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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. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  2. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  3. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  4. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  5. EP250704a/GRB250704B : HCT optical and NIR upper limits
  6. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  7. GRB 250708A: Fermi GBM Final Real-time Localization
  8. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  9. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  10. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  11. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  12. GRB 250702F: radio detection with the VLA
  13. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  14. IceCube-250706A: EP-FXT follow-up observations
  15. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  16. GRB 250706B/C: Fermi-LAT detection
  17. IceCube-250706A: Global MASTER-Net observations report
  18. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  19. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  20. GRB 250706B: Swift/UVOT Detection
  21. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  22. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  23. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  24. GRB 250702F: GRANDMA observations
  25. GRB 250706A: Swift-XRT refined Analysis
  26. GRB 250706B: refined SVOM/MXT data analysis
  27. GRB 250706A: Swift/UVOT Upper Limits
  28. GRB 250706B: REM optical observations
  29. GRB 250706A: REM optical/NIR observations
  30. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  31. IceCube-250416A: DDOTI Optical Upper Limit
  32. IceCube-250706A: COLIBRÍ optical upper limits
  33. Swift GRB 250706A: Global MASTER-Net observations report
  34. GRB 250706A: JinShan optical upper limits
  35. GRB 250706A: SAO RAS optical observations
  36. EP250704A: NOWT Detection
  37. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  38. The EP-WXT trigger 01709181580 is likely a flaring star
  39. GRB250706B: Swift-XRT counterpart detection
  40. GRB 250706B: iTelescope optical observations
  41. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  42. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  43. GRB 250706B: SVOM/VT optical observation
  44. GRB 250706B: TRT bright optical counterpart detection
  45. GRB 250706A: GROWTH-India Telescope optical upper limit
  46. GRB 250706B: SVOM detection of a long burst
  47. GRB 250706A: Swift detection of a burst
  48. GRB 250704B: Swift-XRT refined Analysis
  49. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  50. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  51. GRB 250703A: EIRSAT-1 GMOD Detection
  52. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  53. GRB 250704B: Swift/UVOT Upper Limits
  54. GRB 250704A: Swift/UVOT Detection
  55. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  56. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  57. GRB 250704B: Insight-HXMT detection
  58. Konus-Wind detection of GRB 250703A
  59. IPN triangulation of GRB 250703A
  60. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  61. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  62. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  63. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  64. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  65. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  66. GRB 250702F: Kilonova-Catcher optical afterglow detection
  67. GRB 250702F: Monte Agliale Observatory optical observations
  68. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  69. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  70. EP250704a / GRB 250704B: JinShan optical observations
  71. GRB 250704A: SVOM/VT optical observation
  72. EP250704a / GRB 250704B: SAO RAS optical observations
  73. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  74. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  75. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  76. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  77. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  78. EP 250704a: BOOTES-5 optical detection
  79. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  80. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  81. GRB 250702A: Insight-HXMT detection
  82. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  83. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  84. EP250704a / GRB250704B: Swift-XRT counterpart detection
  85. GRB 250704A: Swift-XRT afterglow detection
  86. GRB 250702B / EP2050702a: FTW optical and NIR observations
  87. Konus-Wind detection of GRB 250702F
  88. EP250704a / GRB 250704B - REM observations
  89. GRB 250702F: GROWTH-India Telescope optical observations
  90. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  91. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  92. EP250702a: WFST optical observations
  93. EP250704a: COLIBRÍ optical counterpart candidate
  94. EP250704a: Einstein Probe detection of an X-ray transient
  95. GRB 250704B: SVOM/GRM observation of a short burst
  96. GRB 250702F: optical photometry from Konkoly
  97. GRB 250704A: REM detection of the optical afterglow
  98. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  99. GRB 250702F: SVOM/VT optical observation
  100. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate

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