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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').
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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"

32532 results found.

  1. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  2. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  3. GRB 250702F: GRANDMA observations
  4. GRB 250706B: refined SVOM/MXT data analysis
  5. GRB 250706A: Swift/UVOT Upper Limits
  6. GRB 250706B: REM optical observations
  7. GRB 250706A: REM optical/NIR observations
  8. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  9. IceCube-250416A: DDOTI Optical Upper Limit
  10. IceCube-250706A: COLIBRÍ optical upper limits
  11. Swift GRB 250706A: Global MASTER-Net observations report
  12. GRB 250706A: JinShan optical upper limits
  13. GRB 250706A: SAO RAS optical observations
  14. EP250704A: NOWT Detection
  15. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  16. GRB250706B: Swift-XRT counterpart detection
  17. GRB 250706B: iTelescope optical observations
  18. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  19. GRB 250706B: SVOM/VT optical observation
  20. GRB 250706B: TRT bright optical counterpart detection
  21. GRB 250706A: GROWTH-India Telescope optical upper limit
  22. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  23. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  24. GRB 250703A: EIRSAT-1 GMOD Detection
  25. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  26. GRB 250704B: Swift/UVOT Upper Limits
  27. GRB 250704A: Swift/UVOT Detection
  28. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  29. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  30. GRB 250704B: Insight-HXMT detection
  31. Konus-Wind detection of GRB 250703A
  32. IPN triangulation of GRB 250703A
  33. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  34. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  35. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  36. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  37. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  38. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  39. GRB 250702F: Kilonova-Catcher optical afterglow detection
  40. GRB 250702F: Monte Agliale Observatory optical observations
  41. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  42. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  43. EP250704a / GRB 250704B: JinShan optical observations
  44. GRB 250704A: SVOM/VT optical observation
  45. EP250704a / GRB 250704B: SAO RAS optical observations
  46. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  47. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  48. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  49. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  50. EP 250704a: BOOTES-5 optical detection
  51. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  52. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  53. GRB 250702A: Insight-HXMT detection
  54. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  55. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  56. EP250704a / GRB250704B: Swift-XRT counterpart detection
  57. GRB 250704A: Swift-XRT afterglow detection
  58. GRB 250702B / EP2050702a: FTW optical and NIR observations
  59. Konus-Wind detection of GRB 250702F
  60. EP250704a / GRB 250704B - REM observations
  61. GRB 250702F: GROWTH-India Telescope optical observations
  62. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  63. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  64. EP250702a: WFST optical observations
  65. EP250704a: COLIBRÍ optical counterpart candidate
  66. EP250704a: Einstein Probe detection of an X-ray transient
  67. GRB 250702F: optical photometry from Konkoly
  68. GRB 250704A: REM detection of the optical afterglow
  69. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  70. GRB 250702F: SVOM/VT optical observation
  71. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  72. GRB 250702F: Swift/UVOT Detection
  73. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  74. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  75. Fermi GRB 250703A: Global MASTER-Net observations report
  76. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  77. GRB 250702F: Fermi GBM Observation
  78. GRB 250702F: Leavitt Observatory optical observations
  79. GRB 250702F: AKO Optical Afterglow Detection
  80. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  81. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  82. GRB 250702A: GECAM-B detection
  83. GRB 250702F: Skynet Optical Observations
  84. GRB 250424A: VIRT Optical Upper Limit
  85. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  86. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  87. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  88. GRB 250702F: TRT Optical Observation
  89. GRB 250703A: DDOTI Optical Upper Limit
  90. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  91. GRB 250702F: REM optical afterglow detection
  92. EP250702a: Global MASTER-Net observations report
  93. GRB 250702F: DDOTI Optical Observation
  94. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  95. GRB 250702F: COLIBRÍ Observations of the Afterglow
  96. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  97. Fermi GRB 250702E: Global MASTER-Net observations report
  98. Fermi GRB 250702B: Global MASTER-Net observations report
  99. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  100. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520

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