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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"

24887 results found.

  1. GRB 250628B: Swift-XRT observations
  2. GRB 250628B: EP-FXT counterpart detection
  3. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  4. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  5. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  6. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  7. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  8. GRB 250628A: REM optical/NIR upper limits
  9. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  10. GRB 250628B: SVOM detection of a long burst
  11. GRB 250628A: VLT/X-shooter upper limits
  12. GRB 250628A: Swift/UVOT Upper Limits
  13. GRB 250628A: Swift-XRT refined Analysis
  14. GRB 250628A: Enhanced Swift-XRT position
  15. GRB 250628A: Swift detection of a burst
  16. GRB 250625A: Swift-BAT refined analysis
  17. GRB 250625A: Leavitt Observatory afterglow detection
  18. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  19. GRB 250625A: SVOM/C-GFT upper limit in early phase
  20. GRB 250625A: Swift/UVOT Upper Limits
  21. GRB 250625A: ABObservatory afterglow detection
  22. GRB 250625A: OHP/T193 optical detection
  23. GRB 250625A: COLIBRÍ optical observations
  24. GRB 250625A: Swift-XRT refined Analysis
  25. GRB 250625A: JinShan optical observations
  26. GRB250625A: Fermi GBM Observation
  27. GRB 250620B: Fermi GBM Observation
  28. GRB 250625A: SAO RAS possible optical afterglow
  29. GRB 250625A: Enhanced Swift-XRT position
  30. GRB 250625A: Swift detection of a burst
  31. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  32. GRB 241018A: Maidanak optical observations
  33. GRB 250620C: AstroSat CZTI detection
  34. Fermi GRB 250624A: Global MASTER-Net observations report
  35. GRB 250521A: VZLUSAT-2 detection
  36. GRB 250617B: Swift-BAT refined analysis
  37. Fermi trigger No 772190032: Global MASTER-Net observations report
  38. IPN triangulation of GRB 250620С (long/bright)
  39. GRB 250620C: SVOM/GRM observation
  40. GRB 250620A: SVOM/GRM observation of a short burst
  41. GRB250620A: Fermi GBM Observation
  42. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  43. GRB 250619B: Fermi GBM Observation
  44. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  45. GRB250620C: Fermi GBM Observation
  46. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  47. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  48. Fermi trigger No 772128434: Global MASTER-Net observations report
  49. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  50. GRB 250617B: Nickel telescope optical observations
  51. GRB 250615A: Kilonova-Catcher optical upper limits
  52. GRB 250617B: Assy AZT-20 Optical Observations
  53. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  54. Fermi GRB 250617A: Global MASTER-Net observations report
  55. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  56. GRB 250617B: Swift/UVOT Detection
  57. GRB 250617B: Kilonova-Catcher optical afterglow detection
  58. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  59. GRB 250617B: COLIBRÍ optical observations
  60. GRB 250617B: NOT NIR observations of the afterglow
  61. GRB 250617B: Swift-XRT refined Analysis
  62. GRB 250617B: NUTTelA-TAO early time optical observations
  63. GRB 250617B: Enhanced Swift-XRT position
  64. GRB 250617B: Fermi GBM Observation
  65. GRB 250615A: Swift-BAT refined analysis
  66. GRB 250617B: SAO RAS optical observations
  67. GRB 250617B: Swift detection of a burst with an optical counterpart
  68. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  69. EP#01709178975: Swift-XRT counterpart detection
  70. EP-WXT trigger 01709178975: GOTO optical upper limit
  71. GRB 250615A / EP250615a: AstroSat CZTI detection
  72. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  73. GRB 250615A: COLIBRÍ optical upper limit
  74. GRB 250615A: DDOTI Optical Upper Limit
  75. GRB 250615A: Swift/UVOT Upper Limits
  76. GRB 250615A: Swift-XRT refined Analysis
  77. sb25061207/SVOM: T120 OHP optical upper limit
  78. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  79. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  80. GRB 250615A: Enhanced Swift-XRT position
  81. GRB 250615A: Swift detection of a burst
  82. Fermi trigger No 771718064: Global MASTER-Net observations report
  83. sb25061207: Mephisto optical upper limits
  84. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  85. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  86. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  87. sb25061218: Swift-XRT observations
  88. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  89. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  90. sb25061207: EP-FXT follow-up observation and afterglow candidate
  91. GRB 250612B: Fermi GBM Observation
  92. EP250612a: SVOM/VT optical candidate
  93. GRB 250612C: Fermi GBM Observation
  94. sb25061218: SVOM detection of a X-ray transient
  95. sb25061207: Swift-XRT observations
  96. EP250612a/GRB 250612B: JinShan optical upper limit
  97. sb25061207: SVOM/VT optical counterpart
  98. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  99. GRB 250610B: Swift-XRT refined Analysis
  100. EP250610a: Upper limit from Fermi-GBM Observations

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