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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"

32485 results found.

  1. LIGO/Virgo/KAGRA S250331o: Updated Sky localization
  2. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  3. GRB 250331D: Swift ToO observations
  4. Swift GRB 250331C: Global MASTER-Net observations report
  5. Swift GRB 250331B: Global MASTER-Net observations report
  6. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  7. Konus-Wind detection of GRB 250327B
  8. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  9. GRB 250329B: Swift-XRT confirmation of fading
  10. GRB 250330A: VLT/FORS2 Afterglow Detection
  11. GRB20250327B: 45th Parallel Observatory upper limit
  12. GRB 250328A: Swift/UVOT Detection
  13. GRB 250328A: Swift-XRT refined Analysis
  14. Fermi-LAT gamma-ray observations of IceCube-250330A
  15. SVOM/sb25033102 is a false trigger
  16. GRB 250330A: Fermi GBM Observation
  17. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  18. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  19. GRB 250330A: SVOM/VT optical upper limit
  20. GRB 250314A: VLA detection
  21. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  22. Fermi GRB 250330B: Global MASTER-Net observations report
  23. Fermi GRB 250330A: Global MASTER-Net observations report
  24. GRB 250330A: BOOTES-7 early optical upper limit
  25. GRB 250330A: Swift/UVOT Upper Limits
  26. GRB 250328A: 1.6m Mephisto optical observations
  27. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  28. GRB 250330A: Fermi GBM Final Localization
  29. GRB 250330A: VLT/FORS2 Optical Observations
  30. GRB 250330A: Prompt Swift-XRT position
  31. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  32. GRB 250329B: SVOM/C-GFT optical upper limit
  33. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  34. GRB 250327B: ALMA detection
  35. GRB 250327B: VLA detection
  36. GRB 250329B: SVOM/VT optical upper limit
  37. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  38. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  39. GRB250329A: REM optical afterglow detection
  40. GRB 250329B: GWAC-F50A optical upper limit
  41. GRB 250329A: Swift-XRT afterglow detection
  42. GRB 250328A: SVOM/VT optical observation
  43. GRB 250329A: Fading optical counterpart detection by LCO.
  44. GRB 250328A: SVOM/C-GFT optical upper limit
  45. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  46. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  47. GRB 250329A: VLT/X-shooter redshift z = 2.921
  48. GRB 250329A: SVOM/VT optical counterpart confirmation
  49. GRB 250327B: J-band observations with WINTER
  50. GRB 250327B: MASTER detection of OT rebrightening
  51. GRB 250327B: LCO optical counterpart detection
  52. GRB 250328A: GWAC-F50A optical upper limit
  53. FRB 20250316A: FTW optical observations
  54. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  55. GRB 250327B: CrAO and SAO RAS Optical Observations
  56. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  57. GRB 250327B: further optical observations by LCOGT
  58. EP250315a: Pan-STARRS r and i-band imaging and photometry
  59. GRB 250327b: Liverpool Telescope optical observations
  60. GRB 250322A: GRANDMA/TNOT optical upper limits
  61. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  62. GRB 250327A: SVOM/VT upper limits on the XRT position
  63. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  64. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  65. GRB 250327B: Las Cumbres optical counterpart detection
  66. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  67. GRB 250327B: 1.6m Mephisto optical observations
  68. GRB 250327B: NOT spectroscopic redshift z = 3.035
  69. GRB 250327B: GOTO optical counterpart detection
  70. GRB 250327B: SVOM/VT optically bright counterpart
  71. GRB 250327B: SAO RAS optical candidate
  72. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  73. GRB 250327A: J-band observations with WINTER
  74. GRB 250327A: SVOM/VT optical candidate
  75. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  76. GRB 250327A: Fermi GBM observation
  77. Fermi GRB 250327A: Global MASTER-Net observations report
  78. Swift GRB 250327A: Global MASTER-Net observations report
  79. GRB 250327A: DDOTI Optical Observations
  80. GRB 250327A: COLIBRÍ optical upper limit
  81. GRB 250327A: Swift detection of a burst
  82. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  83. Konus-Wind detection of GRB 250322A (short)
  84. IPN triangulation of GRB 250322B
  85. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  86. EP250321a: Mondy AZT-33IK Continued Optical Observations
  87. GRB 250322A: third epoch of NOT optical observations
  88. GRB 250322A: Swift-BAT refined analysis
  89. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  90. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  91. GRB 250322A: further NOT optical observations
  92. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  93. GRB 250322A: Swift/UVOT Upper Limits
  94. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  95. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  96. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  97. EP250321a: TNOT Observation of Optical Counterpart
  98. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  99. GRB 250322A: Gemini-North redshift of candidate host galaxy
  100. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm

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