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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"

20960 results found.

  1. GRB 250706B: REM optical observations
  2. GRB 250706A: REM optical/NIR observations
  3. IceCube-250416A: DDOTI Optical Upper Limit
  4. IceCube-250706A: COLIBRÍ optical upper limits
  5. Swift GRB 250706A: Global MASTER-Net observations report
  6. GRB 250706A: JinShan optical upper limits
  7. GRB 250706A: SAO RAS optical observations
  8. EP250704A: NOWT Detection
  9. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  10. GRB250706B: Swift-XRT counterpart detection
  11. GRB 250706B: iTelescope optical observations
  12. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  13. GRB 250706B: TRT bright optical counterpart detection
  14. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  15. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  16. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  17. GRB 250704B: Swift/UVOT Upper Limits
  18. GRB 250704A: Swift/UVOT Detection
  19. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  20. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  21. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  22. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  23. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  24. GRB 250702F: Kilonova-Catcher optical afterglow detection
  25. GRB 250702F: Monte Agliale Observatory optical observations
  26. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  27. EP250704a / GRB 250704B: JinShan optical observations
  28. EP250704a / GRB 250704B: SAO RAS optical observations
  29. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  30. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  31. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  32. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  33. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  34. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  35. EP250704a / GRB250704B: Swift-XRT counterpart detection
  36. GRB 250702B / EP2050702a: FTW optical and NIR observations
  37. EP250704a / GRB 250704B - REM observations
  38. GRB 250702F: GROWTH-India Telescope optical observations
  39. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  40. EP250702a: WFST optical observations
  41. EP250704a: COLIBRÍ optical counterpart candidate
  42. GRB 250702F: optical photometry from Konkoly
  43. GRB 250704A: REM detection of the optical afterglow
  44. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  45. GRB 250702F: Swift/UVOT Detection
  46. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  47. Fermi GRB 250703A: Global MASTER-Net observations report
  48. GRB 250702F: Leavitt Observatory optical observations
  49. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  50. GRB 250702F: Skynet Optical Observations
  51. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  52. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  53. GRB 250702F: TRT Optical Observation
  54. GRB 250703A: DDOTI Optical Upper Limit
  55. GRB 250702F: REM optical afterglow detection
  56. EP250702a: Global MASTER-Net observations report
  57. GRB 250702F: DDOTI Optical Observation
  58. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  59. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  60. GRB 250702F: COLIBRÍ Observations of the Afterglow
  61. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  62. Fermi GRB 250702E: Global MASTER-Net observations report
  63. Fermi GRB 250702B: Global MASTER-Net observations report
  64. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  65. GRB 250702F: NOT observations of the optical afterglow
  66. GRB 250702F: MASTER optical afterglow observation
  67. Fermi GRB 250702F: Global MASTER-Net observations report
  68. Fermi GRB 250702C: Global MASTER-Net observations report
  69. GRB 250702F: GOTO optical counterpart detection
  70. GRB 250702F: Ondrejov D50 optical afterglow detection
  71. Swift GRB 250702F: Global MASTER-Net observations report
  72. GRB 250628B: Swift-XRT observations
  73. GRB 250628B: SVOM/VT optical upper limit
  74. GRB 250628A: REM optical/NIR upper limits
  75. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  76. GRB 250628A: Swift/UVOT Upper Limits
  77. Fermi GRB 250626A: Global MASTER-Net observations report
  78. Swift GRB 250628A: Global MASTER-Net observations report
  79. GRB 250625A: Leavitt Observatory afterglow detection
  80. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  81. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  82. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  83. GRB 250625A: SVOM/C-GFT upper limit in early phase
  84. GRB 250625A: Swift/UVOT Upper Limits
  85. GRB 250625A: ABObservatory afterglow detection
  86. GRB 250625A: OHP/T193 optical detection
  87. GRB 250625A: COLIBRÍ optical observations
  88. GRB 250625A: JinShan optical observations
  89. Swift GRB 250625A: Global MASTER-Net observations report
  90. GRB 250625A: SAO RAS possible optical afterglow
  91. Fermi GRB 250625A: Global MASTER-Net observations report
  92. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  93. GRB 241018A: Maidanak optical observations
  94. Fermi GRB 250624A: Global MASTER-Net observations report
  95. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  96. Fermi GRB 250623A: Global MASTER-Net observations report
  97. Fermi trigger No 772190032: Global MASTER-Net observations report
  98. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  99. Fermi GRB 250621A: Global MASTER-Net observations report
  100. GRB 250506A - SVOM/ECLAIRs Refined analysis

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