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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"

15710 results found.

  1. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  2. EP250730a: COLIBRÍ optical upper limit
  3. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  4. GRB 250725A: PRIME near-infrared observations
  5. GRB 250728A: COLIBRÍ optical upper limit
  6. GRB 250727A: AST3-2 Upper limit
  7. GRB250727A: SVOM/VT optical upper limit
  8. GRB 250725A: SVOM/GRM observation
  9. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  10. GRB 250725A: Swift/UVOT Upper Limits
  11. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  12. GRB 250725A: BOOTES-7 early optical detection
  13. GRB 250725A: SVOM/VT optical candidate
  14. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  15. Swift GRB 250725A: Global MASTER-Net OT detection
  16. SVOM J195836+32283/sb25072103: Second VT observation
  17. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  18. GRB 250717B: SVOM/GRM observation
  19. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  20. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  21. GRB 250717B: COLIBRÍ optical upper limit
  22. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  23. GRB 270713A: Kitab and AbAO Optical Observations
  24. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  25. GRB 250716A: GOTO tentative optical counterpart candidate
  26. GRB 250714A: SVOM/GRM observation
  27. GRB 250713A: Mephisto optical upper limits
  28. GRB 250713A: SVOM/VT optical upper limit
  29. GRB 250713A: NOT optical upper limits
  30. GRB 250706B/C: 7DT Follow-up Observations
  31. EP250711a: COLIBRÍ continuous optical observations
  32. GRB 250713A: JinShan optical upper limits
  33. GRB 250711A: DDOTI Optical Upper Limit
  34. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  35. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  36. GRB 250711A: SVOM/GRM observation
  37. EP250711a: NOT optical counterpart candidate
  38. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  39. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  40. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  41. EP/WXT 01709181970: GOTO observations confirm stellar variability
  42. EP250704a/GRB 250704B: 10 GHz VLA detection
  43. IceCube-250706A: No Candidates from WINTER
  44. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  45. GRB 250704B / EP250704a: VLA radio detection
  46. EP250704a/GRB250704B : HCT optical and NIR upper limits
  47. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  48. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  49. GRB 250702F: radio detection with the VLA
  50. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  51. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  52. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  53. GRB 250706B: Swift/UVOT Detection
  54. GRB 250702F: GRANDMA observations
  55. GRB 250706B: refined SVOM/MXT data analysis
  56. GRB 250706A: Swift/UVOT Upper Limits
  57. GRB 250706B: REM optical observations
  58. GRB 250706A: REM optical/NIR observations
  59. IceCube-250416A: DDOTI Optical Upper Limit
  60. IceCube-250706A: COLIBRÍ optical upper limits
  61. GRB 250706A: JinShan optical upper limits
  62. GRB 250706A: SAO RAS optical observations
  63. EP250704A: NOWT Detection
  64. GRB250706B: Swift-XRT counterpart detection
  65. GRB 250706B: iTelescope optical observations
  66. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  67. GRB 250706B: SVOM/VT optical observation
  68. GRB 250706B: TRT bright optical counterpart detection
  69. GRB 250706A: GROWTH-India Telescope optical upper limit
  70. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  71. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  72. GRB 250704B: Swift/UVOT Upper Limits
  73. GRB 250704A: Swift/UVOT Detection
  74. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  75. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  76. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  77. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  78. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  79. GRB 250702F: Kilonova-Catcher optical afterglow detection
  80. GRB 250702F: Monte Agliale Observatory optical observations
  81. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  82. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  83. EP250704a / GRB 250704B: JinShan optical observations
  84. GRB 250704A: SVOM/VT optical observation
  85. EP250704a / GRB 250704B: SAO RAS optical observations
  86. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  87. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  88. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  89. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  90. EP 250704a: BOOTES-5 optical detection
  91. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  92. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  93. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  94. EP250704a / GRB250704B: Swift-XRT counterpart detection
  95. GRB 250702B / EP2050702a: FTW optical and NIR observations
  96. EP250704a / GRB 250704B - REM observations
  97. GRB 250702F: GROWTH-India Telescope optical observations
  98. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  99. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  100. EP250702a: WFST optical observations

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