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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"

24592 results found.

  1. GRB 250327A: COLIBRÍ optical upper limit
  2. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  3. IPN triangulation of GRB 250322B
  4. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  5. EP250321a: Mondy AZT-33IK Continued Optical Observations
  6. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  7. GRB 250322A: third epoch of NOT optical observations
  8. GRB 250322A: Swift-BAT refined analysis
  9. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  10. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  11. GRB 250322A: further NOT optical observations
  12. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  13. GRB 250322A: Swift/UVOT Upper Limits
  14. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  15. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  16. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  17. GRB 250321B: Swift-XRT observations
  18. GRB 250322A: Swift-XRT refined Analysis
  19. EP250321a: TNOT Observation of Optical Counterpart
  20. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  21. SVOM/sb25032302: SVOM detection of a long X-ray transient
  22. GRB 250322B: AstroSat CZTI detection of a bright long burst
  23. GRB 250322A: VLT optical observations
  24. GRB 250322A: VLT near-infrared observations
  25. FRB 250316A: DDOTI Continued Optical Observations
  26. GRB 250322A: NOT optical upper limits
  27. GRB 250322A: Enhanced Swift-XRT position
  28. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  29. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  30. EP250321a: Liverpool Telescope optical follow-up
  31. EP250321a: Mondy AZT-33IK Optical Observations
  32. GRB 250322A: Swift detection of a short burst
  33. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  34. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  35. EP250321A: COLIBRÍ Continuing Optical Observations
  36. EP250321a: WFST optical observations
  37. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  38. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  39. GRB 250320B: Fermi GBM Observation
  40. EP250321a: Xinglong 216 decaying optical observations
  41. GRB 250321A: Swift-BAT refined analysis
  42. GRB 250321A: Swift-XRT refined Analysis
  43. EP 250321A: Optical counterpart detection by LCO.
  44. EP250321a: Kinder optical follow-up observations
  45. GRB 250321A: Swift/UVOT Upper Limits
  46. GRB 250320B: SVOM/GRM observation of a long burst
  47. EP250321a: LCO optical counterpart detection
  48. EP250321a: Swift-XRT detection of an X-ray source
  49. EP250321A: COLIBRÍ Optical Observations
  50. GRB 250320B: AstroSat CZTI detection
  51. EP250321a: REM optical/NIR afterglow detection
  52. EP250321a: TRT optical counterpart detection
  53. Swift GRB 250321A: Global MASTER-Net observations report
  54. EP250321a: Einstein Probe detection of an X-ray transient
  55. GRB 250321A: GOTO optical upper limits
  56. GRB 250314A: Keck/NIRC2 J-band upper limit
  57. EP250226a/GRB 250226A: KAIT optical observations
  58. GRB 250321A: Fermi GBM Observation
  59. GRB 250321A: Swift detection of a burst
  60. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  61. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  62. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  63. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  64. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  65. GRB 250317D: EIRSAT-1 GMOD Detection
  66. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  67. GRB 250314A: ATCA radio upper limits
  68. GRB 250317B: OHP/T193 continued follow-up
  69. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  70. GRB 250317C: SVOM/GRM observation of a long burst
  71. GRB 250317B: Leavitt Observatory optical upper limit
  72. GRB 250317B: Mondy AZT-33IK Optical Observations
  73. GRB 250317B: NOT optical observations suggest an optical plateau phase
  74. GRB 250317C: GECAM-B detection
  75. GRB 250317B: OHP/T193 optical observations
  76. GRB250312A: Swift/UVOT Upper Limits
  77. GRB 250317B: REM optical/NIR observations
  78. GRB 250317B: Swift-XRT observations
  79. GRB 250316A: Swift/UVOT Upper Limits
  80. GRB 250314A: REM optical/NIR upper limits
  81. GRB 250316A: AbAO AS-32 Optical Upper Limit
  82. EP 250317B: Fading optical counterpart detection by LCO
  83. GRB 250316A: Swift-XRT afterglow detection
  84. GRB 250317B: LCO detection of the fading optical afterglow
  85. GRB250317B: SVOM/VT detection of an optical candidate from VHF data
  86. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  87. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  88. GRB 250317B: SVOM detection of a burst
  89. GRB 250316A: Fermi GBM Observation
  90. GRB 250316A: Swift-XRT observations
  91. GRB 250314A: SVOM/GRM analysis
  92. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  93. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  94. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  95. GRB 250314A: EP-FXT afterglow detection
  96. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  97. GRB 250314A: Swift/UVOT Upper Limits
  98. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  99. GRB 250314A: Swift XRT Detection
  100. EP250315a: optical counterpart candidate detected by Gemini North

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