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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"

24761 results found.

  1. EP250321a: Liverpool Telescope optical follow-up
  2. EP250321a: Mondy AZT-33IK Optical Observations
  3. GRB 250322A: Swift detection of a short burst
  4. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  5. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  6. EP250321A: COLIBRÍ Continuing Optical Observations
  7. EP250321a: WFST optical observations
  8. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  9. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  10. GRB 250320B: Fermi GBM Observation
  11. EP250321a: Xinglong 216 decaying optical observations
  12. GRB 250321A: Swift-BAT refined analysis
  13. GRB 250321A: Swift-XRT refined Analysis
  14. EP 250321A: Optical counterpart detection by LCO.
  15. EP250321a: Kinder optical follow-up observations
  16. GRB 250321A: Swift/UVOT Upper Limits
  17. GRB 250320B: SVOM/GRM observation of a long burst
  18. EP250321a: LCO optical counterpart detection
  19. EP250321a: Swift-XRT detection of an X-ray source
  20. EP250321A: COLIBRÍ Optical Observations
  21. GRB 250320B: AstroSat CZTI detection
  22. EP250321a: REM optical/NIR afterglow detection
  23. EP250321a: TRT optical counterpart detection
  24. Swift GRB 250321A: Global MASTER-Net observations report
  25. EP250321a: Einstein Probe detection of an X-ray transient
  26. GRB 250321A: GOTO optical upper limits
  27. GRB 250314A: Keck/NIRC2 J-band upper limit
  28. EP250226a/GRB 250226A: KAIT optical observations
  29. GRB 250321A: Fermi GBM Observation
  30. GRB 250321A: Swift detection of a burst
  31. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  32. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  33. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  34. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  35. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  36. GRB 250317D: EIRSAT-1 GMOD Detection
  37. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  38. GRB 250314A: ATCA radio upper limits
  39. GRB 250317B: OHP/T193 continued follow-up
  40. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  41. GRB 250317C: SVOM/GRM observation of a long burst
  42. GRB 250317B: Leavitt Observatory optical upper limit
  43. GRB 250317B: Mondy AZT-33IK Optical Observations
  44. GRB 250317B: NOT optical observations suggest an optical plateau phase
  45. GRB 250317C: GECAM-B detection
  46. GRB 250317B: OHP/T193 optical observations
  47. GRB250312A: Swift/UVOT Upper Limits
  48. GRB 250317B: REM optical/NIR observations
  49. GRB 250317B: Swift-XRT observations
  50. GRB 250316A: Swift/UVOT Upper Limits
  51. GRB 250314A: REM optical/NIR upper limits
  52. GRB 250316A: AbAO AS-32 Optical Upper Limit
  53. EP 250317B: Fading optical counterpart detection by LCO
  54. GRB 250316A: Swift-XRT afterglow detection
  55. GRB 250317B: LCO detection of the fading optical afterglow
  56. GRB250317B: SVOM/VT detection of an optical candidate from VHF data
  57. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  58. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  59. GRB 250317B: SVOM detection of a burst
  60. GRB 250316A: Fermi GBM Observation
  61. GRB 250316A: Swift-XRT observations
  62. GRB 250314A: SVOM/GRM analysis
  63. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  64. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  65. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  66. GRB 250314A: EP-FXT afterglow detection
  67. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  68. GRB 250314A: Swift/UVOT Upper Limits
  69. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  70. GRB 250314A: Swift XRT Detection
  71. EP250315a: optical counterpart candidate detected by Gemini North
  72. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  73. EP250315a: Einstein Probe detection of an X-ray transient
  74. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  75. SVOM/MXT upper limit on GRB 250314A
  76. GRB 250314A: SVOM/VT upper limit
  77. GRB 250314A: NOT near-infrared candidate counterpart
  78. GRB 250313A: Fermi GBM Detection
  79. GRB 250312B: Fermi GBM Observation
  80. GRB 250313A: Swift-XRT observations
  81. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  82. GRB 250314A: SVOM detection of a burst
  83. GRB 250313A: AstroSat CZTI detection of a bright long burst
  84. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  85. GRB 250313A: Fermi-LAT detection
  86. EP250304a: Pan-STARRS r and i-band imaging and photometry
  87. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  88. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  89. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  90. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  91. GRB 250312A: Swift-XRT refined Analysis
  92. GRB 250312A: Enhanced Swift-XRT position
  93. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  94. GRB 250226B: Fermi GBM Observation
  95. GRB 250302A: Fermi GBM Observation
  96. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  97. GRB 250312A: Swift detection of a burst
  98. GRB 241213A: VIRT Optical Upper Limit
  99. GRB 241228A: VIRT Optical Upper Limit
  100. GRB 250311A/EP250311a: Optical upper limits with Kinder observations

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