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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"

23661 results found.

  1. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  2. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  3. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  4. The EP-WXT trigger 01709200994 is likely a flaring star
  5. GRB 250828B: Swift-BAT refined analysis
  6. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  7. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  8. GRB 250808B: SVOM detection of a burst through offline search
  9. Swift GRB 250828B: Global MASTER-Net observations report
  10. EP250828a: Global MASTER-Net observations report
  11. EP250828a: KAIT optical upper limit
  12. EP250828a: NOT optical counterpart confirmation
  13. EP250828a: SVOM/VT optical candidate
  14. EP250828a: Seimei/TriCCS optical counterpart detection
  15. GRB 250828B: Swift detection of a burst
  16. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  17. EP250828a: Optical upper limit with Kinder observations
  18. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  19. GRB 250828A: Fermi GBM Final Localization
  20. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  21. Fermi GRB 250827A: Global MASTER-Net observations report
  22. EP250827a: GOTO observation of the optical afterglow
  23. GRB 250827A: Fermi GBM Final Real-time Localization
  24. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  25. The EP-WXT trigger 01709200800 is likely a flaring star
  26. EP250827a: BOOTES-7 early optical dectection
  27. EP250827a: Gemini-South redshift z = 1.613
  28. EP250827a: Global MASTER-Net observations report
  29. EP250827a: Gemini-South optical counterpart detection
  30. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  31. Fermi GRB 250826A: Global MASTER-Net observations report
  32. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  33. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  34. Fermi trigger No 777883624: Global MASTER-Net observations report
  35. GRB 250826A: Fermi GBM Final Real-time Localization
  36. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  37. Fermi GRB 250824B: Global MASTER-Net observations report
  38. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  39. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  40. GRB 250823A: Swift-BAT refined analysis
  41. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  42. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  43. EP250821a: MeerKAT radio counterpart
  44. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  45. GRB 250824B: Fermi GBM Final Real-time Localization
  46. The EP-WXT trigger 01709200707 is likely a flaring star
  47. The EP-WXT trigger 01709200706 is likely a flaring star
  48. GRB 250823A: SVOM/VT optical observation
  49. GRB 250824A: Fermi GBM Final Real-time Localization
  50. GRB 250823A: NOT optical observations
  51. GRB 250823A: Fermi GBM Observation
  52. GRB 250823A: LCOGT Optical Detection
  53. GRB 250823A: BOOTES6/DPRT early optical detection
  54. GRB 250823A: Liverpool Telescope optical detection
  55. GRB 250823A: Fermi GBM Final Real-time Localization
  56. Swift GRB250823.84: Global MASTER-Net observations report
  57. Konus-Wind detection of GRB 250821B
  58. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  59. GRB 250806A: Gemini observations of host galaxy candidate
  60. IPN triangulation of GRB 250821B (long/bright)
  61. GRB 250812A: SVOM/ECLAIRs refined analysis
  62. GRB 250821A: Swift-BAT refined analysis
  63. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  64. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  65. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  66. GRB 250821B: SVOM/GRM observation
  67. EP250821a: SVOM/VT optical observation
  68. Fermi GRB 250821B: Global MASTER-Net observations report
  69. GRB 250821C: Fermi GBM Final Real-time Localization
  70. GRB 250821A: KAIT optical upper limit
  71. Swift GRB 250821A: Global MASTER-Net observations report
  72. GRB 250821B: Fermi GBM Detection
  73. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  74. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  75. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  76. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  77. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  78. GRB 250821A: LCOGT Optical Upper Limits
  79. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  80. GRB 250821A: Swift detection of a burst
  81. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  82. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  83. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  84. LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
  85. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  86. IPN triangulation of GRB 250816A (short)
  87. IPN triangulation of GRB 250814C (short)
  88. IPN triangulation of GRB 250804B (short)
  89. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  90. GRB 250818B: Liverpool Telescope optical detections
  91. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  92. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  93. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  94. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  95. LIGO/Virgo/KAGRA S250818k: Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  96. GRB 250820A: Fermi GBM Final Real-time Localization
  97. GRB 250818B: TRT Optical Observation
  98. Fermi GRB 250816A: Global MASTER-Net observations report
  99. Swift GRB 250818A: Global MASTER-Net observations report
  100. GRB 250818B: NOT optical observations

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