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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"

24378 results found.

  1. EP250901a: Mephisto optical upper limits
  2. GRB 250830C: GECAM-B detection
  3. EP250901a: Global MASTER-Net observations report
  4. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  5. EP250831a: EP-FXT follow-up observation
  6. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  7. IceCube Alert 250831.75: Global MASTER-Net observations report
  8. EP250831a: Global MASTER-Net observations report
  9. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  10. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  11. GRB 250831A: SVOM detection of a soft burst
  12. GRB 250830B: Swift-XRT observations
  13. EP250830a: Global MASTER-Net observations report
  14. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  15. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  16. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  17. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  18. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  19. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  20. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  21. The EP-WXT trigger 01709200994 is likely a flaring star
  22. GRB 250828B: Swift-BAT refined analysis
  23. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  24. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  25. GRB 250808B: SVOM detection of a burst through offline search
  26. Swift GRB 250828B: Global MASTER-Net observations report
  27. EP250828a: Global MASTER-Net observations report
  28. EP250828a: KAIT optical upper limit
  29. EP250828a: NOT optical counterpart confirmation
  30. EP250828a: SVOM/VT optical candidate
  31. EP250828a: Seimei/TriCCS optical counterpart detection
  32. GRB 250828B: Swift detection of a burst
  33. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  34. EP250828a: Optical upper limit with Kinder observations
  35. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  36. GRB 250828A: Fermi GBM Final Localization
  37. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  38. Fermi GRB 250827A: Global MASTER-Net observations report
  39. EP250827a: GOTO observation of the optical afterglow
  40. GRB 250827A: Fermi GBM Final Real-time Localization
  41. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  42. The EP-WXT trigger 01709200800 is likely a flaring star
  43. EP250827a: BOOTES-7 early optical dectection
  44. EP250827a: Gemini-South redshift z = 1.613
  45. EP250827a: Global MASTER-Net observations report
  46. EP250827a: Gemini-South optical counterpart detection
  47. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  48. Fermi GRB 250826A: Global MASTER-Net observations report
  49. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  50. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  51. Fermi trigger No 777883624: Global MASTER-Net observations report
  52. GRB 250826A: Fermi GBM Final Real-time Localization
  53. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  54. Fermi GRB 250824B: Global MASTER-Net observations report
  55. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  56. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  57. GRB 250823A: Swift-BAT refined analysis
  58. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  59. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  60. EP250821a: MeerKAT radio counterpart
  61. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  62. GRB 250824B: Fermi GBM Final Real-time Localization
  63. The EP-WXT trigger 01709200707 is likely a flaring star
  64. The EP-WXT trigger 01709200706 is likely a flaring star
  65. GRB 250823A: SVOM/VT optical observation
  66. GRB 250824A: Fermi GBM Final Real-time Localization
  67. GRB 250823A: NOT optical observations
  68. GRB 250823A: Fermi GBM Observation
  69. GRB 250823A: LCOGT Optical Detection
  70. GRB 250823A: BOOTES6/DPRT early optical detection
  71. GRB 250823A: Liverpool Telescope optical detection
  72. GRB 250823A: Fermi GBM Final Real-time Localization
  73. Swift GRB250823.84: Global MASTER-Net observations report
  74. Konus-Wind detection of GRB 250821B
  75. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  76. GRB 250806A: Gemini observations of host galaxy candidate
  77. IPN triangulation of GRB 250821B (long/bright)
  78. GRB 250812A: SVOM/ECLAIRs refined analysis
  79. GRB 250821A: Swift-BAT refined analysis
  80. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  81. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  82. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  83. GRB 250821B: SVOM/GRM observation
  84. EP250821a: SVOM/VT optical observation
  85. Fermi GRB 250821B: Global MASTER-Net observations report
  86. GRB 250821C: Fermi GBM Final Real-time Localization
  87. GRB 250821A: KAIT optical upper limit
  88. Swift GRB 250821A: Global MASTER-Net observations report
  89. GRB 250821B: Fermi GBM Detection
  90. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  91. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  92. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  93. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  94. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  95. GRB 250821A: LCOGT Optical Upper Limits
  96. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  97. GRB 250821A: Swift detection of a burst
  98. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  99. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  100. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst

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