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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"

24373 results found.

  1. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  2. IceCube Alert 250831.75: Global MASTER-Net observations report
  3. EP250831a: Global MASTER-Net observations report
  4. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  5. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  6. GRB 250831A: SVOM detection of a soft burst
  7. GRB 250830B: Swift-XRT observations
  8. EP250830a: Global MASTER-Net observations report
  9. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  10. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  11. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  12. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  13. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  14. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  15. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  16. The EP-WXT trigger 01709200994 is likely a flaring star
  17. GRB 250828B: Swift-BAT refined analysis
  18. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  19. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  20. GRB 250808B: SVOM detection of a burst through offline search
  21. Swift GRB 250828B: Global MASTER-Net observations report
  22. EP250828a: Global MASTER-Net observations report
  23. EP250828a: KAIT optical upper limit
  24. EP250828a: NOT optical counterpart confirmation
  25. EP250828a: SVOM/VT optical candidate
  26. EP250828a: Seimei/TriCCS optical counterpart detection
  27. GRB 250828B: Swift detection of a burst
  28. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  29. EP250828a: Optical upper limit with Kinder observations
  30. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  31. GRB 250828A: Fermi GBM Final Localization
  32. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  33. Fermi GRB 250827A: Global MASTER-Net observations report
  34. EP250827a: GOTO observation of the optical afterglow
  35. GRB 250827A: Fermi GBM Final Real-time Localization
  36. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  37. The EP-WXT trigger 01709200800 is likely a flaring star
  38. EP250827a: BOOTES-7 early optical dectection
  39. EP250827a: Gemini-South redshift z = 1.613
  40. EP250827a: Global MASTER-Net observations report
  41. EP250827a: Gemini-South optical counterpart detection
  42. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  43. Fermi GRB 250826A: Global MASTER-Net observations report
  44. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  45. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  46. Fermi trigger No 777883624: Global MASTER-Net observations report
  47. GRB 250826A: Fermi GBM Final Real-time Localization
  48. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  49. Fermi GRB 250824B: Global MASTER-Net observations report
  50. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  51. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  52. GRB 250823A: Swift-BAT refined analysis
  53. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  54. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  55. EP250821a: MeerKAT radio counterpart
  56. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  57. GRB 250824B: Fermi GBM Final Real-time Localization
  58. The EP-WXT trigger 01709200707 is likely a flaring star
  59. The EP-WXT trigger 01709200706 is likely a flaring star
  60. GRB 250823A: SVOM/VT optical observation
  61. GRB 250824A: Fermi GBM Final Real-time Localization
  62. GRB 250823A: NOT optical observations
  63. GRB 250823A: Fermi GBM Observation
  64. GRB 250823A: LCOGT Optical Detection
  65. GRB 250823A: BOOTES6/DPRT early optical detection
  66. GRB 250823A: Liverpool Telescope optical detection
  67. GRB 250823A: Fermi GBM Final Real-time Localization
  68. Swift GRB250823.84: Global MASTER-Net observations report
  69. Konus-Wind detection of GRB 250821B
  70. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  71. GRB 250806A: Gemini observations of host galaxy candidate
  72. IPN triangulation of GRB 250821B (long/bright)
  73. GRB 250812A: SVOM/ECLAIRs refined analysis
  74. GRB 250821A: Swift-BAT refined analysis
  75. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  76. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  77. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  78. GRB 250821B: SVOM/GRM observation
  79. EP250821a: SVOM/VT optical observation
  80. Fermi GRB 250821B: Global MASTER-Net observations report
  81. GRB 250821C: Fermi GBM Final Real-time Localization
  82. GRB 250821A: KAIT optical upper limit
  83. Swift GRB 250821A: Global MASTER-Net observations report
  84. GRB 250821B: Fermi GBM Detection
  85. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  86. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  87. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  88. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  89. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  90. GRB 250821A: LCOGT Optical Upper Limits
  91. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  92. GRB 250821A: Swift detection of a burst
  93. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  94. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  95. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  96. LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
  97. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  98. IPN triangulation of GRB 250816A (short)
  99. IPN triangulation of GRB 250814C (short)
  100. IPN triangulation of GRB 250804B (short)

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