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

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