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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"

3112 results found.

  1. GRB 250905A: Swift detection of a burst
  2. GRB 250903A: Swift-XRT observations
  3. GRB 250903A: TRT optical counterpart detection
  4. GRB 250902B: AstroSat CZTI detection
  5. Fermi GRB 250902B: Global MASTER-Net observations report
  6. EP250827b: Liverpool Telescope observations
  7. Fermi GRB 250827A: Global MASTER-Net observations report
  8. GRB 250827A: Fermi GBM Final Real-time Localization
  9. EP250827a: BOOTES-7 early optical dectection
  10. EP250827a: Global MASTER-Net observations report
  11. Fermi GRB 250826A: Global MASTER-Net observations report
  12. Fermi trigger No 777883624: Global MASTER-Net observations report
  13. Fermi GRB 250824B: Global MASTER-Net observations report
  14. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  15. IPN triangulation of GRB 250821B (long/bright)
  16. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  17. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  18. GRB 250820A: Fermi GBM Final Real-time Localization
  19. Fermi trigger No 776849714: Global MASTER-Net observations report
  20. LIGO/Virgo/KAGRA S250818k: Candidates from the Zwicky Transient Facility
  21. sb25081602: Swift-XRT observations
  22. SVOM/sb25081602: detection of a likely X-ray transient
  23. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  24. Fermi trigger No 776818276: Global MASTER-Net observations report
  25. Subject GRB 250813B: SVOM/MXT refined analysis
  26. EP250812a: SVOM/VT optical counterpart
  27. IceCube Alert 250813.14: Global MASTER-Net observations report
  28. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  29. GRB 250807A: AstroSat CZTI detection of bright long burst
  30. GRB 250807A: SVOM/VT optical observation
  31. GRB 250807A: Swift detection of a burst with an optical counterpart
  32. EP250730a: SVOM/VT optical upper limit
  33. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  34. EP250730a: Global MASTER-Net observations report
  35. GRB 250725A: Swift-BAT refined analysis
  36. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  37. GRB 250725A: SVOM/VT optical candidate
  38. GRB 250725A: Enhanced Swift-XRT position
  39. GRB 250725A: Swift detection of a burst
  40. Fermi GRB 250725A: Global MASTER-Net observations report
  41. GRB 250717B: SVOM/GRM observation
  42. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  43. GRB 250717B: Swift-XRT observations
  44. GRB 250716A: Fermi GBM Observation
  45. Fermi GRB 250715A: Global MASTER-Net observations report
  46. Fermi GRB 250714A: Global MASTER-Net observations report
  47. Fermi GRB 250711A: Global MASTER-Net observations report
  48. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  49. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  50. IPN triangulation of GRB 250703A
  51. GRB 250702B / EP2050702a: FTW optical and NIR observations
  52. Fermi GRB 250703A: Global MASTER-Net observations report
  53. GRB 250702F: Leavitt Observatory optical observations
  54. Fermi GRB 250702F: Global MASTER-Net observations report
  55. GRB 250628A: Swift-XRT refined Analysis
  56. Fermi GRB 250626A: Global MASTER-Net observations report
  57. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  58. Fermi trigger No 772190032: Global MASTER-Net observations report
  59. Konus-Wind detection of GRB 250620C
  60. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  61. GRB250620C: Fermi GBM Observation
  62. GRB 250620A: Fermi GBM Final Real-time Localization
  63. EP-WXT trigger 01709178975: GOTO optical upper limit
  64. Fermi trigger No 771752663: Global MASTER-Net observations report
  65. sb25061218: Swift-XRT observations
  66. GRB 250605A: Swift-BAT refined analysis
  67. GRB 250609A: Fermi GBM Observation
  68. Fermi trigger No 771072240: Global MASTER-Net observations report
  69. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  70. GRB 250609A: Fermi GBM Final Real-time Localization
  71. GRB 250605A: Enhanced Swift-XRT position
  72. Fermi GRB 250606A: Global MASTER-Net observations report
  73. The EP-WXT trigger 01709177873 is likely a flaring star
  74. GRB 250605A: LT optical observations
  75. GRB 250605A: Swift detection of a burst
  76. Fermi GRB 250601A: Global MASTER-Net observations report
  77. GRB 250602A: Fermi GBM Final Real-time Localization
  78. Fermi trigger No 770470765: Global MASTER-Net observations report
  79. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  80. GRB 250521D: LAST tentative optical counterpart candidate
  81. Fermi GRB 250516A: Global MASTER-Net observations report
  82. GRB 250515A: 1.6m Mephisto optical detection
  83. EP250512a: Global MASTER-Net observations report
  84. Fermi GRB 250510C: Global MASTER-Net observations report
  85. Fermi GRB 250510B: Global MASTER-Net observations report
  86. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  87. EP250508a: Global MASTER-Net observations report
  88. EP250508a: Einstein Probe detection of an X-ray transient
  89. IceCube Alert 250506.59: Global MASTER-Net observations report
  90. GRB 250504A: Swift-XRT refined Analysis
  91. EP250428b: SAO RAS optical upper limit
  92. EP250427a / GRB 250427A: LCO optical counterpart detection
  93. GRB 250424A: BlackGEM optical afterglow detection
  94. IceCube-250421A: DDOTI Detection of the LAST Candidate
  95. IceCube Alert 250421.71: Global MASTER-Net observations report
  96. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  97. GRB 250419A: MASTER optical afterglow observation
  98. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  99. EP250416a: Global MASTER-Net observations report
  100. EP250404a: Nanshan 0.43m Telescope optical observatios

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