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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"

4044 results found.

  1. Fermi GRB 251208C: Global MASTER-Net observations report
  2. GRB 251208D: Swift-XRT observations
  3. GRB 251205A: ZTF and ATLAS optical afterglow detections
  4. GRB 251205A: Swift/UVOT Detection
  5. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  6. GRB 251205A: Swift detection of a burst with an optical afterglow
  7. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  8. GRB 251129B: Glowbug gamma-ray detection of a short burst
  9. EP251130a: JinShan near-infrared observations
  10. GRB 251129B: AstroSat CZTI detection
  11. EP251129a/GRB 251129A: NOWT Detection
  12. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  13. EP251130a: SAO RAS optical observations
  14. GRB 251201A: MAXI/GSC detection
  15. Fermi GRB 251130B: Global MASTER-Net observations report
  16. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  17. GRB 251129A / EP251129a: SAO RAS optical observations
  18. GRB 251126A: SAO RAS optical observations
  19. SVOM GRB 251129A : MASTER optical counterpart detection
  20. EP251129a: Global MASTER-Net observations report
  21. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  22. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  23. SVOM GRB251129A: Global MASTER-Net observations report
  24. Fermi GRB 251125B: Global MASTER-Net observations report
  25. Fermi GRB 251125A: Global MASTER-Net observations report
  26. Fermi GRB 251124a: Global MASTER-Net observations report
  27. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  28. Konus-Wind detection of GRB 251118C (EP251118a)
  29. LAT GRB251118.86: Global MASTER-Net observations report
  30. EP251118a: Einstein Probe detected of a fast X-ray transient
  31. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  32. LAT GRB251117.51: Global MASTER-Net observations report
  33. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  34. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  35. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  36. GRB 251025B: further Mondy optical observations
  37. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  38. Konus-Wind detection of GRB 251108C
  39. Fermi trigger No 784717756: Global MASTER-Net observations report
  40. Fermi GRB 251114A: Global MASTER-Net observations report
  41. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  42. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  43. SVOM GRB251108.54: Global MASTER-Net observations report
  44. SVOM GRB251106.83: Global MASTER-Net observations report
  45. GRB 251106A: MASTER optical observations
  46. GRB 251103A: WFST optical observations
  47. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  48. Fermi GRB 251103A: Global MASTER-Net observations report
  49. Fermi GRB 251102A: Global MASTER-Net observations report
  50. GRB 251027A: Swift-XRT observations
  51. GRB 251026B: Tentative GOTO optical counterpart candidate
  52. Fermi GRB 251026B: Global MASTER-Net observations report
  53. Fermi GRB 251025C: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  55. GRB 251003A: VLA Detection
  56. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  57. EP251023a: COLIBRÍ optical observations
  58. Fermi GRB 251023A: Global MASTER-Net observations report
  59. GRB 250911A: MAXI/GSC detection
  60. IceCube-251018A: Global MASTER-Net observations report
  61. Fermi GRB 251016B: Global MASTER-Net observations report
  62. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  63. Fermi GRB 251013C: Global MASTER-Net observations report
  64. Fermi GRB 251013B: Global MASTER-Net observations report
  65. GRB 251011B : MASTER optical observations
  66. GRB 251011A: AstroSat CZTI detection
  67. GRB 250916A: TERI Gamma-ray detection
  68. EP251006a: Global MASTER-Net observations report
  69. GRB 251007B: SVOM/C-GFT upper limit
  70. EP251003a: LCO and VST fading optical counterpart
  71. Fermi GRB 251006B: Global MASTER-Net observations report
  72. GRB 251003A: Enhanced Swift-XRT position
  73. GRB 251003A: Prompt enhanced Swift-XRT position
  74. GRB 251003A: Swift detection of a burst
  75. Fermi GRB 250929A: Global MASTER-Net observations report
  76. GRB 250929A: Fermi GBM Final Real-time Localization
  77. GRB 250916A: SVOM/VT optical observation
  78. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  79. Fermi trigger No 780609036: Global MASTER-Net observations report
  80. GRB 250924A: COLIBRÍ optical observations
  81. GRB 250924A: Swift detection of a burst with an optical counterpart
  82. Konus-Wind detection of GRB 250911A
  83. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  84. GRB 250917B: KAIT optical upper limit
  85. GRB 250920B: Swift/UVOT Detection
  86. GRB250920C: LCOGT Optical Detection
  87. GRB 250920C: GOTO optical counterpart candidate
  88. Konus-Wind detection of GRB 250919A
  89. GRB 250919A / EP250919a: Insight-HXMT detection
  90. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  91. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  92. GRB 250919A: SVOM/GRM observation of a very bright GRB
  93. EP250919a: Global MASTER-Net observations report
  94. GRB 250916A: Fermi GBM Observation
  95. GRB 250916A: further SAO RAS optical observations
  96. GRB 250916A: Glowbug gamma-ray detection
  97. GRB 250917B: Swift detection of a short burst
  98. GRB 250916A: AstroSat CZTI detection of a bright long burst
  99. GRB 250916A: Fermi GBM Final Real-time Localization
  100. GRB 250911A: Insight-HXMT detection

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