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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"

35939 results found.

  1. Fermi GRB 250330B: Global MASTER-Net observations report
  2. GRB 250330B: Fermi GBM Final Real-time Localization
  3. Fermi GRB 250330A: Global MASTER-Net observations report
  4. GRB 250330A: BOOTES-7 early optical upper limit
  5. GRB 250330A: Swift/UVOT Upper Limits
  6. GRB 250330A: Swift-XRT afterglow detection
  7. GRB 250328A: 1.6m Mephisto optical observations
  8. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  9. GRB 250330A: Fermi GBM Final Localization
  10. GRB 250330A: VLT/FORS2 Optical Observations
  11. GRB 250330A: Prompt Swift-XRT position
  12. GRB 250329B: Swift-XRT afterglow detection
  13. GRB 250330A: Swift detection of a burst
  14. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  15. GRB 250329B: SVOM/C-GFT optical upper limit
  16. GRB 250327B: ALMA detection
  17. GRB 250327B: VLA detection
  18. GRB 250329B: SVOM/VT optical upper limit
  19. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  20. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  21. GRB 250329B: GWAC-F50A optical upper limit
  22. GRB 250329B: SVOM detection of a faint transient
  23. GRB 250329A: Swift-XRT afterglow detection
  24. GRB 250328A: SVOM/VT optical observation
  25. GRB 250329A: Fading optical counterpart detection by LCO.
  26. GRB 250328A: SVOM/C-GFT optical upper limit
  27. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  28. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  29. GRB 250329A: VLT/X-shooter redshift z = 2.921
  30. GRB 250329A: SVOM/VT optical counterpart confirmation
  31. GRB 250329A: SVOM detection of a burst
  32. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  33. GRB 250327B: J-band observations with WINTER
  34. GRB 250327B: MASTER detection of OT rebrightening
  35. GRB 250327B: LCO optical counterpart detection
  36. GRB 250328A: GWAC-F50A optical upper limit
  37. GRB 250328A: SVOM detection of a burst
  38. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  39. GRB 250327B: CrAO and SAO RAS Optical Observations
  40. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  41. GRB 250327B: further optical observations by LCOGT
  42. GRB 250327b: Liverpool Telescope optical observations
  43. GRB 250322A: GRANDMA/TNOT optical upper limits
  44. GRB 250327A: SVOM/VT upper limits on the XRT position
  45. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  46. GRB 250327B: Las Cumbres optical counterpart detection
  47. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  48. GRB 250327B: 1.6m Mephisto optical observations
  49. GRB 250327B: NOT spectroscopic redshift z = 3.035
  50. GRB 250327A: Swift-XRT refined Analysis
  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 250327A: Fermi GBM observation
  58. Fermi GRB 250327A: Global MASTER-Net observations report
  59. Swift GRB 250327A: Global MASTER-Net observations report
  60. GRB 250327A: DDOTI Optical Observations
  61. GRB 250327A: COLIBRÍ optical upper limit
  62. GRB 250327A: Swift detection of a burst
  63. GRB 250327A: Fermi GBM Final Real-time Localization
  64. Konus-Wind detection of GRB 250322A (short)
  65. IPN triangulation of GRB 250322B
  66. EP250321a: Mondy AZT-33IK Continued Optical Observations
  67. GRB 250322A: third epoch of NOT optical observations
  68. GRB 250322A: Swift-BAT refined analysis
  69. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  70. GRB 250322A: further NOT optical observations
  71. GRB 250322A: Swift/UVOT Upper Limits
  72. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  73. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  74. GRB 250321B: Swift-XRT observations
  75. GRB 250322A: Swift-XRT refined Analysis
  76. GRB 250322A: Gemini-North redshift of candidate host galaxy
  77. GRB 250322A: AstroSat CZTI detection of a short burst
  78. GRB 250322B: AstroSat CZTI detection of a bright long burst
  79. GRB 250322A: Gemini-South optical observations
  80. GRB 250322A: VLT optical observations
  81. GRB 250322A: VLT near-infrared observations
  82. GRB 250322A: NOT optical upper limits
  83. GRB 250322A: Enhanced Swift-XRT position
  84. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  85. GRB 250322A: MASTER optical observation
  86. EP250321a: Mondy AZT-33IK Optical Observations
  87. GRB 250322A: Swift detection of a short burst
  88. EP250321a: KAIT optical observations
  89. GRB 250225B: GECAM-A detection
  90. GRB 250312A: GECAM-A detection
  91. GRB 250321B: Swift ToO observations
  92. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  93. GRB 250321C: Fermi GBM Final Real-time Localization
  94. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  95. GRB 250320B: Fermi GBM Observation
  96. GRB 250321A: Swift-BAT refined analysis
  97. GRB 250321A: Swift-XRT refined Analysis
  98. GRB 250320B: Fermi-LAT detection
  99. GRB 250321B: SVOM detection of a sub-threshold transient event
  100. EP 250321A: Optical counterpart detection by LCO.

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