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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. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  2. EP250704a/GRB250704B : HCT optical and NIR upper limits
  3. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  4. GRB 250708A: Fermi GBM Final Real-time Localization
  5. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  6. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  7. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  8. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  9. GRB 250702F: radio detection with the VLA
  10. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  11. IceCube-250706A: EP-FXT follow-up observations
  12. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  13. GRB 250706B/C: Fermi-LAT detection
  14. IceCube-250706A: Global MASTER-Net observations report
  15. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  16. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  17. GRB 250706B: Swift/UVOT Detection
  18. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  19. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  20. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  21. GRB 250702F: GRANDMA observations
  22. GRB 250706A: Swift-XRT refined Analysis
  23. GRB 250706B: refined SVOM/MXT data analysis
  24. GRB 250706A: Swift/UVOT Upper Limits
  25. GRB 250706B: REM optical observations
  26. GRB 250706A: REM optical/NIR observations
  27. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  28. IceCube-250416A: DDOTI Optical Upper Limit
  29. IceCube-250706A: COLIBRÍ optical upper limits
  30. Swift GRB 250706A: Global MASTER-Net observations report
  31. GRB 250706A: JinShan optical upper limits
  32. GRB 250706A: SAO RAS optical observations
  33. EP250704A: NOWT Detection
  34. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  35. The EP-WXT trigger 01709181580 is likely a flaring star
  36. GRB250706B: Swift-XRT counterpart detection
  37. GRB 250706B: iTelescope optical observations
  38. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  39. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  40. GRB 250706B: SVOM/VT optical observation
  41. GRB 250706B: TRT bright optical counterpart detection
  42. GRB 250706A: GROWTH-India Telescope optical upper limit
  43. GRB 250706B: SVOM detection of a long burst
  44. GRB 250706A: Swift detection of a burst
  45. GRB 250704B: Swift-XRT refined Analysis
  46. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  47. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  48. GRB 250703A: EIRSAT-1 GMOD Detection
  49. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  50. GRB 250704B: Swift/UVOT Upper Limits
  51. GRB 250704A: Swift/UVOT Detection
  52. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  53. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  54. GRB 250704B: Insight-HXMT detection
  55. Konus-Wind detection of GRB 250703A
  56. IPN triangulation of GRB 250703A
  57. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  58. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  59. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  60. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  61. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  62. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  63. GRB 250702F: Kilonova-Catcher optical afterglow detection
  64. GRB 250702F: Monte Agliale Observatory optical observations
  65. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  66. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  67. EP250704a / GRB 250704B: JinShan optical observations
  68. GRB 250704A: SVOM/VT optical observation
  69. EP250704a / GRB 250704B: SAO RAS optical observations
  70. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  71. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  72. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  73. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  74. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  75. EP 250704a: BOOTES-5 optical detection
  76. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  77. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  78. GRB 250702A: Insight-HXMT detection
  79. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  80. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  81. EP250704a / GRB250704B: Swift-XRT counterpart detection
  82. GRB 250704A: Swift-XRT afterglow detection
  83. GRB 250702B / EP2050702a: FTW optical and NIR observations
  84. Konus-Wind detection of GRB 250702F
  85. EP250704a / GRB 250704B - REM observations
  86. GRB 250702F: GROWTH-India Telescope optical observations
  87. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  88. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  89. EP250702a: WFST optical observations
  90. EP250704a: COLIBRÍ optical counterpart candidate
  91. EP250704a: Einstein Probe detection of an X-ray transient
  92. GRB 250704B: SVOM/GRM observation of a short burst
  93. GRB 250702F: optical photometry from Konkoly
  94. GRB 250704A: REM detection of the optical afterglow
  95. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  96. GRB 250702F: SVOM/VT optical observation
  97. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  98. GRB 250704A: SVOM detection of a burst
  99. GRB 250702F: Swift/UVOT Detection
  100. GRB 250702A: CALET Gamma-Ray Burst Monitor detection

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