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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"

35952 results found.

  1. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  2. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  3. GRB 250904A: Prompt enhanced Swift-XRT position
  4. GRB 250904A: Swift detection of a burst
  5. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  6. GRB 250902A: VZLUSAT-2 detection
  7. GRB 250903A: Swift-XRT observations
  8. GRB 250830C: VZLUSAT-2 detection
  9. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  10. GRB 250903A: EP-FXT counterpart detection
  11. GRB 250902A: GECAM-B detection
  12. GRB 250903A: LCO optical observation
  13. GRB 250903A: LCO optical afterglow detection
  14. GRB 250903A: SVOM/VT optical confirmation with VHF data
  15. EP250901a: Mondy, Assy and SAO RAS optical limits
  16. Subject GRB 250903A: SVOM/MXT afterglow detection
  17. GRB 250903A: TRT optical counterpart detection
  18. GRB 250902B: AstroSat CZTI detection
  19. GRB 250903A: SVOM detection of a burst
  20. EP 250827B: Detection of supernova counterpart by LCO.
  21. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  22. GRB 250902B: SVOM/GRM observation
  23. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  24. Fermi GRB 250902B: Global MASTER-Net observations report
  25. GRB 250902A: Fermi GBM Detection
  26. GRB 250901A: Swift/UVOT Upper Limit
  27. GRB 250902B: Fermi GBM Final Real-time Localization
  28. GRB 250830B: Swift-XRT afterglow detection
  29. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  30. GRB 250902A: SVOM/GRM observation
  31. GRB 250901A: EP-FXT follow-up observation
  32. GRB 250901A: NOT optical observations
  33. GRB 250902A: Fermi GBM Final Real-time Localization
  34. GRB 250901A: SVOM/VT optical afterglow with VHF data
  35. GRB 250901A: Swift-XRT afterglow detection
  36. GRB 250901A: LCO optical upper limit
  37. GRB 250901A: SVOM detection of a burst
  38. GRB 250831B: SVOM/GRM observation
  39. GRB 250830C: Insight-HXMT detection
  40. GRB 250830C: GECAM-B detection
  41. GRB 250830C: AstroSat CZTI detection of a long burst
  42. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  43. GRB 250831A: Swift-XRT counterpart detection
  44. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  45. GRB 250831A: SVOM/VT upper limit with VHF data
  46. GRB 250831A: SVOM detection of a soft burst
  47. GRB 250830B: Swift-XRT observations
  48. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  49. GRB 250830B: Swift ToO observations
  50. GRB 250830B: MAXI/GSC detection
  51. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  52. GRB 250828B: Swift-BAT refined analysis
  53. GRB 250808B: SVOM detection of a burst through offline search
  54. Swift GRB 250828B: Global MASTER-Net observations report
  55. EP-WXT trigger 01709200800 : KAIT optical observations
  56. EP250828a: KAIT optical upper limit
  57. GRB 250828B: Swift detection of a burst
  58. GRB 250828A: Fermi GBM Final Localization
  59. GRID detection of GRB 250824A
  60. Fermi GRB 250827A: Global MASTER-Net observations report
  61. EP250827a: GOTO observation of the optical afterglow
  62. GRB 250826A: SVOM/GRM observation
  63. GRB 250827A: Fermi GBM Final Real-time Localization
  64. EP250827A: An optical rebrightening was detected by LCO.
  65. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  66. Fermi GRB 250826A: Global MASTER-Net observations report
  67. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  68. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  69. Fermi Gamma-ray Burst Monitor trigger 777883624/250826283 is not a GRB
  70. GRB 250826A: Fermi GBM Final Real-time Localization
  71. Fermi GRB 250824B: Global MASTER-Net observations report
  72. GRB 250823A: Swift-BAT refined analysis
  73. GRB 250821B: AstroSat CZTI detection
  74. GRB 250819A: AstroSat CZTI detection
  75. GRB 250821B: Insight-HXMT detection
  76. GRB 250823A: Swift-XRT refined Analysis
  77. GRB 250824B: Fermi GBM Final Real-time Localization
  78. GRB 250823A: COLIBRÍ optical observations
  79. GRB 250823A: SVOM/VT optical observation
  80. GRB 250824A: Fermi GBM Final Real-time Localization
  81. GRB 250823A: Swift/UVOT Detection
  82. GRB 250823A: NOT optical observations
  83. GRB 250823A: Fermi GBM Observation
  84. GRB 250818B: MeerKAT Detection
  85. GRB 250823A: Enhanced Swift-XRT position
  86. GRB 250823A: LCOGT Optical Detection
  87. GRB 250823A: BOOTES6/DPRT early optical detection
  88. GRB 250823A: Liverpool Telescope optical detection
  89. GRB 250823A: Swift detection of a burst
  90. GRB 250823A: Fermi GBM Final Real-time Localization
  91. Konus-Wind detection of GRB 250821B
  92. GRB 250806A: Gemini observations of host galaxy candidate
  93. IPN triangulation of GRB 250821B (long/bright)
  94. GRB 250821A: Kilonova-Catcher optical upper limits
  95. GRB 250812A: SVOM/ECLAIRs refined analysis
  96. GRB 250821A: Swift-BAT refined analysis
  97. GRB 250821A: VLT/FORS2 Optical Observation
  98. GRB 250821A: GECAM-B detection
  99. GRB 250821B: SVOM/GRM observation
  100. Fermi GRB 250821B: Global MASTER-Net observations report

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