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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"

3106 results found.

  1. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  2. GRB 251222A: SVOM/VT optical candidate
  3. SVOM GRB251219.11: Global MASTER-Net observations report
  4. Fermi trigger No 787736968: Global MASTER-Net observations report
  5. Fermi GRB 251216A: Global MASTER-Net observations report
  6. Fermi GRB 251215A: Global MASTER-Net observations report
  7. EP251214a: Global MASTER-Net observations report
  8. Fermi GRB 251214A: Global MASTER-Net observations report
  9. EP251212a: Global MASTER-Net observations report
  10. IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
  11. Fermi GBM Sub-Threshold Detection of GRB 251205A
  12. Fermi GRB 251208C: Global MASTER-Net observations report
  13. SVOM GRB251208D: Global MASTER-Net observations report
  14. GRB 251205A: COLIBRÍ optical observations
  15. GRB 251205A: Swift detection of a burst with an optical afterglow
  16. GRB 251203C: EP-FXT follow-up observation
  17. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  18. EP251130a: MAO/AZT-22 optical observations
  19. GRB 251201B: Swift detection of a burst with an optical counterpart
  20. EP251130a: SAO RAS optical observations
  21. EP251130a: Global MASTER-Net observations report
  22. GRB 251128A: SVOM/GRM observation of a long burst
  23. GRB 251128A: Fermi GBM Observation
  24. Fermi GRB 251128A: Global MASTER-Net observations report
  25. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  26. EP251118a: Optical detection with Kinder observations
  27. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  28. GRB 251119A: SVOM detection of a possible burst
  29. LAT GRB251118.86: Global MASTER-Net observations report
  30. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  31. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  32. GRB 251116C: LCO optical upper limits
  33. Fermi GRB 251115A: Global MASTER-Net observations report
  34. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  35. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  36. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  37. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  38. GRB 251112B: MAXI/GSC detection
  39. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  40. SVOM GRB251111.42: Global MASTER-Net observations report
  41. Fermi trigger No 784279167: Global MASTER-Net observations report
  42. SVOM GRB251106.83: Global MASTER-Net observations report
  43. GRB 251106A: MASTER optical observations
  44. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  45. Fermi GRB 251105A: Global MASTER-Net observations report
  46. GRB 251103B: MITSuME Akeno optical upper limits
  47. Fermi GRB 251103A: Global MASTER-Net observations report
  48. GRB 251103B: Swift detection of a burst
  49. GRB 251103A: BOOTES-2/TELMA optical afterglow
  50. GRB 251103A: NOT optical afterglow candidate
  51. Fermi GRB 251102A: Global MASTER-Net observations report
  52. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  53. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  54. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
  55. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  56. EP251027.145: COLIBRÍ optical upper limits
  57. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  58. Fermi GRB 251026B: Global MASTER-Net observations report
  59. GRB 251025B: GROWTH-India Telescope optical observations
  60. IceCube-251025A - IceCube observation of a high-energy neutrino candidate track-like event
  61. GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  62. GRB 251024A: Swift detection of a burst
  63. EP251023b: Global MASTER-Net observations report
  64. EP251023b/GRB 251023B : Einstein Probe detection of a fast X-ray transient
  65. GRB 251013C: ISON-Castelgrande observatory optical observations
  66. Fermi GRB 251023A: Global MASTER-Net observations report
  67. GRB 251016B: Fermi GBM Detection
  68. IceCube-251018A: Global MASTER-Net observations report
  69. Fermi GRB 251016B: Global MASTER-Net observations report
  70. GRB 251017A: BOOTES-5/JGT early optical afterglow detection
  71. GRB 251013D: Swift-XRT observations
  72. GRB 251014B: Swift/BAT-GUANO arcminute localization of a short burst
  73. GRB 251013C: ULL-ASTRO-MASTER detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  74. GRB 251013C: SAO RAS optical observations
  75. Fermi GRB 251013A: Global MASTER-Net observations report
  76. GRB 251011B : MASTER optical observations
  77. SVOM/sb25101004: SVOM detection of a stellar flare
  78. IceCube Alert 251008A: Global MASTER-Net observations report
  79. GRB 251007B: SVOM/VT optical candidate
  80. EP251003a: LCO and VST fading optical counterpart
  81. Fermi GRB 251006B: Global MASTER-Net observations report
  82. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  83. Fermi GRB 251002A: Global MASTER-Net observations report
  84. Swift GRB 251001B: Global MASTER-Net observations report
  85. GRB 251001A: Fermi GBM Detection
  86. GRB 250925A: COLIBRÍ photometric redshift
  87. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  88. GRB 250920C: COLIBRÍ optical observations
  89. Fermi GRB 250922B: Global MASTER-Net observations report
  90. GRB 250916A: CrAO ZTSh R-band optical observations
  91. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  92. GRB 250920B: Swift/UVOT Detection
  93. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  94. GRB 250919A/EP250919a: SVOM/VT optical observation
  95. Fermi GRB 250918A: Global MASTER-Net observations report
  96. GRB 250919A: Fermi GBM Final Real-time Localization
  97. Fermi GRB 250910B: Global MASTER-Net observations report
  98. EP250910a: Global MASTER-Net observations report
  99. GRB 250905A: Swift-BAT refined analysis
  100. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40

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