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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"

4179 results found.

  1. EP260128a: Global MASTER-Net observations report
  2. GRB 251222A: SVOM/ECLAIRs refined analysis
  3. GRB 260125A: GOTO candidate optical counterpart
  4. GRB 260120B: SVOM/C-GFT optical counterpart detection
  5. SVOM GRB260119.90: Global MASTER-Net observations report
  6. EP260119a: Global MASTER-Net observations report
  7. EP260119a: COLIBRÍ optical counterpart candidate
  8. SVOM GRB260117.82: Global MASTER-Net observations report
  9. Swift trigger on the HMXB 1A 1118-61
  10. EP 260116a: COLIBRÍ optical upper limit
  11. GRB 260114A: Fermi GBM observation
  12. Swift Trigger 1439093: is probably not GRB 260113A
  13. GRB 260111A: GOTO optical upper limits
  14. EP260110a: SVOM/VT optical upper limits
  15. GRB 260109C: LCO optical upper limits
  16. FRB 20251229A: COLIBRÍ optical upper limits
  17. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  18. Fermi GRB 260104B: Global MASTER-Net observations report
  19. Swift GRB 260104A: Global MASTER-Net observations report
  20. EP251229a: BOOTES-2 early optical upper limit
  21. EP251229a: NOT optical upper limits
  22. EP251229a: Global MASTER-Net observations report
  23. Fermi GRB 251228A: Global MASTER-Net observations report
  24. SVOM GRB251227.07: Global MASTER-Net observations report
  25. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  26. EP251222b/GRB 251222A: SVOM/GRM observation
  27. GRB 251222A: SVOM detection of a long burst
  28. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  29. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  30. SVOM GRB251219.11: Global MASTER-Net observations report
  31. Fermi GRB 251217A: Global MASTER-Net observations report
  32. Fermi GRB 251216A: Global MASTER-Net observations report
  33. Fermi GRB 251215A: Global MASTER-Net observations report
  34. EP251212a: Global MASTER-Net observations report
  35. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  36. Fermi GRB 251208C: Global MASTER-Net observations report
  37. GRB 251208D: Swift-XRT observations
  38. GRB 251205A: ZTF and ATLAS optical afterglow detections
  39. GRB 251205A: Swift/UVOT Detection
  40. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  41. GRB 251205A: Swift detection of a burst with an optical afterglow
  42. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  43. GRB 251129B: Glowbug gamma-ray detection of a short burst
  44. EP251130a: JinShan near-infrared observations
  45. GRB 251129B: AstroSat CZTI detection
  46. EP251129a/GRB 251129A: NOWT Detection
  47. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  48. EP251130a: SAO RAS optical observations
  49. GRB 251201A: MAXI/GSC detection
  50. Fermi GRB 251130B: Global MASTER-Net observations report
  51. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  52. GRB 251129A / EP251129a: SAO RAS optical observations
  53. GRB 251126A: SAO RAS optical observations
  54. SVOM GRB 251129A : MASTER optical counterpart detection
  55. EP251129a: Global MASTER-Net observations report
  56. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  57. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  58. SVOM GRB251129A: Global MASTER-Net observations report
  59. Fermi GRB 251125B: Global MASTER-Net observations report
  60. Fermi GRB 251125A: Global MASTER-Net observations report
  61. Fermi GRB 251124a: Global MASTER-Net observations report
  62. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  63. Konus-Wind detection of GRB 251118C (EP251118a)
  64. LAT GRB251118.86: Global MASTER-Net observations report
  65. EP251118a: Einstein Probe detected of a fast X-ray transient
  66. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  67. LAT GRB251117.51: Global MASTER-Net observations report
  68. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  69. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  70. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  71. GRB 251025B: further Mondy optical observations
  72. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  73. Konus-Wind detection of GRB 251108C
  74. Fermi trigger No 784717756: Global MASTER-Net observations report
  75. Fermi GRB 251114A: Global MASTER-Net observations report
  76. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  77. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  78. SVOM GRB251108.54: Global MASTER-Net observations report
  79. SVOM GRB251106.83: Global MASTER-Net observations report
  80. GRB 251106A: MASTER optical observations
  81. GRB 251103A: WFST optical observations
  82. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  83. Fermi GRB 251103A: Global MASTER-Net observations report
  84. Fermi GRB 251102A: Global MASTER-Net observations report
  85. GRB 251027A: Swift-XRT observations
  86. GRB 251026B: Tentative GOTO optical counterpart candidate
  87. Fermi GRB 251026B: Global MASTER-Net observations report
  88. Fermi GRB 251025C: Global MASTER-Net observations report
  89. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  90. GRB 251003A: VLA Detection
  91. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  92. EP251023a: COLIBRÍ optical observations
  93. Fermi GRB 251023A: Global MASTER-Net observations report
  94. GRB 250911A: MAXI/GSC detection
  95. IceCube-251018A: Global MASTER-Net observations report
  96. Fermi GRB 251016B: Global MASTER-Net observations report
  97. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  98. Fermi GRB 251013C: Global MASTER-Net observations report
  99. Fermi GRB 251013B: Global MASTER-Net observations report
  100. GRB 251011B : MASTER optical observations

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