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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"

45652 results found.

  1. EP250828a: Einstein Probe detection of an X-ray transient
  2. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  3. GRID detection of GRB 250824A
  4. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  5. EP250827A: VLT/X-shooter redshift confirmation
  6. Fermi GRB 250827A: Global MASTER-Net observations report
  7. EP250827a: confirmation of optical rebrightening with LCO
  8. EP250827a: GOTO observation of the optical afterglow
  9. GRB 250826A: SVOM/GRM observation
  10. GRB 250827A: Fermi GBM Final Real-time Localization
  11. EP250827A: An optical rebrightening was detected by LCO.
  12. EP250827a: Swift-XRT counterpart detection
  13. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  14. The EP-WXT trigger 01709200800 is likely a flaring star
  15. EP250827a: TRT optical observations
  16. EP250827a: BOOTES-7 early optical dectection
  17. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  18. EP250827a: Gemini-South redshift z = 1.613
  19. EP250827a: Global MASTER-Net observations report
  20. EP250827a: Las Cumbres independent detection of the optical counterpart
  21. EP250827a: Gemini-South optical counterpart detection
  22. EP250827a: Einstein Probe detection of an X-ray transient
  23. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  24. Fermi GRB 250826A: Global MASTER-Net observations report
  25. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  26. EP250821a: Gemini GMOS Redshift Confirmation
  27. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  28. Fermi trigger No 777883624: Global MASTER-Net observations report
  29. Fermi Gamma-ray Burst Monitor trigger 777883624/250826283 is not a GRB
  30. GRB 250826A: Fermi GBM Final Real-time Localization
  31. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  32. Fermi GRB 250824B: Global MASTER-Net observations report
  33. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  34. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  35. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  36. GRB 250823A: Swift-BAT refined analysis
  37. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  38. GRB 250821B: AstroSat CZTI detection
  39. GRB 250819A: AstroSat CZTI detection
  40. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  41. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  42. GRB 250821B: Insight-HXMT detection
  43. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  44. GRB 250823A: Swift-XRT refined Analysis
  45. EP250821a: MeerKAT radio counterpart
  46. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  47. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  48. GRB 250824B: Fermi GBM Final Real-time Localization
  49. The EP-WXT trigger 01709200707 is likely a flaring star
  50. GRB 250823A: COLIBRÍ optical observations
  51. The EP-WXT trigger 01709200706 is likely a flaring star
  52. GRB 250823A: SVOM/VT optical observation
  53. GRB 250824A: Fermi GBM Final Real-time Localization
  54. GRB 250823A: Swift/UVOT Detection
  55. GRB 250823A: NOT optical observations
  56. LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
  57. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  58. GRB 250823A: Fermi GBM Observation
  59. GRB 250818B: MeerKAT Detection
  60. GRB 250823A: Enhanced Swift-XRT position
  61. GRB 250823A: LCOGT Optical Detection
  62. GRB 250823A: BOOTES6/DPRT early optical detection
  63. GRB 250823A: Liverpool Telescope optical detection
  64. GRB 250823A: Swift detection of a burst
  65. GRB 250823A: Fermi GBM Final Real-time Localization
  66. Swift GRB250823.84: Global MASTER-Net observations report
  67. Konus-Wind detection of GRB 250821B
  68. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  69. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  70. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  71. LIGO/Virgo/KAGRA S250818k: PRIME nIR observations of AT2025ulz
  72. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  73. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  74. LIGO/Virgo/Kagra S250818k: STEP/T80N upper limits on 2025ulz
  75. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  76. GRB 250806A: Gemini observations of host galaxy candidate
  77. IPN triangulation of GRB 250821B (long/bright)
  78. GRB 250821A: Kilonova-Catcher optical upper limits
  79. EP250821a: Swift/XRT counterpart fading
  80. GRB 250812A: SVOM/ECLAIRs refined analysis
  81. GRB 250821A: Swift-BAT refined analysis
  82. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  83. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  84. EP250821a: Swift/UVOT further observations.
  85. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  86. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  87. GRB 250821A: VLT/FORS2 Optical Observation
  88. GRB 250821A: GECAM-B detection
  89. GRB 250821B: SVOM/GRM observation
  90. EP250821a: SVOM/VT optical observation
  91. Fermi GRB 250821B: Global MASTER-Net observations report
  92. GRB 250821A: NOT z-band upper limit
  93. GRB 250821C: Fermi GBM Final Real-time Localization
  94. GRB 250821A: KAIT optical upper limit
  95. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  96. GRB 250821A: Swift-XRT refined Analysis
  97. Swift GRB 250821A: Global MASTER-Net observations report
  98. GRB 250821B: Fermi GBM Detection
  99. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  100. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)

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