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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"

20355 results found.

  1. GRB 250620A: SVOM/GRM observation of a short burst
  2. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  3. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  4. GRB 250506A - SVOM/ECLAIRs Refined analysis
  5. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  6. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  7. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  8. GRB 250617B: Nickel telescope optical observations
  9. GRB 250615A: Kilonova-Catcher optical upper limits
  10. GRB 250617B: Assy AZT-20 Optical Observations
  11. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  12. GRB 250617B: Swift/UVOT Detection
  13. GRB 250617B: Kilonova-Catcher optical afterglow detection
  14. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  15. GRB 250617B: COLIBRÍ optical observations
  16. GRB 250617B: NOT NIR observations of the afterglow
  17. GRB 250617B: NUTTelA-TAO early time optical observations
  18. GRB 250617B: Enhanced Swift-XRT position
  19. GRB 250617B: SAO RAS optical observations
  20. GRB 250617B: Swift detection of a burst with an optical counterpart
  21. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  22. EP-WXT trigger 01709178975: GOTO optical upper limit
  23. Konus-Wind detection of GRB 250615A / EP250615a
  24. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  25. GRB 250615A: COLIBRÍ optical upper limit
  26. GRB 250615A: DDOTI Optical Upper Limit
  27. GRB 250615A: Swift/UVOT Upper Limits
  28. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  29. GRB 250615A: Swift-XRT refined Analysis
  30. sb25061207/SVOM: T120 OHP optical upper limit
  31. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  32. GRB 250615A: Enhanced Swift-XRT position
  33. GRB 250615A: Swift detection of a burst
  34. GRID detection of GRB 250612C
  35. sb25061207: Mephisto optical upper limits
  36. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  37. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  38. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  39. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  40. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  41. EP250612a: SVOM/VT optical candidate
  42. GRB 250612C: Fermi GBM Observation
  43. sb25061207: Swift-XRT observations
  44. EP250612a/GRB 250612B: JinShan optical upper limit
  45. sb25061207: SVOM/VT optical counterpart
  46. GRB 250610B: Swift-XRT refined Analysis
  47. EP250612a: Einstein Probe detection of an X-ray transient
  48. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  49. sb25061207: SVOM detection of a X-ray transient
  50. GRB 250610B - SVOM/ECLAIRs refined analysis
  51. Swift GRB250612.04: Global MASTER-Net observations report
  52. GRB 250610B: Swift/UVOT Detection
  53. EP250610A: Swift/UVOT Upper limits
  54. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  55. EP250610a: TNG NIR upper limit
  56. GRB 250610B: REM optical/NIR observations
  57. EP250610a: Liverpool Telescope optical upper limits
  58. GRB 250610B: additional Liverpool Telescope optical observations
  59. GRB 250610B: SVOM/VT optical counterpart
  60. GRB 250610B: OHP/T120 optical counterpart candidate
  61. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  62. GRB 250610B: SVOM detection of a long burst
  63. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  64. EP250610a: SVOM/VT optical upper limit
  65. EP250610a: REM optical/NIR observations
  66. GRB 250609A: Fermi GBM Observation
  67. GRBAlpha reentry on June 9, 2025
  68. EP250610a: COLIBRÍ optical upper limit
  69. EP250610a: Einstein Probe detection of an X-ray transient
  70. Fermi trigger No 771072240: Global MASTER-Net observations report
  71. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  72. GRB 250605A: Swift/UVOT Upper Limits
  73. GRB 250527C: CrAO Optical Upper Limit
  74. GRB 250607A: SVOM/GRM observation of a long burst
  75. The EP-WXT trigger 01709178244 is likely a flaring star
  76. The EP-WXT trigger 01709178069 is likely a flaring star
  77. GRB 250605A: Enhanced Swift-XRT position
  78. GRB 250605A: Swift detection of a burst
  79. IPN triangulation of GRB 250404B
  80. IPN triangulation of GRB 250529A
  81. GRB 250601A: PRIME H band upper limit.
  82. GRB 250601A: PRIME J band upper limit.
  83. GRB 250601A: VLT/FORS2 Optical Observation
  84. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  85. GRB 250603A: Swift/UVOT Upper Limits
  86. GRB 250603A: Swift-XRT refined Analysis
  87. GRB 250603A: Enhanced Swift-XRT position
  88. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  89. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  90. GRB 250602A: DDOTI Optical Upper Limit
  91. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  92. EP#01709177494: SVOM/VT optical observations
  93. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  94. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  95. GRB 250530C: Enhanced Swift-XRT position
  96. GRB 250530C: Swift detection of a burst
  97. GRB 250530A: SVOM/VT optical upper limit
  98. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  99. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  100. GRB 250530A: SVOM detection of a burst

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