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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"

32510 results found.

  1. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  2. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  3. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  5. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  6. EP250108a / AT2025kg: GMG Optical Observations
  7. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  8. EP250108a / AT2025kg: VLA radio upper limit
  9. Konus-Wind detection of GRB 250116A
  10. GRB 250116A: GECAM-B detection of a long burst
  11. GRB 241217A / EP241217B: radio detection with the VLA
  12. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  13. GRB 250116A: Fermi-LAT detection
  14. GRB 250114B: Swift-XRT afterglow detection
  15. GRB 250114B: SVOM/VT upper limit
  16. EP250108a: MeerKAT radio upper limit
  17. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  18. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  19. Konus-Wind detection of GRB 250113A
  20. IPN triangulation of GRB 250113A
  21. GRB 250114B: Liverpool Telescope optical upper limit
  22. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  23. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  24. GRB 250114A: LCO optical counterpart detection.
  25. GRB 250114B: OHP/T193 optical upper limit
  26. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  27. GRB 250114A: LCOGT optical afterglow i-band detection
  28. GRB 250114B : GIT optical upper limit
  29. GRB 250114B: Swift ToO observations
  30. EP250111a: SAO RAS optical upper limit
  31. EP250108a: correction to GCN 38908
  32. GRB 250113A: INTEGRAL/SPI-ACS detection
  33. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  34. GRB 250114A: REM detection of the optical and NIR counterpart
  35. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  36. GRB 250114A: LCO optical observations
  37. GRB 250114A: TRT optical observations
  38. Swift GRB 250114A: Global MASTER-Net observations report
  39. GRB 250101A: Terskol Zeiss-2000 optical observations
  40. EP250108a / AT 2025kg: SAO RAS optical observations
  41. EP241021a: SMA radio observation
  42. GRB 250107A: VZLUSAT-2 detection
  43. GRB 250109A / EP250109a: GRBAlpha detection
  44. GRB 250107D: GRBAlpha detection
  45. EP250111a: KAIT optical observations
  46. GRB 250109A / EP250109a: Mephisto optical upper limits
  47. EP250108a: Mephisto detection
  48. EP250111a: Mondy optical observation
  49. EP250108a / AT 2025kg: LCO optical observations
  50. EP250111a: Global MASTER-Net observations report
  51. EP250111a: Swift/XRT detection and fading
  52. EP250108a / AT 2025kg: Swift UVOT detections
  53. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  54. EP250108a: optical follow-up observations with the Liverpool Telescope
  55. EP250111a: NOT likely optical counterpart
  56. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  57. GRB 250101B: Fermi GBM Observation
  58. EP250108a: further NOT optical observations
  59. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  60. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  61. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  62. GRB 250108A: Swift/XRT afterglow fading
  63. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  64. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  65. Konus-Wind detection of GRB 250107C
  66. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  67. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  68. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  69. GRB 250101A: CMO RC-500 optical observations
  70. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  71. EP250108a: EP-FXT follow-up observation
  72. GRB 250109A: Fermi GBM Observation
  73. EP250108a: NOT optical observations
  74. GRB 250109a: GMG Optical Upper Limit
  75. EP250109a: Swift/UVOT non-detection
  76. Konus-Wind detection of GRB 250107D (short/hard)
  77. IPN triangulation of GRB 250107D (short/hard)
  78. IPN triangulation of GRB 250107C
  79. EP250108a: Liverpool Telescope likely optical counterpart
  80. GRB 250108B: Gemini-North likely redshift z = 2.197
  81. GRB 250108B: Swift-BAT refined analysis
  82. GRB 250108B: 1.3m DFOT upper limit
  83. GRB 250108B: REM optical/NIR upper limits
  84. GRB 250109A /EP250109a: Fermi GBM Final Localization
  85. EP250109a: SVOM/VT optical candidate
  86. EP250109a: Global MASTER-Net observations report
  87. GRB 250101A: Terskol K-800 optical observations
  88. EP250109a: GOTO optical upper limits
  89. EP250109a: Swift/XRT non-detection
  90. GRB 250108A: Swift/UVOT Upper Limits
  91. EP250108a: Global MASTER-Net observations report
  92. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  93. GRB 250108A: NOT optical upper limit
  94. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  95. Swift GRB 250108B: Global MASTER-Net observations report
  96. Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB
  97. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  98. GRB 250103A: 1.6m Mephisto optical observations
  99. GRB 250108A:SVOM/VT optical candidate
  100. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate

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