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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"

15683 results found.

  1. GRB 250713A: SVOM/VT optical upper limit
  2. GRB 250713A: NOT optical upper limits
  3. GRB 250706B/C: 7DT Follow-up Observations
  4. EP250711a: COLIBRÍ continuous optical observations
  5. GRB 250713A: JinShan optical upper limits
  6. GRB 250711A: DDOTI Optical Upper Limit
  7. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  8. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  9. GRB 250711A: SVOM/GRM observation
  10. EP250711a: NOT optical counterpart candidate
  11. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  12. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  13. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  14. EP/WXT 01709181970: GOTO observations confirm stellar variability
  15. EP250704a/GRB 250704B: 10 GHz VLA detection
  16. IceCube-250706A: No Candidates from WINTER
  17. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  18. GRB 250704B / EP250704a: VLA radio detection
  19. EP250704a/GRB250704B : HCT optical and NIR upper limits
  20. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  21. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  22. GRB 250702F: radio detection with the VLA
  23. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  24. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  25. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  26. GRB 250706B: Swift/UVOT Detection
  27. GRB 250702F: GRANDMA observations
  28. GRB 250706B: refined SVOM/MXT data analysis
  29. GRB 250706A: Swift/UVOT Upper Limits
  30. GRB 250706B: REM optical observations
  31. GRB 250706A: REM optical/NIR observations
  32. IceCube-250416A: DDOTI Optical Upper Limit
  33. IceCube-250706A: COLIBRÍ optical upper limits
  34. GRB 250706A: JinShan optical upper limits
  35. GRB 250706A: SAO RAS optical observations
  36. EP250704A: NOWT Detection
  37. GRB250706B: Swift-XRT counterpart detection
  38. GRB 250706B: iTelescope optical observations
  39. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  40. GRB 250706B: SVOM/VT optical observation
  41. GRB 250706B: TRT bright optical counterpart detection
  42. GRB 250706A: GROWTH-India Telescope optical upper limit
  43. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  44. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  45. GRB 250704B: Swift/UVOT Upper Limits
  46. GRB 250704A: Swift/UVOT Detection
  47. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  48. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  49. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  50. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  51. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  52. GRB 250702F: Kilonova-Catcher optical afterglow detection
  53. GRB 250702F: Monte Agliale Observatory optical observations
  54. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  55. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  56. EP250704a / GRB 250704B: JinShan optical observations
  57. GRB 250704A: SVOM/VT optical observation
  58. EP250704a / GRB 250704B: SAO RAS optical observations
  59. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  60. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  61. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  62. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  63. EP 250704a: BOOTES-5 optical detection
  64. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  65. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  66. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  67. EP250704a / GRB250704B: Swift-XRT counterpart detection
  68. GRB 250702B / EP2050702a: FTW optical and NIR observations
  69. EP250704a / GRB 250704B - REM observations
  70. GRB 250702F: GROWTH-India Telescope optical observations
  71. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  72. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  73. EP250702a: WFST optical observations
  74. EP250704a: COLIBRÍ optical counterpart candidate
  75. GRB 250702F: optical photometry from Konkoly
  76. GRB 250704A: REM detection of the optical afterglow
  77. GRB 250702F: SVOM/VT optical observation
  78. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  79. GRB 250702F: Leavitt Observatory optical observations
  80. GRB 250702F: AKO Optical Afterglow Detection
  81. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  82. GRB 250702F: Skynet Optical Observations
  83. GRB 250424A: VIRT Optical Upper Limit
  84. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  85. GRB 250702F: TRT Optical Observation
  86. GRB 250703A: DDOTI Optical Upper Limit
  87. GRB 250702F: REM optical afterglow detection
  88. GRB 250702F: DDOTI Optical Observation
  89. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  90. GRB 250702F: COLIBRÍ Observations of the Afterglow
  91. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  92. GRB 250702F: NOT observations of the optical afterglow
  93. GRB 250702F: MASTER optical afterglow observation
  94. GRB 250702F: GOTO optical counterpart detection
  95. GRB 250702F: Ondrejov D50 optical afterglow detection
  96. GRB 250702F: Swift detection of a burst with an optical counterpart
  97. GRB 250628B: SVOM/VT optical upper limit
  98. GRB 250628A: REM optical/NIR upper limits
  99. GRB 250628B: SVOM detection of a long burst
  100. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position

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