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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"

4252 results found.

  1. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  2. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  3. SVOM GRB251219.11: Global MASTER-Net observations report
  4. Fermi GRB 251217A: Global MASTER-Net observations report
  5. Fermi GRB 251216A: Global MASTER-Net observations report
  6. Fermi GRB 251215A: Global MASTER-Net observations report
  7. EP251212a: Global MASTER-Net observations report
  8. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  9. Fermi GRB 251208C: Global MASTER-Net observations report
  10. GRB 251208D: Swift-XRT observations
  11. GRB 251205A: ZTF and ATLAS optical afterglow detections
  12. GRB 251205A: Swift/UVOT Detection
  13. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  14. GRB 251205A: Swift detection of a burst with an optical afterglow
  15. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  16. GRB 251129B: Glowbug gamma-ray detection of a short burst
  17. EP251130a: JinShan near-infrared observations
  18. GRB 251129B: AstroSat CZTI detection
  19. EP251129a/GRB 251129A: NOWT Detection
  20. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  21. EP251130a: SAO RAS optical observations
  22. GRB 251201A: MAXI/GSC detection
  23. Fermi GRB 251130B: Global MASTER-Net observations report
  24. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  25. GRB 251129A / EP251129a: SAO RAS optical observations
  26. GRB 251126A: SAO RAS optical observations
  27. SVOM GRB 251129A : MASTER optical counterpart detection
  28. EP251129a: Global MASTER-Net observations report
  29. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  30. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  31. SVOM GRB251129A: Global MASTER-Net observations report
  32. Fermi GRB 251125B: Global MASTER-Net observations report
  33. Fermi GRB 251125A: Global MASTER-Net observations report
  34. Fermi GRB 251124a: Global MASTER-Net observations report
  35. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  36. Konus-Wind detection of GRB 251118C (EP251118a)
  37. LAT GRB251118.86: Global MASTER-Net observations report
  38. EP251118a: Einstein Probe detected of a fast X-ray transient
  39. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  40. LAT GRB251117.51: Global MASTER-Net observations report
  41. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  42. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  43. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  44. GRB 251025B: further Mondy optical observations
  45. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  46. Konus-Wind detection of GRB 251108C
  47. Fermi trigger No 784717756: Global MASTER-Net observations report
  48. Fermi GRB 251114A: Global MASTER-Net observations report
  49. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  50. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  51. SVOM GRB251108.54: Global MASTER-Net observations report
  52. SVOM GRB251106.83: Global MASTER-Net observations report
  53. GRB 251106A: MASTER optical observations
  54. GRB 251103A: WFST optical observations
  55. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  56. Fermi GRB 251103A: Global MASTER-Net observations report
  57. Fermi GRB 251102A: Global MASTER-Net observations report
  58. GRB 251027A: Swift-XRT observations
  59. GRB 251026B: Tentative GOTO optical counterpart candidate
  60. Fermi GRB 251026B: Global MASTER-Net observations report
  61. Fermi GRB 251025C: Global MASTER-Net observations report
  62. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  63. GRB 251003A: VLA Detection
  64. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  65. EP251023a: COLIBRÍ optical observations
  66. Fermi GRB 251023A: Global MASTER-Net observations report
  67. GRB 250911A: MAXI/GSC detection
  68. IceCube-251018A: Global MASTER-Net observations report
  69. Fermi GRB 251016B: Global MASTER-Net observations report
  70. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  71. Fermi GRB 251013C: Global MASTER-Net observations report
  72. Fermi GRB 251013B: Global MASTER-Net observations report
  73. GRB 251011B : MASTER optical observations
  74. GRB 251011A: AstroSat CZTI detection
  75. GRB 250916A: TERI Gamma-ray detection
  76. EP251006a: Global MASTER-Net observations report
  77. GRB 251007B: SVOM/C-GFT upper limit
  78. EP251003a: LCO and VST fading optical counterpart
  79. Fermi GRB 251006B: Global MASTER-Net observations report
  80. GRB 251003A: Enhanced Swift-XRT position
  81. GRB 251003A: Prompt enhanced Swift-XRT position
  82. GRB 251003A: Swift detection of a burst
  83. Fermi GRB 250929A: Global MASTER-Net observations report
  84. GRB 250929A: Fermi GBM Final Real-time Localization
  85. GRB 250916A: SVOM/VT optical observation
  86. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  87. Fermi trigger No 780609036: Global MASTER-Net observations report
  88. GRB 250924A: COLIBRÍ optical observations
  89. GRB 250924A: Swift detection of a burst with an optical counterpart
  90. Konus-Wind detection of GRB 250911A
  91. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  92. GRB 250917B: KAIT optical upper limit
  93. GRB 250920B: Swift/UVOT Detection
  94. GRB250920C: LCOGT Optical Detection
  95. GRB 250920C: GOTO optical counterpart candidate
  96. Konus-Wind detection of GRB 250919A
  97. GRB 250919A / EP250919a: Insight-HXMT detection
  98. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  99. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  100. GRB 250919A: SVOM/GRM observation of a very bright GRB

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