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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"

19387 results found.

  1. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  2. GRB 250628B: EP-FXT counterpart detection
  3. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  5. GRB 250628A: REM optical/NIR upper limits
  6. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  7. GRB 250628B: SVOM detection of a long burst
  8. GRB 250628A: VLT/X-shooter upper limits
  9. GRB 250628A: Swift/UVOT Upper Limits
  10. GRB 250628A: Enhanced Swift-XRT position
  11. GRB 250628A: Swift detection of a burst
  12. GRB 250625A: Leavitt Observatory afterglow detection
  13. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  14. GRB 250625A: SVOM/C-GFT upper limit in early phase
  15. GRB 250625A: Swift/UVOT Upper Limits
  16. GRB 250625A: ABObservatory afterglow detection
  17. GRB 250625A: OHP/T193 optical detection
  18. GRB 250625A: COLIBRÍ optical observations
  19. GRB 250625A: Fermi-LAT detection
  20. GRB 250625A: JinShan optical observations
  21. GRB 250625A: SAO RAS possible optical afterglow
  22. GRB 250625A: Enhanced Swift-XRT position
  23. GRB 250625A: Swift detection of a burst
  24. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  25. GRB 241018A: Maidanak optical observations
  26. GRB 250620C: AstroSat CZTI detection
  27. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  28. GRB 250521A: VZLUSAT-2 detection
  29. Konus-Wind detection of GRB 250620C
  30. IPN triangulation of GRB 250620С (long/bright)
  31. GRB 250620C: SVOM/GRM observation
  32. GRB 250620A: SVOM/GRM observation of a short burst
  33. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  34. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  35. GRB 250506A - SVOM/ECLAIRs Refined analysis
  36. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  37. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  38. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  39. GRB 250617B: Nickel telescope optical observations
  40. GRB 250615A: Kilonova-Catcher optical upper limits
  41. GRB 250617B: Assy AZT-20 Optical Observations
  42. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  43. GRB 250617B: Swift/UVOT Detection
  44. GRB 250617B: Kilonova-Catcher optical afterglow detection
  45. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  46. GRB 250617B: COLIBRÍ optical observations
  47. GRB 250617B: NOT NIR observations of the afterglow
  48. GRB 250617B: NUTTelA-TAO early time optical observations
  49. GRB 250617B: Enhanced Swift-XRT position
  50. GRB 250615A: Swift-BAT refined analysis
  51. GRB 250617B: SAO RAS optical observations
  52. GRB 250617B: Swift detection of a burst with an optical counterpart
  53. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  54. EP-WXT trigger 01709178975: GOTO optical upper limit
  55. Konus-Wind detection of GRB 250615A / EP250615a
  56. GRB 250615A / EP250615a: AstroSat CZTI detection
  57. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  58. GRB 250615A: COLIBRÍ optical upper limit
  59. GRB 250615A: DDOTI Optical Upper Limit
  60. GRB 250615A: Swift/UVOT Upper Limits
  61. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  62. sb25061207/SVOM: T120 OHP optical upper limit
  63. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  64. GRB 250615A: Enhanced Swift-XRT position
  65. GRB 250615A: Swift detection of a burst
  66. Swift GRB250615.93: Global MASTER-Net observations report
  67. sb25061207: Mephisto optical upper limits
  68. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  69. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  70. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  71. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  72. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  73. EP250612a: SVOM/VT optical candidate
  74. EP250612a/GRB 250612B: JinShan optical upper limit
  75. sb25061207: SVOM/VT optical counterpart
  76. GRB 250610B: Swift-XRT refined Analysis
  77. EP250612a: Einstein Probe detection of an X-ray transient
  78. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  79. sb25061207: SVOM detection of a X-ray transient
  80. GRB 250610B - SVOM/ECLAIRs refined analysis
  81. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  82. Fermi GBM Sub-Threshold Detection of GRB 250610B
  83. GRB 250610B: Swift/UVOT Detection
  84. EP250610A: Swift/UVOT Upper limits
  85. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  86. EP250610a: TNG NIR upper limit
  87. GRB 250610B: REM optical/NIR observations
  88. EP250610a: Liverpool Telescope optical upper limits
  89. GRB 250610B: additional Liverpool Telescope optical observations
  90. GRB 250610B: SVOM/VT optical counterpart
  91. GRB 250610B: OHP/T120 optical counterpart candidate
  92. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  93. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  94. EP250610a: SVOM/VT optical upper limit
  95. EP250610a: REM optical/NIR observations
  96. EP250610a: COLIBRÍ optical upper limit
  97. EP250610a: Einstein Probe detection of an X-ray transient
  98. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  99. GRB 250605A: Swift/UVOT Upper Limits
  100. The EP-WXT trigger 01709178283 is likely a flaring star

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