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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"

3797 results found.

  1. GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
  2. GRB 251013C: BOOTES-6 early optical detection
  3. GRB 251013A: SVOM/GRM observation
  4. GRB 250919A: TERI gamma-ray detection
  5. EP251006a: Global MASTER-Net observations report
  6. EP250911a: Koshka Zeiss-1000 Optical Upper Limit
  7. Swift GRB 251007A: Global MASTER-Net observations report
  8. GRB 251007B: SVOM detection of a faint burst
  9. GRB 250702B/EP250702a: JWST/NIRCam Observations
  10. Fermi GRB 251006B: Global MASTER-Net observations report
  11. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  12. Fermi trigger No 780609036: Global MASTER-Net observations report
  13. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  14. Fermi GRB 250926A: Global MASTER-Net observations report
  15. Konus-Wind detection of GRB 250911A
  16. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  17. GRB 250920C: Swift-BAT refined analysis
  18. GRB 250920B: Swift-BAT refined analysis
  19. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  20. GRB 250920A: Fermi GBM Final Localization
  21. Fermi GRB 250917B: Global MASTER-Net observations report
  22. GRB 250916A: GOTO optical counterpart candidate
  23. The EP-WXT trigger 01709240768 is likely a flaring star
  24. EP250911a: Global MASTER-Net observations report
  25. EP250911a: Upper limit from Fermi-GBM Observations
  26. GRB 250911A: Swift-BAT refined analysis
  27. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  28. EP#01709240653: Swift-XRT observations
  29. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  30. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  31. EP250908b: SVOM/VT optical candidate
  32. EP250908c: Global MASTER-Net observations report
  33. GRB 250903A: Swift-XRT afterglow detection
  34. IceCube Alert 250905.84: Global MASTER-Net observations report
  35. GRB 250903A: Swift/UVOT detection
  36. Swift GRB 250904A: Global MASTER-Net observations report
  37. GRB 250903A: Swift-XRT observations
  38. GRB 250903A: SVOM/VT optical confirmation with VHF data
  39. EP250901a: Mondy, Assy and SAO RAS optical limits
  40. GRB 250830B: Swift-XRT afterglow detection
  41. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  42. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  43. GRB 250831A: Swift-XRT counterpart detection
  44. GRB 250830B: Swift-XRT observations
  45. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  46. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  47. GRB 250830B: Swift ToO observations
  48. GRB 250830B: MAXI/GSC detection
  49. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  50. The EP-WXT trigger 01709200994 is likely a flaring star
  51. EP250828a: Global MASTER-Net observations report
  52. Fermi GRB 250827A: Global MASTER-Net observations report
  53. EP250827a: Global MASTER-Net observations report
  54. Fermi GRB 250824B: Global MASTER-Net observations report
  55. GRB 250823A: SVOM/VT optical observation
  56. GRB 250821A: KAIT optical upper limit
  57. LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
  58. Fermi trigger No 776849714: Global MASTER-Net observations report
  59. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  60. GRB 250814A: Further GRAWITA TNG NIR observations
  61. Fermi trigger No 776818276: Global MASTER-Net observations report
  62. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  63. IceCube Alert 250813.14: Global MASTER-Net observations report
  64. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  65. EP250807a: COLIBRÍ optical upper limit
  66. EP250806a: Global MASTER-Net observations report
  67. GRB 250805A: Swift-BAT refined analysis
  68. GRB 250804C: AstroSat CZTI detection of a long burst
  69. GRB 250805A: Swift detection of a burst
  70. EP250711a: CrAO and Assy optical observations
  71. EP250730a: Global MASTER-Net observations report
  72. GRB 250727A: EP-FXT follow-up observation
  73. GRB 250725A: Swift-BAT refined analysis
  74. GRB 250721A: Fermi GBM Observation
  75. GRB 250721A: Swift-XRT observations
  76. GRB 250721A: Tiled Swift observations
  77. GRB 250721A: MAXI/GSC detection
  78. GRB 250720B: Fermi GBM Final Localization Correction
  79. Swift GRB250718.01: Global MASTER-Net observations report
  80. Fermi GRB 250716A: Global MASTER-Net observations report
  81. GRB 250706B/C: 7DT Follow-up Observations
  82. EP250711a: COLIBRÍ continuous optical observations
  83. Fermi GRB 250711A: Global MASTER-Net observations report
  84. GRB 250704B / EP250704a: VLA radio detection
  85. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  86. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  87. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  88. GRB 250702F: Leavitt Observatory optical observations
  89. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  90. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  91. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  92. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  93. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  94. GRB 250702F: Swift detection of a burst with an optical counterpart
  95. GRB 250628A: Swift detection of a burst
  96. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  97. GRB 250625A: Fermi GBM Final Real-time Localization
  98. Fermi GRB 250624A: Global MASTER-Net observations report
  99. Fermi GRB 250623A: Global MASTER-Net observations report
  100. Fermi trigger No 772190032: Global MASTER-Net observations report

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