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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"

35258 results found.

  1. GRB 250322A: NOT optical upper limits
  2. GRB 250322A: Enhanced Swift-XRT position
  3. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  4. GRB 250322A: MASTER optical observation
  5. EP250321a: Mondy AZT-33IK Optical Observations
  6. GRB 250322A: Swift detection of a short burst
  7. EP250321a: KAIT optical observations
  8. GRB 250225B: GECAM-A detection
  9. GRB 250312A: GECAM-A detection
  10. GRB 250321B: Swift ToO observations
  11. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  12. GRB 250321C: Fermi GBM Final Real-time Localization
  13. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  14. GRB 250320B: Fermi GBM Observation
  15. GRB 250321A: Swift-BAT refined analysis
  16. GRB 250321A: Swift-XRT refined Analysis
  17. GRB 250320B: Fermi-LAT detection
  18. GRB 250321B: SVOM detection of a sub-threshold transient event
  19. EP 250321A: Optical counterpart detection by LCO.
  20. GRB 250321A: Swift/UVOT Upper Limits
  21. GRB 250320B: SVOM/GRM observation of a long burst
  22. GRB 250320B: AstroSat CZTI detection
  23. Fermi GRB 250320B: Global MASTER-Net observations report
  24. Swift GRB 250321A: Global MASTER-Net observations report
  25. Fermi GRB 250321A: Global MASTER-Net observations report
  26. GRB 250321A: GOTO optical upper limits
  27. GRB 250321A: Swift-XRT localisation
  28. GRB 250314A: Keck/NIRC2 J-band upper limit
  29. EP250226a/GRB 250226A: KAIT optical observations
  30. GRB 250321A: Fermi GBM Observation
  31. GRB 250321A: Swift detection of a burst
  32. GRB 250321A: Fermi GBM Final Real-time Localization
  33. GRB 250320B: Fermi GBM Final Real-time Localization
  34. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  35. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  36. GRB 250320A: Fermi GBM Final Real-time Localization
  37. Fermi GRB 250319B: Global MASTER-Net observations report
  38. GRB 250313A: GRBAlpha detection
  39. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  40. GRB 250319B: Fermi GBM Final Localization
  41. GRB 250319A: Fermi GBM Final Localization
  42. GRB 250317D: EIRSAT-1 GMOD Detection
  43. GRB 250314A: ATCA radio upper limits
  44. GRB 250317B: OHP/T193 continued follow-up
  45. GRB 250317C: SVOM/GRM observation of a long burst
  46. GRB 250317B: Leavitt Observatory optical upper limit
  47. GRB 250309B/AT2025dws: further ATCA observations
  48. GRB 250317B: Mondy AZT-33IK Optical Observations
  49. GRB 250317C: AstroSat CZTI detection
  50. GRB 250317B: NOT optical observations suggest an optical plateau phase
  51. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  52. GRB 250317C: GECAM-B detection
  53. GRB 250317B: OHP/T193 optical observations
  54. GRB250312A: Swift/UVOT Upper Limits
  55. GRB 250317B: REM optical/NIR observations
  56. GRB 250317B: Swift-XRT observations
  57. GRB 250316A: Swift/UVOT Upper Limits
  58. GRB 250314A: REM optical/NIR upper limits
  59. GRB 250316A: AbAO AS-32 Optical Upper Limit
  60. EP 250317B: Fading optical counterpart detection by LCO
  61. GRB 250316A: Swift-XRT afterglow detection
  62. GRB 250317B: LCO detection of the fading optical afterglow
  63. GRB 250317B: refined SVOM/MXT analysis
  64. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  65. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  66. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  67. GRB 250317B: SVOM detection of a burst
  68. GRB 250316A: Fermi GBM Observation
  69. GRB 250316A: Swift-XRT observations
  70. GRB 250317A: Fermi GBM Final Real-time Localization
  71. Fermi GRB 250316A: Global MASTER-Net observations report
  72. GRB 250314A: SVOM/GRM analysis
  73. GRB 250316A: Swift ToO observations
  74. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  75. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  76. GRB 250316A: Fermi GBM Final Real-time Localization
  77. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  78. GRB 250314A: EP-FXT afterglow detection
  79. GRB 250314A: Swift/UVOT Upper Limits
  80. GRB 250312B: GRBAlpha detection
  81. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  82. GRB 250314A: Swift XRT Detection
  83. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  84. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  85. SVOM/MXT upper limit on GRB 250314A
  86. GRB 250314A: SVOM/VT upper limit
  87. GRB 250314A: NOT near-infrared candidate counterpart
  88. GRB 250313A: Fermi GBM Detection
  89. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  90. GRB 250312B: Fermi GBM Observation
  91. GRB 250313A: Swift-XRT observations
  92. Konus-Wind detection of GRB 250313A
  93. Konus-Wind detection of GRB 250308A
  94. GRB 250314A: SVOM detection of a burst
  95. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  96. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  97. GRB 250313A: SVOM/GRM observation of a bright long burst
  98. GRB 250313A: AstroSat CZTI detection of a bright long burst
  99. GRB 250313A: Fermi-LAT detection
  100. GRB 250313A: Swift ToO observations

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