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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"

3757 results found.

  1. EP250612a: Einstein Probe detection of an X-ray transient
  2. Swift GRB250612.04: Global MASTER-Net observations report
  3. Fermi trigger No 771072240: Global MASTER-Net observations report
  4. GRB 250527C: CrAO Optical Upper Limit
  5. GRB 250606A: Fermi GBM Final Real-time Localization
  6. Fermi trigger No 770867684: Global MASTER-Net observations report
  7. GRB 250605A: LT optical observations
  8. Fermi GRB 250531A: Global MASTER-Net observations report
  9. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  10. Fermi trigger No 770058372: Global MASTER-Net observations report
  11. GRB 250314A: CIDER NB1008 upper limit
  12. EP250526a: Einstein Probe detection of a fast X-ray transient
  13. Fermi GRB 250516A: Global MASTER-Net observations report
  14. Konus-Wind detection of GRB 250506A
  15. EP250511a: COLIBRÍ optical counterpart candidate
  16. Fermi GRB 250510C: Global MASTER-Net observations report
  17. Fermi GRB 250510B: Global MASTER-Net observations report
  18. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  19. GRB 250506A: Swift-XRT observations
  20. Fermi GRB 250504A: Global MASTER-Net observations report
  21. Fermi trigger No 767975731: Global MASTER-Net observations report
  22. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  23. EP250428b: SAO RAS optical upper limit
  24. EP250427a / GRB 250427A: OHP/T193 photometric observations
  25. EP250427a: Lesedi optical counterpart detection
  26. EP250427A: COLIBRÍ Continuing Optical Observations
  27. EP250427a: LT optical counterpart detection
  28. EP250421a: Upper limits from Fermi-GBM Observations
  29. IceCube-250421A: DDOTI Detection of the LAST Candidate
  30. Fermi GRB 250421A: Global MASTER-Net observations report
  31. EP250421a: Einstein Probe detection of an X-ray transient
  32. IceCube Alert 250421.71: Global MASTER-Net observations report
  33. EP250416a: Global MASTER-Net observations report
  34. SVOM/sb25041603: SVOM detection of an X-ray transient
  35. EP250304a: ATCA radio observations
  36. Fermi trigger No 766148493: Global MASTER-Net observations report
  37. Fermi trigger No 766173972: Global MASTER-Net observations report
  38. Fermi GRB 250407A: Global MASTER-Net observations report
  39. IPN triangulation of GRB 250406B (short/hard)
  40. IceCube Alert 250406.95: Global MASTER-Net observations report
  41. Fermi trigger No 765619921: Global MASTER-Net observations report
  42. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  43. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  44. GRB 250404A / EP250404a: Mondy optical observations
  45. Fermi GRB 250404A: Global MASTER-Net observations report
  46. EP250404a: Global MASTER-Net observations report
  47. GRB 250327B: VIRT Optical Upper Limit
  48. GRB 250402A: Mondy optical observations
  49. Fermi GRB 250403A: Global MASTER-Net observations report
  50. GRB 250403A: GOTO optical counterpart follow-up observations
  51. GRB 250403A: GOTO detection of the optical afterglow
  52. GRB 250402A: REM optical/NIR upper limits
  53. GRB 250328A: AbAO AS-32 Optical Observations
  54. GRB 250322B possible detection by the AstroSat Satellite
  55. GRB 250331B: Swift detection of a burst
  56. GRB 250328A: 1.6m Mephisto optical observations
  57. IceCube Alert 250330.35: Global MASTER-Net observations report
  58. GRB 250327B: MASTER detection of OT rebrightening
  59. GRB 250327B: LCO optical counterpart detection
  60. FRB 20250316A: FTW optical observations
  61. GRB 250327B: further optical observations by LCOGT
  62. GRB 250327b: Liverpool Telescope optical observations
  63. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  64. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  65. GRB 250327B: SAO RAS optical candidate
  66. EP250321a: Xinglong 216 decaying optical observations
  67. GRB 250321B: SVOM detection of a sub-threshold transient event
  68. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  69. GRB 250317B: Mondy AZT-33IK Optical Observations
  70. Fermi trigger No 763933627: Global MASTER-Net observations report
  71. GRB 250314A: REM optical/NIR upper limits
  72. GRB 250317B: LCO detection of the fading optical afterglow
  73. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  74. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  75. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  76. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  77. Fermi GRB 250313A: Global MASTER-Net observations report
  78. Fermi GRB 250312B: Global MASTER-Net observations report
  79. GRB 241228A: VIRT Optical Upper Limit
  80. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  81. GRB 250228A: Fermi GBM Observation
  82. GRB 250225B: Swift-BAT refined analysis
  83. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  84. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  85. GRB 250309B / AT2025dws: SAO RAS optical observations
  86. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  87. IceCube Alert 250309.32: Global MASTER-Net observations report
  88. EP250308a: FTW optical and NIR upper limits
  89. GRB 250305A: AstroSat CZTI detection
  90. EP250302a:Xinglong optical observations
  91. Fermi trigger No 762963055: Global MASTER-Net observations report
  92. GRB 250305A: SVOM/GRM observation of a burst
  93. GRB 250305A: Fermi GBM Final Real-time Localization
  94. EP250302a: Mondy Continued Optical Observations
  95. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  96. EP250304a: Global MASTER-Net observations report
  97. GRB 250226A: GRANDMA Optical Observations
  98. Fermi GRB 250302A: Global MASTER-Net observations report
  99. EP250302a: FTW optical and NIR detection
  100. GRB 250228A: Fermi GBM Final Localization

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