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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"

25035 results found.

  1. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  2. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  3. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  4. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  5. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  6. EP250704a / GRB250704B: Swift-XRT counterpart detection
  7. GRB 250704A: Swift-XRT afterglow detection
  8. EP250704a / GRB 250704B - REM observations
  9. GRB 250702F: GROWTH-India Telescope optical observations
  10. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  11. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  12. EP250702a: WFST optical observations
  13. EP250704a: COLIBRÍ optical counterpart candidate
  14. EP250704a: Einstein Probe detection of an X-ray transient
  15. GRB 250704A: REM detection of the optical afterglow
  16. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  17. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  18. GRB 250704A: SVOM detection of a burst
  19. GRB 250702F: Swift/UVOT Detection
  20. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  21. GRB 250702F: Swift-XRT refined Analysis
  22. GRB 250702F: Fermi GBM Observation
  23. GRB 250702F: Leavitt Observatory optical observations
  24. GRB 250702F: AKO Optical Afterglow Detection
  25. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  26. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  27. GRB 250702F: Skynet Optical Observations
  28. GRB 250424A: VIRT Optical Upper Limit
  29. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  30. GRB 250702F: TRT Optical Observation
  31. GRB 250703A: DDOTI Optical Upper Limit
  32. GRB 250702F: REM optical afterglow detection
  33. EP250702a: Global MASTER-Net observations report
  34. GRB 250702F: DDOTI Optical Observation
  35. GRB 250702F: COLIBRÍ Observations of the Afterglow
  36. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  37. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  38. GRB 250702F: Enhanced Swift-XRT position
  39. GRB 250702F: NOT observations of the optical afterglow
  40. GRB 250702F: Swift detection of a burst with an optical counterpart
  41. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  42. GRB 250702A: Fermi GBM Detection
  43. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  44. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  45. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  46. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  47. GRB 250628B: Swift-XRT observations
  48. GRB 250628B: EP-FXT counterpart detection
  49. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  50. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  51. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  52. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  53. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  54. GRB 250628A: REM optical/NIR upper limits
  55. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  56. GRB 250628B: SVOM detection of a long burst
  57. GRB 250628A: VLT/X-shooter upper limits
  58. GRB 250628A: Swift/UVOT Upper Limits
  59. GRB 250628A: Swift-XRT refined Analysis
  60. GRB 250628A: Enhanced Swift-XRT position
  61. GRB 250628A: Swift detection of a burst
  62. GRB 250625A: Swift-BAT refined analysis
  63. GRB 250625A: Leavitt Observatory afterglow detection
  64. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  65. GRB 250625A: SVOM/C-GFT upper limit in early phase
  66. GRB 250625A: Swift/UVOT Upper Limits
  67. GRB 250625A: ABObservatory afterglow detection
  68. GRB 250625A: OHP/T193 optical detection
  69. GRB 250625A: COLIBRÍ optical observations
  70. GRB 250625A: Swift-XRT refined Analysis
  71. GRB 250625A: JinShan optical observations
  72. GRB250625A: Fermi GBM Observation
  73. GRB 250620B: Fermi GBM Observation
  74. GRB 250625A: SAO RAS possible optical afterglow
  75. GRB 250625A: Enhanced Swift-XRT position
  76. GRB 250625A: Swift detection of a burst
  77. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  78. GRB 241018A: Maidanak optical observations
  79. GRB 250620C: AstroSat CZTI detection
  80. Fermi GRB 250624A: Global MASTER-Net observations report
  81. GRB 250521A: VZLUSAT-2 detection
  82. GRB 250617B: Swift-BAT refined analysis
  83. Fermi trigger No 772190032: Global MASTER-Net observations report
  84. IPN triangulation of GRB 250620С (long/bright)
  85. GRB 250620C: SVOM/GRM observation
  86. GRB 250620A: SVOM/GRM observation of a short burst
  87. GRB250620A: Fermi GBM Observation
  88. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  89. GRB 250619B: Fermi GBM Observation
  90. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  91. GRB250620C: Fermi GBM Observation
  92. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  93. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  94. Fermi trigger No 772128434: Global MASTER-Net observations report
  95. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  96. GRB 250617B: Nickel telescope optical observations
  97. GRB 250615A: Kilonova-Catcher optical upper limits
  98. GRB 250617B: Assy AZT-20 Optical Observations
  99. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  100. Fermi GRB 250617A: Global MASTER-Net observations report

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