J/ApJ/874/82 Follow-up photometry & spectroscopy of PTF14jg (Hillenbrand+, 2019)
PTF14jg: the remarkable outburst and post-burst evolution of a previously
anonymous Galactic star.
Hillenbrand L.A., Miller A.A., Carpenter J.M., Kasliwal M.M., Isaacson H.,
Tang S., Joshi V., Banerjee D.P.K., Cutri R.M.
<Astrophys. J., 874, 82 (2019)>
=2019ApJ...874...82H 2019ApJ...874...82H
ADC_Keywords: Stars, variable; Photometry, ugriz; Spectra, optical;
Spectra, infrared
Keywords: circumstellar matter ; infrared: stars ; stars: activity ;
stars: pre-main sequence ; stars: variables: general ;
stars: winds, outflows
Abstract:
We report the outbursting source PTF 14jg, which, prior to the onset
of its late 2013 eruption, was a faint, unstudied, and virtually
uncataloged star. The salient features of the PTF 14jg outburst are
(i) projected location near the W4 HII region and radial velocity
consistent with physical association; (ii) a light curve that
underwent an ∼6-7mag optical (R-band) through mid-infrared (L-band)
brightening on a timescale of a few months, peaked and then faded by
∼3mag, but plateaued still >3.5mag above quiescence by ∼8 months
post-peak, lasting to at least 4yr after eruption; (iii) strong
outflow signatures with velocities reaching -530km/s; (iv) a
low-gravity and broad (∼100-150km/s FWHM) optical absorption-line
spectrum that systematically changes its spectral type with
wavelength; (v) lithium; and (vi) ultraviolet and infrared excess. We
tentatively identify the outburst as exhibiting characteristics of a
young star FU Ori event. However, the burst would be unusually hot,
with an absorption spectrum exhibiting high-excitation (∼11000-15000K)
lines in the optical and no evidence of CO in the near-infrared, in
addition to exhibiting an unusual light curve. We thus also consider
alternative scenarios-including various forms of novae,
nuclear-burning instabilities, massive star events, and
mergers-finding them all inferior to the atypically hot FU Ori star
classification. The source eventually may be interpreted as a new
category of young star outburst with a larger amplitude and shorter
rise time than most FU Ori-like events.
Description:
The (intermediate) Palomar Transient Factory (iPTF) monitored the
W3/W4/W5 complex in the R band beginning in the summer of 2013. A new
source was identified as a candidate transient on 2014 January 24 and
given the name PTF 14jg. We estimate that PTF 14jg achieved peak
brightness around 2014 February 9.
The photometry reported in Table 1 was obtained with the Palomar 48
inch telescope (P48) and the PTF Survey Camera as part of routine iPTF
operations. The RPTF band is approximately a Mould R filter. See
Section 2 for further explanations.
Our follow-up to the dramatic optical brightening event in PTF 14jg
includes photometric and spectroscopic observations, in addition to
continued Palomar 48 inch R-band monitoring. Optical and near-infrared
photometric data were obtained at the Palomar 60 inch telescope
(ugriz) and Mount Abu 1.2m telescope (JHKs), while optical and
infrared spectra were obtained at the Apache Point Observatory,
Palomar Observatory, and Keck Observatory. We also acquired
bluer-wavelength ultraviolet and X-ray data from UVOT on board Swift
and redder-wavelength mid-infrared (Spitzer, NEOWISE) and millimeter
(CARMA) observations. All follow-up observations occurred after the
light-curve peak in early February of 2014. See Section 4 for details.
As summarized in Table 6, a number of telescopes and instruments were
used to characterize the spectroscopic evolution of PTF 14jg as it
reached its photometric peak and then faded in brightness. The spectra
were obtained at the Apache Point Observatory (DIS optical spectra at
R∼2400, TripleSpec infrared spectrum at R∼3500), Palomar Observatory
(DBSP optical spectra at R∼2000, TripleSpec infrared spectrum at
R∼3000), and Keck Observatory (HIRES optical spectra at R∼34000-48000,
DEIMOS optical spectrum at R∼2200, MOSFIRE infrared spectrum at R∼3300).
See Section 4.6.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
02 40 30.14 +60 52 45.5 PTF 14jg = PTF 14jg
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 21 280 P48 R-band observations
table3.dat 115 151 P60 ugriz observations
fig6a.dat 21 1189 The PTF 14jg low-dispersion APO/DIS optical
spectra of Feb. 3rd, 2014
fig6b.dat 21 4646 The PTF 14jg low-dispersion Palomar 200"/DBSP
optical spectra of Nov. 11th, 2017
fig7a.dat 29 7275 PTF14jg infrared spectrum from APO/TSpec
on Feb. 2nd, 2014
fig7b.dat 29 6384 PTF14jg infrared spectrum from Palomar/TSpec
on March 23rd, 2014
table6.dat 86 21 Summary of spectroscopic observations
--------------------------------------------------------------------------------
See also:
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2014)
III/166 : A New Library of Optical Spectra (Silva + 1992)
II/313 : Palomar Transient Factory (PTF) photometric catalog 1.0 (Ofek+, 2012)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
II/363 : The band-merged unWISE Catalog (Schlafly+, 2019)
J/ApJS/99/135 : Rotation and Spectral Peculiarities (Abt+ 1995)
J/A+A/337/403 : Low-mass stars evolutionary models (Baraffe+ 1998)
J/ApJ/551/852 : FCRAO CO survey of the outer Galaxy (Heyer+, 2001)
J/MNRAS/373/781 : JHK photometry of faint standard stars (Leggett+, 2006)
J/ApJS/166/526 : Compact extragalactic radio sources (Xu+, 2006)
J/A+A/480/91 : Gal. disk stars vertical distribution. IV. (Soubiran+, 2008)
J/AJ/140/34 : Classification of nova light curves (Strope+, 2010)
J/ApJ/748/14 : ONC population data from WFI observations (Da Rio+, 2012)
J/AJ/147/140 : SED of 24 class I & II FU Orionis stars (Gramajo+, 2014)
J/ApJ/792/30 : NEOWISE magnitudes for near-Earth objects (Mainzer+, 2014)
J/ApJ/815/4 : V899 Mon long-term monitoring (Ninan+, 2015)
J/ApJ/831/133 : Follow-up of probable young star ASASSN-15qi (Herczeg+, 2016)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.3 d MJD [56491.369/57628.499] Modified Julian Date
11 A1 --- l_Rmag The 4σ statistical upper limit flag on Rmag
12- 16 F5.2 mag Rmag [14.96/22.63] PTF R band apparent magnitude
18- 21 F4.2 mag e_Rmag [0.07/0.36]? Uncertainty in Rmag
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.3 d MJD-u [56706.15/56838.5]? Modified Julian Date
of u band observation
11 A1 --- l_umag The 5σ statistical upper limit flag on umag
12- 17 F6.3 mag umag [18.15/20.47]? Apparent u band magnitude (1)
19- 23 F5.3 mag e_umag [0.03/0.32]? Uncertainty in umag
25- 33 F9.3 d MJD-g [56697.1/57366.2]? Modified Julian Date
of g band observation
35- 40 F6.3 mag gmag [16.04/19.24]? Apparent g band magnitude (2)
42- 46 F5.3 mag e_gmag [0.014/0.21]? Uncertainty in gmag
48- 56 F9.3 d MJD-r [56683.3/57366.2]? Modified Julian Date
of r band observation
58- 63 F6.3 mag rmag [15/18]? Apparent r band magnitude (2)
65- 69 F5.3 mag e_rmag [0.006/0.06]? Uncertainty in rmag
71- 79 F9.3 d MJD-i [56697.1/57366.2]? Modified Julian Date
of i band observation
81- 86 F6.3 mag imag [14.5/17.4]? Apparent i band magnitude (2)
88- 92 F5.3 mag e_imag [0.005/0.2]? Uncertainty in imag
94-102 F9.3 d MJD-z [56706.15/57078.22]? Modified Julian Date
of z band observation
104-109 F6.3 mag zmag [14.27/16.81]? Apparent z band magnitude (2)
111-115 F5.3 mag e_zmag [0.019/0.11]? Uncertainty in zmag
--------------------------------------------------------------------------------
Note (1): Calibrated relative to Swift UVOT observations of the same field.
5σ statistical upper limit.
Note (2): Calibrated relative to SDSS stars (see text).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: fig6[ab].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.3 0.1nm lambda [3330.7/10500.4] Wavelength in Angstroms
11- 21 E11.4 10-15cW/m2/nm Flux [-2.1e-17/5.1e-15] Flux density
in 10-15erg/s/cm2/Å
--------------------------------------------------------------------------------
Byte-by-byte Description of file: fig7[ab].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 F6.4 um lambda [0.9/2.5] Wavelength
8- 18 E11.4 10-15cW/m2/nm Flux [-1.3e-13/1.3e-13] Flux density
in 10-15erg/s/cm2/Å
20- 29 E10.4 10-15cW/m2/nm e_Flux [4.6e-18/3.2e-12] Uncertainty in Flux
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Set "Opt" or "IR" spectra
5- 14 A10 "date" Date UT date of observation
16- 20 I5 d MJD [56690/58068] Modified Julian Date
of observation
22- 25 I4 d tPk [-7/1371] Post-peak days
27- 31 F5.2 mag Rmag [15/18.5]? RPTF magnitude
33- 53 A21 --- Tel Telescope/Instrument
55- 86 A32 --- Obs Observers/Reducers
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 28-Aug-2020