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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"

646 results found.

  1. Konus-Wind detection of GRB 260924A
  2. GRB 260922A: Swift-BAT refined analysis
  3. GRB 260921A: AstroSat CZTI detection
  4. GRB 260921A: Swift-BAT refined analysis
  5. EP260920a: COLIBRÍ optical upper limits
  6. EP Alert 260918.24: Global MASTER-Net observations report
  7. SVOM GRB260918.16: Global MASTER-Net observations report
  8. The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
  9. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  10. Fermi GRB 260805A: Global MASTER-Net observations report
  11. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  12. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  13. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  14. GRB 260616A: SVOM/GRM observation
  15. Fermi GRB 260523A: Global MASTER-Net observations report
  16. EP260509a: Global MASTER-Net observations report
  17. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  18. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  19. Fermi GRB 260221A: Global MASTER-Net observations report
  20. Fermi GRB 260219A: Global MASTER-Net observations report
  21. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  22. EP260209a: Global MASTER-Net observations report
  23. Fermi GRB 260208C: Global MASTER-Net observations report
  24. GRB 260208B: Fermi GBM Detection
  25. GRB 260206A: Swift-XRT observations
  26. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  27. Konus-Wind detection of GRB 260128A / EP260128a
  28. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  29. EP260119a: SVOM/VT optical observation
  30. Swift trigger on the HMXB 1A 1118-61
  31. Swift triggered on the HMXB 1A 1118-61
  32. IceCube Alert 260111A: Global MASTER-Net observations report
  33. Swift GRB 251214B: Global MASTER-Net observations report
  34. SVOM GRB251211.12: Global MASTER-Net observations report
  35. GRB 251208A: SVOM/GRM observation of a short burst
  36. Fermi GRB 251127A: Global MASTER-Net observations report
  37. Fermi trigger No 784279167: Global MASTER-Net observations report
  38. GRB 251103A: NOT spectroscopic redshift z = 0.76
  39. Fermi GRB 251013A: Global MASTER-Net observations report
  40. GRB 250909A: AstroSat CZTI detection
  41. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  42. EP250901a: Mondy, Assy and SAO RAS optical limits
  43. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  44. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  45. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  46. GRB 250831A: Swift-XRT counterpart detection
  47. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  48. GRB 250831A: SVOM/VT upper limit with VHF data
  49. sb25081602: Swift-XRT observations
  50. SVOM/sb25081602: detection of a likely X-ray transient
  51. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  52. EP250711a: COLIBRÍ continuous optical observations
  53. IceCube-250708A: Global MASTER-Net observations report
  54. EP250610a: Global MASTER-Net observations report
  55. GRB 250516A: Swift-BAT refined analysis
  56. MAXI GRB250515.65: Global MASTER-Net observations report
  57. GRB 250430A: Swift-BAT refined analysis
  58. Fermi GRB 250502B: Global MASTER-Net observations report
  59. Fermi-LAT gamma-ray observations of IceCube-250421A
  60. GRB 250327A: Swift-XRT refined Analysis
  61. GRB 250327A: SVOM/VT optical candidate
  62. GRB 250322A: AstroSat CZTI detection of a short burst
  63. Fermi trigger No 763509110: Global MASTER-Net observations report
  64. Fermi GRB 250309B: Global MASTER-Net observations report
  65. GRB 250226A: Fermi GBM Observation
  66. Fermi GRB 250223A: Global MASTER-Net observations report
  67. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  68. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  69. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  70. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  71. GRB 250207A: REM IR afterglow detection
  72. GRB 250207A: REM optical afterglow detection
  73. GRB 250114B: OHP/T193 optical upper limit
  74. GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
  75. GRB 241207C: MASTER optical observations
  76. Fermi trigger No 755225799: Global MASTER-Net observations report
  77. Swift GRB 241128A: Global MASTER-Net observations report
  78. Swift GRB241127.91: Global MASTER-Net observations report
  79. GRB 241113A: Swift/UVOT Detection
  80. GRB 240716A: Swift/BAT-GUANO localization skymap of a long burst
  81. Fermi GRB 240918A: Global MASTER-Net observations report
  82. EP EP240913a: Global MASTER-Net observations report
  83. GRB 240905E: NUTTelA-TAO / BSTI Optical Limits
  84. GRB 240829A: Swift-BAT refined analysis
  85. LAT GRB240828.62: Global MASTER-Net observations report
  86. Fermi trigger No 745866488: Global MASTER-Net observations report
  87. Fermi trigger No 745057312: Global MASTER-Net observations report
  88. Swift GRB 240811A: Global MASTER-Net observations report
  89. GRB 240727C: AstroSat CZTI detection of a long burst
  90. Konus-Wind detection of GRB 240627A
  91. Fermi GRB 240702A: Global MASTER-Net observations report
  92. Fermi trigger No 741211696: Global MASTER-Net observations report
  93. Swift Trigger 1232465: consistent with noise
  94. Konus-Wind detection of GRB 240529A
  95. GRB 240502C: Zeiss-1000 at Koshka observations of GOTO24bao optical counterpart candidate
  96. GRB 240419B: Swift-BAT refined analysis
  97. LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
  98. LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61
  99. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam upper limits on the Swift/XRT source S240422ed_X61
  100. Swift GRB 240419B: Global MASTER-Net observations report

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