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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"

21207 results found.

  1. GRB 250702F: Leavitt Observatory optical observations
  2. GRB 250702F: AKO Optical Afterglow Detection
  3. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  4. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  5. GRB 250702F: Skynet Optical Observations
  6. GRB 250424A: VIRT Optical Upper Limit
  7. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  8. GRB 250702F: TRT Optical Observation
  9. GRB 250703A: DDOTI Optical Upper Limit
  10. GRB 250702F: REM optical afterglow detection
  11. GRB 250702F: DDOTI Optical Observation
  12. GRB 250702F: COLIBRÍ Observations of the Afterglow
  13. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  14. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  15. GRB 250702F: Enhanced Swift-XRT position
  16. GRB 250702F: NOT observations of the optical afterglow
  17. GRB 250702F: Swift detection of a burst with an optical counterpart
  18. Konus-Wind detection of GRB 250627A
  19. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  20. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  21. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  22. GRB 250628B: EP-FXT counterpart detection
  23. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  24. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  25. GRB 250628A: REM optical/NIR upper limits
  26. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  27. GRB 250628B: SVOM detection of a long burst
  28. GRB 250628A: VLT/X-shooter upper limits
  29. GRB 250628A: Swift/UVOT Upper Limits
  30. GRB 250628A: Enhanced Swift-XRT position
  31. GRB 250628A: Swift detection of a burst
  32. GRB 250625A: Leavitt Observatory afterglow detection
  33. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  34. GRB 250625A: SVOM/C-GFT upper limit in early phase
  35. GRB 250625A: Swift/UVOT Upper Limits
  36. GRB 250625A: ABObservatory afterglow detection
  37. GRB 250625A: OHP/T193 optical detection
  38. GRB 250625A: COLIBRÍ optical observations
  39. GRB 250625A: Fermi-LAT detection
  40. GRB 250625A: JinShan optical observations
  41. GRB 250625A: SAO RAS possible optical afterglow
  42. GRB 250625A: Enhanced Swift-XRT position
  43. GRB 250625A: Swift detection of a burst
  44. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  45. GRB 241018A: Maidanak optical observations
  46. GRB 250620C: AstroSat CZTI detection
  47. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  48. GRB 250521A: VZLUSAT-2 detection
  49. Konus-Wind detection of GRB 250620C
  50. IPN triangulation of GRB 250620C (long/bright)
  51. GRB 250620C: SVOM/GRM observation
  52. GRB 250620A: SVOM/GRM observation of a short burst
  53. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  54. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  55. GRB 250506A - SVOM/ECLAIRs Refined analysis
  56. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  57. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  58. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  59. GRB 250617B: Nickel telescope optical observations
  60. GRB 250615A: Kilonova-Catcher optical upper limits
  61. GRB 250617B: Assy AZT-20 Optical Observations
  62. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  63. GRB 250617B: Swift/UVOT Detection
  64. GRB 250617B: Kilonova-Catcher optical afterglow detection
  65. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  66. GRB 250617B: COLIBRÍ optical observations
  67. GRB 250617B: NOT NIR observations of the afterglow
  68. GRB 250617B: NUTTelA-TAO early time optical observations
  69. GRB 250617B: Enhanced Swift-XRT position
  70. GRB 250615A: Swift-BAT refined analysis
  71. GRB 250617B: SAO RAS optical observations
  72. GRB 250617B: Swift detection of a burst with an optical counterpart
  73. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  74. EP-WXT trigger 01709178975: GOTO optical upper limit
  75. Konus-Wind detection of GRB 250615A / EP250615a
  76. GRB 250615A / EP250615a: AstroSat CZTI detection
  77. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  78. GRB 250615A: COLIBRÍ optical upper limit
  79. GRB 250615A: DDOTI Optical Upper Limit
  80. GRB 250615A: Swift/UVOT Upper Limits
  81. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  82. sb25061207/SVOM: T120 OHP optical upper limit
  83. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  84. GRB 250615A: Enhanced Swift-XRT position
  85. GRB 250615A: Swift detection of a burst
  86. Swift GRB 250615A: Global MASTER-Net observations report
  87. sb25061207: Mephisto optical upper limits
  88. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  89. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  90. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  91. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  92. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  93. EP250612a: SVOM/VT optical candidate
  94. EP250612a/GRB 250612B: JinShan optical upper limit
  95. sb25061207: SVOM/VT optical counterpart
  96. GRB 250610B: Swift-XRT refined Analysis
  97. EP250612a: Einstein Probe detection of an X-ray transient
  98. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  99. sb25061207: SVOM detection of a X-ray transient
  100. GRB 250610B - SVOM/ECLAIRs refined analysis

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