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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"

5154 results found.

  1. GRB 251002A: Swift-XRT afterglow detection
  2. GRB 251002A: FRAM-ORM afterglow detection
  3. GRB 251001B: Swift-XRT refined Analysis
  4. GRB 250930A: SVOM/GRM observation
  5. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  6. GRB 250925A: Mondy and AbAO optical observations
  7. Fermi GRB 250926A: Global MASTER-Net observations report
  8. GRB 250924A: 1.6m Mephisto optical upper limits
  9. GRB 250924A: SAO RAS optical observations
  10. GRB 250924A: AstroSat CZTI detection
  11. GRB 250924A: Swift-XRT refined Analysis
  12. GRB 250924A: GROWTH-India Telescope Upper Limits
  13. GRB 250924A: Mondy optical observations, afterglow fading
  14. GRB 250924B: Fermi GBM Final Localization
  15. GRB 250924A: COLIBRÍ optical observations
  16. Swift GRB 250924A: Global MASTER-Net observations report
  17. GRB 250924A: DDOTI Detection of the Optical Counterpart
  18. Fermi trigger No 780156732: Global MASTER-Net observations report
  19. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  20. GRB 250920B: Swift-XRT refined Analysis
  21. GRB 250919A/EP250919a: SVOM/VT optical observation
  22. EP250916a: EP-FXT follow-up observation
  23. GRB 250917B: Fermi GBM Observation
  24. Fermi GRB 250917B: Global MASTER-Net observations report
  25. GRB 250916A: GOTO optical counterpart candidate
  26. GRB 250916A: AstroSat CZTI detection of a bright long burst
  27. GRB 250912A: SVOM detection of a burst
  28. GRB 250911A: Swift-XRT refined Analysis
  29. EP250911a: Optical detection with Kinder observations
  30. Fermi GRB 250910B: Global MASTER-Net observations report
  31. EP250910a: Global MASTER-Net observations report
  32. GRB 250903A: SVOM/ECLAIRs refined analysis
  33. EP250908C: GROND observation of the fading optical counterpart
  34. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  35. GRB 250905A: Swift-XRT refined Analysis
  36. IceCube Alert 250905.84: Global MASTER-Net observations report
  37. GRB 250904A: Swift-XRT refined Analysis
  38. GRB 250903A: Swift-XRT observations
  39. The EP-WXT trigger 01709201209 is likely a flaring star
  40. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  41. GRB 250903A: SVOM detection of a burst
  42. Fermi GRB 250902B: Global MASTER-Net observations report
  43. GRB 250901A: Swift-XRT afterglow detection
  44. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  45. EP250827b: FTW Observations of AT 2025wkm
  46. EP250831a: Swift-XRT observations
  47. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  48. GRB 250831A: Swift-XRT counterpart detection
  49. EP250830a: Global MASTER-Net observations report
  50. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  51. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  52. EP250828a: Optical counterpart detection with Kinder observations
  53. GRB 250828B: Swift detection of a burst
  54. GRID detection of GRB 250824A
  55. Fermi GRB 250827A: Global MASTER-Net observations report
  56. GRB 250826A: SVOM/GRM observation
  57. EP250827a: Global MASTER-Net observations report
  58. GRB 250826A: Fermi GBM Final Real-time Localization
  59. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  60. Fermi GRB 250824B: Global MASTER-Net observations report
  61. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  62. GRB 250823A: Swift-XRT refined Analysis
  63. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  64. GRB 250824B: Fermi GBM Final Real-time Localization
  65. GRB 250823A: COLIBRÍ optical observations
  66. GRB 250824A: Fermi GBM Final Real-time Localization
  67. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  68. GRB 250823A: Liverpool Telescope optical detection
  69. Swift GRB250823.84: Global MASTER-Net observations report
  70. Fermi GRB 250821B: Global MASTER-Net observations report
  71. GRB 250821A: Swift-XRT refined Analysis
  72. Swift GRB 250821A: Global MASTER-Net observations report
  73. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  74. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  75. IPN triangulation of GRB 250814C (short)
  76. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  77. Fermi trigger No 776849714: Global MASTER-Net observations report
  78. sb25081602: Swift-XRT observations
  79. SVOM/sb25081602: detection of a likely X-ray transient
  80. GRB 250814A: Swift-BAT refined analysis
  81. GRB 250814C: SVOM/GRM observation of a short burst
  82. GRB 250814A: Swift-XRT refined Analysis
  83. GRB 240814A: Fermi GBM Observation
  84. GRB 250814A: DDOTI Optical Upper Limit
  85. IceCube Alert 250813.14: Global MASTER-Net observations report
  86. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  87. Corrected Swift-XRT Refined Analysis of GRB 250809A
  88. GRB 250809A: Swift-XRT refined Analysis
  89. GRB 250807B: SVOM/VT optical observation
  90. Fermi GRB 250808A: Global MASTER-Net observations report
  91. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  92. GRB 250807B: Swift-XRT refined Analysis
  93. EP 250807.979: GOTO optical upper limit
  94. IceCube Alert 250804.84: Global MASTER-Net observations report
  95. GRB 250806A: Swift-XRT counterpart detection
  96. EP250806a: COLIBRÍ optical upper limit
  97. GRB 250805A: SVOM/VT optical counterpart
  98. GRB 250805A: Swift-XRT refined Analysis
  99. GRB 250805A: Enhanced Swift-XRT position
  100. GRB 250805A: Swift-XRT observations

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