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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"

45477 results found.

  1. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  2. GRB 250706B: Swift/UVOT Detection
  3. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  4. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  5. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  6. GRB 250702F: GRANDMA observations
  7. GRB 250706A: Swift-XRT refined Analysis
  8. GRB 250706B: refined SVOM/MXT data analysis
  9. GRB 250706A: Swift/UVOT Upper Limits
  10. GRB 250706B: REM optical observations
  11. GRB 250706A: REM optical/NIR observations
  12. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  13. IceCube-250416A: DDOTI Optical Upper Limit
  14. IceCube-250706A: COLIBRÍ optical upper limits
  15. Swift GRB 250706A: Global MASTER-Net observations report
  16. GRB 250706A: JinShan optical upper limits
  17. GRB 250706A: SAO RAS optical observations
  18. EP250704A: NOWT Detection
  19. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  20. The EP-WXT trigger 01709181580 is likely a flaring star
  21. GRB250706B: Swift-XRT counterpart detection
  22. GRB 250706B: iTelescope optical observations
  23. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  24. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  25. GRB 250706B: SVOM/VT optical observation
  26. GRB 250706B: TRT bright optical counterpart detection
  27. GRB 250706A: GROWTH-India Telescope optical upper limit
  28. GRB 250706B: SVOM detection of a long burst
  29. GRB 250706A: Swift detection of a burst
  30. GRB 250704B: Swift-XRT refined Analysis
  31. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  32. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  33. GRB 250703A: EIRSAT-1 GMOD Detection
  34. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  35. GRB 250704B: Swift/UVOT Upper Limits
  36. GRB 250704A: Swift/UVOT Detection
  37. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  38. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  39. GRB 250704B: Insight-HXMT detection
  40. Konus-Wind detection of GRB 250703A
  41. IPN triangulation of GRB 250703A
  42. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  43. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  44. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  45. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  46. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  47. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  48. GRB 250702F: Kilonova-Catcher optical afterglow detection
  49. GRB 250702F: Monte Agliale Observatory optical observations
  50. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  51. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  52. EP250704a / GRB 250704B: JinShan optical observations
  53. GRB 250704A: SVOM/VT optical observation
  54. EP250704a / GRB 250704B: SAO RAS optical observations
  55. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  56. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  57. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  58. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  59. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  60. EP 250704a: BOOTES-5 optical detection
  61. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  62. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  63. GRB 250702A: Insight-HXMT detection
  64. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  65. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  66. EP250704a / GRB250704B: Swift-XRT counterpart detection
  67. GRB 250704A: Swift-XRT afterglow detection
  68. GRB 250702B / EP2050702a: FTW optical and NIR observations
  69. Konus-Wind detection of GRB 250702F
  70. EP250704a / GRB 250704B - REM observations
  71. GRB 250702F: GROWTH-India Telescope optical observations
  72. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  73. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  74. EP250702a: WFST optical observations
  75. EP250704a: COLIBRÍ optical counterpart candidate
  76. EP250704a: Einstein Probe detection of an X-ray transient
  77. GRB 250704B: SVOM/GRM observation of a short burst
  78. GRB 250702F: optical photometry from Konkoly
  79. GRB 250704A: REM detection of the optical afterglow
  80. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  81. GRB 250702F: SVOM/VT optical observation
  82. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  83. GRB 250704A: SVOM detection of a burst
  84. GRB 250702F: Swift/UVOT Detection
  85. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  86. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  87. Fermi GRB 250703A: Global MASTER-Net observations report
  88. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  89. GRB 250702F: Swift-XRT refined Analysis
  90. GRB 250702F: Fermi GBM Observation
  91. GRB 250702F: Leavitt Observatory optical observations
  92. GRB 250702F: AKO Optical Afterglow Detection
  93. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  94. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  95. GRB 250702A: GECAM-B detection
  96. GRB 250702F: Skynet Optical Observations
  97. GRB 250424A: VIRT Optical Upper Limit
  98. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  99. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  100. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation

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