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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

32561 results found.

  1. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  2. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  3. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  4. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  5. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  6. GRB 250830B: Swift ToO observations
  7. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  8. GRB 250828B: Swift-BAT refined analysis
  9. EP250821a: SOAR observations
  10. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  11. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  12. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  13. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  14. EP250828a: Optical counterpart detection with Kinder observations
  15. EP250828a: Liverpool Telescope upper limits
  16. Swift GRB 250828B: Global MASTER-Net observations report
  17. EP250828a: Global MASTER-Net observations report
  18. EP-WXT trigger 01709200800 : KAIT optical observations
  19. EP250828a: KAIT optical upper limit
  20. EP250827a: Swift/UVOT Detection
  21. EP250828a: NOT optical counterpart confirmation
  22. EP250828a: SVOM/VT optical candidate
  23. EP250828a: Seimei/TriCCS optical counterpart detection
  24. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  25. EP250828a: Optical upper limit with Kinder observations
  26. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  27. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  28. EP250827a: LCO observations show fading optical counterpart
  29. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  30. GRID detection of GRB 250824A
  31. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  32. EP250827A: VLT/X-shooter redshift confirmation
  33. Fermi GRB 250827A: Global MASTER-Net observations report
  34. EP250827a: confirmation of optical rebrightening with LCO
  35. EP250827a: GOTO observation of the optical afterglow
  36. GRB 250826A: SVOM/GRM observation
  37. EP250827A: An optical rebrightening was detected by LCO.
  38. EP250827a: Swift-XRT counterpart detection
  39. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  40. EP250827a: TRT optical observations
  41. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  42. EP250827a: Gemini-South redshift z = 1.613
  43. EP250827a: Global MASTER-Net observations report
  44. EP250827a: Las Cumbres independent detection of the optical counterpart
  45. EP250827a: Gemini-South optical counterpart detection
  46. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  47. Fermi GRB 250826A: Global MASTER-Net observations report
  48. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  49. EP250821a: Gemini GMOS Redshift Confirmation
  50. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  51. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  52. Fermi GRB 250824B: Global MASTER-Net observations report
  53. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  54. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  55. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  56. GRB 250823A: Swift-BAT refined analysis
  57. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  58. GRB 250821B: AstroSat CZTI detection
  59. GRB 250819A: AstroSat CZTI detection
  60. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  61. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  62. GRB 250821B: Insight-HXMT detection
  63. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  64. EP250821a: MeerKAT radio counterpart
  65. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  66. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  67. GRB 250823A: COLIBRÍ optical observations
  68. GRB 250823A: SVOM/VT optical observation
  69. GRB 250823A: Swift/UVOT Detection
  70. GRB 250823A: NOT optical observations
  71. LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
  72. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  73. GRB 250823A: Fermi GBM Observation
  74. GRB 250818B: MeerKAT Detection
  75. GRB 250823A: LCOGT Optical Detection
  76. GRB 250823A: BOOTES6/DPRT early optical detection
  77. GRB 250823A: Liverpool Telescope optical detection
  78. Konus-Wind detection of GRB 250821B
  79. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  80. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  81. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  82. LIGO/Virgo/KAGRA S250818k: PRIME nIR observations of AT2025ulz
  83. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  84. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  85. LIGO/Virgo/Kagra S250818k: STEP/T80N upper limits on 2025ulz
  86. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  87. GRB 250806A: Gemini observations of host galaxy candidate
  88. IPN triangulation of GRB 250821B (long/bright)
  89. GRB 250821A: Kilonova-Catcher optical upper limits
  90. EP250821a: Swift/XRT counterpart fading
  91. GRB 250812A: SVOM/ECLAIRs refined analysis
  92. GRB 250821A: Swift-BAT refined analysis
  93. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  94. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  95. EP250821a: Swift/UVOT further observations.
  96. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  97. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  98. GRB 250821A: VLT/FORS2 Optical Observation
  99. GRB 250821A: GECAM-B detection
  100. GRB 250821B: SVOM/GRM observation

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