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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: Global MASTER-Net observations report
  2. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  3. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  4. GRB 250706B: Swift/UVOT Detection
  5. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  6. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  7. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  8. GRB 250702F: GRANDMA observations
  9. GRB 250706A: Swift-XRT refined Analysis
  10. GRB 250706B: refined SVOM/MXT data analysis
  11. GRB 250706A: Swift/UVOT Upper Limits
  12. GRB 250706B: REM optical observations
  13. GRB 250706A: REM optical/NIR observations
  14. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  15. IceCube-250416A: DDOTI Optical Upper Limit
  16. IceCube-250706A: COLIBRÍ optical upper limits
  17. Swift GRB 250706A: Global MASTER-Net observations report
  18. GRB 250706A: JinShan optical upper limits
  19. GRB 250706A: SAO RAS optical observations
  20. EP250704A: NOWT Detection
  21. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  22. The EP-WXT trigger 01709181580 is likely a flaring star
  23. GRB250706B: Swift-XRT counterpart detection
  24. GRB 250706B: iTelescope optical observations
  25. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  26. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  27. GRB 250706B: SVOM/VT optical observation
  28. GRB 250706B: TRT bright optical counterpart detection
  29. GRB 250706A: GROWTH-India Telescope optical upper limit
  30. GRB 250706B: SVOM detection of a long burst
  31. GRB 250706A: Swift detection of a burst
  32. GRB 250704B: Swift-XRT refined Analysis
  33. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  34. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  35. GRB 250703A: EIRSAT-1 GMOD Detection
  36. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  37. GRB 250704B: Swift/UVOT Upper Limits
  38. GRB 250704A: Swift/UVOT Detection
  39. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  40. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  41. GRB 250704B: Insight-HXMT detection
  42. Konus-Wind detection of GRB 250703A
  43. IPN triangulation of GRB 250703A
  44. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  45. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  46. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  47. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  48. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  49. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  50. GRB 250702F: Kilonova-Catcher optical afterglow detection
  51. GRB 250702F: Monte Agliale Observatory optical observations
  52. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  53. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  54. EP250704a / GRB 250704B: JinShan optical observations
  55. GRB 250704A: SVOM/VT optical observation
  56. EP250704a / GRB 250704B: SAO RAS optical observations
  57. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  58. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  59. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  60. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  61. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  62. EP 250704a: BOOTES-5 optical detection
  63. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  64. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  65. GRB 250702A: Insight-HXMT detection
  66. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  67. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  68. EP250704a / GRB250704B: Swift-XRT counterpart detection
  69. GRB 250704A: Swift-XRT afterglow detection
  70. GRB 250702B / EP2050702a: FTW optical and NIR observations
  71. Konus-Wind detection of GRB 250702F
  72. EP250704a / GRB 250704B - REM observations
  73. GRB 250702F: GROWTH-India Telescope optical observations
  74. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  75. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  76. EP250702a: WFST optical observations
  77. EP250704a: COLIBRÍ optical counterpart candidate
  78. EP250704a: Einstein Probe detection of an X-ray transient
  79. GRB 250704B: SVOM/GRM observation of a short burst
  80. GRB 250702F: optical photometry from Konkoly
  81. GRB 250704A: REM detection of the optical afterglow
  82. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  83. GRB 250702F: SVOM/VT optical observation
  84. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  85. GRB 250704A: SVOM detection of a burst
  86. GRB 250702F: Swift/UVOT Detection
  87. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  88. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  89. Fermi GRB 250703A: Global MASTER-Net observations report
  90. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  91. GRB 250702F: Swift-XRT refined Analysis
  92. GRB 250702F: Fermi GBM Observation
  93. GRB 250702F: Leavitt Observatory optical observations
  94. GRB 250702F: AKO Optical Afterglow Detection
  95. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  96. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  97. GRB 250702A: GECAM-B detection
  98. GRB 250702F: Skynet Optical Observations
  99. GRB 250424A: VIRT Optical Upper Limit
  100. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization

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