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