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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"

3674 results found.

  1. GRB 250628A: REM optical/NIR upper limits
  2. GRB 250628C: Fermi GBM Final Real-time Localization
  3. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  4. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  5. GRB 250628A: VLT/X-shooter upper limits
  6. Fermi GRB 250626A: Global MASTER-Net observations report
  7. Swift GRB 250628A: Global MASTER-Net observations report
  8. GRB 250625A: SVOM/C-GFT upper limit in early phase
  9. GRB 250625A: OHP/T193 optical detection
  10. Swift GRB 250625A: Global MASTER-Net observations report
  11. Fermi GRB 250623A: Global MASTER-Net observations report
  12. Fermi trigger No 772190032: Global MASTER-Net observations report
  13. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  14. Fermi trigger No 772058337: Global MASTER-Net observations report
  15. GRB 250617B: SAO RAS optical observations
  16. Fermi trigger No 771752663: Global MASTER-Net observations report
  17. Fermi trigger No 771424081: Global MASTER-Net observations report
  18. EP250612a: Einstein Probe detection of an X-ray transient
  19. Swift GRB250612.04: Global MASTER-Net observations report
  20. Fermi trigger No 771072240: Global MASTER-Net observations report
  21. GRB 250527C: CrAO Optical Upper Limit
  22. GRB 250606A: Fermi GBM Final Real-time Localization
  23. Fermi trigger No 770867684: Global MASTER-Net observations report
  24. GRB 250605A: LT optical observations
  25. Fermi GRB 250531A: Global MASTER-Net observations report
  26. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  27. Fermi trigger No 770058372: Global MASTER-Net observations report
  28. GRB 250314A: CIDER NB1008 upper limit
  29. EP250526a: Einstein Probe detection of a fast X-ray transient
  30. Fermi GRB 250516A: Global MASTER-Net observations report
  31. Konus-Wind detection of GRB 250506A
  32. EP250511a: COLIBRÍ optical counterpart candidate
  33. Fermi GRB 250510C: Global MASTER-Net observations report
  34. Fermi GRB 250510B: Global MASTER-Net observations report
  35. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  36. GRB 250506A: Swift-XRT observations
  37. Fermi GRB 250504A: Global MASTER-Net observations report
  38. Fermi trigger No 767975731: Global MASTER-Net observations report
  39. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  40. EP250428b: SAO RAS optical upper limit
  41. EP250427a / GRB 250427A: OHP/T193 photometric observations
  42. EP250427a: Lesedi optical counterpart detection
  43. EP250427A: COLIBRÍ Continuing Optical Observations
  44. EP250427a: LT optical counterpart detection
  45. EP250421a: Upper limits from Fermi-GBM Observations
  46. IceCube-250421A: DDOTI Detection of the LAST Candidate
  47. Fermi GRB 250421A: Global MASTER-Net observations report
  48. EP250421a: Einstein Probe detection of an X-ray transient
  49. IceCube Alert 250421.71: Global MASTER-Net observations report
  50. EP250416a: Global MASTER-Net observations report
  51. SVOM/sb25041603: SVOM detection of an X-ray transient
  52. EP250304a: ATCA radio observations
  53. Fermi trigger No 766148493: Global MASTER-Net observations report
  54. Fermi trigger No 766173972: Global MASTER-Net observations report
  55. Fermi GRB 250407A: Global MASTER-Net observations report
  56. IPN triangulation of GRB 250406B (short/hard)
  57. IceCube Alert 250406.95: Global MASTER-Net observations report
  58. Fermi trigger No 765619921: Global MASTER-Net observations report
  59. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  60. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  61. GRB 250404A / EP250404a: Mondy optical observations
  62. Fermi GRB 250404A: Global MASTER-Net observations report
  63. EP250404a: Global MASTER-Net observations report
  64. GRB 250327B: VIRT Optical Upper Limit
  65. GRB 250402A: Mondy optical observations
  66. Fermi GRB 250403A: Global MASTER-Net observations report
  67. GRB 250403A: GOTO optical counterpart follow-up observations
  68. GRB 250403A: GOTO detection of the optical afterglow
  69. GRB 250402A: REM optical/NIR upper limits
  70. GRB 250328A: AbAO AS-32 Optical Observations
  71. GRB 250322B possible detection by the AstroSat Satellite
  72. GRB 250331B: Swift detection of a burst
  73. GRB 250328A: 1.6m Mephisto optical observations
  74. IceCube Alert 250330.35: Global MASTER-Net observations report
  75. GRB 250327B: MASTER detection of OT rebrightening
  76. GRB 250327B: LCO optical counterpart detection
  77. FRB 20250316A: FTW optical observations
  78. GRB 250327B: further optical observations by LCOGT
  79. GRB 250327b: Liverpool Telescope optical observations
  80. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  81. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  82. GRB 250327B: SAO RAS optical candidate
  83. EP250321a: Xinglong 216 decaying optical observations
  84. GRB 250321B: SVOM detection of a sub-threshold transient event
  85. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  86. GRB 250317B: Mondy AZT-33IK Optical Observations
  87. Fermi trigger No 763933627: Global MASTER-Net observations report
  88. GRB 250314A: REM optical/NIR upper limits
  89. GRB 250317B: LCO detection of the fading optical afterglow
  90. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  91. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  92. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  93. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  94. Fermi GRB 250313A: Global MASTER-Net observations report
  95. Fermi GRB 250312B: Global MASTER-Net observations report
  96. GRB 241228A: VIRT Optical Upper Limit
  97. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  98. GRB 250228A: Fermi GBM Observation
  99. GRB 250225B: Swift-BAT refined analysis
  100. GRB 250311A/MAXI J1457-026: MAXI/GSC detection

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