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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"

44276 results found.

  1. GRB 250706B: REM optical observations
  2. GRB 250706A: REM optical/NIR observations
  3. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  4. IceCube-250416A: DDOTI Optical Upper Limit
  5. IceCube-250706A: COLIBRÍ optical upper limits
  6. Swift GRB 250706A: Global MASTER-Net observations report
  7. GRB 250706A: JinShan optical upper limits
  8. GRB 250706A: SAO RAS optical observations
  9. EP250704A: NOWT Detection
  10. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  11. The EP-WXT trigger 01709181580 is likely a flaring star
  12. GRB250706B: Swift-XRT counterpart detection
  13. GRB 250706B: iTelescope optical observations
  14. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  15. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  16. GRB 250706B: SVOM/VT optical observation
  17. GRB 250706B: TRT bright optical counterpart detection
  18. GRB 250706A: GROWTH-India Telescope optical upper limit
  19. GRB 250706B: SVOM detection of a long burst
  20. GRB 250706A: Swift detection of a burst
  21. GRB 250704B: Swift-XRT refined Analysis
  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. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  50. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  51. EP 250704a: BOOTES-5 optical detection
  52. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  53. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  54. GRB 250702A: Insight-HXMT detection
  55. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  56. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  57. EP250704a / GRB250704B: Swift-XRT counterpart detection
  58. GRB 250704A: Swift-XRT afterglow detection
  59. GRB 250702B / EP2050702a: FTW optical and NIR observations
  60. Konus-Wind detection of GRB 250702F
  61. EP250704a / GRB 250704B - REM observations
  62. GRB 250702F: GROWTH-India Telescope optical observations
  63. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  64. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  65. EP250702a: WFST optical observations
  66. EP250704a: COLIBRÍ optical counterpart candidate
  67. EP250704a: Einstein Probe detection of an X-ray transient
  68. GRB 250704B: SVOM/GRM observation of a short burst
  69. GRB 250702F: optical photometry from Konkoly
  70. GRB 250704A: REM detection of the optical afterglow
  71. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  72. GRB 250702F: SVOM/VT optical observation
  73. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  74. GRB 250704A: SVOM detection of a burst
  75. GRB 250702F: Swift/UVOT Detection
  76. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  77. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  78. Fermi GRB 250703A: Global MASTER-Net observations report
  79. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  80. GRB 250702F: Swift-XRT refined Analysis
  81. GRB 250702F: Fermi GBM Observation
  82. GRB 250702F: Leavitt Observatory optical observations
  83. GRB 250702F: AKO Optical Afterglow Detection
  84. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  85. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  86. GRB 250702A: GECAM-B detection
  87. GRB 250702F: Skynet Optical Observations
  88. GRB 250424A: VIRT Optical Upper Limit
  89. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  90. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  91. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  92. GRB 250702F: TRT Optical Observation
  93. GRB 250703A: DDOTI Optical Upper Limit
  94. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  95. GRB 250702F: REM optical afterglow detection
  96. EP250702a: Global MASTER-Net observations report
  97. GRB 250702F: DDOTI Optical Observation
  98. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  99. GRB 250703A: Fermi GBM Final Real-time Localization
  100. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits

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