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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"

4169 results found.

  1. GRB 260114A: Fermi GBM observation
  2. Swift Trigger 1439093: is probably not GRB 260113A
  3. GRB 260111A: GOTO optical upper limits
  4. EP260110a: SVOM/VT optical upper limits
  5. GRB 260109C: LCO optical upper limits
  6. FRB 20251229A: COLIBRÍ optical upper limits
  7. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  8. Fermi GRB 260104B: Global MASTER-Net observations report
  9. Swift GRB 260104A: Global MASTER-Net observations report
  10. EP251229a: BOOTES-2 early optical upper limit
  11. EP251229a: NOT optical upper limits
  12. EP251229a: Global MASTER-Net observations report
  13. Fermi GRB 251228A: Global MASTER-Net observations report
  14. SVOM GRB251227.07: Global MASTER-Net observations report
  15. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  16. EP251222b/GRB 251222A: SVOM/GRM observation
  17. GRB 251222A: SVOM detection of a long burst
  18. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  19. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  20. SVOM GRB251219.11: Global MASTER-Net observations report
  21. Fermi GRB 251217A: Global MASTER-Net observations report
  22. Fermi GRB 251216A: Global MASTER-Net observations report
  23. Fermi GRB 251215A: Global MASTER-Net observations report
  24. EP251212a: Global MASTER-Net observations report
  25. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  26. Fermi GRB 251208C: Global MASTER-Net observations report
  27. GRB 251208D: Swift-XRT observations
  28. GRB 251205A: ZTF and ATLAS optical afterglow detections
  29. GRB 251205A: Swift/UVOT Detection
  30. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  31. GRB 251205A: Swift detection of a burst with an optical afterglow
  32. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  33. GRB 251129B: Glowbug gamma-ray detection of a short burst
  34. EP251130a: JinShan near-infrared observations
  35. GRB 251129B: AstroSat CZTI detection
  36. EP251129a/GRB 251129A: NOWT Detection
  37. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  38. EP251130a: SAO RAS optical observations
  39. GRB 251201A: MAXI/GSC detection
  40. Fermi GRB 251130B: Global MASTER-Net observations report
  41. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  42. GRB 251129A / EP251129a: SAO RAS optical observations
  43. GRB 251126A: SAO RAS optical observations
  44. SVOM GRB 251129A : MASTER optical counterpart detection
  45. EP251129a: Global MASTER-Net observations report
  46. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  47. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  48. SVOM GRB251129A: Global MASTER-Net observations report
  49. Fermi GRB 251125B: Global MASTER-Net observations report
  50. Fermi GRB 251125A: Global MASTER-Net observations report
  51. Fermi GRB 251124a: Global MASTER-Net observations report
  52. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  53. Konus-Wind detection of GRB 251118C (EP251118a)
  54. LAT GRB251118.86: Global MASTER-Net observations report
  55. EP251118a: Einstein Probe detected of a fast X-ray transient
  56. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  57. LAT GRB251117.51: Global MASTER-Net observations report
  58. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  59. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  60. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  61. GRB 251025B: further Mondy optical observations
  62. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  63. Konus-Wind detection of GRB 251108C
  64. Fermi trigger No 784717756: Global MASTER-Net observations report
  65. Fermi GRB 251114A: Global MASTER-Net observations report
  66. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  67. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  68. SVOM GRB251108.54: Global MASTER-Net observations report
  69. SVOM GRB251106.83: Global MASTER-Net observations report
  70. GRB 251106A: MASTER optical observations
  71. GRB 251103A: WFST optical observations
  72. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  73. Fermi GRB 251103A: Global MASTER-Net observations report
  74. Fermi GRB 251102A: Global MASTER-Net observations report
  75. GRB 251027A: Swift-XRT observations
  76. GRB 251026B: Tentative GOTO optical counterpart candidate
  77. Fermi GRB 251026B: Global MASTER-Net observations report
  78. Fermi GRB 251025C: Global MASTER-Net observations report
  79. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  80. GRB 251003A: VLA Detection
  81. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  82. EP251023a: COLIBRÍ optical observations
  83. Fermi GRB 251023A: Global MASTER-Net observations report
  84. GRB 250911A: MAXI/GSC detection
  85. IceCube-251018A: Global MASTER-Net observations report
  86. Fermi GRB 251016B: Global MASTER-Net observations report
  87. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  88. Fermi GRB 251013C: Global MASTER-Net observations report
  89. Fermi GRB 251013B: Global MASTER-Net observations report
  90. GRB 251011B : MASTER optical observations
  91. GRB 251011A: AstroSat CZTI detection
  92. GRB 250916A: TERI Gamma-ray detection
  93. EP251006a: Global MASTER-Net observations report
  94. GRB 251007B: SVOM/C-GFT upper limit
  95. EP251003a: LCO and VST fading optical counterpart
  96. Fermi GRB 251006B: Global MASTER-Net observations report
  97. GRB 251003A: Enhanced Swift-XRT position
  98. GRB 251003A: Prompt enhanced Swift-XRT position
  99. GRB 251003A: Swift detection of a burst
  100. Fermi GRB 250929A: Global MASTER-Net observations report

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