 260204A: Swift-XRT afterglow detection
  24. GRB 260208A: Fermi GBM Observation
  25. GRB 260208B: Swift-XRT observations
  26. GRB 260204A: Swift/UVOT Upper Limits
  27. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  28. GRB 260208A: Swift-XRT observations
  29. GRB 260208B: Fermi GBM Detection
  30. GRB 260208B: Fermi-LAT detection
  31. GRB 260208A: Fermi-LAT detection
  32. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  33. GRB 260206A: Swift-XRT observations
  34. GRB 260204A: Swift-XRT observations
  35. Konus-Wind detection of GRB 260131A/B
  36. GRB 260131A/B: Fermi GBM Observation
  37. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  38. GRB 260130A: Fermi GBM Detection
  39. GRB 260127B: Fermi GBM Detection
  40. GRB 260127B: Swift-XRT observations
  41. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  42. GRB 260127A: Fermi GBM Observation
  43. GRB 260127A: Swift-XRT refined Analysis
  44. GRB 260127A: Prompt enhanced Swift-XRT position
  45. GRB 260125A: Swift-XRT observations
  46. EP260126a: EP-FXT follow-up observation
  47. EP260126a: Optical upper limit with Kinder observations
  48. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  49. EP260119a: Mondy and SAO RAS optical upper limits
  50. GRB 260120B: Swift-XRT refined Analysis
  51. GRB 260120B: Fermi GBM Observation
  52. EP260119a: update of EP-FXT follow-up observation
  53. EP260119a: NOT optical observations
  54. EP260119a: SAO RAS optical observations
  55. GRB 260117A: Swift-XRT afterglow detection
  56. EP260119a: EP-WXT detection of a fast X-ray transient
  57. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  58. GRB 260117A: Swift-XRT observations
  59. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  60. GRB 260114A: Swift-XRT refined Analysis
  61. GRB 260114A: NOT optical observations
  62. GRB 260114A: Fermi GBM observation
  63. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  64. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  65. Konus-Wind detection of GRB 260101A
  66. GRB 260111A: Swift-XRT observations
  67. Swift Trigger 1439093: is probably not GRB 260113A
  68. GRB 260111A: Fermi GBM Observation
  69. IceCube Alert 260111A: Global MASTER-Net observations report
  70. Swift Trigger 1434591: possible GRB 260109C
  71. GRB 260102A: Swift-XRT afterglow detection
  72. GRB 260105B: Fermi GBM Detection
  73. GRB 260104A: Swift-XRT refined Analysis
  74. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  75. GRB 260102A: Swift-XRT observations
  76. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  77. GRB 260101A: Fermi GBM Observation
  78. GRB 260101A: Swift-XRT refined Analysis
  79. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  80. EP251229a: Optical upper limit with Kinder observations
  81. GRB 251230A: Swift-XRT refined Analysis
  82. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  83. GRB 251230A: Early optical counterpart detection by LCO.
  84. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  85. GRB 251222A: NUTTelA-TAO Early Measurements
  86. GRB 251222A/EP251222b: Optical detection with Kinder observations
  87. EP251222a: Optical upper limit with Kinder observations
  88. GRB 251222A: Fermi GBM Observation
  89. Konus-Wind detection of GRB 251222A / EP251222b
  90. GRB 251222A: Swift-XRT afterglow detection
  91. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  92. EP251222a: GSP Optical Counterpart Detection
  93. GRB 251221A: Swift-XRT refined Analysis
  94. GRB 251221A: Fermi GBM Observation
  95. EP251220a: EP-FXT follow-up observation
  96. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  97. GRB 251215A: Swift-XRT afterglow detection
  98. GRB 251215A: Swift/UVOT Upper LImits
  99. GRB 251215A: Fermi GBM Observation
  100. GRB 251215A: Swift-XRT observations

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