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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').
Advanced Search

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.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

32688 results found.

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

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