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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"

24809 results found.

  1. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  2. GRB 250327A: SVOM/VT upper limits on the XRT position
  3. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  4. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  5. GRB 250327B: Las Cumbres optical counterpart detection
  6. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  7. GRB 250327B: 1.6m Mephisto optical observations
  8. GRB 250327A: Swift-XRT refined Analysis
  9. GRB 250327B: SVOM/VT optically bright counterpart
  10. GRB 250327B: SAO RAS optical candidate
  11. GRB 250327B: SVOM detection of a burst
  12. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  13. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  14. GRB 250327A: J-band observations with WINTER
  15. GRB 250327A: SVOM/VT optical candidate
  16. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  17. GRB 250327A: DDOTI Optical Observations
  18. GRB 250327A: COLIBRÍ optical upper limit
  19. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  20. IPN triangulation of GRB 250322B
  21. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  22. EP250321a: Mondy AZT-33IK Continued Optical Observations
  23. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  24. GRB 250322A: third epoch of NOT optical observations
  25. GRB 250322A: Swift-BAT refined analysis
  26. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  27. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  28. GRB 250322A: further NOT optical observations
  29. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  30. GRB 250322A: Swift/UVOT Upper Limits
  31. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  32. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  33. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  34. GRB 250321B: Swift-XRT observations
  35. GRB 250322A: Swift-XRT refined Analysis
  36. EP250321a: TNOT Observation of Optical Counterpart
  37. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  38. SVOM/sb25032302: SVOM detection of a long X-ray transient
  39. GRB 250322B: AstroSat CZTI detection of a bright long burst
  40. GRB 250322A: VLT optical observations
  41. GRB 250322A: VLT near-infrared observations
  42. FRB 250316A: DDOTI Continued Optical Observations
  43. GRB 250322A: NOT optical upper limits
  44. GRB 250322A: Enhanced Swift-XRT position
  45. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  46. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  47. EP250321a: Liverpool Telescope optical follow-up
  48. EP250321a: Mondy AZT-33IK Optical Observations
  49. GRB 250322A: Swift detection of a short burst
  50. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  51. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  52. EP250321A: COLIBRÍ Continuing Optical Observations
  53. EP250321a: WFST optical observations
  54. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  55. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  56. GRB 250320B: Fermi GBM Observation
  57. EP250321a: Xinglong 216 decaying optical observations
  58. GRB 250321A: Swift-BAT refined analysis
  59. GRB 250321A: Swift-XRT refined Analysis
  60. EP 250321A: Optical counterpart detection by LCO.
  61. EP250321a: Kinder optical follow-up observations
  62. GRB 250321A: Swift/UVOT Upper Limits
  63. GRB 250320B: SVOM/GRM observation of a long burst
  64. EP250321a: LCO optical counterpart detection
  65. EP250321a: Swift-XRT detection of an X-ray source
  66. EP250321A: COLIBRÍ Optical Observations
  67. GRB 250320B: AstroSat CZTI detection
  68. EP250321a: REM optical/NIR afterglow detection
  69. EP250321a: TRT optical counterpart detection
  70. Swift GRB 250321A: Global MASTER-Net observations report
  71. EP250321a: Einstein Probe detection of an X-ray transient
  72. GRB 250321A: GOTO optical upper limits
  73. GRB 250314A: Keck/NIRC2 J-band upper limit
  74. EP250226a/GRB 250226A: KAIT optical observations
  75. GRB 250321A: Fermi GBM Observation
  76. GRB 250321A: Swift detection of a burst
  77. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  78. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  79. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  80. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  81. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  82. GRB 250317D: EIRSAT-1 GMOD Detection
  83. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  84. GRB 250314A: ATCA radio upper limits
  85. GRB 250317B: OHP/T193 continued follow-up
  86. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  87. GRB 250317C: SVOM/GRM observation of a long burst
  88. GRB 250317B: Leavitt Observatory optical upper limit
  89. GRB 250317B: Mondy AZT-33IK Optical Observations
  90. GRB 250317B: NOT optical observations suggest an optical plateau phase
  91. GRB 250317C: GECAM-B detection
  92. GRB 250317B: OHP/T193 optical observations
  93. GRB250312A: Swift/UVOT Upper Limits
  94. GRB 250317B: REM optical/NIR observations
  95. GRB 250317B: Swift-XRT observations
  96. GRB 250316A: Swift/UVOT Upper Limits
  97. GRB 250314A: REM optical/NIR upper limits
  98. GRB 250316A: AbAO AS-32 Optical Upper Limit
  99. EP 250317B: Fading optical counterpart detection by LCO
  100. GRB 250316A: Swift-XRT afterglow detection

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