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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"

31730 results found.

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

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