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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"

23151 results found.

  1. GRB 250625A: ABObservatory afterglow detection
  2. GRB 250625A: OHP/T193 optical detection
  3. GRB 250625A: COLIBRÍ optical observations
  4. GRB 250625A: Swift-XRT refined Analysis
  5. Swift GRB 250625A: Global MASTER-Net observations report
  6. GRB 250625A: NOT z-band upper limit
  7. GRB 250625A: SAO RAS possible optical afterglow
  8. GRB 250625A: Swift detection of a burst
  9. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  10. GRB 250620A: AstroSat CZTI detection
  11. GRB 250620C: AstroSat CZTI detection
  12. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  13. GRB 250521A: VZLUSAT-2 detection
  14. GRB 250617B: Swift-BAT refined analysis
  15. Konus-Wind detection of GRB 250620C
  16. IPN triangulation of GRB 250620C (long/bright)
  17. GRB 250506A - SVOM/ECLAIRs Refined analysis
  18. GRB 250617B: Nickel telescope optical observations
  19. GRB 250615A: Kilonova-Catcher optical upper limits
  20. GRB 250617B: Assy AZT-20 Optical Observations
  21. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  22. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  23. GRB 250617B: Swift/UVOT Detection
  24. GRB 250617B: Kilonova-Catcher optical afterglow detection
  25. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  26. GRB 250617B: COLIBRÍ optical observations
  27. GRB 250617B: Swift-XRT refined Analysis
  28. GRB 250617B: NUTTelA-TAO early time optical observations
  29. GRB 250617B: GOTO optical upper limit
  30. GRB 250615A: Swift-BAT refined analysis
  31. The EP-WXT trigger 01709178990 is likely a flaring star
  32. GRB 250617B: Ondrejov D50 optical afterglow detection
  33. GRB 250617B: SAO RAS optical observations
  34. GRB 250617B: Swift detection of a burst with an optical counterpart
  35. IPN triangulation of GRB 250612C (short/hard)
  36. EP#01709178975: Swift-XRT counterpart detection
  37. EP-WXT trigger 01709178975: GOTO optical upper limit
  38. Konus-Wind detection of GRB 250615A / EP250615a
  39. GRB 250615A / EP250615a: AstroSat CZTI detection
  40. GRB 250615A: COLIBRÍ optical upper limit
  41. GRB 250615A: DDOTI Optical Upper Limit
  42. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  43. GRB 250615A: Swift-XRT refined Analysis
  44. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  45. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  46. sb25061207: Mephisto optical upper limits
  47. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  48. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  49. sb25061218: Swift-XRT observations
  50. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  51. sb25061207: EP-FXT follow-up observation and afterglow candidate
  52. sb25061207: Swift-XRT observations
  53. EP250610a: Upper limit from Fermi-GBM Observations
  54. GRB 250610B - SVOM/ECLAIRs refined analysis
  55. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  56. EP250610A: Swift/UVOT Upper limits
  57. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  58. EP250610a: TNG NIR upper limit
  59. GRB 250610B: REM optical/NIR observations
  60. GRB 250610B: Swift-XRT counterpart detection
  61. GRB 250610B: GOTO optical upper limit
  62. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  63. GRB 250605A: Swift-BAT refined analysis
  64. EP250610a: REM optical/NIR observations
  65. GRBAlpha reentry on June 9, 2025
  66. EP250610a: Swift-XRT counterpart detection
  67. EP250610a: COLIBRÍ optical upper limit
  68. GRB 250605A: Swift/UVOT Upper Limits
  69. The EP-WXT trigger 01709178283 is likely a flaring star
  70. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  71. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  72. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  73. GRB 250605A: Swift-XRT refined Analysis
  74. EP/WXT 01709177873: GOTO observations confirm stellar variability
  75. GRB 250606A: Fermi GBM Final Real-time Localization
  76. GRB 250605A: Swift detection of a burst
  77. Konus-Wind detection of GRB 250601A
  78. IPN triangulation of GRB 250529A
  79. GRB 250601A: PRIME H band upper limit.
  80. GRB 250530A: SVOM/GRM analysis
  81. GRB 250601A: PRIME J band upper limit.
  82. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  83. GRB 250603A: Swift/UVOT Upper Limits
  84. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  85. GRB 250602A: DDOTI Optical Upper Limit
  86. GRB 250530C: Swift-BAT refined analysis
  87. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  88. EP#01709177494: Swift-XRT counterpart detection of known source
  89. GRB 250530C: BOOTES-7 optical upper limit
  90. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  91. GRB 250530C: Swift-XRT refined Analysis
  92. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  93. GRB 250530C: Swift detection of a burst
  94. GRB 250530A: Swift-XRT counterpart detection
  95. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  96. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  97. GRB 250530A: SVOM detection of a burst
  98. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  99. GRB 250527C: Swift/UVOT Upper Limits
  100. EP J1350.0-8622: EP-FXT follow-up observation

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