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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"

27322 results found.

  1. GRB 250706A: Swift-BAT refined analysis
  2. GRB 250702F: Swift-BAT refined analysis
  3. GRB 250628A: Swift-BAT refined analysis
  4. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  5. GRB 250713A: JinShan optical upper limits
  6. GRB 250713A: SVOM detection of a long burst
  7. EP250711a: Global MASTER-Net observations report
  8. GRB 250711A: DDOTI Optical Upper Limit
  9. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  10. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  11. GRB 250711A: SVOM/GRM observation
  12. EP250711a: NOT optical counterpart candidate
  13. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  14. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  15. GRB 250704A: GRANDMA observations
  16. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  17. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  18. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  19. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  20. IceCube-250708A: No Candidates from WINTER
  21. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  22. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  23. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  24. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  25. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  26. EP250704a/GRB 250704B: 10 GHz VLA detection
  27. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  28. IceCube-250706A: No Candidates from WINTER
  29. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  30. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  31. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  32. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  33. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  34. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  35. EP250704a/GRB250704B : HCT optical and NIR upper limits
  36. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  37. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  38. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  39. GRB 250702F: radio detection with the VLA
  40. IceCube-250706A: EP-FXT follow-up observations
  41. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  42. GRB 250706B/C: Fermi-LAT detection
  43. IceCube-250706A: Global MASTER-Net observations report
  44. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  45. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  46. GRB 250706B: Swift/UVOT Detection
  47. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  48. GRB 250702F: GRANDMA observations
  49. GRB 250706A: Swift-XRT refined Analysis
  50. GRB 250706B: refined SVOM/MXT data analysis
  51. GRB 250706A: Swift/UVOT Upper Limits
  52. GRB 250706B: REM optical observations
  53. GRB 250706A: REM optical/NIR observations
  54. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  55. IceCube-250416A: DDOTI Optical Upper Limit
  56. IceCube-250706A: COLIBRÍ optical upper limits
  57. GRB 250706A: JinShan optical upper limits
  58. GRB 250706A: SAO RAS optical observations
  59. EP250704A: NOWT Detection
  60. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  61. GRB250706B: Swift-XRT counterpart detection
  62. GRB 250706B: iTelescope optical observations
  63. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  64. GRB 250706B: SVOM/VT optical observation
  65. GRB 250706B: TRT bright optical counterpart detection
  66. GRB 250706A: GROWTH-India Telescope optical upper limit
  67. GRB 250706B: SVOM detection of a long burst
  68. GRB 250706A: Swift detection of a burst
  69. GRB 250704B: Swift-XRT refined Analysis
  70. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  71. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  72. GRB 250703A: EIRSAT-1 GMOD Detection
  73. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  74. GRB 250704B: Swift/UVOT Upper Limits
  75. GRB 250704A: Swift/UVOT Detection
  76. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  77. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  78. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  79. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  80. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  81. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  82. GRB 250702F: Kilonova-Catcher optical afterglow detection
  83. GRB 250702F: Monte Agliale Observatory optical observations
  84. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  85. EP250704a / GRB 250704B: JinShan optical observations
  86. EP250704a / GRB 250704B: SAO RAS optical observations
  87. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  88. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  89. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  90. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  91. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  92. EP250704a / GRB250704B: Swift-XRT counterpart detection
  93. GRB 250704A: Swift-XRT afterglow detection
  94. EP250704a / GRB 250704B - REM observations
  95. GRB 250702F: GROWTH-India Telescope optical observations
  96. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  97. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  98. EP250702a: WFST optical observations
  99. EP250704a: COLIBRÍ optical counterpart candidate
  100. EP250704a: Einstein Probe detection of an X-ray transient

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