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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"

2797 results found.

  1. EP241115a/GRB 241115D: Swift/XRT follow-up observation
  2. EP 241113a: LBT possible optical counterpart
  3. IceCube-241113A - IceCube observation of a high-energy neutrino candidate track-like event
  4. LIGO/Virgo/KAGRA S241109bn: ATLAS observations and discovery of the potential counterpart AT2024aawt
  5. GRB 241030A: Mondy optical observations
  6. LIGO/Virgo/KAGRA S241102br: OHP/T193 optical observations
  7. EP241101a: Possible detection of an optical counterpart with FTW
  8. GRB 241030A / EP241030a: GMG possible spectroscopic redshift at z ~ 1.4
  9. GRB 241030A: detection of the bright optical counterpart in ATLAS forced photometry
  10. GRB 241030A: Keck/LRIS spectroscopic redshift z = 1.411
  11. EP 241026b: LBT possible optical counterpart (brightening source)
  12. GRB 240821A: Keck/LRIS spectroscopic observations
  13. GRB 241026A: SAO RAS observations of possible optical afterglow
  14. IceCube-241006A - IceCube observation of a high-energy neutrino candidate track-like event
  15. EP trigger ID 01709064214: GOTO confirms detection as a flare star
  16. IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
  17. EP240918a: Swift-XRT observation
  18. EP240918a: YAHPT Optical Upper Limit
  19. GRB 240912A: Swift-BAT refined analysis
  20. Fast X-ray Transient EP240801a: GMRT radio observations
  21. GRB 240905E: CrAO Optical Afterglow observations, possible OT candidate
  22. GRB 240819A as a likely X-Ray Flash
  23. GRB 240828B : Detection of a possible very soft X-ray transient by SVOM/ECLAIRs
  24. EP240801a: Keck/LRIS spectroscopic redshift confirmation
  25. IceCube-240808A - IceCube observation of a high-energy neutrino candidate track-like event
  26. The EP-WXT trigger 01709018832 on August 7th is likely a flaring star
  27. EP240801a: NOT optical observations
  28. IceCube-240725A - IceCube observation of a high-energy neutrino candidate track-like event
  29. IceCube-240721A - IceCube observation of a high-energy neutrino candidate track-like event
  30. EP240708a: X-ray follow-up observations with Swift/XRT
  31. The EP-WXT source triggered on July 14th is likely a flaring star
  32. GRB 240713A: J-band upper limit from WINTER
  33. GRB240713A: X-ray follow-up observation with EP-FXT
  34. EP240708a: X-ray follow-up observations with EP/FXT and Swift/XRT
  35. EP240703a and EP240703b: Swift/XRT upper limits
  36. EP240702a: Swift/XRT upper limit
  37. EP240626a: Montarrenti Observatory optical upper limit
  38. EP240618a: NOT further optical observations
  39. X-ray transient EP240618a: Fermi/GBM non-detection
  40. EP240618a: Swift/XRT upper limit
  41. EP240617a: tentative Swift/XRT detection of the afterglow
  42. GRB 240615A: possible transient detection from Wendelstein observations
  43. EP240618a: OHP/T193 MISTRAL i' and Y band upper limits
  44. Swift Trigger 1235109: a possible GRB 240606A
  45. GRB 240603B: Swift detection of a possible burst
  46. GRB 240529A: MASTER prompt OT detection
  47. The EP-WXT source triggered on June 1st is likely a flaring star
  48. EP240518a: GSP optical upper limit
  49. EP240518a: possibly identified with a flare star by EP-FXT
  50. GRB 240514E: A possible candidate BD-21 1074
  51. GRB 240502C: Zeiss-1000 at Koshka observations of GOTO24bao optical counterpart candidate
  52. GRB 240514B: GOTO candidate optical counterpart
  53. LIGO/Virgo/KAGRA S240422ed: P200 observations of AT2024hit
  54. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfr and AT2024hfs
  55. GRB 240502C: Zeiss-1000 at Koshka observatory observations of GOTO optical counterpart candidates
  56. IPN triangulation of GRB 240501B and GRB 240501A - possible episodes of ultra long GRB
  57. GRB 240502C: GOTO possible optical counterpart candidates
  58. LIGO/Virgo/KAGRA S240422ed: Host redshifts of AT2024hfq, AT2024hfu, and AT2024hmo from DBSP
  59. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  60. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  61. LIGO/Virgo/KAGRA S240422ed: BOOTES-6/DPRT optical upper limits for EP240426a
  62. LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
  63. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  64. EP240426a: YAHPT optical upper limit
  65. LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
  66. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  67. LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations
  68. LIGO/Virgo/KAGRA S240422ed: EP-FXT detection of a candidate counterpart EP240426a
  69. LIGO/Virgo/KAGRA S240422ed: Magellan Follow-up Observations of Swift/XRT candidates
  70. S240422ed: BlackGEM/MeerLICHT transient detection AT2024hgl/MLTJ080628.10-250116.4
  71. S240422ed: MeerLICHT/BlackGEM photometry on AT2024hfx and archival ZTF detection
  72. LIGO/Virgo/KAGRA S240422ed: Magellan Spectrum of GW-MMADS Candidate AT2024hdo Indicates a Type II SN
  73. LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
  74. LIGO/Virgo/KAGRA S240422ed: Vetting of DECam Candidates Using Real-Time Resources and SAGUARO Infrastructure
  75. IceCube-240424A - IceCube observation of a high-energy neutrino candidate track-like event
  76. LIGO/Virgo/KAGRA S240422ed: MOSFIRE spectroscopy of the DECam GW-MMADS candidate AT 2024hdn
  77. LIGO/Virgo S240422ed: Swift-XRT detection of 3 possible counterparts
  78. LIGO/Virgo/KAGRA S240422ed: Continued Imaging of Mag24a
  79. LIGO/Virgo/KAGRA S240422ed: Magellan Detection of a Potential Electromagnetic Counterpart
  80. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  81. GRB 240419A: Possible ATCA radio detection
  82. LIGO/Virgo/KAGRA S240422ed: Magellan Observations
  83. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  84. GRB240418A - Candidate afterglow from NIRES
  85. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  86. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  87. EP240417a: YAHPT Optical Upper Limits
  88. LIGO/Virgo/KAGRA S240413p: STEP - T80S Search and Candidate Counterpart Identification
  89. EP240416a: Kinder optical counterpart candidate
  90. GRB 240415A: Mondy optical transient detection
  91. LXT 240402A/GRB 240402B: Swift follow-up observations
  92. EP240414a: Kinder optical counterpart candidate possibly associated with the galaxy SDSS J124601.99-094309.3
  93. EP240413a: possible detection of the X-ray emission with EP-FXT after 14 hours
  94. GRB 240414A: Swift detection of a burst
  95. IceCube-240412A - IceCube observation of a high-energy neutrino candidate track-like event
  96. EP240408a: Swift follow-up observation
  97. X-ray transient EP240331a: Kinder optical upper limits
  98. IceCube-240327B - IceCube observation of a high-energy neutrino candidate track-like event
  99. IceCube-240327A - IceCube observation of a high-energy neutrino candidate track-like event
  100. X-ray transient EP240315a: e-MERLIN radio observations

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