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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"

2036 results found.

  1. GRB 250314A: ALMA detection
  2. GRB 250329B: Swift/UVOT Upper Limit
  3. GRB 250329A: Swift/UVOT Upper Limit
  4. GRB 250327B: Swift/UVOT Detection
  5. GRB 250331E: SVOM/GRM observation
  6. GRB 250327B: Kilonova-Catcher Observations
  7. GRB 250330B: SVOM/GRM observation of a short burst
  8. GRB 250329B: CAHA 2.2m telescope optical limit
  9. Konus-Wind detection of GRB 250327B
  10. GRB 250320C : SVOM detection of a burst through offline search
  11. GRB20250327B: 45th Parallel Observatory upper limit
  12. GRB 250328A: Swift/UVOT Detection
  13. GRB 250328A: Swift-XRT refined Analysis
  14. SVOM/sb25033102 is a false trigger
  15. GRB 250330A: SVOM/VT optical upper limit
  16. SVOM/sb25033102: SVOM detection of an X-ray transient
  17. GRB 250314A: VLA detection
  18. GRB 250328A: 1.6m Mephisto optical observations
  19. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  20. GRB 250329B: Swift-XRT afterglow detection
  21. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  22. GRB 250329B: SVOM/C-GFT optical upper limit
  23. GRB 250329B: SVOM/VT optical upper limit
  24. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  25. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  26. GRB250329A: REM optical afterglow detection
  27. GRB 250329B: GWAC-F50A optical upper limit
  28. GRB 250329B: SVOM detection of a faint transient
  29. GRB 250329A: Swift-XRT afterglow detection
  30. GRB 250328A: SVOM/VT optical observation
  31. GRB 250329A: Fading optical counterpart detection by LCO.
  32. GRB 250328A: SVOM/C-GFT optical upper limit
  33. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  34. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  35. GRB 250329A: VLT/X-shooter redshift z = 2.921
  36. GRB 250329A: SVOM/VT optical counterpart confirmation
  37. GRB 250329A: SVOM detection of a burst
  38. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  39. GRB 250327B: MASTER detection of OT rebrightening
  40. GRB 250327B: LCO optical counterpart detection
  41. GRB 250328A: GWAC-F50A optical upper limit
  42. GRB 250328A: SVOM detection of a burst
  43. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  44. GRB 250327B: further optical observations by LCOGT
  45. GRB 250327A: SVOM/VT upper limits on the XRT position
  46. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  47. GRB 250327B: Las Cumbres optical counterpart detection
  48. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  49. GRB 250327B: 1.6m Mephisto optical observations
  50. GRB 250327B: NOT spectroscopic redshift z = 3.035
  51. GRB 250327B: GOTO optical counterpart detection
  52. GRB 250327B: SVOM/VT optically bright counterpart
  53. GRB 250327B: SAO RAS optical candidate
  54. GRB 250327B: SVOM detection of a burst
  55. GRB 250327A: J-band observations with WINTER
  56. GRB 250327A: SVOM/VT optical candidate
  57. GRB 250321B: Swift-XRT observations
  58. SVOM/sb25032302: SVOM detection of a long X-ray transient
  59. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  60. GRB 250225B: GECAM-A detection
  61. GRB 250321B: Swift ToO observations
  62. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  63. GRB 250320B: Fermi GBM Observation
  64. GRB 250320B: Fermi-LAT detection
  65. GRB 250321B: SVOM detection of a sub-threshold transient event
  66. EP250321a: SVOM/VT optical observation
  67. GRB 250320B: SVOM/GRM observation of a long burst
  68. GRB 250314A: Keck/NIRC2 J-band upper limit
  69. GRB 250313A: GRBAlpha detection
  70. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  71. GRB 250317C: SVOM/GRM observation of a long burst
  72. GRB 250317B: Leavitt Observatory optical upper limit
  73. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  74. GRB 250317B: REM optical/NIR observations
  75. GRB 250317B: Swift-XRT observations
  76. GRB 250314A: REM optical/NIR upper limits
  77. EP 250317B: Fading optical counterpart detection by LCO
  78. GRB 250317B: LCO detection of the fading optical afterglow
  79. GRB 250317B: refined SVOM/MXT analysis
  80. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  81. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  82. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  83. GRB 250317B: SVOM detection of a burst
  84. GRB 250314A: SVOM/GRM analysis
  85. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  86. GRB 250314A: EP-FXT afterglow detection
  87. GRB 250314A: Swift/UVOT Upper Limits
  88. GRB 250314A: Swift XRT Detection
  89. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  90. SVOM/MXT upper limit on GRB 250314A
  91. GRB 250314A: SVOM/VT upper limit
  92. GRB 250314A: NOT near-infrared candidate counterpart
  93. GRB 250313A: Fermi GBM Detection
  94. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  95. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  96. Konus-Wind detection of GRB 250313A
  97. Konus-Wind detection of GRB 250308A
  98. GRB 250314A: SVOM detection of a burst
  99. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  100. GRB 250313A: SVOM/GRM observation of a bright long burst

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