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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"

16204 results found.

  1. GRB 250128B: TNG optical upper limit
  2. GRB 250129A: Swift/UVOT Detection
  3. GRB 250128B: VLT/HAWKI near-infrared observations
  4. GRB 250127A: CrAO and Terskol optical upper limits
  5. GRB 250129A: Enhanced Swift-XRT position
  6. GRB 250128B: NOT optical upper limit
  7. GRB 250128B: VLT/FORS2 optical observations
  8. GRB 250129A: REM optical/NIR afterglow detection
  9. GRB 250129A: OHP/T193 optical and spectroscopy observations
  10. GRB 250129A: Early afterglow detection by LCO.
  11. GRB 250128B: OHP/T193 optical upper limit
  12. GRB 250129A: LCO optical observations
  13. GRB 250128B: Enhanced Swift-XRT position
  14. The EP-WXT trigger 01709131085 is likely a flaring star
  15. Fermi GRB 250128B: Global MASTER-Net observations report
  16. GRB 250129A: Swift detection of a burst with an optical counterpart
  17. GRB 250128B: Swift-XRT refined Analysis
  18. GRB 250128B: Fermi GBM Observation
  19. GRB 250128B: GOTO optical upper limit
  20. GRB 250128B: LCO optical observations
  21. GRB 250128B: Swift detection of a short burst
  22. GRB 250127A: Swift-XRT observations
  23. GRB 250127B: DDOTI Upper Limit on the Afterglow
  24. GRB 250127A: EP-FXT afterglow detection
  25. IPN triangulation of GRB 250119C
  26. GRB 250127A: LCO optical upper limit
  27. EP250125a: Optical upper limit with Kinder observations
  28. EP250125a: REM optical counterpart detection
  29. EP250125a: a new X-ray transient detected by Einstein Probe
  30. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  31. The EP-WXT trigger 01709130758 is a false trigger
  32. The EP-WXT trigger 01709130758 is a false trigger
  33. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  34. EP250108a: AbAO, CMO and Terskol optical upper limits
  35. IPN triangulation of GRB 250118B
  36. IPN triangulation of GRB 250119B
  37. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  38. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  39. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  40. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  41. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  42. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  43. IPN triangulation of GRB 250117A (short)
  44. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  45. EP 250108A: Late-time optical observation by LCO
  46. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  47. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  48. EP250108a / AT2025kg: GMG Optical Observations
  49. GRB 241217A / EP241217B: radio detection with the VLA
  50. GRB 250114B: Swift-XRT afterglow detection
  51. EP250108a: MeerKAT radio upper limit
  52. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  53. IPN triangulation of GRB 250113A
  54. GRB 250114B: Liverpool Telescope optical upper limit
  55. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  56. GRB 250114A: LCO optical counterpart detection.
  57. GRB 250114B: OHP/T193 optical upper limit
  58. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  59. GRB 250114A: Swift-XRT refined Analysis
  60. GRB 250114A: LCOGT optical afterglow i-band detection
  61. GRB 250114B : GIT optical upper limit
  62. EP250111a: SAO RAS optical upper limit
  63. GRB 250114A: Enhanced Swift-XRT position
  64. GRB 250114A: REM detection of the optical and NIR counterpart
  65. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  66. GRB 250114A: LCO optical observations
  67. GRB 250114A: TRT optical observations
  68. GRB 250114A: Swift detection of a burst with an optical counterpart
  69. GRB 250101A: Terskol Zeiss-2000 optical observations
  70. EP250108a / AT 2025kg: SAO RAS optical observations
  71. EP241021a: SMA radio observation
  72. GRB 250113A: SVOM/GRM observation of a long burst
  73. GRB 250107A: VZLUSAT-2 detection
  74. EP250109b: optical upper limits with the Liverpool Telescope
  75. GRB 250106A: Swift-XRT afterglow detection
  76. Fermi trigger No 758442826: Global MASTER-Net observations report
  77. EP250111a: KAIT optical observations
  78. GRB 250109A / EP250109a: Mephisto optical upper limits
  79. EP250108a: Mephisto detection
  80. EP250111a: Mondy optical observation
  81. EP250108a / AT 2025kg: LCO optical observations
  82. EP250111a: NOT likely optical counterpart
  83. EP250111a: a new X-ray transient detected by Einstein Probe
  84. EP250108a: further NOT optical observations
  85. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  86. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  87. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  88. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  89. GRB 250101A: CMO RC-500 optical observations
  90. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  91. EP250108a: EP-FXT follow-up observation
  92. The EP-WXT trigger 01709130111 is likely a flaring star
  93. EP250108a: NOT optical observations
  94. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  95. GRB 250109a: GMG Optical Upper Limit
  96. EP250109a: Swift/UVOT non-detection
  97. IPN triangulation of GRB 250107D (short/hard)
  98. EP250108a: Liverpool Telescope likely optical counterpart
  99. GRB 250108B: 1.3m DFOT upper limit
  100. GRB 250108B: REM optical/NIR upper limits

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