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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').
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"

24795 results found.

  1. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  2. GRB 250314A: Swift/UVOT Upper Limits
  3. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  4. GRB 250314A: Swift XRT Detection
  5. EP250315a: optical counterpart candidate detected by Gemini North
  6. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  7. EP250315a: Einstein Probe detection of an X-ray transient
  8. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  9. SVOM/MXT upper limit on GRB 250314A
  10. GRB 250314A: SVOM/VT upper limit
  11. GRB 250314A: NOT near-infrared candidate counterpart
  12. GRB 250313A: Fermi GBM Detection
  13. GRB 250312B: Fermi GBM Observation
  14. GRB 250313A: Swift-XRT observations
  15. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  16. GRB 250314A: SVOM detection of a burst
  17. GRB 250313A: AstroSat CZTI detection of a bright long burst
  18. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  19. GRB 250313A: Fermi-LAT detection
  20. EP250304a: Pan-STARRS r and i-band imaging and photometry
  21. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  22. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  23. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  24. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  25. GRB 250312A: Swift-XRT refined Analysis
  26. GRB 250312A: Enhanced Swift-XRT position
  27. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  28. GRB 250226B: Fermi GBM Observation
  29. GRB 250302A: Fermi GBM Observation
  30. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  31. GRB 250312A: Swift detection of a burst
  32. GRB 241213A: VIRT Optical Upper Limit
  33. GRB 241228A: VIRT Optical Upper Limit
  34. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  35. GRB 250311A: Swift-XRT observations
  36. GRB 230509B: 1.3m DFOT Optical observations
  37. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  38. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  39. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  40. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  41. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  42. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  43. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  44. GRB 250309B: PRIME near-infrared detection
  45. GRB 250225B: Swift-BAT refined analysis
  46. GRB 250311A/EP250311a: TRT optical upper limit
  47. EP250311a/GRB 250311A: EP-WXT detection
  48. GRB 250311B: SVOM detection of a burst
  49. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  50. GRB 250309B / AT2025dws: further SAO RAS optical observations
  51. EP250308a: 1.6m Mephisto optical upper limits
  52. Konus-Wind detection of GRB 250309B
  53. IPN triangulation of GRB 250308A (short)
  54. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  55. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  56. GRB 250309B: Swift-XRT refined Analysis
  57. GRB 250309B / IceCube-250309A: GECAM-B observations
  58. GRB 250309B / AT2025dws: SAO RAS optical observations
  59. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  60. GRB 250309B: Fermi GBM Observation
  61. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  62. IceCube-250309A: No candidates from the Zwicky Transient Facility
  63. Fermi-LAT gamma-ray observations of IceCube-250309A
  64. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  65. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  66. EP250308a: GSP optical upper limit
  67. EP250308a: Einstein Probe detection of an X-ray transient
  68. EP250308a: NOT optical upper limit
  69. GRB 250306A: EIRSAT-1 GMOD detection
  70. GRB 250306A: Swift-BAT refined analysis
  71. GRB 250306A: NuSTAR detection of the prompt emission
  72. EP250304a: MeerKAT detection of a possible radio counterpart
  73. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  74. GRB 250305A: AstroSat CZTI detection
  75. EP250302a:Xinglong optical observations
  76. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  77. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  78. GRB250101A: Radio upper limits from VLA observations
  79. GRB 250305A: SVOM/GRM observation of a burst
  80. The EP-WXT trigger 01709132323 is likely a flaring star
  81. EP250304A: Upper limits from Fermi-GBM Observations
  82. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  83. EP250302a: Optical Observations at CrAO and SAO RAS
  84. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  85. EP 250304A: Optical counterpart detection by LCO
  86. EP250302A: 1.3m DFOT optical afterglow detection
  87. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  88. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  89. EP250304a: REM NIR upper limits
  90. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  91. EP250302a: Mondy Continued Optical Observations
  92. EP250304a: Swift-XRT detection of a fading X-ray source
  93. EP250304a: TRT optical counterpart detection
  94. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  95. EP250304a: Einstein Probe detection of an X-ray transient
  96. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  97. EP250302a: SAO RAS optical observations
  98. EP250302a : GIT optical follow-up
  99. EP250225a: the candidate optical counterpart is an AGN
  100. EP250302a: Kinder optical follow-up observations

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