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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

21855 results found.

  1. GRB 250702F: Skynet Optical Observations
  2. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  3. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  4. GRB 250702F: TRT Optical Observation
  5. GRB 250703A: DDOTI Optical Upper Limit
  6. GRB 250702F: REM optical afterglow detection
  7. EP250702a: Global MASTER-Net observations report
  8. GRB 250702F: DDOTI Optical Observation
  9. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  10. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  11. GRB 250702F: COLIBRÍ Observations of the Afterglow
  12. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  13. Fermi GRB 250702E: Global MASTER-Net observations report
  14. Fermi GRB 250702B: Global MASTER-Net observations report
  15. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  16. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  17. GRB 250702F: NOT observations of the optical afterglow
  18. Fermi GRB 250702F: Global MASTER-Net observations report
  19. Fermi GRB 250702C: Global MASTER-Net observations report
  20. GRB 250702F: GOTO optical counterpart detection
  21. GRB 250702F: Ondrejov D50 optical afterglow detection
  22. Swift GRB 250702F: Global MASTER-Net observations report
  23. GRB 250628B: Swift-XRT observations
  24. GRB 250628B: SVOM/VT optical upper limit
  25. GRB 250628A: REM optical/NIR upper limits
  26. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  27. GRB 250628A: Swift/UVOT Upper Limits
  28. Fermi GRB 250626A: Global MASTER-Net observations report
  29. Swift GRB 250628A: Global MASTER-Net observations report
  30. GRB 250625A: Leavitt Observatory afterglow detection
  31. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  32. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  33. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  34. GRB 250625A: SVOM/C-GFT upper limit in early phase
  35. GRB 250625A: Swift/UVOT Upper Limits
  36. GRB 250625A: ABObservatory afterglow detection
  37. GRB 250625A: OHP/T193 optical detection
  38. GRB 250625A: COLIBRÍ optical observations
  39. GRB 250625A: JinShan optical observations
  40. Swift GRB 250625A: Global MASTER-Net observations report
  41. GRB 250625A: SAO RAS possible optical afterglow
  42. Fermi GRB 250625A: Global MASTER-Net observations report
  43. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  44. GRB 241018A: Maidanak optical observations
  45. Fermi GRB 250624A: Global MASTER-Net observations report
  46. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  47. Fermi GRB 250623A: Global MASTER-Net observations report
  48. Fermi trigger No 772190032: Global MASTER-Net observations report
  49. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  50. Fermi GRB 250621A: Global MASTER-Net observations report
  51. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  52. GRB 250506A - SVOM/ECLAIRs Refined analysis
  53. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  54. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  55. Fermi trigger No 772128434: Global MASTER-Net observations report
  56. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  57. GRB 250617B: Nickel telescope optical observations
  58. Fermi trigger No 772058337: Global MASTER-Net observations report
  59. GRB 250615A: Kilonova-Catcher optical upper limits
  60. GRB 250617B: Assy AZT-20 Optical Observations
  61. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  62. Fermi GRB 250617A: Global MASTER-Net observations report
  63. GRB 250615A/EP250615a: FTW optical and NIR observations
  64. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  65. GRB 250617B: Swift/UVOT Detection
  66. GRB 250617B: Kilonova-Catcher optical afterglow detection
  67. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  68. GRB 250617B: COLIBRÍ optical observations
  69. GRB 250617B: NOT NIR observations of the afterglow
  70. GRB 250617B: NUTTelA-TAO early time optical observations
  71. Fermi trigger No 771886893: Global MASTER-Net observations report
  72. Swift GRB 250617B: Global MASTER-Net observations report
  73. GRB 250617B: GOTO optical upper limit
  74. GRB 250617B: SAO RAS optical observations
  75. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  76. EP#01709178975: Swift-XRT counterpart detection
  77. EP-WXT trigger 01709178975: GOTO optical upper limit
  78. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  79. GRB 250615A: DDOTI Optical Upper Limit
  80. GRB 250615A: Swift/UVOT Upper Limits
  81. Fermi trigger No 771752663: Global MASTER-Net observations report
  82. Swift GRB 250615A: Global MASTER-Net observations report
  83. Fermi trigger No 771718064: Global MASTER-Net observations report
  84. sb25061207: Mephisto optical upper limits
  85. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  86. Fermi trigger No 771494087: Global MASTER-Net observations report
  87. sb25061218: Swift-XRT observations
  88. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  89. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  90. Fermi trigger No 771424081: Global MASTER-Net observations report
  91. EP250612a: Global MASTER-Net observations report
  92. sb25061207: Swift-XRT observations
  93. EP250612a/GRB 250612B: JinShan optical upper limit
  94. EP250610a: Upper limit from Fermi-GBM Observations
  95. GRB 250610B: Liverpool Telescope continued monitoring
  96. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  97. EP250610a: continuous follow-up observations with EP-FXT
  98. GRB 250610B - SVOM/ECLAIRs refined analysis
  99. Swift GRB250612.04: Global MASTER-Net observations report
  100. Fermi GBM Sub-Threshold Detection of GRB 250610B

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