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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"

3996 results found.

  1. Fermi GRB 251102A: Global MASTER-Net observations report
  2. GRB 251027A: Swift-XRT observations
  3. GRB 251026B: Tentative GOTO optical counterpart candidate
  4. Fermi GRB 251026B: Global MASTER-Net observations report
  5. Fermi GRB 251025C: Global MASTER-Net observations report
  6. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  7. GRB 251003A: VLA Detection
  8. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  9. EP251023a: COLIBRÍ optical observations
  10. Fermi GRB 251023A: Global MASTER-Net observations report
  11. GRB 250911A: MAXI/GSC detection
  12. IceCube-251018A: Global MASTER-Net observations report
  13. Fermi GRB 251016B: Global MASTER-Net observations report
  14. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  15. Fermi GRB 251013C: Global MASTER-Net observations report
  16. Fermi GRB 251013B: Global MASTER-Net observations report
  17. GRB 251011B : MASTER optical observations
  18. GRB 251011A: AstroSat CZTI detection
  19. GRB 250916A: TERI Gamma-ray detection
  20. EP251006a: Global MASTER-Net observations report
  21. GRB 251007B: SVOM/C-GFT upper limit
  22. EP251003a: LCO and VST fading optical counterpart
  23. Fermi GRB 251006B: Global MASTER-Net observations report
  24. GRB 251003A: Enhanced Swift-XRT position
  25. GRB 251003A: Prompt enhanced Swift-XRT position
  26. GRB 251003A: Swift detection of a burst
  27. Fermi GRB 250929A: Global MASTER-Net observations report
  28. GRB 250929A: Fermi GBM Final Real-time Localization
  29. GRB 250916A: SVOM/VT optical observation
  30. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  31. Fermi trigger No 780609036: Global MASTER-Net observations report
  32. GRB 250924A: COLIBRÍ optical observations
  33. GRB 250924A: Swift detection of a burst with an optical counterpart
  34. Konus-Wind detection of GRB 250911A
  35. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  36. GRB 250917B: KAIT optical upper limit
  37. GRB 250920B: Swift/UVOT Detection
  38. GRB250920C: LCOGT Optical Detection
  39. GRB 250920C: GOTO optical counterpart candidate
  40. Konus-Wind detection of GRB 250919A
  41. GRB 250919A / EP250919a: Insight-HXMT detection
  42. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  43. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  44. GRB 250919A: SVOM/GRM observation of a very bright GRB
  45. EP250919a: Global MASTER-Net observations report
  46. GRB 250916A: Fermi GBM Observation
  47. GRB 250916A: further SAO RAS optical observations
  48. GRB 250916A: Glowbug gamma-ray detection
  49. GRB 250917B: Swift detection of a short burst
  50. GRB 250916A: AstroSat CZTI detection of a bright long burst
  51. GRB 250916A: Fermi GBM Final Real-time Localization
  52. GRB 250911A: Insight-HXMT detection
  53. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  54. GRB 250911A: GECAM-B detection
  55. GRB 250911A: Swift-BAT refined analysis
  56. GRB 250910B: SVOM/GRM observation
  57. EP250911a: Swift-XRT observations
  58. EP250911a: COLIBRÍ optical observations
  59. Fermi GRB 250910B: Global MASTER-Net observations report
  60. EP250911a: LCO optical counterpart discovery
  61. EP250910a: Global MASTER-Net observations report
  62. EP#01709240653: Swift-XRT observations
  63. EP250908c: SVOM/VT optical observation
  64. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  65. EP250908b: SVOM/VT optical candidate
  66. EP250908c: Global MASTER-Net observations report
  67. EP250905b: Global MASTER-Net observations report
  68. IceCube Alert 250905.84: Global MASTER-Net observations report
  69. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  70. GRB 250902A: VZLUSAT-2 detection
  71. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  72. Fermi GRB 250902B: Global MASTER-Net observations report
  73. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  74. EP250827b: Swift observations of AT 2025wkm
  75. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  76. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  77. GRB 250831A: SVOM detection of a soft burst
  78. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  79. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  80. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  81. The EP-WXT trigger 01709200994 is likely a flaring star
  82. EP250821a: SOAR observations
  83. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  84. EP250828a: Liverpool Telescope upper limits
  85. Swift GRB 250828B: Global MASTER-Net observations report
  86. EP250828a: Global MASTER-Net observations report
  87. EP250827a: Swift/UVOT Detection
  88. Fermi GRB 250827A: Global MASTER-Net observations report
  89. EP250827a: Swift-XRT counterpart detection
  90. EP250827a: Global MASTER-Net observations report
  91. EP250827a: Gemini-South optical counterpart detection
  92. Fermi GRB 250824B: Global MASTER-Net observations report
  93. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  94. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  95. EP250821a: Einstein Probe detection of an X-ray transient
  96. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  97. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  98. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  99. Fermi trigger No 776849714: Global MASTER-Net observations report
  100. GRB 250818B: SVOM detection of a short burst

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