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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"

20960 results found.

  1. Fermi trigger No 772128434: Global MASTER-Net observations report
  2. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  3. GRB 250617B: Nickel telescope optical observations
  4. Fermi trigger No 772058337: Global MASTER-Net observations report
  5. GRB 250615A: Kilonova-Catcher optical upper limits
  6. GRB 250617B: Assy AZT-20 Optical Observations
  7. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  8. Fermi GRB 250617A: Global MASTER-Net observations report
  9. GRB 250615A/EP250615a: FTW optical and NIR observations
  10. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  11. GRB 250617B: Swift/UVOT Detection
  12. GRB 250617B: Kilonova-Catcher optical afterglow detection
  13. GRB 250617B: COLIBRÍ optical observations
  14. GRB 250617B: NOT NIR observations of the afterglow
  15. GRB 250617B: NUTTelA-TAO early time optical observations
  16. Fermi trigger No 771886893: Global MASTER-Net observations report
  17. Swift GRB 250617B: Global MASTER-Net observations report
  18. GRB 250617B: GOTO optical upper limit
  19. GRB 250617B: SAO RAS optical observations
  20. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  21. EP#01709178975: Swift-XRT counterpart detection
  22. EP-WXT trigger 01709178975: GOTO optical upper limit
  23. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  24. GRB 250615A: DDOTI Optical Upper Limit
  25. GRB 250615A: Swift/UVOT Upper Limits
  26. Fermi trigger No 771752663: Global MASTER-Net observations report
  27. Swift GRB 250615A: Global MASTER-Net observations report
  28. Fermi trigger No 771718064: Global MASTER-Net observations report
  29. sb25061207: Mephisto optical upper limits
  30. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  31. Fermi trigger No 771494087: Global MASTER-Net observations report
  32. sb25061218: Swift-XRT observations
  33. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  34. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  35. Fermi trigger No 771424081: Global MASTER-Net observations report
  36. EP250612a: Global MASTER-Net observations report
  37. sb25061207: Swift-XRT observations
  38. EP250612a/GRB 250612B: JinShan optical upper limit
  39. EP250610a: Upper limit from Fermi-GBM Observations
  40. GRB 250610B: Liverpool Telescope continued monitoring
  41. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  42. EP250610a: continuous follow-up observations with EP-FXT
  43. GRB 250610B - SVOM/ECLAIRs refined analysis
  44. Swift GRB250612.04: Global MASTER-Net observations report
  45. GRB 250610B: Swift/UVOT Detection
  46. EP250610A: Swift/UVOT Upper limits
  47. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  48. GRB 250610B: REM optical/NIR observations
  49. GRB 250610B: SVOM/VT optical shallow decay
  50. GRB 250610B: additional Liverpool Telescope optical observations
  51. GRB 250610B: Swift-XRT counterpart detection
  52. GRB 250610B: LT detection of the optical counterpart
  53. GRB 250610B: GOTO optical upper limit
  54. EP250610a: Global MASTER-Net observations report
  55. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  56. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  57. EP250610a: REM optical/NIR observations
  58. EP250610a: Swift-XRT counterpart detection
  59. EP250610a: COLIBRÍ optical upper limit
  60. Fermi trigger No 771072240: Global MASTER-Net observations report
  61. GRB 250605A: Swift/UVOT Upper Limits
  62. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  63. GRB 250527C: CrAO Optical Upper Limit
  64. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  65. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  66. GRB 250605A: SVOM/VT optical upper limit
  67. EP/WXT 01709177873: GOTO observations confirm stellar variability
  68. Fermi GRB 250606A: Global MASTER-Net observations report
  69. Fermi trigger No 770867684: Global MASTER-Net observations report
  70. GRB 250605A: LT optical observations
  71. Swift GRB250605.79: Global MASTER-Net observations report
  72. GRB 250601A: PRIME H band upper limit.
  73. GRB 250530A: SVOM/GRM analysis
  74. GRB 250601A: PRIME J band upper limit.
  75. GRB 250601A: VLT/FORS2 Optical Observation
  76. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  77. GRB 250603A: Swift/UVOT Upper Limits
  78. Fermi trigger No 770638414: Global MASTER-Net observations report
  79. Swift GRB250603.05: Global MASTER-Net observations report
  80. GRB 250602A: DDOTI Optical Upper Limit
  81. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  82. GRB 250601A: Swift/XRT candidate afterglow
  83. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  84. GRB 250601A: Swift-XRT observations
  85. Fermi GRB 250601A: Global MASTER-Net observations report
  86. Fermi trigger No 770470765: Global MASTER-Net observations report
  87. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  88. GRB 250601A: Swift ToO observations
  89. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  90. EP#01709177494: SVOM/VT optical observations
  91. Fermi GRB 250531A: Global MASTER-Net observations report
  92. EP#01709177494: Swift-XRT counterpart detection of known source
  93. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  94. Swift GRB 250530C: Global MASTER-Net observations report
  95. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  96. GRB 250530A: SVOM/VT optical upper limit
  97. GRB 250530A: Swift-XRT counterpart detection
  98. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  99. GRB 250527C: Swift/UVOT Upper Limits
  100. GRB 250527B: Swift-XRT observations

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