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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"

36317 results found.

  1. GRB 250327B: 1.6m Mephisto optical observations
  2. GRB 250327B: NOT spectroscopic redshift z = 3.035
  3. GRB 250327A: Swift-XRT refined Analysis
  4. GRB 250327B: GOTO optical counterpart detection
  5. GRB 250327B: SVOM/VT optically bright counterpart
  6. GRB 250327B: SAO RAS optical candidate
  7. GRB 250327B: SVOM detection of a burst
  8. GRB 250327A: J-band observations with WINTER
  9. GRB 250327A: SVOM/VT optical candidate
  10. GRB 250327A: Fermi GBM observation
  11. Fermi GRB 250327A: Global MASTER-Net observations report
  12. Swift GRB 250327A: Global MASTER-Net observations report
  13. GRB 250327A: DDOTI Optical Observations
  14. GRB 250327A: COLIBRÍ optical upper limit
  15. GRB 250327A: Swift detection of a burst
  16. GRB 250327A: Fermi GBM Final Real-time Localization
  17. Konus-Wind detection of GRB 250322A (short)
  18. IPN triangulation of GRB 250322B
  19. EP250321a: Mondy AZT-33IK Continued Optical Observations
  20. GRB 250322A: third epoch of NOT optical observations
  21. GRB 250322A: Swift-BAT refined analysis
  22. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  23. GRB 250322A: further NOT optical observations
  24. GRB 250322A: Swift/UVOT Upper Limits
  25. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  26. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  27. GRB 250321B: Swift-XRT observations
  28. GRB 250322A: Swift-XRT refined Analysis
  29. GRB 250322A: Gemini-North redshift of candidate host galaxy
  30. GRB 250322A: AstroSat CZTI detection of a short burst
  31. GRB 250322B: AstroSat CZTI detection of a bright long burst
  32. GRB250322A: STEP/T80S optical limits
  33. GRB 250322A: Gemini-South optical observations
  34. GRB 250322A: VLT optical observations
  35. GRB 250322A: VLT near-infrared observations
  36. GRB 250322A: NOT optical upper limits
  37. GRB 250322A: Enhanced Swift-XRT position
  38. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  39. GRB 250322A: MASTER optical observation
  40. EP250321a: Mondy AZT-33IK Optical Observations
  41. GRB 250322A: Swift detection of a short burst
  42. EP250321a: KAIT optical observations
  43. GRB 250225B: GECAM-A detection
  44. GRB 250312A: GECAM-A detection
  45. GRB 250321B: Swift ToO observations
  46. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  47. GRB 250321C: Fermi GBM Final Real-time Localization
  48. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  49. GRB 250320B: Fermi GBM Observation
  50. GRB 250321A: Swift-BAT refined analysis
  51. GRB 250321A: Swift-XRT refined Analysis
  52. GRB 250320B: Fermi-LAT detection
  53. GRB 250321B: SVOM detection of a sub-threshold transient event
  54. EP 250321A: Optical counterpart detection by LCO.
  55. GRB 250321A: Swift/UVOT Upper Limits
  56. GRB 250320B: SVOM/GRM observation of a long burst
  57. GRB 250320B: AstroSat CZTI detection
  58. Fermi GRB 250320B: Global MASTER-Net observations report
  59. Swift GRB 250321A: Global MASTER-Net observations report
  60. Fermi GRB 250321A: Global MASTER-Net observations report
  61. GRB 250321A: GOTO optical upper limits
  62. GRB 250321A: Swift-XRT localisation
  63. GRB 250314A: Keck/NIRC2 J-band upper limit
  64. EP250226a/GRB 250226A: KAIT optical observations
  65. GRB 250321A: Fermi GBM Observation
  66. GRB 250321A: Swift detection of a burst
  67. GRB 250321A: Fermi GBM Final Real-time Localization
  68. GRB 250320B: Fermi GBM Final Real-time Localization
  69. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  70. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  71. GRB 250320A: Fermi GBM Final Real-time Localization
  72. Fermi GRB 250319B: Global MASTER-Net observations report
  73. GRB 250313A: GRBAlpha detection
  74. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  75. GRB 250319B: Fermi GBM Final Localization
  76. GRB 250319A: Fermi GBM Final Localization
  77. GRB 250317D: EIRSAT-1 GMOD Detection
  78. GRB 250314A: ATCA radio upper limits
  79. GRB 250317B: OHP/T193 continued follow-up
  80. GRB 250317C: SVOM/GRM observation of a long burst
  81. GRB 250317B: Leavitt Observatory optical upper limit
  82. GRB 250309B/AT2025dws: further ATCA observations
  83. GRB 250317B: Mondy AZT-33IK Optical Observations
  84. GRB 250317C: AstroSat CZTI detection
  85. GRB 250317B: NOT optical observations suggest an optical plateau phase
  86. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  87. GRB 250317C: GECAM-B detection
  88. GRB 250317B: OHP/T193 optical observations
  89. GRB250312A: Swift/UVOT Upper Limits
  90. GRB 250317B: REM optical/NIR observations
  91. GRB 250317B: Swift-XRT observations
  92. GRB 250316A: Swift/UVOT Upper Limits
  93. GRB 250314A: REM optical/NIR upper limits
  94. GRB 250316A: AbAO AS-32 Optical Upper Limit
  95. EP 250317B: Fading optical counterpart detection by LCO
  96. GRB 250316A: Swift-XRT afterglow detection
  97. GRB 250317B: LCO detection of the fading optical afterglow
  98. GRB 250317B: refined SVOM/MXT analysis
  99. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  100. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart

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