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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"

16159 results found.

  1. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  2. GRB 250706B: Swift/UVOT Detection
  3. GRB 250702F: GRANDMA observations
  4. GRB 250706B: refined SVOM/MXT data analysis
  5. GRB 250706A: Swift/UVOT Upper Limits
  6. GRB 250706B: REM optical observations
  7. GRB 250706A: REM optical/NIR observations
  8. IceCube-250416A: DDOTI Optical Upper Limit
  9. IceCube-250706A: COLIBRÍ optical upper limits
  10. GRB 250706A: JinShan optical upper limits
  11. GRB 250706A: SAO RAS optical observations
  12. EP250704A: NOWT Detection
  13. GRB250706B: Swift-XRT counterpart detection
  14. GRB 250706B: iTelescope optical observations
  15. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  16. GRB 250706B: SVOM/VT optical observation
  17. GRB 250706B: TRT bright optical counterpart detection
  18. GRB 250706A: GROWTH-India Telescope optical upper limit
  19. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  20. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  21. GRB 250704B: Swift/UVOT Upper Limits
  22. GRB 250704A: Swift/UVOT Detection
  23. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  24. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  25. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  26. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  27. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  28. GRB 250702F: Kilonova-Catcher optical afterglow detection
  29. GRB 250702F: Monte Agliale Observatory optical observations
  30. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  31. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  32. EP250704a / GRB 250704B: JinShan optical observations
  33. GRB 250704A: SVOM/VT optical observation
  34. EP250704a / GRB 250704B: SAO RAS optical observations
  35. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  36. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  37. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  38. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  39. EP 250704a: BOOTES-5 optical detection
  40. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  41. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  42. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  43. EP250704a / GRB250704B: Swift-XRT counterpart detection
  44. GRB 250702B / EP2050702a: FTW optical and NIR observations
  45. EP250704a / GRB 250704B - REM observations
  46. GRB 250702F: GROWTH-India Telescope optical observations
  47. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  48. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  49. EP250702a: WFST optical observations
  50. EP250704a: COLIBRÍ optical counterpart candidate
  51. GRB 250702F: optical photometry from Konkoly
  52. GRB 250704A: REM detection of the optical afterglow
  53. GRB 250702F: SVOM/VT optical observation
  54. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  55. GRB 250702F: Leavitt Observatory optical observations
  56. GRB 250702F: AKO Optical Afterglow Detection
  57. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  58. GRB 250702F: Skynet Optical Observations
  59. GRB 250424A: VIRT Optical Upper Limit
  60. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  61. GRB 250702F: TRT Optical Observation
  62. GRB 250703A: DDOTI Optical Upper Limit
  63. GRB 250702F: REM optical afterglow detection
  64. GRB 250702F: DDOTI Optical Observation
  65. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  66. GRB 250702F: COLIBRÍ Observations of the Afterglow
  67. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  68. GRB 250702F: NOT observations of the optical afterglow
  69. GRB 250702F: MASTER optical afterglow observation
  70. GRB 250702F: GOTO optical counterpart detection
  71. GRB 250702F: Ondrejov D50 optical afterglow detection
  72. GRB 250702F: Swift detection of a burst with an optical counterpart
  73. GRB 250628B: SVOM/VT optical upper limit
  74. GRB 250628A: REM optical/NIR upper limits
  75. GRB 250628B: SVOM detection of a long burst
  76. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  77. GRB 250628A: Swift/UVOT Upper Limits
  78. GRB 250625A: Leavitt Observatory afterglow detection
  79. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  80. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  81. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  82. GRB 250625A: SVOM/C-GFT upper limit in early phase
  83. GRB 250625A: Swift/UVOT Upper Limits
  84. GRB 250625A: ABObservatory afterglow detection
  85. GRB 250625A: OHP/T193 optical detection
  86. GRB 250625A: COLIBRÍ optical observations
  87. GRB 250625A: JinShan optical observations
  88. GRB 250625A: NOT z-band upper limit
  89. GRB 250625A: SVOM/VT optical confirmation
  90. GRB 250625A: SAO RAS possible optical afterglow
  91. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  92. GRB 241018A: Maidanak optical observations
  93. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  94. GRB 250620C: SVOM/GRM observation
  95. GRB 250620A: SVOM/GRM observation of a short burst
  96. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  97. GRB 250617B: Nickel telescope optical observations
  98. GRB 250615A: Kilonova-Catcher optical upper limits
  99. GRB 250617B: Assy AZT-20 Optical Observations
  100. GRB 250615A/EP250615a: FTW optical and NIR observations

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