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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"

23561 results found.

  1. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  2. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  3. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  4. GRB 250314A: ATCA radio upper limits
  5. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  6. GRB 250317C: SVOM/GRM observation of a long burst
  7. GRB 250317B: Leavitt Observatory optical upper limit
  8. GRB 250317B: Mondy AZT-33IK Optical Observations
  9. GRB 250317C: AstroSat CZTI detection
  10. GRB 250317B: NOT optical observations suggest an optical plateau phase
  11. GRB 250317B: OHP/T193 optical observations
  12. GRB250312A: Swift/UVOT Upper Limits
  13. GRB 250317B: REM optical/NIR observations
  14. GRB 250317B: Swift-XRT observations
  15. GRB 250316A: Swift/UVOT Upper Limits
  16. GRB 250314A: REM optical/NIR upper limits
  17. GRB 250316A: AbAO AS-32 Optical Upper Limit
  18. EP 250317B: Fading optical counterpart detection by LCO
  19. GRB 250316A: Swift-XRT afterglow detection
  20. GRB 250317B: LCO detection of the fading optical afterglow
  21. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  22. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  23. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  24. GRB 250317B: SVOM detection of a burst
  25. GRB 250316A: Swift-XRT observations
  26. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  27. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  28. GRB 250314A: Swift/UVOT Upper Limits
  29. GRB 250314A: Swift XRT Detection
  30. EP250315a: optical counterpart candidate detected by Gemini North
  31. EP250315a: Einstein Probe detection of an X-ray transient
  32. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  33. SVOM/MXT upper limit on GRB 250314A
  34. GRB 250314A: SVOM/VT upper limit
  35. GRB 250314A: NOT near-infrared candidate counterpart
  36. GRB 250313A: Swift-XRT observations
  37. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  38. GRB 250314A: SVOM detection of a burst
  39. GRB 250313A: AstroSat CZTI detection of a bright long burst
  40. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  41. EP250304a: Pan-STARRS r and i-band imaging and photometry
  42. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  43. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  44. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  45. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  46. GRB 250312A: Enhanced Swift-XRT position
  47. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  48. GRB 250312A: Swift detection of a burst
  49. GRB 241213A: VIRT Optical Upper Limit
  50. GRB 241228A: VIRT Optical Upper Limit
  51. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  52. GRB 250311A: Swift-XRT observations
  53. GRB 250309B: 1.3m DFOT Optical observations
  54. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  55. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  56. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  57. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  58. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  59. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  60. GRB 250309B: PRIME near-infrared detection
  61. GRB 250225B: Swift-BAT refined analysis
  62. GRB 250311A/EP250311a: TRT optical upper limit
  63. EP250311a/GRB 250311A: EP-WXT detection
  64. GRB 250309B / AT2025dws: further SAO RAS optical observations
  65. IceCube-250309A: Upper limits from Fermi-GBM Observations
  66. EP250308a: 1.6m Mephisto optical upper limits
  67. IPN triangulation of GRB 250308A (short)
  68. IPN triangulation of GRB 250309B
  69. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  70. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  71. GRB 250309B / IceCube-250309A: GECAM-B observations
  72. GRB 250309B / AT2025dws: SAO RAS optical observations
  73. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  74. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  75. IceCube-250309A: No candidates from the Zwicky Transient Facility
  76. EP250308a: FTW optical and NIR upper limits
  77. EP250308a: Einstein Probe detection of an X-ray transient
  78. EP250308a: NOT optical upper limit
  79. Konus-Wind detection of GRB 250306A
  80. EP250304a: MeerKAT detection of a possible radio counterpart
  81. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  82. EP250302a:Xinglong optical observations
  83. GRB 250306A: AstroSat CZTI detection
  84. GRB 250306A: Swift detection of a burst
  85. GRB250101A: Radio upper limits from VLA observations
  86. GRB 250305A: SVOM/GRM observation of a burst
  87. EP250302a: Optical Observations at CrAO and SAO RAS
  88. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  89. EP 250304A: Optical counterpart detection by LCO
  90. EP250302A: 1.3m DFOT optical afterglow detection
  91. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  92. EP250304a: REM NIR upper limits
  93. IPN triangulation of GRB 250222A
  94. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  95. EP250302a: Mondy Continued Optical Observations
  96. EP250304a: Swift-XRT detection of a fading X-ray source
  97. EP250304a: TRT optical counterpart detection
  98. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  99. EP250304a: Einstein Probe detection of an X-ray transient
  100. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits

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