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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"
  1. IceCube-250706A: EP-FXT follow-up observations
  2. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  3. GRB 250706B/C: Fermi-LAT detection
  4. IceCube-250706A: Global MASTER-Net observations report
  5. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  6. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  7. GRB 250706B: Swift/UVOT Detection
  8. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  9. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  10. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  11. GRB 250702F: GRANDMA observations
  12. GRB 250706A: Swift-XRT refined Analysis
  13. GRB 250706B: refined SVOM/MXT data analysis
  14. GRB 250706A: Swift/UVOT Upper Limits
  15. GRB 250706B: REM optical observations
  16. GRB 250706A: REM optical/NIR observations
  17. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  18. IceCube-250416A: DDOTI Optical Upper Limit
  19. IceCube-250706A: COLIBRÍ optical upper limits
  20. Swift GRB 250706A: Global MASTER-Net observations report
  21. GRB 250706A: JinShan optical upper limits
  22. GRB 250706A: SAO RAS optical observations
  23. EP250704A: NOWT Detection
  24. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  25. The EP-WXT trigger 01709181580 is likely a flaring star
  26. GRB250706B: Swift-XRT counterpart detection
  27. GRB 250706B: iTelescope optical observations
  28. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  29. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  30. GRB 250706B: SVOM/VT optical observation
  31. GRB 250706B: TRT bright optical counterpart detection
  32. GRB 250706A: GROWTH-India Telescope optical upper limit
  33. GRB 250706B: SVOM detection of a long burst
  34. GRB 250706A: Swift detection of a burst
  35. GRB 250704B: Swift-XRT refined Analysis
  36. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  37. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  38. GRB 250703A: EIRSAT-1 GMOD Detection
  39. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  40. GRB 250704B: Swift/UVOT Upper Limits
  41. GRB 250704A: Swift/UVOT Detection
  42. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  43. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  44. GRB 250704B: Insight-HXMT detection
  45. Konus-Wind detection of GRB 250703A
  46. IPN triangulation of GRB 250703A
  47. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  48. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  49. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  50. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  51. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  52. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  53. GRB 250702F: Kilonova-Catcher optical afterglow detection
  54. GRB 250702F: Monte Agliale Observatory optical observations
  55. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  56. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  57. EP250704a / GRB 250704B: JinShan optical observations
  58. GRB 250704A: SVOM/VT optical observation
  59. EP250704a / GRB 250704B: SAO RAS optical observations
  60. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  61. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  62. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  63. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  64. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  65. EP 250704a: BOOTES-5 optical detection
  66. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  67. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  68. GRB 250702A: Insight-HXMT detection
  69. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  70. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  71. EP250704a / GRB250704B: Swift-XRT counterpart detection
  72. GRB 250704A: Swift-XRT afterglow detection
  73. GRB 250702B / EP2050702a: FTW optical and NIR observations
  74. Konus-Wind detection of GRB 250702F
  75. EP250704a / GRB 250704B - REM observations
  76. GRB 250702F: GROWTH-India Telescope optical observations
  77. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  78. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  79. EP250702a: WFST optical observations
  80. EP250704a: COLIBRÍ optical counterpart candidate
  81. EP250704a: Einstein Probe detection of an X-ray transient
  82. GRB 250704B: SVOM/GRM observation of a short burst
  83. GRB 250702F: optical photometry from Konkoly
  84. GRB 250704A: REM detection of the optical afterglow
  85. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  86. GRB 250702F: SVOM/VT optical observation
  87. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  88. GRB 250704A: SVOM detection of a burst
  89. GRB 250702F: Swift/UVOT Detection
  90. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  91. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  92. Fermi GRB 250703A: Global MASTER-Net observations report
  93. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  94. GRB 250702F: Swift-XRT refined Analysis
  95. GRB 250702F: Fermi GBM Observation
  96. GRB 250702F: Leavitt Observatory optical observations
  97. GRB 250702F: AKO Optical Afterglow Detection
  98. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  99. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  100. GRB 250702A: GECAM-B detection

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