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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').
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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"

637 results found.

  1. Fermi GRB 260805A: Global MASTER-Net observations report
  2. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  3. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  4. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  5. GRB 260616A: SVOM/GRM observation
  6. Fermi GRB 260523A: Global MASTER-Net observations report
  7. EP260509a: Global MASTER-Net observations report
  8. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  9. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  10. Fermi GRB 260221A: Global MASTER-Net observations report
  11. Fermi GRB 260219A: Global MASTER-Net observations report
  12. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  13. EP260209a: Global MASTER-Net observations report
  14. Fermi GRB 260208C: Global MASTER-Net observations report
  15. GRB 260208B: Fermi GBM Detection
  16. GRB 260206A: Swift-XRT observations
  17. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  18. Konus-Wind detection of GRB 260128A / EP260128a
  19. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  20. EP260119a: SVOM/VT optical observation
  21. Swift trigger on the HMXB 1A 1118-61
  22. Swift triggered on the HMXB 1A 1118-61
  23. IceCube Alert 260111A: Global MASTER-Net observations report
  24. Swift GRB 251214B: Global MASTER-Net observations report
  25. SVOM GRB251211.12: Global MASTER-Net observations report
  26. GRB 251208A: SVOM/GRM observation of a short burst
  27. Fermi GRB 251127A: Global MASTER-Net observations report
  28. Fermi trigger No 784279167: Global MASTER-Net observations report
  29. GRB 251103A: NOT spectroscopic redshift z = 0.76
  30. Fermi GRB 251013A: Global MASTER-Net observations report
  31. GRB 250909A: AstroSat CZTI detection
  32. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  33. EP250901a: Mondy, Assy and SAO RAS optical limits
  34. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  35. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  36. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  37. GRB 250831A: Swift-XRT counterpart detection
  38. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  39. GRB 250831A: SVOM/VT upper limit with VHF data
  40. sb25081602: Swift-XRT observations
  41. SVOM/sb25081602: detection of a likely X-ray transient
  42. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  43. EP250711a: COLIBRÍ continuous optical observations
  44. IceCube-250708A: Global MASTER-Net observations report
  45. EP250610a: Global MASTER-Net observations report
  46. GRB 250516A: Swift-BAT refined analysis
  47. MAXI GRB250515.65: Global MASTER-Net observations report
  48. GRB 250430A: Swift-BAT refined analysis
  49. Fermi GRB 250502B: Global MASTER-Net observations report
  50. Fermi-LAT gamma-ray observations of IceCube-250421A
  51. GRB 250327A: Swift-XRT refined Analysis
  52. GRB 250327A: SVOM/VT optical candidate
  53. GRB 250322A: AstroSat CZTI detection of a short burst
  54. Fermi trigger No 763509110: Global MASTER-Net observations report
  55. Fermi GRB 250309B: Global MASTER-Net observations report
  56. GRB 250226A: Fermi GBM Observation
  57. Fermi GRB 250223A: Global MASTER-Net observations report
  58. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  59. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  60. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  61. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  62. GRB 250207A: REM IR afterglow detection
  63. GRB 250207A: REM optical afterglow detection
  64. GRB 250114B: OHP/T193 optical upper limit
  65. GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
  66. GRB 241207C: MASTER optical observations
  67. Fermi trigger No 755225799: Global MASTER-Net observations report
  68. Swift GRB 241128A: Global MASTER-Net observations report
  69. Swift GRB241127.91: Global MASTER-Net observations report
  70. GRB 241113A: Swift/UVOT Detection
  71. GRB 240716A: Swift/BAT-GUANO localization skymap of a long burst
  72. Fermi GRB 240918A: Global MASTER-Net observations report
  73. EP EP240913a: Global MASTER-Net observations report
  74. GRB 240905E: NUTTelA-TAO / BSTI Optical Limits
  75. GRB 240829A: Swift-BAT refined analysis
  76. LAT GRB240828.62: Global MASTER-Net observations report
  77. Fermi trigger No 745866488: Global MASTER-Net observations report
  78. Fermi trigger No 745057312: Global MASTER-Net observations report
  79. Swift GRB 240811A: Global MASTER-Net observations report
  80. GRB 240727C: AstroSat CZTI detection of a long burst
  81. Konus-Wind detection of GRB 240627A
  82. Fermi GRB 240702A: Global MASTER-Net observations report
  83. Fermi trigger No 741211696: Global MASTER-Net observations report
  84. Swift Trigger 1232465: consistent with noise
  85. Konus-Wind detection of GRB 240529A
  86. GRB 240502C: Zeiss-1000 at Koshka observations of GOTO24bao optical counterpart candidate
  87. GRB 240419B: Swift-BAT refined analysis
  88. LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
  89. LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61
  90. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam upper limits on the Swift/XRT source S240422ed_X61
  91. Swift GRB 240419B: Global MASTER-Net observations report
  92. GRB 240414A: Swift-BAT refined analysis
  93. LIGO/Virgo/KAGRA S240413p: Global MASTER-Net observations report
  94. Swift Trigger 1220736: detection of 4U 1543-62.
  95. Fermi GRB 240408A: Global MASTER-Net observations report
  96. Konus-Wind detection of LXT 240402A/GRB 240402B
  97. Konus-Wind detection of GRB 240303B
  98. GRB 240109A: Swift-BAT refined analysis
  99. GRB 231215A: radio detection with the VLA
  100. GRB 231129A: Swift-BAT refined analysis

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