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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"

21047 results found.

  1. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  2. GRB 250702F: Leavitt Observatory optical observations
  3. GRB 250702F: AKO Optical Afterglow Detection
  4. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  5. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  6. GRB 250702F: Skynet Optical Observations
  7. GRB 250424A: VIRT Optical Upper Limit
  8. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  9. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  10. GRB 250702F: TRT Optical Observation
  11. GRB 250703A: DDOTI Optical Upper Limit
  12. GRB 250702F: REM optical afterglow detection
  13. GRB 250702F: DDOTI Optical Observation
  14. GRB 250703A: Fermi GBM Final Real-time Localization
  15. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  16. GRB 250702F: COLIBRÍ Observations of the Afterglow
  17. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  18. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  19. GRB 250702F: Enhanced Swift-XRT position
  20. GRB 250702F: NOT observations of the optical afterglow
  21. GRB 250702F: Swift detection of a burst with an optical counterpart
  22. IPN triangulation of GRB 250627A (short)
  23. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  24. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  25. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  26. GRB 250628B: Swift-XRT observations
  27. GRB 250628B: SVOM/VT optical upper limit
  28. GRB 250628B: EP-FXT counterpart detection
  29. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  30. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  31. GRB 250628A: REM optical/NIR upper limits
  32. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  33. GRB 250628A: VLT/X-shooter upper limits
  34. GRB 250628A: Swift/UVOT Upper Limits
  35. GRB 250628A: Swift-XRT refined Analysis
  36. GRB 250628A: Enhanced Swift-XRT position
  37. GRB 250628A: Swift detection of a burst
  38. GRB 250625A: Leavitt Observatory afterglow detection
  39. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  40. GRB 250625A: SVOM/C-GFT upper limit in early phase
  41. GRB 250625A: Swift/UVOT Upper Limits
  42. GRB 250625A: ABObservatory afterglow detection
  43. GRB 250625A: OHP/T193 optical detection
  44. GRB 250625A: COLIBRÍ optical observations
  45. GRB 250625A: JinShan optical observations
  46. GRB250625A: Fermi GBM Observation
  47. GRB 250625A: NOT z-band upper limit
  48. GRB 250625A: SAO RAS possible optical afterglow
  49. GRB 250625A: Enhanced Swift-XRT position
  50. GRB 250625A: Swift detection of a burst
  51. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  52. GRB 241018A: Maidanak optical observations
  53. GRB 250620C: AstroSat CZTI detection
  54. IPN triangulation of GRB 250620С (long/bright)
  55. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  56. GRB 250620C: SVOM/GRM observation
  57. GRB 250620A: SVOM/GRM observation of a short burst
  58. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  59. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  60. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  61. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  62. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  63. GRB 250617B: Nickel telescope optical observations
  64. GRB 250615A: Kilonova-Catcher optical upper limits
  65. GRB 250617B: Assy AZT-20 Optical Observations
  66. GRB 250615A/EP250615a: FTW optical and NIR observations
  67. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  68. GRB 250617B: Swift/UVOT Detection
  69. GRB 250617B: Kilonova-Catcher optical afterglow detection
  70. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  71. GRB 250617B: COLIBRÍ optical observations
  72. GRB 250617B: NOT NIR observations of the afterglow
  73. GRB 250617B: NUTTelA-TAO early time optical observations
  74. GRB 250617B: GOTO optical upper limit
  75. GRB 250617B: Enhanced Swift-XRT position
  76. GRB 250617B: SAO RAS optical observations
  77. GRB 250617B: Swift detection of a burst with an optical counterpart
  78. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  79. IPN triangulation of GRB 250612C (short/hard)
  80. EP#01709178975: Swift-XRT counterpart detection
  81. EP-WXT trigger 01709178975: GOTO optical upper limit
  82. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  83. GRB 250615A: COLIBRÍ optical upper limit
  84. GRB 250615A: DDOTI Optical Upper Limit
  85. GRB 250615A: Swift/UVOT Upper Limits
  86. sb25061207/SVOM: T120 OHP optical upper limit
  87. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  88. GRB 250615A: Enhanced Swift-XRT position
  89. GRB 250615A: Swift detection of a burst
  90. sb25061207: Mephisto optical upper limits
  91. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  92. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  93. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  94. Fermi trigger No 771494087: Global MASTER-Net observations report
  95. sb25061218: Swift-XRT observations
  96. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  97. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  98. EP250612a: SVOM/VT optical candidate
  99. GRB 250612C: Fermi GBM Observation
  100. sb25061207: Swift-XRT observations

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