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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"

32509 results found.

  1. Fermi GRB 250327A: Global MASTER-Net observations report
  2. Swift GRB 250327A: Global MASTER-Net observations report
  3. GRB 250327A: DDOTI Optical Observations
  4. GRB 250327A: COLIBRÍ optical upper limit
  5. GRB 250327A: Swift detection of a burst
  6. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  7. Konus-Wind detection of GRB 250322A (short)
  8. IPN triangulation of GRB 250322B
  9. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  10. EP250321a: Mondy AZT-33IK Continued Optical Observations
  11. GRB 250322A: third epoch of NOT optical observations
  12. GRB 250322A: Swift-BAT refined analysis
  13. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  14. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  15. GRB 250322A: further NOT optical observations
  16. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  17. GRB 250322A: Swift/UVOT Upper Limits
  18. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  19. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  20. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  21. EP250321a: TNOT Observation of Optical Counterpart
  22. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  23. GRB 250322A: Gemini-North redshift of candidate host galaxy
  24. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  25. GRB 250322A: AstroSat CZTI detection of a short burst
  26. GRB250322A: STEP/T80S optical limits
  27. GRB 250322A: Gemini-South optical observations
  28. GRB 250322A: VLT optical observations
  29. GRB 250322A: VLT near-infrared observations
  30. FRB 250316A: DDOTI Continued Optical Observations
  31. GRB 250322A: NOT optical upper limits
  32. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  33. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  34. GRB 250322A: MASTER optical observation
  35. EP250321a: Liverpool Telescope optical follow-up
  36. EP250321a: Mondy AZT-33IK Optical Observations
  37. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  38. EP250321a: KAIT optical observations
  39. EP250321A: COLIBRÍ Continuing Optical Observations
  40. GRB 250225B: GECAM-A detection
  41. GRB 250312A: GECAM-A detection
  42. GRB 250321B: Swift ToO observations
  43. EP250321a: WFST optical observations
  44. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  45. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  46. GRB 250320B: Fermi GBM Observation
  47. EP250321a: Xinglong 216 decaying optical observations
  48. GRB 250321A: Swift-BAT refined analysis
  49. GRB 250320B: Fermi-LAT detection
  50. EP250321a: SVOM/VT optical observation
  51. EP 250321A: Optical counterpart detection by LCO.
  52. EP250321a: Kinder optical follow-up observations
  53. GRB 250321A: Swift/UVOT Upper Limits
  54. GRB 250320B: SVOM/GRM observation of a long burst
  55. EP250321a: LCO optical counterpart detection
  56. EP250321a: Swift-XRT detection of an X-ray source
  57. EP250321A: COLIBRÍ Optical Observations
  58. EP250321a: VLT/X-shooter redshift z = 4.368
  59. GRB 250320B: AstroSat CZTI detection
  60. EP250321a: REM optical/NIR afterglow detection
  61. Fermi GRB 250320B: Global MASTER-Net observations report
  62. EP250321a: TRT optical counterpart detection
  63. EP250321a: Global MASTER-Net observations report
  64. Swift GRB 250321A: Global MASTER-Net observations report
  65. Fermi GRB 250321A: Global MASTER-Net observations report
  66. GRB 250321A: GOTO optical upper limits
  67. GRB 250321A: Swift-XRT localisation
  68. GRB 250314A: Keck/NIRC2 J-band upper limit
  69. EP250226a/GRB 250226A: KAIT optical observations
  70. GRB 250321A: Fermi GBM Observation
  71. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  72. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  73. Fermi GRB 250319B: Global MASTER-Net observations report
  74. GRB 250313A: GRBAlpha detection
  75. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  76. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  77. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  78. GRB 250314A: ATCA radio upper limits
  79. EP250302a: VLA observations
  80. GRB 250317B: OHP/T193 continued follow-up
  81. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  82. GRB 250317C: SVOM/GRM observation of a long burst
  83. GRB 250317B: Leavitt Observatory optical upper limit
  84. GRB 250309B/AT2025dws: further ATCA observations
  85. GRB 250317B: Mondy AZT-33IK Optical Observations
  86. GRB 250317C: AstroSat CZTI detection
  87. GRB 250317B: NOT optical observations suggest an optical plateau phase
  88. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  89. GRB 250317B: OHP/T193 optical observations
  90. GRB250312A: Swift/UVOT Upper Limits
  91. GRB 250317B: REM optical/NIR observations
  92. GRB 250317B: Swift-XRT observations
  93. GRB 250316A: Swift/UVOT Upper Limits
  94. GRB 250314A: REM optical/NIR upper limits
  95. GRB 250316A: AbAO AS-32 Optical Upper Limit
  96. EP 250317B: Fading optical counterpart detection by LCO
  97. GRB 250317B: LCO detection of the fading optical afterglow
  98. GRB 250317B: refined SVOM/MXT analysis
  99. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  100. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart

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