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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

28090 results found.

  1. EP250704a/GRB250704B : HCT optical and NIR upper limits
  2. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  3. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  4. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  5. GRB 250702F: radio detection with the VLA
  6. IceCube-250706A: EP-FXT follow-up observations
  7. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  8. GRB 250706B/C: Fermi-LAT detection
  9. IceCube-250706A: Global MASTER-Net observations report
  10. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  11. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  12. GRB 250706B: Swift/UVOT Detection
  13. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  14. GRB 250702F: GRANDMA observations
  15. GRB 250706A: Swift-XRT refined Analysis
  16. GRB 250706B: refined SVOM/MXT data analysis
  17. GRB 250706A: Swift/UVOT Upper Limits
  18. GRB 250706B: REM optical observations
  19. GRB 250706A: REM optical/NIR observations
  20. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  21. IceCube-250416A: DDOTI Optical Upper Limit
  22. IceCube-250706A: COLIBRÍ optical upper limits
  23. GRB 250706A: JinShan optical upper limits
  24. GRB 250706A: SAO RAS optical observations
  25. EP250704A: NOWT Detection
  26. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  27. GRB250706B: Swift-XRT counterpart detection
  28. GRB 250706B: iTelescope optical observations
  29. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  30. GRB 250706B: SVOM/VT optical observation
  31. GRB 250706B: TRT bright optical counterpart detection
  32. GRB 250706A: GROWTH-India Telescope optical upper limit
  33. GRB 250706B: SVOM detection of a long burst
  34. GRB 250706A: Swift detection of a burst
  35. GRB 250704B: Swift-XRT refined Analysis
  36. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  37. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  38. GRB 250703A: EIRSAT-1 GMOD Detection
  39. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  40. GRB 250704B: Swift/UVOT Upper Limits
  41. GRB 250704A: Swift/UVOT Detection
  42. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  43. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  44. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  45. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  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: JinShan optical observations
  52. EP250704a / GRB 250704B: SAO RAS optical observations
  53. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  54. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  55. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  56. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  57. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  58. EP250704a / GRB250704B: Swift-XRT counterpart detection
  59. GRB 250704A: Swift-XRT afterglow detection
  60. EP250704a / GRB 250704B - REM observations
  61. GRB 250702F: GROWTH-India Telescope optical observations
  62. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  63. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  64. EP250702a: WFST optical observations
  65. EP250704a: COLIBRÍ optical counterpart candidate
  66. EP250704a: Einstein Probe detection of an X-ray transient
  67. GRB 250704A: REM detection of the optical afterglow
  68. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  69. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  70. GRB 250704A: SVOM detection of a burst
  71. GRB 250702F: Swift/UVOT Detection
  72. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  73. GRB 250702F: Swift-XRT refined Analysis
  74. GRB 250702F: Fermi GBM Observation
  75. GRB 250702F: Leavitt Observatory optical observations
  76. GRB 250702F: AKO Optical Afterglow Detection
  77. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  78. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  79. GRB 250702F: Skynet Optical Observations
  80. GRB 250424A: VIRT Optical Upper Limit
  81. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  82. GRB 250702F: TRT Optical Observation
  83. GRB 250703A: DDOTI Optical Upper Limit
  84. GRB 250702F: REM optical afterglow detection
  85. EP250702a: Global MASTER-Net observations report
  86. GRB 250702F: DDOTI Optical Observation
  87. GRB 250702F: COLIBRÍ Observations of the Afterglow
  88. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  89. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  90. GRB 250702F: Enhanced Swift-XRT position
  91. GRB 250702F: NOT observations of the optical afterglow
  92. GRB 250702F: Swift detection of a burst with an optical counterpart
  93. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  94. GRB 250702A: Fermi GBM Detection
  95. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  96. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  97. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  98. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  99. GRB 250628B: Swift-XRT observations
  100. GRB 250628B: EP-FXT counterpart detection

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