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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"

28724 results found.

  1. GRB 250327A: SVOM/VT upper limits on the XRT position
  2. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  3. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  4. GRB 250327B: Las Cumbres optical counterpart detection
  5. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  6. GRB 250327B: 1.6m Mephisto optical observations
  7. GRB 250327B: NOT spectroscopic redshift z = 3.035
  8. GRB 250327B: GOTO optical counterpart detection
  9. GRB 250327B: SVOM/VT optically bright counterpart
  10. GRB 250327B: SAO RAS optical candidate
  11. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  12. GRB 250327A: J-band observations with WINTER
  13. GRB 250327A: SVOM/VT optical candidate
  14. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  15. GRB 250327A: Fermi GBM observation
  16. Fermi GRB 250327A: Global MASTER-Net observations report
  17. Swift GRB 250327A: Global MASTER-Net observations report
  18. GRB 250327A: DDOTI Optical Observations
  19. GRB 250327A: COLIBRÍ optical upper limit
  20. GRB 250327A: Swift detection of a burst
  21. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  22. Konus-Wind detection of GRB 250322A (short)
  23. IPN triangulation of GRB 250322B
  24. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  25. EP250321a: Mondy AZT-33IK Continued Optical Observations
  26. GRB 250322A: third epoch of NOT optical observations
  27. GRB 250322A: Swift-BAT refined analysis
  28. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  29. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  30. GRB 250322A: further NOT optical observations
  31. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  32. GRB 250322A: Swift/UVOT Upper Limits
  33. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  34. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  35. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  36. EP250321a: TNOT Observation of Optical Counterpart
  37. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  38. GRB 250322A: Gemini-North redshift of candidate host galaxy
  39. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  40. GRB 250322A: AstroSat CZTI detection of a short burst
  41. GRB250322A: STEP/T80S optical limits
  42. GRB 250322A: Gemini-South optical observations
  43. GRB 250322A: VLT optical observations
  44. GRB 250322A: VLT near-infrared observations
  45. FRB 250316A: DDOTI Continued Optical Observations
  46. GRB 250322A: NOT optical upper limits
  47. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  48. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  49. GRB 250322A: MASTER optical observation
  50. EP250321a: Liverpool Telescope optical follow-up
  51. EP250321a: Mondy AZT-33IK Optical Observations
  52. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  53. EP250321a: KAIT optical observations
  54. EP250321A: COLIBRÍ Continuing Optical Observations
  55. GRB 250225B: GECAM-A detection
  56. GRB 250312A: GECAM-A detection
  57. GRB 250321B: Swift ToO observations
  58. EP250321a: WFST optical observations
  59. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  60. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  61. GRB 250320B: Fermi GBM Observation
  62. EP250321a: Xinglong 216 decaying optical observations
  63. GRB 250321A: Swift-BAT refined analysis
  64. GRB 250320B: Fermi-LAT detection
  65. EP250321a: SVOM/VT optical observation
  66. EP 250321A: Optical counterpart detection by LCO.
  67. EP250321a: Kinder optical follow-up observations
  68. GRB 250321A: Swift/UVOT Upper Limits
  69. GRB 250320B: SVOM/GRM observation of a long burst
  70. EP250321a: LCO optical counterpart detection
  71. EP250321a: Swift-XRT detection of an X-ray source
  72. EP250321A: COLIBRÍ Optical Observations
  73. EP250321a: VLT/X-shooter redshift z = 4.368
  74. GRB 250320B: AstroSat CZTI detection
  75. EP250321a: REM optical/NIR afterglow detection
  76. Fermi GRB 250320B: Global MASTER-Net observations report
  77. EP250321a: TRT optical counterpart detection
  78. EP250321a: Global MASTER-Net observations report
  79. Swift GRB 250321A: Global MASTER-Net observations report
  80. Fermi GRB 250321A: Global MASTER-Net observations report
  81. GRB 250321A: GOTO optical upper limits
  82. GRB 250321A: Swift-XRT localisation
  83. GRB 250314A: Keck/NIRC2 J-band upper limit
  84. EP250226a/GRB 250226A: KAIT optical observations
  85. GRB 250321A: Fermi GBM Observation
  86. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  87. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  88. Fermi GRB 250319B: Global MASTER-Net observations report
  89. GRB 250313A: GRBAlpha detection
  90. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  91. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  92. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  93. GRB 250314A: ATCA radio upper limits
  94. EP250302a: VLA observations
  95. GRB 250317B: OHP/T193 continued follow-up
  96. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  97. GRB 250317C: SVOM/GRM observation of a long burst
  98. GRB 250317B: Leavitt Observatory optical upper limit
  99. GRB 250309B/AT2025dws: further ATCA observations
  100. GRB 250317B: Mondy AZT-33IK Optical Observations

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