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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"

32493 results found.

  1. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  2. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  3. EP250827b: Liverpool Telescope observations
  4. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  5. GRB 250902A: SVOM/GRM observation
  6. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  7. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  8. GRB 250901A: EP-FXT follow-up observation
  9. GRB 250901A: NOT optical observations
  10. GRB 250901A: SVOM/VT optical afterglow with VHF data
  11. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  12. GRB 250901A: LCO optical upper limit
  13. EP250827b: Swift observations of AT 2025wkm
  14. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  15. EP250827b: Gemini Spectroscopy of AT 2025wkm
  16. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  17. EP250831a: NOT optical observations and tentative afterglow candidate
  18. EP250827b: FTW Observations of AT 2025wkm
  19. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  20. GRB 250830C: Insight-HXMT detection
  21. EP250901a: Mephisto optical upper limits
  22. EP250901a: Global MASTER-Net observations report
  23. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  24. EP250831a: EP-FXT follow-up observation
  25. EP250831a: Swift-XRT observations
  26. EP250831a: Global MASTER-Net observations report
  27. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  28. GRB 250831A: Swift-XRT counterpart detection
  29. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  30. GRB 250831A: SVOM/VT upper limit with VHF data
  31. EP250830a: Global MASTER-Net observations report
  32. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  33. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  34. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  35. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  36. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  37. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  38. GRB 250830B: Swift ToO observations
  39. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  40. GRB 250828B: Swift-BAT refined analysis
  41. EP250821a: SOAR observations
  42. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  43. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  44. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  45. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  46. EP250828a: Optical counterpart detection with Kinder observations
  47. EP250828a: Liverpool Telescope upper limits
  48. Swift GRB 250828B: Global MASTER-Net observations report
  49. EP250828a: Global MASTER-Net observations report
  50. EP-WXT trigger 01709200800 : KAIT optical observations
  51. EP250828a: KAIT optical upper limit
  52. EP250827a: Swift/UVOT Detection
  53. EP250828a: NOT optical counterpart confirmation
  54. EP250828a: SVOM/VT optical candidate
  55. EP250828a: Seimei/TriCCS optical counterpart detection
  56. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  57. EP250828a: Optical upper limit with Kinder observations
  58. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  59. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  60. EP250827a: LCO observations show fading optical counterpart
  61. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  62. GRID detection of GRB 250824A
  63. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  64. EP250827A: VLT/X-shooter redshift confirmation
  65. Fermi GRB 250827A: Global MASTER-Net observations report
  66. EP250827a: confirmation of optical rebrightening with LCO
  67. EP250827a: GOTO observation of the optical afterglow
  68. GRB 250826A: SVOM/GRM observation
  69. EP250827A: An optical rebrightening was detected by LCO.
  70. EP250827a: Swift-XRT counterpart detection
  71. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  72. EP250827a: TRT optical observations
  73. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  74. EP250827a: Gemini-South redshift z = 1.613
  75. EP250827a: Global MASTER-Net observations report
  76. EP250827a: Las Cumbres independent detection of the optical counterpart
  77. EP250827a: Gemini-South optical counterpart detection
  78. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  79. Fermi GRB 250826A: Global MASTER-Net observations report
  80. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  81. EP250821a: Gemini GMOS Redshift Confirmation
  82. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  83. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  84. Fermi GRB 250824B: Global MASTER-Net observations report
  85. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  86. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  87. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  88. GRB 250823A: Swift-BAT refined analysis
  89. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  90. GRB 250821B: AstroSat CZTI detection
  91. GRB 250819A: AstroSat CZTI detection
  92. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  93. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  94. GRB 250821B: Insight-HXMT detection
  95. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  96. EP250821a: MeerKAT radio counterpart
  97. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  98. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  99. GRB 250823A: COLIBRÍ optical observations
  100. GRB 250823A: SVOM/VT optical observation

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