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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').
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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"

28088 results found.

  1. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  2. EP250704a/GRB250704B : HCT optical and NIR upper limits
  3. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  4. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  5. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  6. GRB 250702F: radio detection with the VLA
  7. IceCube-250706A: EP-FXT follow-up observations
  8. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  9. GRB 250706B/C: Fermi-LAT detection
  10. IceCube-250706A: Global MASTER-Net observations report
  11. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  12. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  13. GRB 250706B: Swift/UVOT Detection
  14. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  15. GRB 250702F: GRANDMA observations
  16. GRB 250706A: Swift-XRT refined Analysis
  17. GRB 250706B: refined SVOM/MXT data analysis
  18. GRB 250706A: Swift/UVOT Upper Limits
  19. GRB 250706B: REM optical observations
  20. GRB 250706A: REM optical/NIR observations
  21. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  22. IceCube-250416A: DDOTI Optical Upper Limit
  23. IceCube-250706A: COLIBRÍ optical upper limits
  24. GRB 250706A: JinShan optical upper limits
  25. GRB 250706A: SAO RAS optical observations
  26. EP250704A: NOWT Detection
  27. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  28. GRB250706B: Swift-XRT counterpart detection
  29. GRB 250706B: iTelescope optical observations
  30. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  31. GRB 250706B: SVOM/VT optical observation
  32. GRB 250706B: TRT bright optical counterpart detection
  33. GRB 250706A: GROWTH-India Telescope optical upper limit
  34. GRB 250706B: SVOM detection of a long burst
  35. GRB 250706A: Swift detection of a burst
  36. GRB 250704B: Swift-XRT refined Analysis
  37. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  38. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  39. GRB 250703A: EIRSAT-1 GMOD Detection
  40. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  41. GRB 250704B: Swift/UVOT Upper Limits
  42. GRB 250704A: Swift/UVOT Detection
  43. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  44. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  45. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  46. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  47. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  48. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  49. GRB 250702F: Kilonova-Catcher optical afterglow detection
  50. GRB 250702F: Monte Agliale Observatory optical observations
  51. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  52. EP250704a / GRB 250704B: JinShan optical observations
  53. EP250704a / GRB 250704B: SAO RAS optical observations
  54. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  55. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  56. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  57. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  58. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  59. EP250704a / GRB250704B: Swift-XRT counterpart detection
  60. GRB 250704A: Swift-XRT afterglow detection
  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 250704A: REM detection of the optical afterglow
  69. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  70. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  71. GRB 250704A: SVOM detection of a burst
  72. GRB 250702F: Swift/UVOT Detection
  73. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  74. GRB 250702F: Swift-XRT refined Analysis
  75. GRB 250702F: Fermi GBM Observation
  76. GRB 250702F: Leavitt Observatory optical observations
  77. GRB 250702F: AKO Optical Afterglow Detection
  78. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  79. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  80. GRB 250702F: Skynet Optical Observations
  81. GRB 250424A: VIRT Optical Upper Limit
  82. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  83. GRB 250702F: TRT Optical Observation
  84. GRB 250703A: DDOTI Optical Upper Limit
  85. GRB 250702F: REM optical afterglow detection
  86. EP250702a: Global MASTER-Net observations report
  87. GRB 250702F: DDOTI Optical Observation
  88. GRB 250702F: COLIBRÍ Observations of the Afterglow
  89. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  90. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  91. GRB 250702F: Enhanced Swift-XRT position
  92. GRB 250702F: NOT observations of the optical afterglow
  93. GRB 250702F: Swift detection of a burst with an optical counterpart
  94. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  95. GRB 250702A: Fermi GBM Detection
  96. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  97. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  98. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  99. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  100. GRB 250628B: Swift-XRT observations

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