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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"

26120 results found.

  1. GRB 250327B: CrAO and SAO RAS Optical Observations
  2. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  3. GRB 250322A: GRANDMA/TNOT optical upper limits
  4. GRB 250327A: SVOM/VT upper limits on the XRT position
  5. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  6. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  7. GRB 250327B: 1.6m Mephisto optical observations
  8. GRB 250327B: NOT spectroscopic redshift z = 3.035
  9. GRB 250327A: Swift-XRT refined Analysis
  10. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  11. GRB 250327A: J-band observations with WINTER
  12. GRB 250327A: SVOM/VT optical candidate
  13. GRB 250327A: Fermi GBM observation
  14. Swift GRB 250327A: Global MASTER-Net observations report
  15. GRB 250327A: DDOTI Optical Observations
  16. GRB 250327A: COLIBRÍ optical upper limit
  17. GRB 250327A: Swift detection of a burst
  18. Konus-Wind detection of GRB 250322A (short)
  19. IPN triangulation of GRB 250322B
  20. EP250321a: Mondy AZT-33IK Continued Optical Observations
  21. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  22. GRB 250322A: Swift-BAT refined analysis
  23. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  24. GRB 250322A: further NOT optical observations
  25. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  26. GRB 250322A: Swift/UVOT Upper Limits
  27. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  28. GRB 250321B: Swift-XRT observations
  29. GRB 250322A: Swift-XRT refined Analysis
  30. EP250321a: TNOT Observation of Optical Counterpart
  31. GRB 250322A: Gemini-North redshift of candidate host galaxy
  32. GRB 250322A: AstroSat CZTI detection of a short burst
  33. GRB250322A: STEP/T80S optical limits
  34. GRB 250322A: Gemini-South optical observations
  35. GRB 250322A: VLT optical observations
  36. GRB 250322A: VLT near-infrared observations
  37. GRB 250322A: NOT optical upper limits
  38. GRB 250322A: Enhanced Swift-XRT position
  39. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  40. GRB 250322A: MASTER optical observation
  41. EP250321a: Mondy AZT-33IK Optical Observations
  42. GRB 250322A: Swift detection of a short burst
  43. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  44. EP250321a: KAIT optical observations
  45. GRB 250225B: GECAM-A detection
  46. GRB 250312A: GECAM-A detection
  47. GRB 250321B: Swift ToO observations
  48. EP250321a: WFST optical observations
  49. GRB 250321A: Swift-BAT refined analysis
  50. GRB 250321A: Swift-XRT refined Analysis
  51. GRB 250320B: Fermi-LAT detection
  52. GRB 250321A: Swift/UVOT Upper Limits
  53. EP250321a: LCO optical counterpart detection
  54. EP250321a: Swift-XRT detection of an X-ray source
  55. EP250321a: VLT/X-shooter redshift z = 4.368
  56. EP250321a: REM optical/NIR afterglow detection
  57. EP250321a: BOOTES-5/JGT optical afterglow detection
  58. Swift GRB 250321A: Global MASTER-Net observations report
  59. GRB 250321A: GOTO optical upper limits
  60. GRB 250321A: Swift-XRT localisation
  61. GRB 250314A: Keck/NIRC2 J-band upper limit
  62. EP250226a/GRB 250226A: KAIT optical observations
  63. GRB 250321A: Fermi GBM Observation
  64. GRB 250321A: Swift detection of a burst
  65. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  66. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  67. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  68. GRB 250317B: OHP/T193 continued follow-up
  69. GRB 250317B: Mondy AZT-33IK Optical Observations
  70. GRB 250317B: NOT optical observations suggest an optical plateau phase
  71. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  72. GRB250312A: Swift/UVOT Upper Limits
  73. GRB 250317B: REM optical/NIR observations
  74. GRB 250317B: Swift-XRT observations
  75. GRB 250316A: Swift/UVOT Upper Limits
  76. GRB 250314A: REM optical/NIR upper limits
  77. GRB 250316A: AbAO AS-32 Optical Upper Limit
  78. GRB 250316A: Swift-XRT afterglow detection
  79. GRB 250317B: LCO detection of the fading optical afterglow
  80. GRB 250317B: refined SVOM/MXT analysis
  81. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  82. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  83. GRB 250316A: Fermi GBM Observation
  84. GRB 250316A: Swift-XRT observations
  85. GRB 250316A: Swift ToO observations
  86. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  87. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  88. GRB 250314A: EP-FXT afterglow detection
  89. GRB 250314A: Swift/UVOT Upper Limits
  90. GRB 250312B: GRBAlpha detection
  91. GRB 250314A: Swift XRT Detection
  92. SVOM/MXT upper limit on GRB 250314A
  93. GRB 250314A: NOT near-infrared candidate counterpart
  94. GRB 250312B: Fermi GBM Observation
  95. GRB 250313A: Swift-XRT observations
  96. Konus-Wind detection of GRB 250308A
  97. GRB 250313A: Fermi-LAT detection
  98. GRB 250313A: Swift ToO observations
  99. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  100. EP250304a: SVOM/VT optical observation

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